Diseases / List of Viral Diseases / West Nile Virus Disease / Detailed Disease Description:
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< > Literature Reports of CLINICAL SIGNS for West Nile Virus Disease: Use sub-contents list below, or simply scroll down the page to view findings.

Sick crow with WVN infection. Click here for full-page view with caption Sick crow with WVN infection. Click here for full-page view with caption Sick crow with WVN infection. Click here for full-page view with caption

OVERALL CLINICAL PRESENTATION - Editorial Comment
(Text Replicated on Overall Disease page - West Nile Virus Disease)

Editorial Comment (Editorial Overview Text Replicated on Overall Disease page - West Nile Virus Disease)
  • The presentation of this disease may vary from inapparent infection through a mild non-specific illness, to severe nervous signs and death; there are no pathognomonic findings.
  • The course of the disease is usually short, but convalescence can be prolonged, particularly in the elderly.
  • The predominant presentation in humans is usually pyrexia (fever) and headache, often with fatigue and myalgia/arthralgia; skin rash, enlarged lymph nodes, conjunctival congestion and gastrointestinal signs are also commonly seen. Other less common signs in humans include sore/congested throat and coughing.
  • In severe disease in humans, neurological signs and sometimes profound muscular weakness may be seen while signs such as rash and lymphadenopathy may be absent. In humans, most severe cases have been seen in the elderly.
  • In horses, neurological signs usually predominate in clinically apparent cases; fever may or may not be present. Common signs include ataxia/incoordination, muscle fasciculations, limb paresis or paralysis (particularly of the hind limbs) and leading to recumbency in severe cases, altered behaviour and hyperaesthesia.
  • In other mammals when clinical illness occurs this may include mild non-specific signs such as lethargy and reduced appetite and/or overt neurological signs such as head tilt, torticollis, ataxia and incoordination, tremors, hindlimb paralysis, tetraplegia, loss of righting ability and recumbency. Pyrexia may be present. Continuing neurological signs may occur in survivors.
  • Many affected birds in the USA have been found dead (sudden death) although non-specific, neurological, and respiratory signs have sometimes been noted prior to death.
  • In affected reptiles, neurological signs have been seen.

See also: West Nile Virus Disease - Editorial Overview of Disease Characteristics for specified SPECIES-TAXA

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Observation, General Demeanour and Locomotion

Source Information Aves - Birds (Class)  general:
  • Depression, anorexia, weakness, weight loss, and recumbency. (J26.37.w1, P30.1.w3)
  • Generalised lethargy and ruffled feathers. (J84.9.w2)
Corvus brachyrhynchos - American Crow:
  • General weakness and lethargy.(V.w42)
  • Sedentary. Stand with a crouched, non-erect posture and have difficulty in maintaining balance. (V.w42)
  • Show an inability to walk, perch, stand, fly or to hold the wings in their normal position against the body. (V.w42)
  • Lack of normal response to danger. (V.w42)

Cyanocitta cristata - Blue jay:

  • Unusual posture. (J84.9.w2)
Anser anser domesticus - Domestic goose:
  • Decreased activity, and depression (4/4). (J84.7.w29)
Meleagris galloparvo domesticus - Domestic turkey (Meleagris - (Genus)):
  • No clinical signs.(J5.44.w2)
Gallus gallus domesticus - Domestic chicken (Phasianidae - Grouse, Turkeys, Pheasants, Partridges, etc. (Family)):
  • No clinical signs detected. (J5.44.w1, J84.7.w22)
Accipiter cooperii - Cooper's hawk:
  • Difficulty in standing. (J22.286.w1)

"Owls" (Asio flammeus - Short-eared owl, Bubo virginianus - Great horned owl, Nyctea scandiaca - Snowy owl and Strix varia - Barred owl (Strix (Genus))):

  • In 13 owls clinical signs included weakness, depression, uncoordinated flight, inability to fly and recumbency. (J5.47.w2)

Grus canadensis - Sandhill crane:

  • Progressive ataxia in one naturally infected Florida sandhill crane which was also quiet and unusually non-aggressive. Developing from difficulty in balancing to a need to use a wall or its wings to support itself, with inability to stand unassisted and several falls, later intention tremor of the head and neck and proprioceptive deficits in the wings. (P87.10.w3)
  • Neurological signs in a naturally infected sandhill crane in a zoo, which survived. (J4.224.w1)
  • In hatch-year Mississippi sandhill cranes (Grus canadensis pulla), ataxia and/or weakness for 2-11 days, progressing to recumbency and death. (P87.10.w3)
Equus caballus - Domestic horse:
  • Behavioural:
    • Behavioural changes (depression, fearfulness) sometimes observed. (J89.16.w1)
    • Somnolence in 5/8 horses. (J4.218.w2).
    • Agitation in 3/19 horses (15.8%), USA, 2000. (J84.7.w27).
    • Dull and lethargic (3/19 horses, 15.8%), USA, 2000. (J84.7.w27).
    • Abnormal behaviour 2/76 (3%). (J84.7.w17)
    • Apprehension and reluctance to move, following experimental infection. (P32.1.w13)
    • Hyperexcitability. One horse in Israel in 2000. (J3.151.w1)
    • USA, equine West Nile encephalitis presentation: abnormal mentation in 67%, including nonresponsiveness and somnolence. (P39.4.w4)
    • Depression was recorded in 10/28 (36%) cases in Ontario, Canada, 2002. (J14.44.w1)
    • Abnormal mentation was noted in 31/46 horses (67%) admitted in Florida, 2001. These included four horses which could be roused only with difficulty and four which showed aggression. Four individuals circled or stall-walked compulsively. (J4.222.w1)
    • Abnormal mentation (from somnolence to hyperexcitability or aggression) may be seen. (J484.35.w1)
    • Abnormal mentation and hyperaesthesia may be seen. (J89.22.w1)
    • Lethargy or depression was noted in 43.0% (208/484) equines, altered mentation in 22.1% (107/484), 13/484 were apprehensive and a further eight equines were restless or agitated, in Nebraska and Colorado, USA, 2002. (J4.225.w2)
    • Compulsive behaviour was noted in 6.8% (33/484) of equines in Nebraska and Colorado, USA, 2002. (J4.225.w2)
    • Depression was a common finding, seen in 31.9% of horses in a study in Texas, 2002. (J238.118.w1)
    • Excitability was seen in horses with severe clinical signs requiring euthanasia in Kentucky, USA, 2002. (J305.55.w1)
  • Lameness:
    • Unilateral forelimb lameness progressing to bilateral lameness and ataxia (2/8). (J4.218.w2)
    • Three horses were presented due to lameness in Florida in 2001. (J4.222.w1)
    • Lameness was noted in 20.9% of horses (101/484 horses) in Nebraska and Colorado, USA in 2002. (J4.225.w2)
  • Limb weakness, paresis, paralysis
    • Limb weakness in 48% of cases. (J84.7.w12)
    • Paresis/paralysis in 36/76 horses (47%). (J84.7.w17)
    • In fatal cases (death or euthanasia required), ascending paresis, tetraplegia and recumbency, or early tetraplegia and recumbency, usually with muscle rigidity and hyperreflexia of the hind limbs (6/14 horses) (J87.32.w1)
    • Weakness considered one of the characteristic signs, Camargue, France, 1962 (J84.7.w17)
    • Progressive weakness of the hind quarters prior to recumbency in a horse in Egypt. (J86.57.w1)
    • Developing hindquarter paresis then hind leg paralysis, recumbency, sometimes scraping of a hole with the fore legs. (J85.108.w1)
    • Paresis in two, hindlimb paraplegia in one and quadriplegia in two, from five fatal cases during an outbreak in Israel in 2000. (J73.57.w1)
    • USA, equine West Nile encephalitis presentation: weakness in 94%. (P39.4.w4)
    • Recorded in 23/28 (82%) cases in Ontario, Canada, 2002.  (J14.44.w1)
    • Weakness was noted in 43/46 horses (94%) admitted in Florida, 2001. (J4.222.w1)
    • Paresis or paralysis of one, two or all four limbs is common. (J484.35.w1)
    • Limb weakness may be seen. (J89.22.w1)
    • Generalised weakness was noted in 53.3% (259/484 horses) in Nebraska and Colorado, USA in 2002. (J4.225.w2)
    • Limb weakness or paralysis was noted in 38% and caudal paresis in 29% of horses in North Dakota, USA in 2002, (J4.225.w3)
    • Hind limb paresis was seen in 60/136 (35.3%)of horses in Indiana, USA in 2002. (J4.225.w5)
  • Ataxia/gait abnormalities 
    • Ataxia in 95.7% of cases (J84.7.w27); in 55/76 cases (72%) (J84.7.w17); in 85% of cases. (J84.7.w12)
    • Acute-onset ataxia affecting all four limbs (in 5/8 cases). (J4.218.w2)
    • Ataxia affecting all four limbs in 15/20 cases (75%), in USA, 2000. (J84.7.w27)
    • Ataxia affecting rear limbs in 19/21 cases (90.5%), in USA, 2000. (J84.7.w27)
    • Marked gait abnormalities in all cases, with variable degrees of ataxia and hind limb weakness; sometimes also one or both forelimbs affected. (J87.32.w1)
    • Ataxia considered one of the characteristic signs, Camargue, France, 1962. (J84.7.w17)
    • Ataxia in 95.7% of cases, mainly hind limbs affected (90.5%), usually acute onset (90.5%) (USA, 2000).(J84.7.w27).
    • Limb ataxia or paresis, symmetrical or asymmetrical, most commonly involving the hind limbs but occasionally only affecting the front limbs; signs may be exacerbated by moving the animal backwards (J89.16.w1)..
    • Wide-based stance, hypermetric or staggering gait, stumbling, circling. (J89.16.w1).
    • Development of staggering gait following initial signs in a horse in Egypt. (J86.57.w1)
    • Hypermetria in 4/16 cases (25%) in USA, 2000 (J84.7.w27); may be marked (2/8 cases). (J4.218.w2)
    • Marked gait abnormalities in all cases; with variable degrees of ataxia and hind limb weakness, sometimes also one or both forelimbs affected. In Italy, 1998. (J87.32.w1)
    • Ataxia affecting the hindlimbs or all four limbs. In horses in Israel in 2000. (J3.151.w1)
    • Ataxia was noted in all of five fatal cases during an outbreak in Israel in 2000. (J73.57.w1)
    • USA, equine West Nile encephalitis presentation: ataxia in 72%. (P39.4.w4)
    • Ataxia recorded in 28/28 (100%) cases in Ontario, Canada, 2002. (J14.44.w1)
    • Ataxia was noted in 33/46 horses (72%) admitted in Florida, 2001. (J4.222.w1)
    • Ataxia is a presenting sign. (J484.35.w1)
    • Ataxia was noted in 57.4% (278/484 horses) in Nebraska and Colorado, USA in 2002. (J4.225.w2)
    • Incoordination was noted in in 69% of horses in North Dakota, USA in 2002. (J4.225.w3)
    • Ataxia was seen in 75/136 horses (44/1%) in Indiana, USA in 2002. (J4.225.w5)
    • Ataxia was a common finding, seen in 69.1% of horses in a study in Texas, USA, 2002, (J238.118.w1)
    • Abnormal gait was a common finding, seen in 52.2% of horses in a study in Texas, USA, 2002. (J238.118.w1)
    • Ataxia/incoordination was seen in horses with severe clinical signs requiring euthanasia in Kentucky, USA, 2002. (J305.55.w1)
  • Recumbency:
    • Recumbency (1/8 cases). (J4.218.w2)
    • Recumbency and/or difficulty in rising in 45% of cases. (J84.7.w12)
    • Recumbency (and seizures) (in 2/8 cases). (J4.218.w2).
    • Sometimes inability to rise. (J84.7.w27)
    • Inability to rise, or able to rise only with assistance: "down" in 9/22 cases (40.9%), able to rise with assistance 6/21cases (28.6%). (J84.7.w27)
    • Recumbency developing, sometimes scraping of a hole with the fore legs, horses in Morocco. (J85.108.w1)
    • Recumbency prior to death about 60 hours after the onset of illness, in a horse in Egypt. (J86.57.w1)
    • Recumbency in some horses in Israel in 2000.(J3.151.w1)
    • Recumbency occurred prior to death or euthanasia in all of five fatal cases during an outbreak in Israel in 2000. (J73.57.w1)
    • USA, equine West Nile encephalitis: recumbency in 30% of cases, sometimes intermittent. (P39.4.w4)
    • Recumbency recorded in 10/28 (36%) cases in Ontario, Canada, 2002. (J14.44.w1)
    • Recumbency occurred in 14/46 horses (30%) admitted in Florida, 2001. (J4.222.w1)
    • While 27.5% (133/484 horses) in Nebraska and Colorado, USA, in 2002 were recumbent and unable to rise, a further 24.2% (117/484) were recumbent for long periods but able to rise. (J4.225.w2)
    •  
    • Recumbency or difficulty in rising was noted in 23% of horses in North Dakota, USA in 2002. (J4.225.w3)
    • Recumbency was seen in 13/136 (7.6%)of horses in Indiana, USA in 2002. (J4.225.w5)
    • Recumbency was a common finding, seen in 27.7% of horses in a study in Texas, USA, 2002. (J238.118.w1)
  • Other
    • Knuckling over at the fetlocks. (J84.7.w27)
    • Falling to knees (5/8 cases). (J4.218.w2)
    • Jaundice. One horse in Israel in 2000. (J3.151.w1)
    • Marked hypermetria (2/8). (J4.218.w2)
    • Dysmetria was noted in 18/22 horses (82%) admitted in Florida, 2002. (J4.222.w1)
    • Sudden collapse and knuckling were noted to be associated with forelimb weakness in horses admitted in Florida, 2001. (J4.222.w1)
    • Stiffness or reluctance to move was noted in 36.6% (177/484 horses) in Nebraska and Colorado, USA in 2002. (J4.225.w2)
    • Hypermetria was noted in 6.4% of equines ( 31/484) in Nebraska and Colorado, USA in 2002. (J4.225.w2)
    • It was noted that 10.3% (50/484) used a dog-sitting posture, 3.1% (15/484) used a praying posture and 20.7% (100/484) had abnormal head carriage, in Nebraska and Colorado, USA in 2002. (J4.225.w2)
    • Circling was seen in 6% of horses in North Dakota, USA in 2002. (J4.225.w3)
    • Falling down was noted as one of the less common findings in a study in Texas, USA, 2002. (J238.118.w1)
Homo sapiens - Human:

Malaise and Fatigue:

  • Malaise, fatigue and general weakness are commonly noted, sometimes with drowsiness or somnolence. (J84.5.w2, J84.5.w3, J91.3.w2, J91.5.w1, J101.59.w1, J102.17.w1, J106.55.w1, J115.13.w4, B241.49.w49)
    • Malaise may be noted more frequently in adults than children. (J100.93.w1)
    • General tiredness and weakness commonly accompany the initial fever (J101.64.w1) and may continue during the recovery phase. (J111.72.w1)
    • Generalised weakness is sometimes a prominent sign in patients with encephalitis. (J98.352.w1); e.g. recorded in 8/19 (40% of cases) of individuals with encephalitis, meningitis or meningoencephalitis. (J84.7.w9)
    • Lethargy in 24.6% and general muscle weakness in 56.9% of 188 confirmed cases in Mississippi, 2002. (P48.1.w2)
    • A review of data from 13 patients with WNV infection found that muscle weakness associated with this infection may vary from acute flaccid paralysis, with or without associated fever or meningitis, through severe muscle weakness to disabling fatigue. (J292.28.w1)

Headache and other Pain:

  • Severe headache is commonly noted and in many outbreaks has been considered to be one of the main symptoms. (J84.5.w2, J84.5.w3, J84.7.w9, J84.7.w10, J84.7.w32, J91.5.w1, J99.57.w1, J100.93.w1, J102.17.w1, J103.3.w1; J106.55.w1, J111.72.w1, J115.13.w4, J123.31.w1, J129.42.w1, B243.31.w1)
    • In 80% of cases (P31.6.w1); in 51% of cases (J91.61.w1); seen in 78% of adults and 37% of children. (J100.93.w1); in 57.9% of cases during an outbreak in Israel, 2000. (J84.7.w14); in 77% of 352 individuals with acute aseptic meningitis and encephalitis in Romania in 1996. (J98.352.w1
    • Rarely reported in experimental infection of patients with terminal neoplasia but may have been masked by analgesics. (J91.3.w1)
    • Often frontal. (J101.59.w1)
    • May be primarily occipital. (J91.5.w1)
    • Present in 72.3% of 188 confirmed cases in Mississippi, 2002. (P48.1.w2)
  • Ocular pain has been reported in many cases, sometimes with a note that it has been associated with eye movement; it has been a common sign in some outbreaks (e.g. in 45% of cases (P31.6.w1, J101.64.w1)) although it is generally less common than headache. (P31.6.w1, J84.5.w3, J91.3.w2, J100.93.w1 J101.59.w1, J101.64.w1, J102.17.w1; J111.72.w1, J129.42.w1)
  • Myalgia (muscle aches and pains) may be noted, often generalised. In outbreaks myalgia has been noted in e.g. 15.4% (J84.7.w14), 25% (P31.6.w1), 32% (J84.7.w9), 34.6% (P48.1.w2) 55% (J257.168.w2) of patients. (J84.5.w2, J84.5.w3, J84.7.w14, J84.7.w9, J100.93.w1, J111.72.w1, J115.13.w4, J123.31.w1, J257.168.w2, P31.6.w1, P48.1.w2, B241.49.w49, B243.31.w1)
  • Backache or back pain may be noted as a specific symptom. (J84.5.w2, J100.93.w1, J101.59.w1, J107.36.w1, J129.42.w1, B243.31.w1); in one outbreak this was recorded in 40% of individuals (P31.6.w1, J101.64.w1)
  • Abdominal tenderness or pain has been recorded for some patients (J91.3.w2) and noted in variable percentage of patients during outbreaks (20% of cases) (P31.6.w1), 43% (J91.61.w1)
  • Arthralgia (joint pain) may be noted and has sometimes been a common finding (e.g. in 37% of patients in one outbreak (J91.61.w1), in 2/19 (11% of cases) in another (J84.7.w9)), in 24.5% of 188 patients in Mississippi, 2002 (P48.1.w2), in 15/48 (31%) patients in Ontario, Canada, 2002. (J257.168.w2). (J84.7.w9, J91.61.w1, J111.72.w1, J257.168.w2, P48.1.w2)

Muscle weakness/flaccid paralysis:

  • Mild encephalitis and severe myelitis, described as resembling the polio syndrome. In one individual, 68 years old. (J105.135.w1)
  • Flaccid paresis of the left lower extremity with loss of deep tendon reflexes but without any sensory changes. In one individual, 22 years old. (J107.36.w1)
  • Guillain-Barr Syndrome (acute inflammatory demyelinating polyradiculoneuritis). Progressive weakness including proximal and distal muscles, bilateral weakness of facial muscles, and reduced respiration such that ventilatory support was required. In one individual 69 years old. (J106.55.w2)
  • Muscle weakness (3/19 cases, 16% of cases). During an outbreak in and near New York, USA 2000. (J84.7.w9)
  • Acute flaccid paralysis syndrome in six individuals. One or more limbs affected with normal sensation but hyporeflexia or areflexia and asymmetrical weakness, sometimes flaccidity. (N7.51.w1)
  • Acute flaccid paralysis described in seven patients, three of which did not have other findings suggestive of severe central nervous system involvement. In general, acute, painless asymmetric flaccid paralysis of one or more limbs, sometimes monoplegia, no numbness, paraesthesia or sensory loss, although occasionally myalgia, and often with bowel and/or bladder involvement. (J84.9.w13)
    • Four months after onset at least three individuals remained unable to move the affected limbs. (P48.1.w7)
  • Movement disorders reported include tremor (static/kinetic), sometimes with movement, and occasionally disabling and myoclonus, most frequently involving the upper extremity or face. Movement disorders have generally had onset at more than five days after the initial symptoms. In a prospective series of patients tremor was noted in 15 individuals (94%) and myoclonus in 10 (63%). (P39.4.w3)
  • Parkinsonism was noted in 11 of a prospective series of patients (68%), with cogwheel rigidity, bradykinesia and postural instability, but no tremor at rest. This was seen in individuals with meningitis or encephalitis. (P39.4.w3)
  • Bilateral leg weakness (acute flaccid paralysis) with fever and frontal headache. Marked decreases in motor function of both legs, particularly the right leg, and diminished reflexes in both legs, but intact sensation. (J281.181.w1)
  • A review of data from 13 patients with WNV infection found that muscle weakness associated with this infection may vary from acute flaccid paralysis, with or without associated fever or meningitis, through severe muscle weakness to disabling fatigue. (J292.28.w1)
Chlorocebus aethiops - Savanna monkey (Cercopithecus ethiops centralis):
  • No general signs of illness. (J120.20.w1)
Eulemur (Lemur) fulvus - Brown lemur  (Lemuridae - Large lemurs (Family)):
  • No clinical signs recorded following inoculation with either of two strains of West Nile virus. (J91.34.w1)
Macaca mulatta (Macaca rhesus) - Rhesus macaque (Rhesus monkey) (Cercopithecidae - Old-world monkeys (Family)):
  • Ataxia. (J71.75.w1)
  • Illness from the evening of the fourth day after inoculation, with progressive loss of appetite and later incoordination and weakness in one individual (fatal infection). (J120.20.w1)
  • Hyperactivity, later marked weakness, loss of appetite and apathy in one individual (recovered). (J120.20.w1)
  • Ataxia and prostration following intracerebral inoculation of Egypt strain, 1950. (J122.77.w1)
Macaca radiata - Bonnet macaque  (Cercopithecidae - Old-world monkeys (Family)):
  • Paralysis. (J88.36.w1)

Mus domesticus - Laboratory mouse:

  • Initial hyperactivity and roughing of the coat, later hypoactive, weak, hunched. (J120.20.w1)
  • Hyperirritability and failure to feed were early signs of illness, later falling on back and inability to get up. In suckling mice inoculated intracerebrally with 100 host LD50 of Egypt 101 strain. (J101.86.w2)
  • Mild clinical signs by day six following intraperitoneal inoculation in one mouse, weakness by day 7-9 in two mice, ruffled fur at day eight and death by day nine in one mouse, while another was "very sick" when sacrificed on day eight. (J133.951.w12)
Sciurus carolinensis - Eastern grey squirrel
  • Lethargy, walking in circles and ataxia reported in squirrels in Illinois. (W27.19Sept02.wnv1)

Sciurus niger - Eastern fox squirrel (Sciurus - (Genus)):

  • Weakness and depression, lateral recumbency, uncoordinated movements, inability to right self if pushed over. (J26.40.w1)

Mesocricetus auratus - Golden Hamster:

  • Lethargy and huddling together in corners at six or seven days, with reduced feeding, drinking and grooming. (J84.7.w20)
Cavia porcellus - Domestic guinea pig:
  • No clinical signs following intracerebral or intraperitoneal inoculation. (J100.93.w1, J101.59.w1, J116.5.w1, J120.20.w1, J122.77.w1)

"Cotton rat" (Rodentia - Rodents (Order)):

  • No clinical signs following intracerebral inoculation but development of high titre antibodies. Egypt strain, 1950. (J122.77.w1)

Meriones tristrami - Gerbil (Muridae - Rats, mice, voles, gerbils etc. (Family))

  • Death in 3/5 individuals following intracerebral inoculation. During an outbreak in Israel (Maayan Zvi), 1951. (J100.93.w1)
Oryctolagus cuniculus - European rabbit (Domestic rabbit):
  • No clinical signs following very high dose intracerebral inoculation. (J101.59.w1)
  • No clinical signs following intracerebral inoculation of two adults and only very slight local reaction with intracorneal inoculation. (J120.20.w1)
  • No clinical signs (other than a slight temperature rise) following intracerebral inoculation. During an outbreak in Israel (Maayan Zvi), 1951. (J100.93.w1)
  • No clinical signs following intracerebral inoculation. Egypt strain, 1950. (J122.77.w1)
"Hedgehog" (Erinaceidae - Hedgehogs, moonrats (Family)):
  • No clinical signs following intracerebral inoculation of two individuals. (J120.20.w1)
Ovis aries - Domestic sheep:
  • No general signs reported. (J62.53.w3)
  • Alert and responsive but depressed, inability to stand, progressing to lateral recumbency in one individual. (J275.17.w1)
Sus domesticus - Domestic pig:
  • No clinical signs reported following experimental infection. (J88.38.w1)
Canis familiaris - Domestic dog:
  • "Prostration" in one dog with natural infection. (J3.105.w5)
  • Paresis in one of three dogs following experimental infection. (J3.105.w5, J84.8.w3)
  • Clinical signs of weakness in a dog with concurrent immune mediated disease. In Illinois, USA, 2002. (W27.19Sept02.wnv1)
  • Sore muscles reported in a dog in Nebraska, USA, 2002. (W27.04Oct.wnv2)
  • No clinical signs observed in natural infection in dogs, nor following experimental inoculation.(J42.100.w2, J84.7.w24)
  • In one individual, inability to bear weight on its limbs even while being supported. (J212.15.w3)
  • No change in activity level in four dogs experimentally infected by mosquito bite. (J84.10.w1)
Canis lupus - Wolf ((Canidae - Dogs, foxes (Family)):
  • Lethargy, depression and irritability progressing to anorexia, weakness and ataxia. (J84.9.w17)
Felis catus - Domestic cat:
  • No general signs reported. (J64.19.w1)
  • Mild non-specific clinical signs lasting two to three days in cats experimentally infected via mosquito bite. (P39.4.w16)
  • Lethargy in three of four cats infected by bite of infected mosquitoes but not in any of four cats infected by ingestion of infected mice. (J84.10.w1)

Ursus maritimus - Polar bear:

  • Hind limb paresis/paralysis, with inability to stand, in an adult male bear; the left hind leg was weak and the bear was unable to move his right hind leg; he also appeared depressed. (V.w114)

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Body Condition, Hydration and Growth Rate (Clinically apparent)

Source Information Anser anser domesticus - Domestic goose:
  • Weight loss (4/4 two-week-old goslings, following subcutaneous inoculations). (J84.7.w29)

Grus canadensis - Sandhill crane:

  • Weight loss following experimental challenge with 5,000 pfu of West Nile virus inoculated subcutaneously. Non-vaccinated birds lost 4.5 - 8.5% of body weight while vaccinated individuals lost 2.2- 5.7% of body weight. (J2.40.w3)
  • In adult greater sandhill cranes following experimental inoculation with 5,000 pfu WNV (equivalent to one mosquito dose), mild weight loss of 4-8% of body weight. (P87.10.w3)
  • In hatch-year Mississippi sandhill cranes (Grus canadensis pulla), weight loss of up to 100 g per day. (P87.10.w3)
Mus domesticus - Laboratory mouse:
  • Up to 9% weight loss in mice following intraperitoneal inoculation. (J133.951.w12)

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Body Temperature (Homeostasis)

Source Information Equus caballus - Domestic horse:
  • Low grade fever 38.4-39.4C/101.2-103.0F (4/8 horses). (J4.218.w2)
  • 7/22 horses (31.8% of cases), 101.4-103F, mean 102.4F. (J84.7.w27)
  • Fever (>38.5C) 47/76 cases (62%). (J84.7.w17)
  • Fever 23% of cases, USA 2000. (J84.7.w12)
  • Fever sometimes above 40C (104F), but an inconsistent finding. (J89.16.w1)
  • No fever reported; rectal temperatures normal. (J87.32.w1)
  • Pyrexia. (J85.108.w1)
  • No fever. USA, 1999, experimental infection with an isolate from a crow (Corvus brachyrhynchos - American Crow). (P32.1.w13)
  • Fever with no other signs, virus isolated. In a horse in Israel in 2000. (J3.151.w1)
  • Fever in addition to neurological signs in at least three horses in Israel in 2000. (J3.151.w1)
  • Fever was noted in three of five fatal cases during an outbreak in Israel in 2000. (J73.57.w1)
  • USA, equine West Nile encephalitis presentation: increased temperature in 65%. (P39.4.w4)
  • Fever recorded in 13/28 (46%) cases in Ontario, Canada, 2002. (J14.44.w1)
  • Fever was noted in 30/46 horses (65%) admitted in Florida, 2001. The body temperature was considered raised if the rectal temperature reached at least 38.3C. (J4.222.w1)
  • Fever may be present. (J89.22.w1, J484.35.w1)
  • Fever was noted in 21.1% (102/484 horses) in Nebraska and Colorado, USA in 2002. (J4.225.w2)
  • Fever was noted in 7% of horses in the USA (North Dakota) in 2002. (J4.225.w3)
  • Fever was not a common finding in horses in Indiana, USA in 2002. (J4.225.w5)
Homo sapiens - Human:
  • Fever, sometimes biphasic, is characteristically noted. (J84.5.w2, J123.31.w1, J129.42.w1, B241.49.w49, B242.w1, B243.31.w1)
  • Rapid onset fever, averaging 38.5-39C, with profuse sweating; temperature remained high for five to six days followed by a gradual decline. In children in Egypt. (J91.5.w1)
  • "Fever of 38-39C for several days." In an adult technician in Egypt. (J91.5.w1)
  • Fever in 100% of cases. In the Middle East. (P31.6.w1)
  • Fever in the majority of cases in adults. During an outbreak in Israel in 1957. (J99.54.w1)
  • Fever (38C) with other signs including pancreatitis reported in a 20-year-old woman in Israel, 1969. (J91.23.w1)
  • Abrupt onset fever up to 39-40C. During an outbreak in Volgograd region of Russia, 1999. (J84.7.w32)
  • Fever in 91% of patients. During an outbreak in Romania (southeastern Romania including Bucharest) in 1996. (J98.352.w1)
  • Sudden onset fever with chills, the fever rising quickly and usually ranging between 38C and 40C. High temperatures usually remained for two to three days before gradually returning to normal over the following three days. During an outbreak in Israel, 1952. (J101.59.w1)
  • Fever in 100% of cases, with chills in 35%. During an outbreak in Israel, 1953. (J101.64.w1)
  • Fever in two children along with other signs, in two others "summer fever", fever not recorded in one other individual with other signs, and no clinical signs  had been noted in a further eight individuals in which antibodies were detected from serum samples. In the Czech Republic in 1999. (J84.5.w3)
  • Fever in 86%. During an outbreak in the Democratic Republic of Congo in 1998. (J91.61.w1)
  • Fever, with headache and signs of meningeal involvement in three individuals. In Israel in 1980. (J102.17.w1)
  • Sudden high fever in 7/7 individuals with neurological signs. (J103.3.w1)
  • In one individual, 30 years old: short term fever, with other signs and indications of myocarditis. (J99.57.w1)
  • No fever recorded in one individual, 68 years old: "mild encephalitis and severe myelitis, resembling the "polio syndrome"." (J105.135.w1)
  • In one individual, 15 years old. Fever, with other signs including neurological signs. (J106.55.w1)
  • In one individual, 22 years old. Fever, with other signs including neurological signs. (J107.36.w1)
  • In one individual 69 years old. No fever recorded, clinical diagnosis of Guillaine-Barr syndrome. (J106.55.w2)
  • Clinical findings included fever (17/19 of cases, 90%). During an outbreak of cases with encephalitis, meningitis or meningoencephalitis requiring hospitalisation in nineteen individuals in and near New York, USA 2000. (J84.7.w9)
  • Encephalitis in two individuals, fatal in one case. Fever (to 39.0C) in both individuals. (J84.7.w10)
  • Patients with encephalitis; no record of fever. (N7.48.w1)
  • Signs and symptoms included: fever of 38C or higher (98.3% of cases). Outbreak in Israel, 2000. (J84.7.w14)
  • Clinical illness with encephalitis, one individual, USA, July 2001. No record of fever. (N7.50.w2)
  • Fever (39.0-40.0C) in three children aged two, seven and ten years during a short outbreak of disease due to West Nile virus infection in Ibadan, Nigeria in April to June 1973. (J96.72.w1)
  • Fever in all children and 31/37 adults, reaching 39-39.5C, sometimes 40C; sometimes with chills, usually lasting two or three days, sometimes four to five days and in one individual nine days. A second rise in temperature following one to two days of normal temperature was seen in about 10% of cases, and was accompanied by recurrence of other symptoms. During an outbreak in Israel (Maayan Zvi), 1951. (J100.93.w1)
  • Temperature 99.8F, with other signs. In one individual in Egypt, 1952. (J91.3.w2)
  • Fever alone in 89%, and of no more than 1F above baseline in 27% of these individuals. Fever usually occurred first at 24 hours after intramuscular inoculation of virus and persisted during the period of viraemia. A second period of fever in the third week occurred occasionally. Experimental infection in patients with terminal neoplasia (J91.3.w1)
  • Fever was seen frequently, as were several other signs.. During an epidemic in South Africa, 1974. (J111.72.w1)
  • No report of fever. Severe hepatitis associated with WNV infection (confirmed by virus isolation in four individuals in the Central African Republic. (B241.49.w49)
  • Fever of 39C in one woman with meningoencephalitis and focal neurological signs. During an outbreak in Israel, 2000.(J220.162.w1)
  • Acute fever of 38.7C in one four-year-old boy with meningoencephalitis. During an outbreak in Israel, 2000. (J221.86.w1)
  • Fever was present in 91.5% of 188 confirmed cases in Mississippi, 2002. (P48.1.w2)
  • Fever was present in 61/64 (95%) of cases in Ontario, Canada, 2002. (J257.168.w2)
  • A review of data from 13 patients found that fever may or may not be present in individuals with acute flaccid paralysis due to WNV infection. (J292.28.w1)
Chlorocebus aethiops - Savanna monkey (Cercopithecus ethiops centralis):
  • Temperature exceeding 40.0C on the 7th and 8th days after intracerebral inoculation of one individual and on the 6th and 7th days in a second individual. (J120.20.w1)
Macaca mulatta (Macaca rhesus) - Rhesus macaque (Rhesus monkey) (Cercopithecidae - Old-world monkeys (Family)):
  • Fever not seen following subcutaneous inoculation, but recorded developing 7-8 days after intracerebral inoculation, including in individuals with no other clinical signs. (J71.75.w1)
  • Temperature 40.0C or higher on the fifth, sixth and eighth days after intracerebral inoculation in one individual. Subnormal temperature recorded on the tenth day (moribund); in a second individual fever in excess of 40.0C was noted on the 7th and 8th days. (J120.20.w1)
  • Temperature 40.0C or higher on the seventh and eighth days in one individual and on the fifth to eighth days of a second individual (as well as at four and 20 hours post-inoculation in this individual). (J120.20.w1)
  • Fever noted following intracerebral inoculation. Egypt strain, 1950 (J122.77.w1)
  • Drop in body temperature to below normal when moribund. (J120.20.w1)
"Cotton rat" (Rodentia - Rodents (Order)):
  • Body temperature status not recorded. Following intracerebral inoculation. (J100.93.w1, J122.77.w1)
Meriones tristrami - Gerbil (Muridae - Rats, mice, voles, gerbils etc. (Family)):
  • Body temperature status not recorded. Following intracerebral inoculation. During an outbreak in Israel (Maayan Zvi), 1951. (J100.93.w1)
Oryctolagus cuniculus - European rabbit (Domestic rabbit):
  • One day rise in body temperature in some individuals following intracerebral inoculation. During an outbreak in Israel (Maayan Zvi), 1951. (J100.93.w1)
  • No clinical signs following intracerebral inoculation in other studies. (J101.59.w1, J120.20.w1, J122.77.w1)
Ovis aries - Domestic sheep:
  • Mild biphasic fever following experimental infection of two 7-9 month old sheep and moderate increase in body temperature two days after infection in one of two 18 month old pregnant ewes following experimental infection. (J62.53.w3)
"Hedgehog" (Erinaceidae - Hedgehogs, moonrats (Family)):
  • No clinical signs following intracerebral inoculation of two individuals. (J120.20.w1)

Canis familiaris - Domestic dog:

  • Experimental infection of three dogs resulted in fever in two individuals. (J3.105.w5, J84.8.w3)
  • No clinical signs observed in natural infection, nor following experimental inoculation.(J42.100.w2, J84.7.w24)
  • No clinical disease following experimental infection via mosquito bite. (P39.4.w16)
  • Fever noted in a dog in Nebraska, USA, 2002. (W27.04Oct.wnv2)
  • Fever noted in dogs with natural infection confirmed by the presence of WN virus neutralising antibodies but the virus was not confirmed to be the cause of the illness. In Louisiana, USA, 2002. (W27.18Oct.wnv1, W27.24Oct02.wnv1)
  • In one individual pyrexia (40.3C). (J212.15.w3)
  • No febrile response in three of four dogs experimentally infected by mosquito bite; mild increase in body temperature in one individual within 12 hours of infection; the individual was in prooestrus. (J84.10.w1)

Felis catus - Domestic cat:

  • Increased rectal temperature for days 1-6 after infection in cats experimentally infected via mosquito bite. (P39.4.w16)
  • Fluctuant febrile response in three of four cats infected by bite of infected mosquitoes but not in any of four cats infected by ingestion of infected mice. (J84.10.w1)

(J4.218.w2, J62.53.w3, J71.75.w1, J84.5.w2, J84.5.w3, J84.7.w9, J84.7.w10, J84.7.w12, J84.7.w14, J84.7.w17, J84.7.w27, J84.7.w32, J85.108.w1, J87.32.w1, J89.16.w1, J91.3.w1, J91.3.w2, J91.5.w1, J91.23.w1, J91.61.w1, J96.72.w1, J98.352.w1, J99.54.w1, J99.57.w1, J100.93.w1, J101.59.w1, J101.64.w1, J102.17.w1, J103.3.w1, J105.135.w1, J106.55.w1, J106.55.w2, J107.36.w1, J111.72.w1, J120.20.w1, J122.77.w1, J123.31.w1, J129.42.w1, B241.49.w49, B242.w1, B243.31.w1, P31.6.w1, P32.1.w13, N7.48.w1, N7.50.w2)

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Digestive (Mouth to rectum, including liver and pancreas)

Source Information Equus caballus - Domestic horse:
  • Colic reported early in the fatal illness of one horse, Egypt, natural infection. (J86.57.w1)
  • "Mild signs of colic" and reduced appetite. One horse in Israel in 2000; reduced appetite in another. (J3.151.w1)
  • Difficulty in swallowing (1/8 horses, during recumbent stage). (J4.218.w2)
  • Teeth grinding 7% of cases (J84.7.w12); 3/76 (4% of cases). (J84.7.w17)
  • Tooth grinding. One horse in Israel in 2000. (J3.151.w1)
  • USA, equine West Nile encephalitis presentation: tooth grinding in 20%. (P39.4.w4)
  • Tooth grinding was noted in 9/46 horses (20%) admitted in Florida, 2001. (J4.222.w1)
  • Ptyalism was noted in 3/46 horses (7%) admitted in Florida, 2001. (J4.222.w1)
  • Anorexia was noted in 24/46 horses (58%) admitted in Florida, 2001. (J4.222.w1)
  • Three horses were presented for colic in Florida in 2001. (J4.222.w1)
  • One horse was dysphagic. (J4.222.w1)
  • Dysphagia sometimes occurs. (J89.22.w1, J484.35.w1)
  • Dysphagia was seen in 8.1% (39/484) of equines in Nebraska and Colorado, USA, 2002. (J4.225.w2)
  • Tooth grinding was noted in 8% of horses in North Dakota, USA in 2002. (J4.225.w3)
  • Teeth grinding was seen in horses with severe clinical signs requiring euthanasia in Kentucky, USA, 2002. (J305.55.w1)
  • Inability to swallow was seen in horses with severe clinical signs requiring euthanasia in Kentucky, USA, 2002. (J305.55.w1)
  • Poor appetite was noted in 27.9% (135/484) of equines in Nebraska and Colorado, USA, 2002. (J4.225.w2)
Homo sapiens - Human:
  • Sometimes with gastro-intestinal signs. (J84.5.w2)
  • From endemic disease in Egypt and epidemics in Israel: "Some patients had gastrointestinal disturbances." (B241.49.w49)
  • Sometimes nausea, abdominal pain, diarrhea; vomiting may be seen in cases with neurological signs. (J84.5.w2)
  • Other common signs and symptoms include , gastro-intestinal disturbances (anorexia, nausea, vomiting, diarrhoea). (J129.42.w1)
  • In an adult technician in Egypt: some initial gastric discomfort was noted. (J91.5.w1)
  • In the Middle East with a wide clinical spectrum ranging from inapparent or mild illness to severe encephalitis. Lack of appetite (55% of cases), nausea (25%), vomiting (10%), abdominal pain (20%), diarrhoea (30%), liver enlargement (10%). (P31.6.w1)
  • "In several children there was involvement of the intestinal or respiratory tracts without the appearance of more typical signs and symptoms of West Nile fever."  During an outbreak in Israel in 1957. (J99.54.w1)
  • Acute pancreatitis with abdominal pain and high blood and urine amylase for several days together with more usual clinical signs of fever (38C), macular rash and enlarged lymph nodes reported in a 20-year-old woman in Israel, 1969. (J91.23.w1)
  • In comparison with most previous outbreaks, the diseases seen was generally more severe, with central nervous system involvement frequently observed while rash, conjunctivitis, abdominal pain, diarrhoea, respiratory symptoms and lymphadenopathy were rare.  During an outbreak in Volgograd region of Russia, 1999. (J84.7.w32)
  • "A small number of patients had gastrointestinal disturbances, anorexia, nausea, and dryness in the throat."  (J101.59.w1)
  • Typically fever, together with lymphoglandular swelling and/or rash. Signs and symptoms included: lack of appetite (55%), nausea (25%), vomiting (10%), abdominal pain (20%), diarrhoea (30%), liver enlargement (10%). During an outbreak in Israel, 1953. (J101.64.w1)
  • Fever, sore throat, headache, muscle ache, pronounced fatigue, nausea in two children and in one of these also vomiting. In the Czech Republic in 1999. (J84.5.w3)
  • Abdominal pain (43% of cases), in individuals 12-40 years old. During an outbreak in the Democratic Republic of Congo in 1998. (J91.61.w1)
  • Nausea in one of three individuals In Israel in 1980. (J102.17.w1) 
  • "Eleven patients (58%) had at least one gastrointestinal symptom or had abnormal abdominal findings. Three patients had rash."  nausea (8/19 cases, 42%), vomiting (8/19, 42%), abdominal pain (4/19, 21%), diarrhoea (3/19, 16%), During an outbreak in and near New York, with encephalitis, meningitis or meningoencephalitis requiring hospitalisation in nineteen individuals. USA 2000. (J84.7.w9)
  • Vomiting (31.3% of cases), gastro-intestinal symptoms (abdominal pain, diarrhoea) (18.5%), Outbreak in Israel, 2000 in which "The main clinical presentations were encephalitis (57.9%), febrile disease (24.4%), and meningitis (15.9%)." (J84.7.w14)
  • "The main symptoms of the disease were fever, an exanthem, severe headache, sometimes accompanied by pain in back and limbs, anorexia, vomiting and abdominal pain. Enlarged lymph nodes, angina and diarrhoea were less common symptoms."  Abdominal pains, sometimes with diarrhoea, were noted by 19% of patients; anorexia and nausea were common and vomiting occurred in 45% of children and 19% of adults. During an outbreak in Israel (Maayan Zvi), 1951. (J100.93.w1)
  • Moderate abdominal tenderness and slight liver enlargement. In one individual in Egypt, 1952. (J91.3.w2) 
  • Signs and symptoms "frequently seen included diarrhoea and , nausea, and those less frequently seen included vomiting, and enlarged and tender liver." During an epidemic in South Africa, 1974. (J111.72.w1)
  • Severe hepatitis associated with WNV infection in four individuals in the Central African Republic. (B241.49.w49)
  • Vomiting alongside other signs in a woman with meningoencephalitis and focal neurological signs. One case during the outbreak of WNV infection in Israel in 2000. (J220.162.w1)
  • Nausea present in 50.8% and vomiting in 35.8% of 188 confirmed cases in Mississippi, 2002. (P48.1.w2)
  • In Ontario, Canada in 2002, 46/55 (84) patients had anorexia, 40/58 (69%) nausea and 31/58 (53%) vomiting. (J257.168.w2)

Canis familiaris - Domestic dog:

  • Severe diarrhoea and frothing at the mouth recorded in one dog with fatal infection in Botswana. (J3.105.w5)

Felis catus - Domestic cat:

  • Modest reduction in appetite in three of four cats infected by bite of infected mosquitoes but not in any of four cats infected by ingestion of infected mice. (J84.10.w1)

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Immunological (Lymph nodes, spleen)

Source Information Homo sapiens - Human:
  • Mild, nonspecific symptoms include lymphadenopathy. (J123.31.w1)
  • "Generalized lymphadenopathy is a common finding." (B243.31.w1)
  • Common signs include lymphadenopathy. (J84.5.w2)
  • Common signs and symptoms include lymphadenitis (single node or generalised) and sometimes a palpable (enlarged) spleen. (J129.42.w1)
  • In children in Egypt: moderate enlargement of the cervical, axillary and inguinal lymph nodes (3 cases). (J91.5.w1)
  • In the Middle East: a wide clinical spectrum ranging from inapparent or mild illness to severe encephalitis. Including glandular swelling (occipital region 75% of cases, axillary region 90%, inguinal region 85%); spleen enlargement (20%). (P31.6.w1)
  • In soldiers, lymphadenopathy together with fever and rash. During an outbreak in Israel in 1957. (J99.54.w1)
  • Acute pancreatitis with abdominal pain and high blood and urine amylase for several days together with more usual clinical signs of fever (38C), macular rash and enlarged lymph nodes reported in a 20-year-old woman in Israel, 1969. (J91.23.w1)
  • In comparison with most previous outbreaks, the diseases seen was generally more severe, with central nervous system involvement frequently observed while rash, conjunctivitis, abdominal pain, diarrhoea, respiratory symptoms and lymphadenopathy were rare.  During an outbreak in Volgograd region of Russia, 1999. (J84.7.w32)
  • General enlargement of one or more lymph nodes was a prominent finding and the spleen was sometimes enlarged. During an outbreak in Israel, 1952. (J101.59.w1)
  • Typically fever, together with lymphoglandular swelling and/or rash. glandular swelling (occipital region 75%, axillary region 90%), inguinal region 85%), rash (50%), spleen enlargement (20%). During an outbreak in Israel, 1953. (J101.64.w1)
  • In one individual, 22 years old. Fever, enlarged lymph nodes, mild splenomegaly, together with neurological signs. (J107.36.w1)
  • Lymphadenopathy (4.3%). Outbreak in Israel, 2000. "The main clinical presentations were encephalitis (57.9%), febrile disease (24.4%), and meningitis (15.9%)." (J84.7.w14)
  • Lymph nodes were enlarged less commonly than other signs such as fever, rash and headache; swollen and tender on pressure more commonly in adults (submaxillary and occipital) than in children. During an outbreak in Israel (Maayan Zvi), 1951. (J100.93.w1)
  • Signs and symptoms less frequently seen included enlarged lymph glands. During an epidemic in South Africa, 1974. (J111.72.w1)
  • Described in only 4.3% of cases during an outbreak in Israel, 2000. (J84.7.w14)
  • Not a feature in patients with encephalitis during an outbreak in and near New York, USA 2000. (J84.7.w9)
  • Lymphadenopathy present in only 3.7% of 188 confirmed cases in Mississippi, 2002. (P48.1.w2)
  • Lymphadenopathy present in only 2/64 cases (3%) in Ontario, Canada, 2002. (J257.168.w2)
  • Splenomegaly: noted (J84.5.w2, J129.42.w1); spleen sometimes enlarged ( J101.59.w1); mild splenomegaly (J107.36.w1); spleen enlargement in 20% of cases. (P31.6.w1, J101.64.w1)

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Respiratory

Source Information Equus caballus - Domestic horse:
  • Raised respiratory rate (40-48 per minute), inspiratory dyspnoea and narrowed glottis due to failure to abduct the arytenoids. One horse in Israel in 2000. (J3.151.w1)
  • Abnormal respiration was noted in seven equines, in Nebraska and Colorado, USA, 2002. (J4.225.w2)

Homo sapiens - Human:

  • Respiratory symptoms may be seen. (J84.5.w2)
  • "In several children there was involvement of the intestinal or respiratory tracts without the appearance of more typical signs and symptoms of West Nile fever."  During an outbreak in Israel in 1957. (J99.54.w1).
  • In comparison with most previous outbreaks, the diseases seen was generally more severe, with central nervous system involvement frequently observed while rash, conjunctivitis, abdominal pain, diarrhoea, respiratory symptoms and lymphadenopathy were rare.  During an outbreak in Volgograd region of Russia, 1999. (J84.7.w32)
  • Confirmed infection in individuals diagnosed with acute respiratory infection. During an outbreak in Romania (southeastern Romania including Bucharest) in 1996. (J98.352.w1)
  • Respiratory signs in 23% of cases in individuals 12-40 years old. During an outbreak in the Democratic Republic of Congo in 1998. (J91.61.w1)
  • In one individual 69 years old. Guillain-Barr syndrome with signs including reduced respiration such that ventilatory support was required. (J106.55.w2)
  • Shortness of breath in 2/19 cases, 11%; cough in 3/19 cases, 16%. During an outbreak in and near New York, with encephalitis, meningitis or meningoencephalitis requiring hospitalisation in nineteen individuals. USA 2000. (J84.7.w9)
  • Profound muscle weakness requiring respiratory support seen in some patients with encephalitis. (N7.48.w1)
  • Reduced respiration requiring ventilatory support has been reported associated with central nervous signs. (J106.55.w2)

Ursus maritimus - Polar bear

  • A polar bear with mainly neurological signs (paresis/paralysis) and depression also developed more pronounced breathing. (V.w114)

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Cardiovascular

Source Information Homo sapiens - Human:
  • In one individual, 30 years old: short term fever, headache and anorexia, together with palpitations, stabbing sensation and pressure in the left chest area, with the palpitations and chest discomfort persisting much longer than the fever. ECG changes indicative of myocarditis. (J99.57.w1)
  • Severe angina was present in seven cases. "The main symptoms of the disease were fever, an exanthem, severe headache, sometimes accompanied by pain in back and limbs, anorexia, vomiting and abdominal pain. Enlarged lymph nodes, angina and diarrhoea were less common symptoms."  During an outbreak in Israel (Maayan Zvi), 1951. (J100.93.w1)

Canis familiaris - Domestic dog

  • Cardiac signs noted in a dog with another concurrent immune mediated disease. In Illinois, USA, 2002. (W27.19Sept02.wnv1)

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Ophthalmic

Source Information Phoenicopterus chilensis - Chilean flamingo:
  • Impaired vision in two birds. (J26.37.w1)
Equus caballus - Domestic horse:
  • Blindness 5%. (J84.7.w12)
  • Central blindness (3/8 cases). (J4.218.w2).
  • Morocco: lachrymation reported. (J85.108.w1)
  • In 3/46 horses (7%) the menace reflex was absent. (J4.222.w1)
  • It was noted that 13 of 484 equines had ocular problems such as blindness, in Nebraska and Colorado, USA, in 2002. (J4.225.w2)
  • Blindness was noted in 3% of horses in North Dakota, USA in 2002. (J4.225.w3). 
Homo sapiens - Human:
  • Common signs and symptoms include ocular pain and injected conjunctiva. (J129.42.w1)
  • In children in Egypt: occasionally congestion of the eyes. (J91.5.w1)
  • In the Middle East: A wide clinical spectrum ranging from inapparent or mild illness to severe encephalitis, ocular pain (45% of cases), conjunctival injection (60%). (P31.6.w1)
  • In comparison with most previous outbreaks, the disease seen was generally more severe, with central nervous system involvement frequently observed while rash, conjunctivitis, abdominal pain, diarrhoea, respiratory symptoms and lymphadenopathy were rare.  During an outbreak in Volgograd region of Russia, 1999. (J84.7.w32)
  • Aching of the eyes when moved was a characteristic finding, as were injected conjunctiva. During an outbreak in Israel, 1952. (J101.59.w1)
  • Ocular pain and photophobia in one of three individuals. In Israel in 1980. (J102.17.w1)
  • Photophobia (6/19 cases, 32%). During an outbreak in and near New York, with encephalitis, meningitis or meningoencephalitis requiring hospitalisation in nineteen individuals. USA 2000. (J84.7.w9)
  • Pain in the eyes, particularly on moving the eyeball, was noted by a number of individuals. During an outbreak in Israel (Maayan Zvi), 1951. (J100.93.w1)
  • Slight pain on eye movement. In one individual in Egypt, 1952. (J91.3.w2)
  • Signs and symptoms frequently seen included orbital pain. During an epidemic in South Africa, 1974. (J111.72.w1)
  • Diplopia or ophthalmoplegia in 13%, blurred vision in 9%, nystagmus in 3%. (J257.168.w2)
  • Temporarily decreased visual acuity and development of multiple round, cream-coloured chorioretinal lesions, 300-1000m diameter, scattered in the fundus and persisting for over one year, together with a mild vitritis which cleared after several months, associated with WNV encephalitis (malaise, muscle weakness, dysarthria and gastroenteritis) in an 81-year-old man with long-standing nonproliferative diabetic retinopathy. In a patient in the USA, 2002. (J276.23.w1)
  • Clinical signs of ocular pain and blurred vision affecting one eye, associated with fever, headache, diffuse muscle pain and neck stiffness (WNV meningitis). Ophthalmic examination revealed a swollen slightly pale disc on the clinically affected side and lesser swelling on the other side; optic neuritis was diagnosed. In a young adult in Israel, 2000. (J277.31.w1)
  • Clinical signs of "floaters" in the left eye together with fatigue, left-sided frontal headache and low-grade fever. Anterior uveitis, vitritis and nonnecrotising chorioretinitis were noted in the left eye and milder similar findings in the right eye. Anterior uveitis responded to steroids. Ophthalmological examination showed deep, flat, creamy whitish-yellow outer choroidal lesions, 500-750 um extending superiorly in a linear radial pattern from the optic nerve head in the left eye, and less extensive faint lesions in the right eye. The lesions were actively inflammatory. A moderate vitritis was noted overlying the optic disk and superior retina of the left eye. Small intraretinal haemorrhages, 200um diameter , were present in the right eye and similar haemorrhages were noted associated with some of the lesions in the left eye. Fluorescein angiography revealed blocked fluorescence and leakage from the lesions. Treatment was initiated with local (ocular) 1% prednisolone acetate four times daily. The chorioretinitis healed; two weeks after presentation there was significantly less vitritis and a decrease in fluorescein leakage, while the lesions appeared smaller and pigmented. This was accompanied by an improvement in visual acuity (from 20/25 OD and 20/40 OS to20/30 OS.  In a 62 year old woman in Chicago, confirmed positive for WNV IgM antibodies in serum. (J282.121.w1)

Ovis aries - Domestic sheep:

  • Corneal ulcer of presumed traumatic origin in one individual that was laterally recumbent and had brief convulsions. (J275.17.w1)

Canis lupus - Wolf (Canidae - Dogs, foxes (Family):

  • Development of blindness. (J84.9.w17)

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Ear, Nose, Throat (including tonsils)

Source Information Homo sapiens - Human:
  • Pharyngitis may occur. (B243.31.w1)
  • Sore throat may be seen. (J84.5.w2)
  • Other common signs and symptoms include pharyngitis (sore throat). (J129.42.w1)
  • Occasionally congestion of the throat was noted. In children in Egypt.  (J91.5.w1)
  • Injection of throat sometimes noted. Overall a wide clinical spectrum ranging from inapparent or mild illness to severe encephalitis. In the Middle East. (P31.6.w1)
  • "A small number of patients had gastrointestinal disturbances, anorexia, nausea, and dryness in the throat." A slight redness of the throat was noted in some individuals. (J101.59.w1)
  • The throat was often slightly reddened. "The main symptoms of the disease were fever, an exanthem, severe headache, sometimes accompanied by pain in back and limbs, anorexia, vomiting and abdominal pain. Enlarged lymph nodes, angina and diarrhoea were less common symptoms." During an outbreak in Israel (Maayan Zvi), 1951. (J100.93.w1)
  • Sore throat was among the signs and symptoms less frequently seen. During an epidemic in South Africa, 1974. (J111.72.w1)
  • General signs of meningoencephalitis but later blurred vision, severe vertigo, diplopia and "focal neurological signs including right eyelid ptosis, paralysis of the right lateral rectus muscle, flattening of the right nasolabial fold, multidirectional nystagmus, skew deviation, excessive eye blinking (both eyes), and tongue tremor." Neurological signs worsened, with hyperactive reflexes, particularly on the right side, severe cerebellar ataxia (wide based gait) and unsteadiness, and gradual worsening of visual acuity. There was also "relative afferent pupillary defect on the right eye, swelling of the optic discs (both eyes but more prominent on the right eye), hemorrhages, concentric constriction of the visual fields and a right visual field scotoma." The patient's condition improved gradually with mild improvement first seen after 20 days and discharge from hospital at 30 days. One case during the outbreak of WNV infection in Israel in 2000. (J220.162.w1)

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Neurological

Source Information Corvus brachyrhynchos - American Crow:
  • Sedentary, stand with a crouched, non-erect posture and have difficulty in maintaining balance, inability to walk, perch, stand, fly or to hold the wings in their normal position against the body, lack of normal response to danger, prostration and convulsions prior to death. (V.w42)
Anser anser domesticus - Domestic goose:
  • Nervous signs in 1/4: intermittent torticollis and opisthotonus, rhythmic side-to-side movement of the head. (J84.7.w29)
Accipiter cooperii - Cooper's hawk:
  • Difficulty in standing, spinning in circles, seizures, death. (J22.286.w1)

Larus delawarensis - Ring-billed gull

  • Inability to hold the head upright and ataxia. (J84.9.w2)

"Owls" (Asio flammeus - Short-eared owl, Bubo virginianus - Great horned owl, Nyctea scandiaca - Snowy owl and Strix varia - Barred owl (Strix (Genus))):

  • In 13 owls observed clinical signs included uncoordinated flight, inability to fly, head tilt, torticollis, tremors and seizures. (J5.47.w2)
Aves - Birds (Class) general:
  • Varying degrees of neurological symptoms including: ataxia (3/17 cases), tremors (6/17), abnormal head posture (3/17), circling (1/17), convulsions (1/17), progressive inability to stand in ataxic birds, impaired vision. (J26.37.w1, P30.1.w3)
Equus caballus - Domestic horse:
  • Ocular:
    • Anisocoria and slow pupillary light reflexes in 1/8 cases.(J4.218.w2).
    • Central blindness in 3/8 cases. (J4.218.w2).
    • Blindness in 5% of cases. (J84.7.w12)
    • Amaurosis noted as a characteristic sign during the outbreak in the Camargue, 1962. (J84.7.w17)
    • In 3/46 horses (7%) the menace reflex was absent. (J4.222.w1)
    • It was noted that 13 of 484 equines had ocular problems such as blindness, in Nebraska and Colorado, USA, in 2002. (J4.225.w2)
    • Blindness was noted in 3% of horses in North Dakota, USA in 2002. (J4.225.w3). 
  • Tremors/Muscle fasciculations:
    • Tremors in 4/14 horses. (J87.32.w1)
    • Muscle tremors in 7/76 of cases (9%). (J84.7.w17)
    • Muscle fasciculation, most pronounced in the neck and triceps region (3/8 horses). (J4.218.w2)
    • Muscle fasciculation in 11/20 cases (55%). (J84.7.w27). 
    • Muscle fasciculation in 40% of cases. (J84.7.w12)
    • Muscle fasciculation and tremors (face, lips, trunk, shoulder) particularly in severe cases. (J89.16.w1)
    • Twitching face or muzzle in 13% of cases. (J84.7.w12)
    • Head tremors and lip twitching in 3/6 cases. (J4.218.w2)
    • Drooping and twitching lower lip, following experimental infection. (P32.1.w13)
    • USA, equine West Nile encephalitis presentation: fasciculation in 61%. (P39.4.w4)
    • Muscle fasciculation recorded in 14/28 (50%) cases and noted to be associated with a favourable outcome of infection, in Ontario, Canada, 2002. (J14.44.w1)
    • Fasciculations were noted on the face or neck only in 12/46 horses (26%) and on the whole body in 16/46 horses (35%) admitted in Florida, 2001. (J4.222.w1)
    • Skin fasciculations muscle tremors and rigidity are common findings. (J484.35.w1)
    • Muscle fasciculations may be seen. (J89.22.w1)
    • Muscle fasciculations were noted in 42.6% (206/484) equines in Nebraska and Colorado, USA, 2002. (J4.225.w2)
    • Muscle tremors/twitches were noted in 52% of horses in North Dakota, USA in 2002. (J4.225.w3)
    • Muscle tremors/fasciculations were seen in 60/136 (35.3%) horses in Indiana, USA in 2002. (J4.225.w5)
    • Muscle fasciculations were seen commonly, in 49.4% of horses in a study in Texas, USA, 2002. (J238.118.w1)
    • Face or neck muscle tremors, were seen in horses with severe clinical signs requiring euthanasia in Kentucky, USA, 2002. (J305.55.w1)
  • Proprioceptive defects:
    • Proprioceptive defects seen as toe-dragging. (J89.16.w1).
    • Proprioceptive defects noted in a horse showing clinical signs following experimental infection. (P32.1.w13)
    • Placing deficits were noted in five horses; not all horses were tested. In horses admitted in Florida, 2001. (J4.222.w1)
  • Hypersensitivity to stimuli:
    • Hypersensitivity to touch (6/8 cases). (J4.218.w2)
    • Hypersensitivity to sound (6/8cases). (J4.218.w2)
    • Hyperaesthesia in 6/76 cases (8%). (J84.7.w17)
    • Hyperaesthesia recorded in 11/28 (39%) cases in Ontario, Canada, 2002. (J14.44.w1)
    • Hyperaesthesia may be present. (J484.35.w1)
    • Hyperaesthesia was noted in 19.0% (92/484) equines in Nebraska and Colorado, USA, 2002. (J4.225.w2)
    • Hyperaesthesia was noted as one of the less common signs in horses in a study in Texas, 2002. (J238.118.w1)
  • Seizures:
    • Seizures in two recumbent horses. (J4.218.w2)
    • USA, equine West Nile encephalitis: seizures in a small number of cases. (P39.4.w4)
    • Seizures occurred in 2/46 horses admitted in Florida, 2002. (J4.222.w1)
    • Seizures were noted in 5.0% (24/484) equines in Nebraska and Colorado, USA, 2002. (J4.225.w2)
    • Seizures were noted as one of the less common signs in horses in a study in Texas, 2002. (J238.118.w1)
    • Seizures were seen in horses with severe clinical signs requiring euthanasia in Kentucky, USA, 2002. (J305.55.w1)
  • Behavioural:
    • Behavioural changes (depression, fearfulness) sometimes observed. (J89.16.w1)
    • Somnolence in 5/8 horses. (J4.218.w2).
    • Agitation in 3/19 horses (15.8%) in USA, 2000. (J84.7.w27).
    • Dull and lethargic (3/19 horses, 15.8%) in USA, 2000. (J84.7.w27).
    • Abnormal behaviour 2/76 cases (3%). (J84.7.w17)
    • Apprehension and reluctance to move, following experimental infection. (P32.1.w13)
    • Hyperexcitability. One horse in Israel in 2000. (J3.151.w1)
    • USA, equine West Nile encephalitis presentation: abnormal mentation in 67%, including nonresponsiveness and somnolence. (P39.4.w4)
    • Depression was recorded in 10/28 (36%) cases in Ontario, Canada, 2002. (J14.44.w1)
    • Abnormal mentation was noted in 31/46 horses (67%) admitted in Florida, 2001. These included four horses which could be roused only with difficulty and four which showed aggression. Four individuals circled or stall-walked compulsively. (J4.222.w1)
    • Abnormal mentation, ranging from somnolence to hyperexcitability or aggression, may be seen. (J484.35.w1)
    • Lethargy or depression was noted in 43.0% (208/484) equines, altered mentation in 22.1% (107/484), 13/484 were apprehensive and a further eight equines were restless or agitated, in Nebraska and Colorado, USA, 2002. (J4.225.w2)
    • Compulsive behaviour was noted in 6.8% (33/484) of equines in Nebraska and Colorado, USA, 2002. (J4.225.w2)
    • Depression was a common finding, seen in 31.9% of horses in a study in Texas, 2002. (J238.118.w1)
    • Excitability was seen in horses with severe clinical signs requiring euthanasia in Kentucky, USA, 2002. (J305.55.w1)
  • Weakness, paresis, paralysis:
    • Limb weakness 48% of cases. (J84.7.w12)
    • Paresis/paralysis 36/76 cases (47%). (J84.7.w17)
    • In fatal cases (death or euthanasia required), ascending paresis, tetraplegia and recumbency, or early tetraplegia and recumbency, usually with muscle rigidity and hyperreflexia of the hind limbs (6/14 horses). (J87.32.w1)
    • Weakness considered one of the characteristic signs, Camargue, 1962). (J84.7.w17)
    • Progressive weakness of the hind quarters prior to recumbency in a horse in Egypt. (J86.57.w1)
    • Tetraplegia progressing from ataxia and resulting in recumbency in one horse in Israel in 2000. (J3.151.w1)
    • Paresis in two, hindlimb paraplegia in one and quadriplegia in two, from five fatal cases during an outbreak in Israel in 2000. (J73.57.w1)
    • USA, equine West Nile encephalitis presentation: weakness in 94%. (P39.4.w4)
    • Recorded in 23/28 (82%) cases in Ontario, Canada, 2002.  (J14.44.w1)
    • Weakness was noted in 43/46 horses (94%) admitted in Florida, 2001. (J4.222.w1)
    • Paresis or paralysis of one, two or all four limbs is common. (J484.35.w1)
    • Generalised weakness was noted in 53.3% (259/484 horses) in Nebraska and Colorado, USA in 2002. (J4.225.w2)
    • Limb weakness or paralysis was noted in 38% and caudal paresis in 29% of horses in North Dakota, USA in 2002, (J4.225.w3)
    • Hind limb paresis was seen in 60/136 (35.3%)of horses in Indiana, USA in 2002. (J4.225.w5)
  • Ataxia/gait abnormalities:
    • Ataxia in 95.7% of cases (J84.7.w27); 55/76 of cases (72%) (J84.7.w17); 85% of cases (J84.7.w12).
    • Acute-onset ataxia affecting all four limbs (5/8 cases). (J4.218.w2)
    • Ataxia of all four limbs 15/20 cases (75%) (2000). (J84.7.w27)
    • Ataxia of the rear limbs 19/21 cases (90.5%) (2000). (J84.7.w27)
    • Marked gait abnormalities in all cases; with variable degrees of ataxia and hind limb weakness, sometimes also one or both forelimbs affected. (J87.32.w1)
    • Ataxia considered one of the characteristic signs, Camargue, France, 1962. (J84.7.w17)
    • Ataxia in 95.7%, mainly hind limbs affected (90.5%), usually acute onset (90.5%) (USA, 2000). (J84.7.w27).
    • Limb ataxia or paresis, symmetrical or asymmetrical, most commonly involving the hind limbs but occasionally only affecting the front limbs; signs may be exacerbated by moving the animal backwards. (J89.16.w1)
    • Wide-based stance, hypermetric or staggering gait, stumbling, circling. (J89.16.w1)
    • Development of staggering gait following initial signs in a horse in Egypt. (J86.57.w1)
    • Ataxia affecting the hindlimbs or all four limbs. In horses in Israel in 2000. (J3.151.w1)
    • Ataxia was noted in all of five fatal cases during an outbreak in Israel in 2000. (J73.57.w1)
    • USA, equine West Nile encephalitis presentation: ataxia in 72%. (P39.4.w4)
    • Ataxia recorded in 28/28 (100%) cases in Ontario, Canada, 2002. (J14.44.w1)
    • Ataxia was noted in 33/46 horses (72%) admitted in Florida, 2001. (J4.222.w1)
    • Ataxia is common. (J484.35.w1)
    • Ataxia may be seen. (J89.22.w1)
    • Ataxia was noted in 57.4% (278/484 horses) in Nebraska and Colorado, USA in 2002. (J4.225.w2)
    • Incoordination was noted in in 69% of horses in North Dakota, USA in 2002. (J4.225.w3)
    • Ataxia was seen in 75/136 horses (44/1%) in Indiana, USA in 2002. (J4.225.w5)
    • Ataxia was a common finding, seen in 69.1% of horses in a study in Texas, USA, 2002, (J238.118.w1)
    • Abnormal gait was a common finding, seen in 52.2% of horses in a study in Texas, USA, 2002. (J238.118.w1)
    • Ataxia/incoordination was seen in horses with severe clinical signs requiring euthanasia in Kentucky, USA, 2002. (J305.55.w1)
  • Recumbency:
    • Recumbency in1/8 cases. (J4.218.w2)
    • Recumbency and/or difficulty in rising in 45% of cases. (J84.7.w12)
    • Recumbency (and seizures) in 2/8 cases.(J4.218.w2)
    • Sometimes inability to rise. (J84.7.w27)
    • Inability to rise, or able to rise only with assistance (J84.7.w27): "down" 9/22 cases (40.9%), able to rise with assistance 6/21cases (28.6%).
    • Recumbency, sometimes scraping of a hole with the fore legs, in horses in Morocco. (J85.108.w1)
    • Recumbency prior to death about 60 hours after the onset of illness, in a horse in Egypt. (J86.57.w1)
    • Recumbency prior to death in at least three horses in Israel in 2000. (J3.151.w1)
    • Recumbency occurred prior to death or euthanasia in all of five fatal cases during an outbreak in Israel in 2000. (J73.57.w1)
    • USA, equine West Nile encephalitis: recumbency in 30% of cases, sometimes intermittent. (P39.4.w4)
    • Recumbency recorded in 10/28 (36%) cases in Ontario, Canada, 2002. (J14.44.w1)
    • Recumbency occurred in 14/46 horses (30%) admitted in Florida, 2001. (J4.222.w1)
    • Recumbency may occur as a progression of limb paresis/paralysis. (J484.35.w1)
    • While 27.5% (133/484 horses) in Nebraska and Colorado, USA, in 2002 were recumbent and unable to rise, a further 24.2% (117/484) were recumbent for long periods but able to rise. (J4.225.w2)
    • Recumbency or difficulty in rising was noted in 23% of horses in North Dakota, USA in 2002. (J4.225.w3)
    • Recumbency was seen in 13/136 (7.6%)of horses in Indiana, USA in 2002. (J4.225.w5)
    • Recumbency was a common finding, seen in 27.7% of horses in a study in Texas, USA, 2002. (J238.118.w1)
  • Other:
    • Head tilt. (J89.16.w1)
    • Leaning to one side. (J89.16.w1)
    • Difficulty in swallowing (1/8 horses, during recumbent stage(J4.218.w2)
    • Teeth grinding in 7% of cases (J84.7.w12); 3/76 cases (4%). (J84.7.w17)
    • Tooth grinding. One horse in Israel in 2000. (J3.151.w1)
    • Paralysed or drooping lip in 18% of cases. (J84.7.w12)
    • USA, equine West Nile encephalitis presentation: tooth grinding in 20%. (P39.4.w4)
    • USA, equine West Nile encephalitis presentation: cranial nerve defects in 44%. (P39.4.w4)
    • Cranial nerve deficits were recorded in 3/28 (11%) cases in Ontario, Canada, 2002. (J14.44.w1)
    • Unspecified neurological signs, becoming severe and requiring euthanasia, in one of twelve horses following experimental infection in the USA. (J84.8.w4)
    • Cranial nerve deficits were noted in 20/46 horses (44%) admitted in Florida, 2001. (J4.222.w1)
    • Tooth grinding was noted in 9/46 horses (20%) admitted in Florida, 2001. (J4.222.w1)
    • Ptyalism was noted in 3/46 horses (7%) admitted in Florida, 2001. (J4.222.w1)
    • One horse was dysphagic. (J4.222.w1)
    • Dysmetria was noted in 18/22 horses (82%) admitted in Florida, 2002. (J4.222.w1)
    • Sudden collapse and knuckling were noted to be associated with forelimb weakness in horses admitted in Florida, 2001. (J4.222.w1)
    • Dysphagia, tongue paralysis and facial nerve paralysis have been noted. (J89.22.w1, J484.35.w1)
    • Hypermetria was noted in 6.4% of equines ( 31/484) in Nebraska and Colorado, USA in 2002. (J4.225.w2)
    • It was noted that 10.3% (50/484) used a dog-sitting posture, 3.1% (15/484) used a praying posture and 20.7% (100/484) had abnormal head carriage, in Nebraska and Colorado, USA in 2002. (J4.225.w2)
    • Circling was seen in 6% of horses in North Dakota, USA in 2002. (J4.225.w3)
    • Falling down was noted as one of the less common findings in a study in Texas, USA, 2002. (J238.118.w1)
    • Cranial nerve deficits were noted in 19.0% (92/484) of equines in Nebraska and Colorado, USA, 2002. (J4.225.w2)
    • Dysphagia was seen in 8.1% (39/484) of equines in Nebraska and Colorado, USA, 2002. (J4.225.w2)
    • Head-pressing was noted in 2.7% (13/484) of equines in Nebraska and Colorado, USA, 2002. (J4.225.w2)
    • Lip droop was noted in 21% of horses in North Dakota, USA in 2002. (J4.225.w3)
    • Teeth grinding was noted in 8% of horses in North Dakota, USA in 2002. (J4.225.w3)
    • Head-pressing was noted as one of the less common signs in horses in a study in Texas, 2002. (J238.118.w1)
    • Lip droop was noted as one of the less common signs in horses in a study in Texas, 2002. (J238.118.w1)
    • Head pressing was seen in horses with severe clinical signs requiring euthanasia in Kentucky, USA, 2002. (J305.55.w1)
    • Teeth grinding was seen in horses with severe clinical signs requiring euthanasia in Kentucky, USA, 2002. (J305.55.w1)
    • Inability to swallow was seen in horses with severe clinical signs requiring euthanasia in Kentucky, USA, 2002. (J305.55.w1)
Homo sapiens - Human:
  • Until recently most outbreaks of WNV disease have involved mainly West Nile Fever, with neurological signs indicating central nervous system involvement in only a small percentage of affected individuals. During recent outbreaks (late 1990's onwards), a high percentage of clinical cases have involved neurological signs.
    • Meningitis or meningoencephalitis usually occurs at low incidence, "amounting probably to less than 1 in 100 clinical cases." (P31.6.w1)
    • Rare in young adults, e.g. 1/297 cases in soldiers, but more common in the elderly (16/49 cases). (J99.54.w1)
    • Light and transitory meningeal involvement seen in only a few cases, involving "a stiff neck and Kernig's sign." During an outbreak in Israel, 1952. (J101.59.w1)
    •  CNS involvement may occur more frequently in adults than in children. Encephalitic signs include a depressed sensorium (drowsiness to near coma), involuntary twitching, convulsions, hyperactivity followed by decreased activity of tendon reflexes, cogwheel rigidity, paresis and paralysis. (J129.42.w1)
    • 11% of individuals "showed definite or suggestive clinical signs of diffuse encephalitis" including "depressed sensorium, ranging from drowsiness to near-coma; involuntary twitching of hands, and occasionally of face and legs; and irregular variation of deep tendon reflexes, usually hyperactivity followed by diminished activity. Cogwheel rigidity was usually observed. Paralysis or paresis occurred only once and recovery was complete... pyramidal tract signs were observed only in the one patient with paralysis. Cranial nerves and sensory perception were never affected." Experimental infection in patients with terminal neoplasia (J91.3.w1)
    • Encephalitis, apparently mild, seen in some cases. During an epidemic in South Africa, 1974. (J111.72.w1)
    • Insomnia noted in some cases. During an epidemic in South Africa, 1974. (J111.72.w1)
    • Signs of meningitis or encephalitis seen occasionally. (J84.5.w2)
    • Occasionally meningitis. (B242.w1)
    • Meningeal involvement or meningoencephalitis were reported less commonly and more frequently in older patients. (B241.49.w49)
    • Neurological presentations include meningitis or meningoencephalitis in a small proportion of patients (particularly elderly individuals), anterior myelitis and encephalopolyradiculitis. (B243.31.w1)
    • "Occasionally, acute aseptic meningitis or encephalitis (associated with neck stiffness, vomiting, confusion, disturbed consciousness, somnolence, tremor of extremities, abnormal reflexes, convulsions, pareses, and coma), anterior myelitis." (J84.5.w2)
    • Central nervous system involvement (acute aseptic meningoencephalitis or meningitis) involved frequently during an outbreak in Volgograd region of Russia, 1999 with 480 overt cases of infection. (J84.7.w32)
    • Acute aseptic meningitis and encephalitis in 352 individuals during an outbreak in Romania (southeastern Romania including Bucharest) in 1996. (J98.352.w1)
    • Clinical presentations were of diffuse muscle weakness (40%), encephalitis (27%), aseptic meningitis (24%) and fever with headache (9%) during the outbreak in New York, 1999. (P32.1.w2)
    • Encephalitis, meningitis or meningoencephalitis requiring hospitalisation in nineteen individuals during an outbreak in and near New York, USA 2000. (J84.7.w9)
    • Encephalitis. (N7.50.w2)
  • A variety of neurological signs may be seen:
    • Neck stiffness in 57% of 352 individuals with acute aseptic meningitis and encephalitis in Romania in 1996. (J98.352.w1)
    • Confusion in 34% of 352 individuals with acute aseptic meningitis and encephalitis in Romania in 1996. (J98.352.w1)
    • Disturbed consciousness may be a predominant sign in patients with encephalitis. (J98.352.w1)
    • Disorientation may be a predominant sign in patients with encephalitis. (J98.352.w1)
    • Motor tone may be decreased with hypotonia, or increased with hyper-reflexia and abnormal reflexes. (J98.352.w1)
    • Ataxia and extrapyramidal signs recorded in 17% of patients. (J98.352.w1)
    • Cranial-nerve palsies or seizures recorded in small percentages of patients. (J98.352.w1)
    • Coma resulted in 13% of 352 individuals. (J98.352.w1)
    • Central nervous system involvement in 46% and convulsions in 11%. (J91.61.w1)
    • Signs of meningismus in three individuals, with somnolence in two and dizziness in one.( J102.17.w1)
    • Confusion in 7/7 individuals, with severe somnolence and disorientation in 3/7 individuals, convulsions in 2/7 individuals, dysarthria in 2/7 individuals, urinary incontinence in 1/7 individuals, mild lower paraparesis in 1/7 individuals. Meninigism detected in 6/7 individuals on neurological examination and pyramidal signs in 5/7 patients. (J103.3.w1)
    • Mild encephalitis and severe myelitis, described as resembling the polio syndrome. In one individual, 68 years old. (J105.135.w1)
    • Brainstem and cortical nervous signs including confusion, cranial nerve defects, ataxia and brisk tendon reflexes. Anterior horn cell involvement was indicated by weakness and tongue fasciculations. In one individual, 15 years old. (J106.55.w1)
    • Mild weakness of the left face accompanied by fasciculations, and flaccid paresis of the left lower extremity with loss of deep tendon reflexes but without any sensory changes. In one individual, 22 years old. (J107.36.w1)
    • Guillain-Barr Syndrome (acute inflammatory demyelinating polyradiculoneuritis). Progressive weakness including proximal and distal muscles, bilateral weakness of facial muscles, and reduced respiration such that ventilatory support was required. In one individual 69 years old. (J106.55.w2)
    • Clinical findings included altered mental status (11/19 cases, 58% of cases), abnormal reflexes (four hyporeflexive, two with abnormal plantar responses) (6/19 cases, 32% of cases), stiff neck (6/19 cases, 32% of cases), seizures (3/19 cases, 16% of cases), cerebellar abnormality (ataxia) (2/19 cases, 11% of cases), cranial nerve palsy (2/19 cases, 1% of cases), nystagmus (one case, fatal), depressed gag reflex (one case, fatal), muscle weakness (3/19 cases, 16% of cases) During an outbreak in and near New York, USA 2000. (J84.7.w9)
    • Encephalitis in two individuals, fatal in one case. In one patient confusion, disorientation, somnolence and aphasia, progressing to decreased responsiveness, limb spasticity, bilateral ptosis, facial nerve paralysis, bilateral Babinski response and requirement for mechanical ventilation. In the second individual progression: "became stuporous with severe respiratory acidosis; mechanical ventilation was begun... The patient remained febrile and stuporous and died on day 33 of hospitalization." (J84.7.w10)
    • Patients with encephalitis, some of whom had profound muscle weakness (with axonal neuropathy by electromyelogram and requiring respiratory support). (N7.48.w1)
    • 57.9% of cases presented with encephalitis and 15.9% with meningitis. Neurological signs included a change in level of consciousness (46.8% of cases), confused state (39.5% of cases), nuchal rigidity (28.7% of cases), coma (16.7% of cases) and focal neurological signs (9.4% of cases) during an outbreak in Israel, 2000. (J84.7.w14).
    • Brudzinski's sign indicating meningitis in ten children. (J100.93.w1)
    • In one patient, in addition to signs of meningeal irritation, signs of cortical, brainstem and multiple cranial nerve lesions, including optic neuritis. (J220.162.w1)
    • Complete motor aphagia complicating meningoencephalitis in one four-year-old boy. (J221.86.w1)
    • Confusion (disorientation and difficulty in following commands) in one 89-year-old man with encephalitis, slow recovery over a period of more than one month, with disorientation remaining at one month after onset. In Massachusetts, USA, during 2001. (J221.346.w1)
    • Acute flaccid paralysis syndrome in six individuals. One or more limbs affected with normal sensation but hyporeflexia or areflexia and asymmetrical weakness, sometimes flaccidity. (N7.51.w1)
    • Meningoencephalitis was found in 84.0% of 188 confirmed cases in Mississippi, 2002. Neurological signs included altered mental status (34.6%), stiff neck (29.8%) and seizures (2.1%).(P48.1.w2)
    • In Ontario, Canada in 2002, a decreased level of consciousness was noted in 75% of patients, neuromuscular weakness in 41%, dysphagia in 34%, ataxia in 31%, dysarthria in 17%, vertigo in 14%, intention tremor in 13%, diplopia or ophthalmoplegi in 13%, facial weakness in 11%, blurred vision in 9%, dysdiadokinesis in 8%, seizure in 6%, incontinence in 5%, tongue weakness in 5%, myelopathy in 3%, nystagmus in 3%, Parkinsonism in 3%. (J257.168.w2)
  • Acute flaccid paralysis described in seven patients, three of which did not have other findings suggestive of severe central nervous system involvement. In general, acute, painless asymmetric flaccid paralysis of one or more limbs, sometimes monoplegia, no numbness, paraesthesia or sensory loss, although occasionally myalgia, and often with bowel and/or bladder involvement. (J84.9.w13)
    • Four months after onset at least three individuals remained unable to move the affected limbs. (P48.1.w7)
  • Movement disorders reported include tremor (static/kinetic), sometimes with movement, and occasionally disabling and myoclonus, most frequently involving the upper extremity or face. Movement disorders have generally had onset at more than five days after the initial symptoms. In a prospective series of patients tremor was noted in 15 individuals (94%) and myoclonus in 10 (63%). (P39.4.w3)
  • Parkinsonism was noted in 11 of a prospective series of patients (68%), with cogwheel rigidity, bradykinesia and postural instability, but no tremor at rest. This was seen in individuals with meningitis or encephalitis. (P39.4.w3)
  • Bilateral leg weakness (acute flaccid paralysis) with fever and frontal headache. Marked decreases in motor function of both legs, particularly the right leg, and diminished reflexes in both legs, but intact sensation. (J281.181.w1)

Macaca radiata - Bonnet macaque  (Cercopithecidae - Old-world monkeys (Family)):

  • "Symptoms suggestive of viral encephalitis" including paralysis. (J88.36.w1)

Ovis aries - Domestic sheep:

  • Hind limb paralysis progressing to convulsions and death in one individual. (W27.16Sept02.wnv1)
  • Diffuse muscle fasciculations and inability to stand, progressing to lateral recumbency. Also apparent hyperaesthesia, intermittent rigid extension of the hind limbs, occasional but increasing tonic-clonic convulsions, distended urinary bladder in one individual. (J275.17.w1)
Mus domesticus - Laboratory mouse:
  • Hind quarter paralysis sometimes seen. (J120.20.w1)
  • Coma prior to death at 12-72 hours after the onset of clinical signs. (J120.20.w1)
  • Neurological signs including ataxia, weakness and bilateral limb paralysis on days 7-9 in two individuals out of a group of mice, following intraperitoneal inoculation. (J133.951.w12)
Laboratory rat (Rattus norvegicus - Brown rat):
  • Encephalitic signs such as sluggishness and hyperirritability. Following intracerebral inoculation of Egypt 101 strain. (J101.86.w2)
Sciurus carolinensis - Eastern grey squirrel
  • Lethargy, walking in circles and ataxia, biting at their own paws and vocalising/crying out as if in pain reported in squirrels in Illinois. (W27.19Sept02.wnv1)
Sciurus niger - Eastern fox squirrel (Sciurus - (Genus)):
  • Weakness and depression, lateral recumbency, uncoordinated movements, inability to right self if pushed over. Head tilt and torticollis, scratching at the forehead with feet, tremors. (J26.40.w1)

Mesocricetus auratus - Golden Hamster:

  • Frequently signs of encephalitis prior to death. (J101.59.w1)
  • Paralysis (and death) in 3/3 hamsters following intracerebral inoculation and in 2/4 hamsters following intraperitoneal inoculation. During an outbreak in Israel (Maayan Zvi), 1951. (J100.93.w1)
  • Neurological signs at seven to ten days, such as hind limb paralysis, tremors, difficulty in walking, tremors, loss of balance. (J84.7.w20)
  • Animals which survived sometimes had residual nervous signs: tremors, muscle weakness, difficulty in walking. (J84.7.w20)

Oryctolagus cuniculus - European rabbit:

  • A rabbit (Oryctolagus cuniculi) has reportedly shown clinical signs and mortality associated with West Nile virus infection. (B519.1.w1)

Canis familiaris - Domestic dog:

  • Prostration progressing to coma with convulsions and death recorded in one dog with fatal infection. (J3.105.w5)
  • Experimental infection of three dogs resulted in paresis in one of the individuals. (J3.105.w5, J84.8.w3)
  • No clinical signs observed in natural infection, nor following experimental inoculation.(J42.100.w2, J84.7.w24)
  • No clinical disease following experimental infection via mosquito bite. (P39.4.w16)
  • Clinical signs of weakness, progressing to neurological and cardiac signs in a dog with another concurrent immune mediated disease. In Illinois, USA, 2002. (W27.19Sept02.wnv1)
  • Neurological signs (and fever) was noted in four naturally infected dogs; WNV infection was confirmed by the presence of WN virus neutralising antibodies but the virus was not confirmed to be the cause of the illness. In Louisiana, USA, 2002. (W27.18Oct.wnv1, W27.24Oct02.wnv1)
  • In one individual, inability to bear weight on its limbs even while being supported, conscious deficits in proprioception of the pelvic limbs, and altered mentation. (J212.15.w3)

Canis lupus - Wolf (Canidae - Dogs, foxes (Family):

  • Lethargy, depression and irritability progressing to anorexia, weakness, ataxia and blindness. (J84.9.w17)
Felis catus - Domestic cat:
  • Seizures reported in a single cat. Euthanised. (J64.19.w1)

Florida Alligators (Alligator mississippiensis - American alligator (Alligatoridae - Alligators & Caimans (Family))):

  • Epizootic characterised by neurological signs. (P39.4.w16)

Crocodile monitor (Varana salvidorii) (Varanidae - Monitors (Family))):

  • Neurological clinical signs. (P39.3.w8)

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Dermatological (including nails, hooves, horns and bills)

Source Information Equus caballus - Domestic horse:
  • In Italy, 1998: traumatic lesions of the forelimbs and head in recumbent animals, associated with compulsive movements. (J87.32.w1)
(Homo sapiens - Human):
  • Onset: rash may appear during the febrile phase or after it. (J101.64.w1, J129.42.w1, B243.31.w1)
  • Duration: may last for only several hours, commonly for less than a day, but sometimes for several days, even a week. (J101.59.w1, J101.64.w1 J129.42.w1, B243.31.w1)
  • Description: papular (J91.5.w1), maculopapular (J84.5.w2, J84.5.w3, J115.13.w4, B241.49.w49) or roseolar (J84.5.w2, J101.64.w1); characterised as non-painful, non-itching and not followed by desquamation. (J129.42.w1, B243.31.w1)
  • Location: Occurs most commonly on the trunk, less commonly on the face and upper extremities, not normally on the lower extremities. (J84.5.w2, J101.59.w1, J101.64.w1, J129.42.w1)
  • Mild, nonspecific symptoms include rash. (J123.31.w1)
  • "Rash occurs in approximately half of the cases; onset of rash is either during the febrile phase or at the end of it. The rash is roseolar or maculopapular, is nonirritating, and principally involves the chest, back, and upper extremities. Rash may persist for up to a week and resolves without desquamation." (B243.31.w1)
  • "Maculopapular or roseolar rash (in approximately half the cases, spreading from the trunk to the extremities and head)." (J84.5.w2)
  • Rash is the second most common sign and is seen most frequently in children. It may appear during or after the fever and lasts usually less than 24 hours but occasionally several days. It is seen mainly on the trunk, less commonly on the face and extremities, is bright pink, discrete, maculo-papular, non-painful, non-itching and not followed by desquamation. In adults severe headache is a common complaint. (J129.42.w1)
  • A fine papular rash in five cases, during an outbreak in children in Egypt. (J91.5.w1)
  • Acute pancreatitis with abdominal pain and high blood and urine amylase for several days together with more usual clinical signs of fever (38C), macular rash and enlarged lymph nodes reported in a 20-year-old woman in Israel, 1969. (J91.23.w1)
  • A maculopapular rash of short duration, spreading mostly over the trunk, was present in many patients. During an outbreak in Israel, 1952. (J101.59.w1)
  • Rash in 50% of cases (typical cases involved fever with lymphoglandular swelling and/or rash) (50%). The rash, when present, appeared at any time from the second to the fifth day of illness and lasted for a period of several hours to days. Forms of rash included discrete pale roseolar spots, diffuse small spotted pale roseolar exanthema, and mottling of the skin - pale roseolar maculae of varying size with an indefinite border. Rash appeared most commonly on the upper chest, back, upper arms, less commonly on the face, flanks and abdomen, and did not appear on the lower extremities. During an outbreak in Israel, 1953. (J101.64.w1)
  • Skin rash with other signs in one of three individuals. In Israel in 1980. (J102.17.w1)
  • Rash was observed in three patients during an outbreak in and near New York, USA 2000 with encephalitis, meningitis or meningoencephalitis requiring hospitalisation in nineteen individuals. (J84.7.w9)
  • "The main symptoms of the disease were fever, an exanthem, severe headache, sometimes accompanied by pain in back and limbs, anorexia, vomiting and abdominal pain. Enlarged lymph nodes, angina and diarrhoea were less common symptoms."  Exanthem (bright pinkish, round discrete macules and slightly raised papules, 2-4mm diameter, often on the body and limbs, sometimes on the face, appearing during the fever and sometimes after the fever, often lasting less than 24 hours but sometimes for several days) present most commonly in younger individuals (87% of those less than two years old, 73% of those up to five years old, but reducing to 25% and 20% of older children and 14% of adults). During an outbreak in Israel (Maayan Zvi), 1951. (J100.93.w1)
  • Rash was rare in the outbreak in Volgograd region of Russia, 1999. (J84.7.w32)
  • Rash was present in 25% of 188 confirmed cases in Mississippi, 2002. (P48.1.w2)
  • Rash was present in 17/64 (27%) cases in Ontario, Canada, 2002. (J257.168.w2)

Ovis aries - Domestic sheep:

  • Abrasions on one side of the face in an animal that was laterally recumbent. (J275.17.w1)

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Mammary Glands (including udder and teats)

Source Information
  • No data for West Nile Virus

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Reproductive

Source Information Ovis aries - Domestic sheep:
  • Of twins born to an experimentally infected ewe in which fever and viraemia were detected, one lamb was clinically normal while the other was weak and “dumb”; this lamb died at two days old and hydroencephaly was observed. (J62.53.w3)

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Authors & Referees

Authors Debra Bourne (V.w5)
Referee Suzanne I. Boardman (V.w6); John Chitty BVetMed CertZooMed MRCVS (V.w123); Becki Lawson (V.w26)

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