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Diseases / List of Parasitic Diseases / Disease description:

Leucocytozoonosis in Waterfowl

INFORMATION AVAILABLE

GENERAL INFORMATION

CLINICAL CHARACTERISTICS & PATHOLOGY

INVESTIGATION & DIAGNOSIS

TREATMENT & CONTROL

SUSCEPTIBILITY & TRANSMISSION

ENVIRONMENT & GEOGRAPHY

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General and References

Disease Summary
WATERFOWL A haematozoan (blood parasite) infection, which can cause high mortality in juveniles.

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Alternative Names (Synonyms)
  • Leucocytozoon infection
  • Hemosporidian Infection
  • Haematozoan Infection

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Disease Type
 Parasitic - Single-celled/Protozoa

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Infectious/Non-Infectious Agent associated with the Disease
 Leucocytozoon simondi, a haematozoan parasite. Leucocytozoon anatis and L. anseris are now considered synonyms of L. simondi (B15).

VECTORS: Simuliidae (black-flies): Simulium anatinum, Simulium rugglesi, Simulium venustum, Simulium innocens; also Culicoides midges in Asia

Infective "Taxa"

Non-infective agents

 --

Physical agents

 -- Indirect / Secondary

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References

Disease Author

 Debra Bourne
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Major References / Reviews

Code and Title List

 B10.26.w5:- Zoo and Wild Animal Medicine, Second Edition
B14:- Avian Medicine and Surgery Second Edition
B15:- Diseases of Wild Waterfowl
B16.19.w1:- Diseases of Exotic Animals Medical and Surgical Management
B36.24.w24:- Field Manual of Wildlife Diseases
B37.x.w1:- Handbook of Avian Medicine
B48.23.w23: - Infectious and Parasitic Diseases of Wild Birds
P10.33.w1:- Transactions of North American Wildlife and Natural Resources Conference
J30.53.w1:- Canadian Journal of Zoology

Other References

Code and Title List

 J1.14.w1, J1.11.w1, J1.30.w2, J1.18.w1, J1.17.w1, J1.16.w1, J1.16.w2, J1.16.w3, J1.15.w1, J1.13.w2, J1.10.w1, J1.11.w1, J1.14.w1, J1.32.w1, J1.33.w1:- Journal of Wildlife Diseases
J7.17.w1:- The Wildfowl Trust Seventeenth Annual Report, 1964-1965 (Wildfowl).
J31.13.w1:- Journal of Protozoology

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Clinical Characteristics and Pathology

Detailed Clinical and Pathological Characteristics

General

 WATERFOWL Listlessness and anaemia; causes massive die-offs of young ducklings and goslings in some areas, although often only a sub-clinical infection (J1.11.w1, B10.26.w5, B15, P10.33.w1).

Clinical Characteristics

 WATERFOWL
  • Variation from inapparent to sudden death (B15).
  • Listlessness, depression, inappetance, weakness, sometimes dyspnoea, associated with anaemia. Poor growth and difficulty in walking have also been described. Listlessness and loss of normal wariness may be seen in adults (B10.26.w5, B14, B15, B16.19.w1, B37.x.w1, B48.23.w23).

Incubation

 WATERFOWL
  • Variable. Disease course normally 2-5 days, but death may occur within 24 hrs in susceptible downies; slower development of signs in adults (B15, B16.19.w1, B48.23.w23).
  • Prepatent period (before detectable parasitaemia) 4 to 7 days. Clinical disease and even death may precede patent infection, although a high parasitaemia is usually present at the time of death. Peak parasitaemia occurs 9 to 10 days post infection (J1.11.w1, B15).
  • Decrease in red blood cell count (anaemia) occurs starting about the time that parasitaemia begins and is usually most severe at or prior to the peak parasitaemia. (J31.13.w1).

Mortality / Morbidity

 WATERFOWL
  • Morbidity varies from year to year, even in one area, but can reach 100%.
  • Mortality is variable and can be high in juveniles (70-80%), particularly if massive infection. Mortality is rare in older birds (P10.33.w1, J1.11.w1, B10.26.w5, B15, B48.23.w23).

Pathology

 WATERFOWL Clinical pathology:
  • Anaemia, leucocytosis, non-pigmented parasites in blood cells.

Gross pathology:

  • Pale tissues, thin watery blood (PCV may be as low as 20%), hepatomegaly, splenomegaly.

Histopathology:

  • First five days post infection (dpi) , numerous schizonts in hepatocytes. Cells rupture 5dpi, causes dilatation & congestion hepatic sinusoids. Megaloschizonts (40-160µ m) appear in the spleen, lymphoid tissue & other tissues by 7dpi and hepatic sinusoids become distended with round gametocytes. Megaloschizonts rupture releasing merozoites by 12-13dpi, leaving haemorrhagic scars. Inflammatory response at time of megaloschizont rupture.
  • Widespread central necrosis liver, marked periportal and diffuse lymphocytic infiltration. Prominent Kupffer cells containing haemosiderin, also pigment bearing macrophages in necrotic areas.
  • Pulmonary congestion, lymphocytic infiltration myocardium; in brain, accumulation large mononuclear cells in/adjacent to small blood vessels and in association with megaloschizonts. Bone marrow hyperplastic.
  • N.B. Overwhelming infection with schizont stages in tissue but no parasitaemia described in young goslings (J1.11.w1).

(B15, B37.x.w1, B48.23.w23)

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Human Health Considerations
None (B36.24.w24, B37.x.w1).

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Susceptibility / Transmission

General information on Susceptibility / Transmission
WATERFOWL Susceptibility:
  • A wide variety (possibly all species) of waterfowl may be infected by Leucocytozoon simondi, but there are species differences in susceptibility to the development of clinical disease (P10.33.w1, B15).
  • Clinical disease is seen mainly in juveniles (e.g. Canada goose goslings under 7 weeks old), with the greatest mortality when waterfowl are infected in their first week of life; stressed birds are also more likely to develop clinical disease. (J1.11.w1, P10.33.w1, B10.26.w5, B15, B36.24.w24, B37.x.w1).
  • Blood-sucking by black-flies (Simulium spp.) may contribute to production of anaemia (J31.13.w1).
  • Re-infection is not prevented by presence of chronic infection (B15).
  • Recurrence of parasitaemia (relapse) in adults (both sexes) at the time of the start of egg-laying provides parasites for uptake by the vectors (J1.11.w1).

Transmission

  • Transmission is by Simuliidae (black-flies): Simulium anatinum, Simulium rugglesi, Simulium venustum, Simulium innocens; also Culicoides midges in Asia (B10.26.w5, B14, B15, B16.19.w1).

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Disease / Agent has been reported in either the wild or in captivity in:
Disease reported in:
  • Canada goose Branta canadensis goslings, USA; also reported as a pathogen in domestic geese in Central Europe (J1.11w1).
  • Canada goose Branta canadensis goslings; also infection but no disease in mallard ducklings Anas platyrhynchos (J1.11w1).
  • Mallard Anas platyrhynchos duckling (B15).
  • Mallard Anas platyrhynchos and Pekin ducks Anas platyrhynchos domesticus (experimental infection of ducklings); domestic and wild ducklings in Michigan (P10.33.w1).
  • Pekin ducklings (after deliberate exposure to black-flies or experimental infection) (J31.13.w1).
  • N.B. Leucocytozoonosis Leucocytozoonosis is considered to be an important cause of mortality and a possible population-limiting factor in wild ducklings and goslings in some areas of North America (B15, B26.26.w11, B36.24.w24).

Infection has also been reported in:

  • Greater scaup Aythya marila, Eurasian wigeon Anas penelope, European pochard Aythya ferina and green-winged teal Anas crecca in the UK, also mallard Anas platyrhynchos, northern pintail Anas acuta, northern shoveler Anas clypeata, mandarin duck Aix galericulata, common goldeneye Bucephala clangula, long-tailed duck Clangula hyemalis, red-breasted merganser Mergus serrator, greylag goose Anser anser, white-fronted goose Anser albifrons, Canada goose Branta canadensis (J7.17.w1)
  • Wood duck Aix sponsa, American black duck Anas rubripes, Canada goose Branta canadensis (P10.33.w1).
  • Northern pintail Anas acuta, American wigeon Anas americana, northern shoveler Anas clypeata, green-winged teal Anas crecca, blue-winged teal Anas discors, mallard, Anas platyrhynchos, gadwall, Anas strepera, snow goose Anser caerulescens, redhead Aythya collaris Alberta and Saskatchewan, Canada (J1.18.w1).
  • Mallard Anas platyrhynchos, baldpate (American wigeon) Anas americana, northern pintail Anas acuta and northern shoveler Anas clypeata California, USA (J11.37.w1).
  • Lesser snow goose Anser caerulescens caerulescens goslings in Canada (J1.32.w1)
  • Wood ducks Aix sponsa Georgia, USA Atlantic flyway (J1.33.w1).
  • American black duck Anas rubripes, mallard, Anas platyrhynchos, mallard x American black duck, blue-winged teal Anas discors, green-winged teal Anas crecca, wood duck Anas sponsa, hooded merganser Lophodytes cucullatus Atlantic flyway (J1.10.w1)
  • Mallard Anas platyrhynchos and northern pintail Anas acuta , Central Alberta and Mackenzie Delta, Northwest Territories, Canada (J1.13.w2).
  • Mallard Anas platyrhynchos, American wigeon Anas americana, blue-winged teal Anas discors, green-winged teal, Anas crecca, Canada goose Branta canadensis Oklahoma, USA (J1.15.w1).
  • Lesser scaup Aythya affinis, blue-winged teal Anas discors, ring-necked duck Aythya collaris, wintering in Texas (J1.16.w3).
  • Wood duck Aix sponsa along the Atlantic flyway, USA (J1.16.w2).
  • Mallard Anas platyrhynchos in Washington, Pacific flyway USA (J1.16.w1).
  • Trumpeter swan Cygnus (Olor) buccinator, in Alberta, Canada (J1.17.w1)
  • Wood duck Aix sponsa in Missouri, USA (J1.30.w1).
  • Cygnus (olor) columbianus - tundra swan, Anser albifrons - white-fronted goose, Anser anser - greylag, Anser (Chen) caerulescens - Snow goose, Branta canadensis - Canada goose, Aix sponsa - Wood duck, Anas acuta - Northern pintail, Anas americana - American wigeon, Anas clypeata - northern shoveler, Anas crecca - Green-winged teal, Anas discors - Blue-winged teal, Anas penelope- Eurasian wigeon, Anas platyrhynchus - Mallard, Anas rubripes - American black duck, Anas strepera - Gadwall, Aythya affinis - lesser scaup, Aythya americana - Redhead, Aythya collaris - Ring-necked duck, Aythya fuligula - tufted duck, Aythya marila - Greater scaup, Aythya valisineria - Canvasback, Bucephala albeola - Bufflehead, Bucephala clangula - Common goldeneye, Lophodytes cucullatus - Hooded merganser, Melanitta perspicillata - surf scoter, Mergus merganser - common merganser, Mergus serrator - red-breasted merganser, Somateria mollissima- Common eider in North America (J30.53.w1).

WATERFOWL Host Species List

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Disease / Agent has been specifically reported in Free-ranging populations of:
Disease reported in:
  • Canada geese Branta canadensis (J1.11w1, B15).
  • N.B. Leucocytozoon infection is considered to be an important cause of mortality and a possible population-limiting factor in wild ducklings and goslings in some areas of North America (B15, B26.26.w11, B36.24.w24).

Infection has also been reported in:

  • Scaup Aythya marila, wigeon Anas penelope, pochard Aythya ferina and teal Anas crecca in the UK (J7.17.w1)
  • Wood duck Aix sponsa, American black duck Anas rubripes, Canada goose Branta canadensis (P10.33.w1).
  • Northern pintail Anas acuta, American wigeon Anas americana, northern shoveler Anas clypeata, green-winged teal Anas crecca, blue-winged teal Anas discors, mallard, Anas platyrhynchos, gadwall, Anas strepera, snow goose Anser caerulescens, redhead Aythya collaris Alberta and Saskatchewan, Canada (J1.18.w1).
  • Mallard Anas platyrhynchos, baldpate (American wigeon) Anas americana, northern pintail Anas acuta and northern shoveler Anas clypeata California, USA (J11.37.w1).
  • Wood ducks Aix sponsa Georgia, USA Atlantic flyway (J1.33.w1).
  • American black duck Anas rubripes, mallard, Anas platyrhynchos, mallard x American black duck, blue-winged teal Anas discors, green-winged teal Anas crecca, wood duck Anas sponsa, hooded merganser Lophodytes cucullatus in Massachusetts, Atlantic flyway (J1.10.w1).
  • Mallard Anas platyrhynchos and northern pintail Anas acuta , Central Alberta and Mackenzie Delta, Northwest Territories, Canada (J1.13.w2).
  • Mallard Anas platyrhynchos, American wigeon Anas americana, blue-winged teal Anas discors, green-winged teal, Anas crecca, Canada goose Branta canadensis Oklahoma, USA (J1.15.w1)
  • Lesser scaup Aythya affinis, blue-winged teal Anas discors, ring-necked duck Aythya collaris, wintering in Texas (J1.16.w3).
  • Wood duck Aix sponsa along the Atlantic flyway, USA (J1.16.w2).
  • Mallard Anas platyrhynchos in Washington, Pacific flyway USA (J1.16.w1).
  • Trumpeter swan Cygnus (Olor) buccinator, in Alberta, Canada (J1.17.w1)
  • Wood duck Aix sponsa in Missouri, USA (J1.30.w1).
  • Cygnus (olor) columbianus - tundra swan, Anser albifrons - white-fronted goose, Anser anser - greylag, Anser (Chen) caerulescens - Snow goose, Branta canadensis - Canada goose, Aix sponsa - Wood duck, Anas acuta - Northern pintail, Anas americana - American wigeon, Anas clypeata - northern shoveler, Anas crecca - Green-winged teal, Anas discors - Blue-winged teal, Anas penelope- Eurasian wigeon, Anas platyrhynchus - Mallard, Anas rubripes - American black duck, Anas strepera - Gadwall, Aythya affinis - lesser scaup, Aythya americana - Redhead, Aythya collaris - Ring-necked duck, Aythya fuligula - tufted duck, Aythya marila - Greater scaup, Aythya valisineria - Canvasback, Bucephala albeola - Bufflehead, Bucephala clangula - Common goldeneye, Lophodytes cucullatus - Hooded merganser, Melanitta perspicillata - surf scoter, Mergus merganser - common merganser, Mergus serrator - red-breasted merganser, Somateria mollissima- Common eider in North America (J30.53.w1)

WATERFOWL Host Species List

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Environment/Geography

General Information on Environmental Factors/Events and Seasonality
  • Leucocytozoon infection occurs where parasite, vector (black flies Simulium spp.) and hosts all occur, in the northern Hemisphere. Simulium spp. require running water for their larval stages.
  • Seasonal disease – transmission dependant on Simulium (vector) as well as parasite availability, therefore highest rate of infection, and clinical disease, in spring when the vector is active and parasitaemia recurs in adults.
  • High juvenile mortality depends on environmental factors leading to high numbers of infected vectors at the time of greatest vulnerability: i.e. in young ducklings and goslings, in first few weeks after hatching. Stressful events also increase susceptibility.

(J30.53.w1, B14, B15, B36.24.w24, B37.x.w1, B48.23.w23)

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

USA, Canada, Mexico, Europe, Asia (B15, B36.24.w24).

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

USA, Canada, Mexico, Europe (B15, B36.24.w24).

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General Investigation / Diagnosis

General Information on Investigation / Diagnosis
WATERFOWL
  • Clinical signs (listlessness, depression, anaemia) in birds with known of possible exposure to blackflies Simulium spp.(B15, B48.23.w23).
  • Giemsa stained blood smears: large, non-pigmented parasites (gametocytes) in blood cells (both leukocytes and erythrocytes), distorting the cell. Cell may be enlarged and elongated, with horn-like extensions at either end. (B14, B15, B16.19.w1, B48.23.w23)
  • Pathological findings of hepatosplenomegaly, presence of megaloschizonts in impression smears of tissues, histopathological findings (B14, B15, B37.x.w1).

N.B. 1) Presence of Leucocytozoon gametocytes in blood may be incidental; 2) birds are not always parasitaemic at the time of serious clinical disease and death from Leucocytozoon infection (J1.11.w1, B15).
Related Techniques
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Similar Diseases (Differential Diagnosis)
WATERFOWL
  • Other causes of acute die-offs, particularly in young waterfowl (B37.x.w1).
  • Avian malaria (Avian Malaria) (Plasmodium spp.) and Haemoproteus infection (Haemoproteus Infection): both also produce parasites in blood cells, but these parasites are smaller than Leucocytozoon simondi, and pigmented. (B14, B15, B37.x.w1)

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Treatment and Control

Specific Medical Treatment
WATERFOWL
  • Possibly no effective treatment for waterfowl (B15).
  • Sulfaquinoxaline in drinking water at .005%; quinine may be useful early in the infection, before adult gametocytes appear (B16.19.w1, B48.23.w23)
Related Techniques

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General Nursing and Surgical Techniques
WATERFOWL  
Related Techniques

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Preventative Measures
Vaccination WATERFOWL --
Prophylactic Treatment

WATERFOWL

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Environmental and Population Control Measures
General Environment Changes, Cleaning and Disinfection

WATERFOWL
  • If possible, avoid contact between waterfowl, particularly juveniles, and blackflies. Total control of blackflies is impractical as they can travel more than 3km.
  • Local control by spraying with malathion may be useful to protect captive birds.
  • Screens to protect valuable young birds from blackflies may be useful in known problem areas

(B16.19.w1, B15, B37.x.w1, B48.23.w23).
Population Control Measures WATERFOWL --

 
Isolation, Quarantine and Screening WATERFOWL --
Related Techniques
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