Diseases / List of Viral Diseases / Disease description:

Avian Pox (with special reference to Waterfowl and Cranes)

Cutaneous pox lesions on the legs of a crane. Click here for full-page view with caption. Cutaneous pox lesions on the legs of a crane. Click here for full-page view with caption.










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General and References

Disease Summary

A viral infection usually producing self-limiting wart-like lesions on non-feathered areas; may also be severe even fatal disease.

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Alternative Names (Synonyms)

  • Avian diphtheria (‘wet’ form of avian pox) (B36.19.w19, B48.4.w4)
  • Avipoxvirus infection
  • Borreliota avium infection (B220)
  • Contagious epithelioma (B36.19.w19, B48.4.w4)
  • Fowl pox (B36.19.w19, B48.4.w4)
  • Geflugelpocken (B48.4.w4)
  • Molluscum contagiosum (B48.4.w4)
  • Poxvirus avium infection (B48.4.w4)
  • Poxvirus infection (B36.19.w19)
  • Virula aviare (B48.4.w4)
  • Variole aviaire (B48.4.w4)

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Disease Type


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Infectious/Non-Infectious Agent associated with the Disease

  • Avipoxvirus (B15)
  • Poxvirus avium (B48.4.w4)
  • Borreliota avium (B220)
  • Fowlpox, turkeypox, canarypox, pigeonpox, quailpox, sparrowpox, starlingpox, juncopox, psittacine pox viruses (B227.1.w1)
  • Some Avipox viruses appear to infect only a single species, while others can affect different species within a genus, family or even larger taxonomic grouping. (B13.32.w3, D48)
  • Natural infection has been reported in about 232 species within 23 orders of birds. (J6.28.w1)

Further information on Disease Agents has only been incorporated for agents recorded in species for which a full Wildpro "Health and Management" module has been completed (i.e. for which a comprehensive literature review has been undertaken). Agents with further information available are listed below:

Infective "Taxa" recorded in Waterfowl

Non-infective agents recorded in Waterfowl


Physical agents recorded in Waterfowl

Indirect / Secondary

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Disease Author

Debra Bourne MA VetMB PhD MRCVS (V.w5)s
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Major References / Reviews

Code and Title List

B12.19.w12, B13.32.w3, B14, B32.24.w36, B48.4.w4, B118.10.w10, B220, B227.1.w1, B365.74.w74

.34.w2, B11.35.w3, B11.36.w4, B15, B36.19.w19, B37.x.w1
J1.15.w3, J1.16.w5

B22.24.w16, B115.8.w4
.11.w12, J1.47.w5, J436.25.w1

Other References

Code and Title List



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Clinical Characteristics and Pathology

Detailed Clinical and Pathological Characteristics


Wart-type lesions, usually self limiting, on featherless areas. Sometimes mucous membrane lesions. Can be fatal.

Clinical Characteristics

Clinical course:
  • Subacute, generally about three to four weeks from the first signs to recovery. (B13.32.w3); lesions usually disseminate and grow over about one to two weeks and may not start to regress for four to six weeks; regression is usually rapid once it begins. (B12.19.w12)
  • Subacute to chronic; acute with the septicaemic form. (B14)
  • The disease course can be prolonged. (B36.19.w19)
  • In chickens, individual bird infections may last about four weeks. More prolonged disease courses have been recorded in other species.
  • Durations of up to 13 months have been recorded for this disease in wild birds. (B365.74.w74)

There are two main types of pox lesions, cutaneous (dry pox) and diphtheroid (wet pox). The two forms can be seen at the same time within an outbreak, and even at the same time in a single individual. Septicaemic disease may occur with either of these two forms. (B13.32.w3)

In addition to the main lesions, affected birds may be weak and emaciated if lesions have interfered with feeding, and dyspnoeic if respiratory passages are blocked. (B36.19.w19) Conjunctivitis, with half-closed eyes, may be seen. (D48)

Cutaneous form ("dry pox"):

  • The disease usually takes this form in many passerines and raptors. (B13.32.w3)
  • Discrete, warty/nodular, proliferative (tumour-like) lesions on the featherless areas, which then degenerate and slough; these may occur on the feet and/or the face and leave minor scars. (B12.19.w12, B32.24.w36, B36.19.w19, B48.4.w4)
    • Lesions vary in number and size. (B12.19.w12)
    • Small initial lesions may coalesce. (B227.1.w1)
    • Small lesions usually regress in a few weeks. (B336.77.w77)
    • Lesions may grow quite large and appear like tumours. Individual lesions can cover large areas of the normal anatomy of the head (B336.77.w77)
      • Large masses may take longer to regress. (B336.77.w77)
      • Large masses may interfere with sight and with prehension of food. (B12.19.w12)
  • Lesions are usually on non-feathered areas (face, feet, lower legs) including:
    • the bill (at the tip or in the commisures (corner of the mouth)), or on the cere;
    • the head particularly the eyelids, also the comb or wattles of gallinaceous birds;
    • the legs or feet.

    (B32.24.w36, B48.4.w4)

  • Lesions in feathered areas occur occasionally. (J4.171.w4)

  • Initially small blisters, develop into wart-like nodules then raised brownish scabs which finally drop off the bird. (D48)
  • Papules, yellow becoming brown, developing to vesicles, opening then drying to form crusts. (B13.32.w3)
    • Papules may also become hyperplastic, forming nodules around the eyes, nares, sinus infraorbitalis or on the tongue, and may cause dyspnoea or even asphyxia. (B13.32.w3)
    • With periorbital lesions, blepharitis, keratitis, uveitis and opthalmopthitis may develop. (B13.32.w3)
  • Secondary bacterial or fungal infection can affect the appearance and progression of lesions. (B13.32.w3)
  • Papillomata or wart-type nodules, sometimes necrotic, sometimes bleeding. Macules, papules, ulcers, scabs and raised necrotic areas have all been described.
  • Lesions develop as epithelial proliferation, then necrose and slough.
  • Lesions heal without leaving a scar, or with minor scarring.
    • Pigmented areas may be left discoloured. (B13.32.w3)
  • Limping, general debility and weight loss may be noted in affected birds and foot lesions can be sufficiently severe as to require euthanasia.
  • Lesions affecting the eyelids may affect vision and cause heavy mortality by preventing affected birds from seeing to find food. (B48.4.w4)
  • Nonpurulent conjunctivitis may be seen. (J5.11.w3, B14, D48)
  • Lesions may become secondarily infected with bacteria or fungi. (B48.4.w4)
    • Because pox lesions are elevated above the normal skin surface, they are more prone to abrasion, trauma and contamination. (B48.4.w4)
  • Growth retardation may occur in young birds. (B227.1.w1)
  • Transient reduction in egg production may occur in laying hens. (B227.1.w1)
  • Affected birds may be weak and emaciated if lesions have interfered with feeding, and dyspnoeic if respiratory passages are blocked. (B36.19.w19, D48)
  • Note: rapidly growing, wart-like, efflorescent tumours, which bleed easily, may grow in birds following infection with some avipox viruses. (B13.32.w3)
  • In Uria aalge - Common murre, during rehabilitation in California, lesions occurred on the eyelids, bill commisures, face and sublingual mucosa, with early proliferative lesions a few mm in diameter, developing to large lesions (e.g. 2 cm diameter), some becoming ulcerative an degenerating, and sometimes with secondary bacterial infection. (J196.73.w1)

‘Wet’ form (avian diphtheria, "wet pox"):

  • The disease commonly takes this form in psittacines. (B13.32.w3) and in canaries (B12.19.w12)
  • This form is reported only infrequently in wild birds. (B48.4.w4)
  • Blepharitis, chemosis and conjunctivitis initially. (B12.19.w12)
  • White raised lesions on the mucous membranes of the oral cavity, trachea and conjunctiva. (B336.77.w77)
  • Necrotic, moist diphtheritic lesions on the mucous membranes of the mouth, upper gastro-intestinal tract, upper respiratory tract. (B36.19.w19, P4.1990.w1)
    • Coalescing lesions may form a cheesy pseudomembrane. (B48.4.w4)
  • Lesions form most commonly on the tongue, pharynx and larynx, and only rarely in the bronchi, oesophagus or crop. (B13.32.w3); in the mouth and trachea. (B12.19.w12)
  • Lesions are fibrinous, caseous, grey to brown. (B13.32.w3)
  • Lesions are slightly elevated and whitish initially, but may coalesce, forming a cheesy yellow necrotic pseudodiphtheritic or diphtheritic membrane. (B32.24.w36, B227.1.w1)
  • Lesions bleed profusely if the covering exudate is disturbed. (B13.32.w3, B14, B32.24.w36, B227.1.w1)
  • Coalescing foci may prevent swallowing of food or lead to dyspnoea or asphyxiation. (B13.32.w3)
  • Lesions may become large and ulcerative.
  • The bird may show difficulty in eating or drinking associated with lesions on the tongue, palate, oesophagus or crop. (B14)
  • The bird may show laboured breathing associated with lesions in the upper respiratory tract. (B227.1.w1)
  • Death may occur due to occlusion of the respiratory tract by proliferative growth or diphtheritic membranes. (B12.19.w12, B227.1.w1)
  • Mild blepharitis, conjunctivitis and watery discharge from the eyes may be seen, with oedematous, partially closed eyelids; later ulcerative lesions may develop along the margins of the eyelids and at the canthus. (B227.1.w1)
  • Eyelid lesions are erosive and crusted. (B12.19.w12)
    • Secondary conjunctivitis, keratitis, and corneal ulceration and perforation may occur. (B12.19.w12)
    • Long term ocular problems may result in survivors. (B12.19.w12)
  • Corneal ulceration or cataracts may persist after the poxvirus infection has been cleared. (B336.77.w77)
  • In canaries, severe eyelid swelling in combination with depression, respiratory distress and anorexia is common, and is often rapidly fatal. Typical skin lesions may develop on survivors. (B336.77.w77)
  • Secondary bacterial or fungal infection commonly occurs. (B12.19.w12)

Septicaemic form

  • This may occur with either the cutaneous or diphtheritic forms of lesions. (B13.32.w3)
  • Acute onset disease, with ruffled plumage, depression/somnolence, cyanosis and anorexia. (B12.19.w12, B13.32.w3)
  • Cutaneous lesions may not be present, making ante-mortem diagnosis difficult. (B13.32.w3)
    • Cutaneous lesions only develop if the bird survives the initial illness. (B12.19.w12)
  • Common in canaries. (B14)

(J6.28.w1, J16.33.w1, B13.32.w3, B36.19.w19, B48.4.w4, B118.10.w10, B227.1.w1, D48, P4.1990.w1)

  • Wart like lesions occur most commonly on the feet (B197.11.w11), particularly the interdigital webs. (B13.32.w3)
  • Typical viral papillomas, brownish (B11.35.w3, B11.36.w4)
  • On the feet, pocks have been noted to appear along the blood vessels in experimental infection of waterfowl with a fowl-pox virus strain. (J5.11.w3)
    • Cloudiness around the blood vessels of the web, then pin-head spherical elevations, irregularly places along the vessels, scattered or in clumps, often coalescing and sloughing, reaching the size of small peas, and sometimes with sloughing of large areas of necrotic tissue, such that blood-tinged ulcerations remained. Resolving to dark brown granulation tissue and finally healing without leaving a scar. (J5.11.w3)
    • Non-purulent conjunctivitis also developed. (J5.11.w3)
    • Dry nodular masses, large necrotic lesions, macules, papules, ulcers and scabs have all been described with pox infection in waterfowl. (B15)
  • Lesions around the eyes or in the pharynx occur rarely in waterfowl. (B197.11.w11)
  • More widespread lesions can occur; 
    • On the head, lesions may be found on the bill, particularly at the commisures, in the gape and in the pharynx or the sinuses. (B11.34.w2)
    • The lores, upper and lower mandibles, eye rings, tarsi, feet and webs were all affected in one case in a Cygnus columbianus - Tundra swan. (J4.177.w1)
    • Wartlike lesions occurred on the face, eyelids and feet of domestic ducks. B15
    • The beak and legs were affected in domestic geese. (J16.33.w1);  lesions were found on the leg of a Branta canadensis - Canada goose. (J1.16.w5)
    • Confluent lesions over the head, and extension of lesions into the nasal sinuses, has been described in a Cygnus olor - Mute swan. (B15)
    • The bill was affected in an American green-winged teal (Anas crecca - Common teal). (J1.15.w3)
  • Lesions vary in size and may be a few millimetre to a centimetre or more in diameter, or confluent. (J1.15.w3, J1.16.w5, B15)
  • In four Grus canadensis - Sandhill cranes (one wild, live-trapped adult and three pen-reared subadults 16 months old), on the head, legs or feet, prominent, variable-sized, rough surfaced, white-yellow elevations. In three birds only a few (two to six) lesions were present while on one of the subadult birds about 30 lesions were visible. (J1.11.w12)


  • Variable depending on the strain of virus and the species of bird: e.g. four to 10 days in domestic chickens, turkeys and pigeons (B32.24.w36), about four days in canaries (B32.24.w36) and one month in the yellow-shafted flicker Colaptes auratus. (B32.24.w36)
  • About 7-10 days, but can be longer. (B336.77.w77)
WATERFOWL Minor changes in the webs may appear by as early as four to eight days after inoculation, but four to six weeks are required for typical pox lesions to appear (J1.16.w5, J5.11.w3).

Mortality / Morbidity

  • The prevalence in wild bird populations is not known, but may be increasing. The "wet pox" form may be under-reported in wild birds, because it is less obviously visible. (B36.19.w19)
  • In one UK survey, disease was apparently prevalent in woodpigeons and relatively common in sparrows, and possibly in other small passerine birds. (D48)


  • In wild birds, reports often indicate mild self-limiting disease. (B48.4.w4, B118.10.w10, B365.74.w74)
    • "Wet pox" causes higher morbidity and mortality than "dry pox". (B36.19.w19)
    • "Wet pox" (diphtheritic form) occurs only infrequently in wild birds. (B365.74.w74)
  • High mortality has been reported in epornitics in captive passerines. (B365.74.w74)
  • In canaries, quail and pigeons the disease may cause high mortality; disease due to canarypox virus causes the highest mortality: mortality may reach 100% in infected canaries (B227.1.w1)
  • Mortality can be high with the diphtheritic form in birds such as domestic chickens, and Phasianus colchinus pheasants. (B48.4.w4)
  • Mortality can also be high with cutaneous pox in some circumstances, such as if lesions cover the eyes and prevent feeding, or in conjunction with secondary infection of lesions. (B48.4.w4)
  • Mortality of 70-99% within three days of development of the septicaemic form of the disease. Deaths can also occur associated with the "dry pox" or "wet pox" forms. (B13.32.w3)
  • Mild cases may occur relatively commonly. Lesions around the eyes or in the pharynx occur rarely in waterfowl. (B197.11.w11)
  • Mortality is generally low. 
  • Infection is usually self-limiting in 6-8 weeks; lesions regress, minor scars remain. 
  • Secondary bacterial infection sometimes occurs and a disease course of some five months has been reported 
  • (J23.16.w1, B11.36.w4, B15).
  • This disease is probably not important to wild waterfowl populations. (B15)


BIRDS Gross pathology:

Cutaneous form ("dry pox"):

  • Typical papular skin lesions, which may show self-mutilation and secondary bacterial infection. (B336.77.w77)
  • Discrete warty proliferative lesions on the skin of featherless areas. (B48.4.w4)
  • In chickens, nodules are first small white foci, then larger and yellowish. The base becomes inflamed and haemorrhagic after about two weeks, the scab may last one or two weeks after which the degenerated epithelial lager desquamates to leave a smooth scar, not always visible. (B32.24.w36)

‘Wet’ form (avian diphtheria, "wet pox"):

  • Necrotic, moist diphtheritic lesions or membranes on the mucous membranes of the mouth, upper gastro-intestinal tract, upper respiratory tract. (P4.1990.w1, B336.77.w77)
    • Initially lesions are discrete, whitish and slightly raised. (B32.24.w36)
    • Coalescing lesions may form a yellowish cheesy pseudomembrane. (B32.24.w36, B48.4.w4)

Septicaemic canarypox: 

  • Fibrinous inflammation of serous membranes, liver degeneration or necrosis, lung oedema and hyperaemia, and fibrinous pneumonitis. (B48.4.w4)
  • Respiratory tract: extensive lesions of the air sacs, pneumonia. (B12.19.w12)


  • Localised proliferation of epithelial cells, with the basal germinal layer of epithelial cells showing an increased rate of multiplication. (B32.24.w36, B48.4.w4)
  • In layers above the stratum germinosum, hypertrophy of maturing cells, and appearance of large granular eosinophilic (acidophilic) intracytoplasmic inclusions. (B48.4.w4)
  • Septicaemic form: respiratory: bronchial and parabronchial epithelium shows marked proliferation. (B12.19.w12)

B118.10.w10, B227.1.w1, D48

WATERFOWL Gross lesions:
  • Warty or ulcerative/necrotic lesions, depending on the form of the disease.
  • Cutaneous form:
    • Lesions mainly on non-feathered areas (face, feet, lower legs). 
    • Nodular, warty or tumourlike swellings (J16.33.w1)
    • Papillomata or wart-type nodules, sometimes necrotic, sometimes bleeding. Macules, papules, ulcers, scabs and raised necrotic areas have all been described. (J1.15.w3)
  • ‘Wet’ form (avian diphtheria):
    • Necrotic, moist diphtheritic lesions on the mucous membranes of the mouth, upper gastro-intestinal tract, upper respiratory tract.
    • Lesions may become large and ulcerative.
    • Conjunctivitis.
  • (J1.15.w3, J1.16.w5, J16.33.w1, B15)


  • Epithelial hyperplasia and hypertrophy, with cuboidal cells in the basal layer, larger/more columnar cells further from the stratum germinatum. (J1.15.w3, J1.16.w5, J16.33.w1)
  • Large eosinophilic intracytoplasmic inclusion bodies, increasing in size as the cells increase in size. (J1.15.w3, J4.177.w1, J16.33.w1)
  • May be necrosis of epithelial cells.(J16.33.w1)
  • Typical poxvirus morphology of virus particles (large, brick-shaped, about 298-324 by 143-192 nm) seen in the inclusion bodies using electron microscopy. (J16.33.w1)

(J1.15.w3, J1.16.w5, J16.33.w1, B15)

CRANES Gross pathology
  • In a four-month-old Grus japonensis - Red-crowned crane crane chick (with concurrent aspergillosis and inclusion body hepatitis). (J436.25.w1)
    • On the skin of the head, small papules. (J436.25.w1)
  • In 6/167 wild Grus grus - Common crane in Germany, 1998-2008, cauliflower-like lesions (crusty epidermal proliferations) around the eyes, the upper beak, and on the legs (particularly the intertarsal joints). [2011] (J1.47.w5)


  • Lesions removed from four Grus canadensis - Sandhill cranes by use of a sharp blade: (J1.11.w12)
    • Surface epithelial cells showed hypertrophy and hyperplasia. In the cytoplasm of the cells, eosinophilic inclusion bodies were prominent, usually displacing the nucleus to the cell periphery, or with associated pyknosis, karyorrhexis and karyolysis. (J1.11.w12)
    • Surface epithelial ulceration with associated inflammatory invasion particularly involving heterophils. (J1.11.w12)
    • Electron microscopy revealed immature viral particles, which were "granular, free in the cytoplasm and were completely or incompletely surrounded by an electron opaque membrane" and sometimes contained an eccentric nucleoid. Within the inclusion bodies, which varied in size, were mature virions, ovoid, and containing a dumbbell-shaped nucleoid, at the periphery of the inclusion, while the central area consisted of an electron-translucent matrix, apparently lipid, containing rodlets, which in some inclusins were also found at the periphery, mixed with mature virions. Additionally, elongated filaments, with transverse periodicity, arranged in loose bundles each of three to six units, were found in the cytoplasm of affected cells. (J1.11.w12)
  • In 6/167 wild Grus grus - Common crane in Germany, 1998-2008, hyperkeratosis with eosinophilic intracytoplasmic inclusion bodies. [2011] (J1.47.w5)
    • EM: transmission electron microscopy revealed multiple poxvirus particles. (J1.47.w5)

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Human Health Considerations

None; there is no evidence that avian pox viruses infect humans. (B36.19.w19, D48).

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Susceptibility / Transmission

General information on Susceptibility / Transmission

  • Transmission is by mechanical transmission to lacerated or otherwise injured skin or mucous membranes. (B32.24.w36, B227.1.w1, D48) This may occur by:
    • Direct contact between infected and susceptible individuals. (B36.19.w19, B48.4.w4, B118.10.w10, B336.77.w77)
    • Indirect contact via contaminated objects or contaminated airborne particles (e.g. from scabs). (B36.19.w19, B48.4.w4, B118.10.w10, B336.77.w77)
    • Mechanical transmission by insects such as mosquitoes and even flies. (B36.19.w19, B48.4.w4, B118.10.w10, B336.77.w77, D48)
      • Mosquitoes can transmit infection from latently infected birds to susceptible individuals. Once having bitten an infected bird, infectious virus may remain in the mosquito's salivary glands for two to eight weeks. (B13.32.w3, B36.19.w19)
      • While the virus cannot penetrate intact skin, traumatic lesions caused by mosquitoes and other biting arthropods, including mites and ticks, are sufficient to allow entry. (B13.32.w3)
      • Maintenance of the disease in a wild population over time is unlikely without mosquitoes for transmission between birds. (B36.19.w19)
  • Infection does not occur through unbroken skin but may occur through even minor abrasions in the skin or mucous membranes. (B48.4.w4)
    • Territorial interactions leading to skin damage allows direct transmission between birds. (B13.32.w3, D48)
  • The virus survives a long time in dry scabs in the environment. (D48)
  • Disease carriers, without clinical signs, can spread the disease both locally and along migratory routes. (B36.19.w19)
    • Latent carriers may shed the virus intermittently. (B365.74.w74)
  • In captivity, contamination of perches etc. may allow the disease to be perpetuated in the absence of mosquitoes. (B36.19.w19)
  • Note: Close confinement, as occurs during rehabilitation and in aviaries, facilitates transmission, including to species which do not normally come into contact with pox viruses in the wild. (B36.19.w19)
  • In situations where there are large numbers of birds housed in close quarters, such as canary aviaries, transmission may occur by inhalation of virus-laden dust (containing particles of feather, skin or scabs). (B48.4.w4)
  • With strains which can cross between species, there is the potential for transmission between wild and captive birds. (B336.77.w77)
  • Infection with other diseases, such as avian malaria or aspergillosis, may be synergistic with poxvirus infection. (B336.77.w77)

(B36.19.w1, B48.4.w4, B118.10.w10, B227.1.w1, B336.77.w77, D48)


  • It is probable that most, if not all, bird species are susceptible to one or more avipox strains. (B48.4.w4, B227.1.w1, D48)
  • This disease is seen most commonly in canaries, pigeons, galliformes, waterfowl and diurnal raptors (but it has not been seen in owls); it is also seen in various passerines including endangered species in Hawaii. (B336.77.w77)
  • Susceptibility is variable depending on the host species and virus type: different avian pox viruses vary in their host specificity (B48.4.w4, B227.1.w1, D48).
  • Pox is uncommon in raptors, common in passeriformes. Within the psittacines, it is more common in the south American than in the Australian species. (B14)
  • All ages of birds are susceptible (B12.19.w12, B227.1.w1); disease is most common in young birds. (B12.19.w12, B13.32.w3)
  • Stress may reactivate latent infection. (B227.1.w1, B336.77.w77)

Distribution within the host:

  • Infection may remain localised to the initial site of entry, or spread to other areas of the skin, or a viraemia may develop. (B13.32.w3, B336.77.w77)
    • Strains which are nonpathogenic or only slightly pathogenic, and modified live vaccine strains, usually remain localised at the site of entry, , causing localised lesions at that site (B227.1.w1) and do not cause a secondary viraemia. (B13.32.w3)
    • Following the initial viraemia, pathogenic strains of the virus become distributed to the liver and bone marrow, followed by replication, secondary viraemia and generalised clinical disease. (B13.32.w3)

Note: Avian pox may be seen as a secondary disease in birds being treated following Oiling. (P4.1990.w1)

  • Transmission is through contact - through abraded skin or the conjunctiva. Arthropods may act as mechanical vectors, particularly mosquitoes if they feed on a bird with viraemia or on secretions from lesions, then on an uninfected bird.
    • Transmission from experimentally infected ducks or geese to healthy cage mates occurred "readily" in experimental infection. (J5.11.w3)
  • Susceptibility: All species are susceptible (B197.11.w11) although avian pox is uncommon in waterfowl.
  • Canarypox, fowlpox and turkeypox have all been transmitted to waterfowl. (B15)

(B15, B36.19.w19, B48.4.w4).


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Disease / Agent has been reported in either the wild or in captivity in:

  • "Approximately 60 free-living bird species representing about 20 families have been reported with avian pox." (B36.19.w19).
  • Colaptes auratus - Yellow-shafted flicker, Junco hyemalis - Slate-colored junco, Melospiza melodia - Song sparrow, Spizella pusilla - Field sparrow, domestic canary, Spizella passerina - Chipping sparrow, Phaisinus colchicus - Common pheasant, Phaethon rubricauda - Red-tailed tropic bird, Passerculus sandwichensis (Savannah sparrow), domestic goose, domestic duck, pigeon, house sparrow (Passer domesticus - House sparrow), Brown creeper (Certhiidae), Crow (corvidae), bullfinch (Pyrrhula pyrrhula - Eurasian bullfinch), chaffinch (Fringilla coelebs - Chaffinch), towee, tree sparrow, white-throated sparrow (Fringillidae), cowbird, grackle (Isteridae), Mimus polyglottos - mockingbird (Mimidae), Cape-May warbler, yellow-breasted chat, yellowthroat (Parulidae), quail (Phaisianidae), ruffed grouse, Centrocercus urophaisianus - sage grouse (Tetraonidae), Dendragapus fuliginosus - Sooty grouse, American robin, Gray-cheeked thrush, Swainson's thrush, Wood thrush (Turdidae)(B48.4.w4)
  • Sparrows, magpies, canaries, mourning dove, sooty grouse, quail, partridge, pheasant, wild and domestic pigeons (B220)
  • Sparrows, pheasants, woodpigeons (Columba palumbas - Common wood-pigeon) (J35.121.w1).
  • Raptors, game birds, domestic poultry, pigeons, woodpigeons (Columba palumbas - Common wood-pigeon) and various passerines including house sparrows (Passer domesticus - House sparrow), blackbird (Turdus merula - Eurasian blackbird), dunnock (Prunella modularis - Hedge accentor), starling (Sturnus vulgaris - Common starling)(D48).
  • Uria aalge - Common murre (guillemots) during rehabilitation in California following Oiling. (B36.19.w19)
  • During an epornitic in wild birds in four cities of Contra Costa County, California, house finches (Carpodacus mexicanus - House finch), mourning doves (Zenaida macroura - Mourning dove), house sparrows (Passer domesticus - House sparrow), a robin (Turdus migratorius - American robin) and a golden eagle (Aquila chrysaetos - Golden eagle) were found with lesions. (J4.171.w4)
  • Sanderlings (Calidris alba - Sanderling) in Florida, USA. (J1.35.w3)


  • American green-winged teal Anas crecca carolinensis in Alaska (J1.15.w3).
  • Canada goose Branta canadensis in Ontario (J1.16.w5).
  • Chinese geese (Anser cygnoides domesticus) (J16.33.w1).
  • Hawaiian goose Branta sandvicensis and possible Ross's goose Anser rossii; N.B. not confirmed as no inclusion bodies visible (J23.16.w1).
  • Mute swan Cygnus olor, green-winged teal Anas crecca, Canada goose Branta canadensis, Goldeneye Bucephala sp., Lesser Scaup Aythya affinis, Cape Barren goose Cereopsis novaehollandiae, captive common scoters, and domestic ducks and geese (B15).
  • Green-winged teal Anas crecca, blue-winged teal Anas discors, mallard Anas platyrhynchos, wood duck Aix sponsa, redhead Aythya americana, common goldeneye Bucephala clangula, harlequin Histrionicus histrionicus, common scoter Melanitta nigra, trumpeter swan Cygnus buccinator, whistling swan Cygnus columbianus columbianus and mute swan Cygnus olor, all in North America (B36.19.w19).
  • Domestic geese Anser anser domesticus, greylag goose Anser anser, swan goose Anser cygnoides, bean goose Anser fabalis, Hawaiian goose (Nene) Branta sandvicensis, Bar-headed goose Anser indicus (Eulabeia indica), Canada goose Branta canadensis, mute swan Cygnus olor, black swan Cygnus atratus (Chenopis atrata), ruddy shelduck Tadorna ferruginea, mallard Anas platyrhynchos, Muscovy duck Cairina moschata, Mandarin Aix (Dendronessa) galericulata, European wigeon Anas (Mareca) penelope, common (green-winged) teal Anas (Nettion) crecca, common (Northern) shoveler Anas (Spatula) clypeata, black (common) scoter Melanitta nigra, 'duck' (J6.28.w1).
  • Experimental infection with fowl-pox in domestic (Khaki Campbell and White Pekin) ducklings (Anas platyrhynchus domesticus - Domestic Duck) and White China goslings (Anser cygnoides domesticus - Chinese goose). (J5.11.w3)
  • Natural infection in a whistling swan Cygnus columbianus, developing during rehabilitation. (J4.177.w1)


  • One wild, live-trapped adult and three pen-reared Florida sandhill cranes Grus canadensis pratensis (Grus canadensis - Sandhill crane). (J1.11.w12)
  • A four-month-old Grus japonensis - Red-crowned crane crane chick in Japan (with concurrent aspergillosis and inclusion body hepatitis). (J436.25.w1)
  • Poxvirus infection was diagnosed as the cause of death in 3/167 wild Grus grus - Common crane in Germany, 1998-2008, two juveniles and one subadult, all female. [2011] (J1.47.w5)
  • Poxvirus lesions were detected on the bill, near the nares, in two sibling Florida sandhill cranes (Grus canadensis - Sandhill crane) in 1993, with suspicious but unconfirmed lesions in other birds. (B702.19.w19)

Further information on Host species has only been incorporated for species groups for which a full Wildpro "Health and Management" module has been completed (i.e. for which a comprehensive literature review has been undertaken). Host species with further information available are listed below:

Host Species List


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Disease / Agent has been specifically reported in Free-ranging populations of:


  • American green-winged teal Anas crecca carolinensis in Alaska (J1.15.w3).
  • Canada goose Branta canadensis in Ontario (J1.16.w5).
  • Mute swan Cygnus olor, green-winged teal Anas crecca, Canada goose Branta canadensis, Hawaiian goose Branta sandvicensis, Goldeneye Bucephala sp., Lesser Scaup Aythya affinis, Cape Barren goose Cereopsis novaehollandiae (B15).


  • One wild, live-trapped adult Florida sandhill cranes Grus canadensis pratensis (Grus canadensis - Sandhill crane). (J1.11.w12)
  • Poxvirus infection was diagnosed as the cause of death in 3/167 wild Grus grus - Common crane in Germany, 1998-2008, two juveniles and one subadult, all female. [2011] (J1.47.w5)
  • Poxvirus lesions were detected on the bill, near the nares, in two sibling Florida sandhill cranes (Grus canadensis - Sandhill crane) in 1993, with suspicious but unconfirmed lesions in other birds. (B702.19.w19)

Further information on Host species has only been incorporated for species groups for which a full Wildpro "Health and Management" module has been completed (i.e. for which a comprehensive literature review has been undertaken). Host species with further information available are listed below:

Host Species List



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General Information on Environmental Factors/Events and Seasonality

  • Infections in wild birds have been recorded all times of the year. (B48.4.w4)
  • Temperature, humidity and cover all affect avipoxvirus survival outside the host and environmental conditions affecting insect vectors such as mosquitoes could also influence spread. (B36.19.w19)
    • Where the virus is spread mainly by mosquitoes, the disease is most prevalent in late summer through to autumn. (B13.32.w3)
      • Outbreaks may subside when colder weather and frosts reduce mosquito populations. (B48.4.w4)
    • In chickens, the disease occurs most commonly in young birds during autumn and winter; dry pox may be seen in autumn and early winter, with wet pox becoming more prevalent in late winter. (B48.4.w4)
  • Overcrowding and close confinement may increase transmission by direct or indirect contact. (B36.19.w19, B336.77.w77)
    • This may occur, for example, during importation and quarantine, or in farmed bird flocks. (B336.77.w77)

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Regions / Countries where the Infectious Agent or Disease has been recorded

Worldwide (B36.19.w19); Germany, UK, China, Canada, USA, Australia, Netherlands, Italy, India, France (J6.28.w1).

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Regions / Countries where the Infectious Agent or Disease has been recorded in Free-ranging populations

In waterfowl: USA, Canada, Australia (B15).
  • Reports in free-living waterfowl are uncommon. (B36.19.w19)

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General Investigation / Diagnosis

General Information on Investigation / Diagnosis

  • Clinical signs of the cutaneous form (wart-like lesions on featherless areas of the bird) are characteristic, allowing initial diagnosis. (B12.19.w12, B36.19.w19, J6.28.w1)
  • Proliferative lesions are characteristic, but these may be affected by bacterial or fungal secondary infection. (B12.19.w12)
  • Histologically, Bollinger bodies (large, acidophilic intracytoplasmic inclusions) can be found in biopsy samples from lesions. (B12.19.w12, B13.32.w3, B14, B32.24.w36, B36.19.w19, B48.4.w4, B227.1.w1)
    • Epithelial cells are hypertrophied and contain typical eosinophilic inclusion bodies. (B336.77.w77)
    • Elementary (Borrel) bodies, individual pox virions, may be visible within inclusions if Gimenez stain is used. (B227.1.w1)
    • Scrapings, impression smears (stained with Giminez stain) or biopsies may be examined histologically. (B336.77.w77)
    • There may be necrotic areas containing masses of bacteria or fungi, usually near the surface of the lesions. (B48.4.w4)
    • In the mucosal form, Bollinger bodies may be rare. (B12.19.w12)
  • Direct electron microscopy of negatively stained preparations from skin scabs or pharyngeal swabs allows diagnosis by visualisation of the large poxvirus particles in a homogenous matrix. (J6.28.w1, B48.4.w4)
  • Virus isolation in embryonated chicken eggs (on the chorioallantoic membrane) or on avian embryo fibroblast cultures, allows a diagnosis of infection with an Avipox virus, but does not identify the virus species. It may be possible to develop molecular methods allowing more accurate information. (B48.4.w4, B336.77.w77, J6.28.w1)
    • Some avipox virus strains do not grow with these culture techniques. (B336.77.w77)
  • Serology is not useful, since immunity is mainly cell-mediated, with little humeral response. (B13.32.w3)
  • Serological testing can be carried out using virus neutralisation, ELISA, agar diffusion or haemagglutination inhibition test. (B336.77.w77)
  • Cutaneous tumours associated with avipox virus infections are "characterised by a palisade-like arrangement of epithelial cords containing Bollinger bodies." (B13.32.w3)
  • Detection of carrier birds may be possible by repeated fecal cultures, since the virus may be shed intermittently by such individuals. (B13.32.w3)
  • Initial diagnosis is based on the typical gross appearance of the lesions.
  • Definitive diagnosis is based on the histological appearance, poxvirus particles visible using an electron microscope, and virus isolation. N.B. inclusion bodies  (large, intracytoplasmic, acidophilic) may not always be demonstrable in pox infection.

(J1.16.w5, J5.11.w3, J6.28.w1, B15, B36.19.w19, B197.11.w11, B227.1.w1)

  • In four Grus canadensis - Sandhill cranes, light microscopic findings of intracytoplasmic inclusion bodies and electron microscopic findings of filaments and immature virions free in the cytoplasm, and mature virions in the inclusions, were considered diagnostic. (J1.11.w12)
  • In a four-month-old Grus japonensis - Red-crowned crane, diagnosed by histology. (J436.25.w1)
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Similar Diseases (Differential Diagnosis)

  • Dry pox: trauma, avian ringworm (see Favus in Waterfowl), or Knemidokoptes mite infection. (B13.32.w3); neoplastic lesions (tumours) (Neoplasias). ectoparasitism, bacterial dermatitis and papillomavirus infection. In young domestic chickens, lesions due to pantothenic acid deficiency, biotin deficiency, or T-2 toxin. (B32.24.w36, B336.77.w77)
  • Wet pox: trichomoniasis (D48, B32.24.w36, B227.1.w1), candidiasis, aspergillosis, hypovitaminosis A, capillariasis, also (depending on species), pigeon herpesvirus, herpesvirus infection of chickens, infectious laryngotracheitis, and Amazon tracheitis virus. (B13.32.w3, B14, B227.1.w1, B336.77.w77)
  • Newcastle Disease. (B14)

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Treatment and Control

Specific Medical Treatment

None; however the disease is usually self-limiting (B118.10.w10, B227.1.w1, B336.77.w77, J6.28.w1, D48).
  • In chickens, aspirin has been shown to reduce lesions development and severity. (B336.77.w77)
WATERFOWL None; however the disease is usually self-limiting (B11.36.w4).
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General Nursing and Surgical Techniques

Supportive care is the main treatment for this disease. (B12.19.w12)
  • Antimicrobial treatment may be used to treat or prevent development of secondary infections (B336.77.w77, D48)
  • Ophthalmic ointments may be used to protect the eyes and keep the eyes and eyelids moist. (B336.77.w77, B365.74.w74)
  • Ensure that a nutritionally complete diet is provided. (B365.74.w74)
  • Supplementation with vitamin A is recommended. (B12.19.w12, B336.77.w77)
    • In parrots a dose of 10,000 to 25,000 IU Vitamin A per 300 g bodyweight intramuscularly has been suggested. (B12.19.w12)
    • 200 IU/kg Vitamin A has been suggested for passerines. (B365.74.w74)
  • Vitamin C at 50 g/kg. (B365.74.w74)
  • General nursing care; make sure the affected bird is able to find and consume food and water; assist if necessary. (B336.77.w77, D48)
    • Fluids and tube feeding may be required in birds which are anorexic. (B12.19.w12, J4.171.w1)
  • Maintain strict sanitation. (B365.74.w74)
  • Avoid unnecessary stress. (B365.74.w74)
  • Antibiotics and antifungal medication may be required with secondary infections. (B12.19.w12, J4.171.w1)
  • Masses around the eyes and mouth which are interfering with feeding may be removed. (B365.74.w74, v)
  • Note: surgical removal of large lesions is not recommended, since masses regrow. (B12.19.w120)
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Preventative Measures

  • Vaccination may be practical in some situations; vaccines have been developed for some species such as chickens, turkeys, pigeons, canaries, quail and are considered protective for about one year (J6.28.w1, B48.4.w4).
  • Vaccines are suggested for use where the disease is endemic and on premises in which the disease has been known to occur previously (B227.1.w1).
  • Vaccination is the best control method when an appropriate vaccine is available. Commercially produced vaccines are available for psittacine poxvirus. Healthy canary flocks can also be vaccinated. (B13.32.w3)
    • Care should be taken not to use vaccine in an actively infected flock, due to the risk of recombination between field and vaccine strains of virus, which might result in severe disease. (B13.32.w3)
    • Use a new/freshly sterilised needle for each canary to prevent spread of virus during vaccination. (B13.32.w3)
    • Canary vaccines give protection for about three months. (B13.32.w3)
    • In gallinaceous birds, vaccination is usually cutaneous, into the wingweb or feather follicles. Formation of a typical pox lesion at the site of inoculation (checked after nine to ten days) indicates successful vaccination and immunity. (B13.32.w3)
    • In ostriches, fowlpox vaccine is effective and should be given at 10-14 days in areas with high mosquito densities. (B13.32.w3)
  • Note: cross-immunity between strains is variable. (B48.4.w4)
  • Fowl pox virus of chick embryo origin can be used to vaccinate chickens (at four weeks old) and pullets (one to two months before egg production) in the wing web, or turkeys in the inner thigh at about two to three months old. (B32.24.w36, B227.1.w1)
  • Attenuated cell culture origin vaccines can be used also, and one has been used for oral vaccination. (B32.24.w36)
  • Live pigeon pox virus can be used to vaccinate pigeons my inoculation in the wing web, and can also be used on chickens and turkeys in the wing web. (B32.24.w36)
    • Pigeon pox vaccine can also be applied to denuded feather follicles using a brush (B227.1.w1)
  • A modified live-virus canarypox vaccine has been commercially produced, as have live vaccine of quail pox virus origin and a live nonattenuated turkey pox vaccine. (B32.24.w36, B227.1.w1)
  • Prophylactic vaccination should be carried out in spring/summer where disease is likely to occur in autumn/winter, or at any time in tropical regions. (B32.24.w36)
  • Vaccination is recommended under various conditions:
    • A flock on the premises was infected the previous year. (B32.24.w36, B227.1.w1)
    • Where the disease is prevalent/endemic. (B32.24.w36, B227.1.w1)
Prophylactic Treatment --
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Environmental and Population Control Measures

General Environment Changes, Cleaning and Disinfection
  • General good hygiene.
  • Decontaminate in-contact surfaces (perches, cages etc.), for example with 5% bleach. (B36.19.w19)
    • Potassium hydroxide, sodium hydroxide, heating, steam and 5% phenol are effective for inactivation of the virus. (B336.77.w77)
  • Control insect vectors: screening birds from mosquitoes, or destroying mosquitoes, may be useful if an outbreak is suspected to involve these as vectors.
    • Control of adult mosquito populations and identification and elimination of breeding sites should be considered. (B36.19.w19)
  • Dust should be controlled where this may be a factor in transmission.
  • Note that the virus can survive for a long time (more than a year) in dried pox scabs in the environment. (B12.19.w12, D48)
  • In the face of an outbreak in wild birds, members of the public who fed wild birds were requested to clean and disinfect their bird feeding stations, and to stop feeding the birds for a month to reduce both direct and indirect transmission. (J4.171.w1)

(B36.19.w19, B48.4.w4, B197.11.w11, B227.1.w1, B336.77.w77, J4.171.w1)

Population Control Measures
  • Reduce contact between birds. (B336.77.w77)
  • Reducing crowding e.g. at feeding stations for wild birds may reduce spread (D48).
Isolation, Quarantine and Screening
  • Remove infected birds from the population (B36.19.w19). Isolate infected birds until the lesions heal, remembering that transmission may occur both by direct contact and by indirect contact, such as via mosquitoes (B48.4.w4, P4.1990.w1).
Related Techniques
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