Haemoproteus spp are the most common blood parasites in birds, especially nondomestic birds. More than 130 species have been reported.
Haemoproteus spp are found in free-living ducks, quail, and turkeys but are rare to absent in commercial flocks, probably because of limited vector exposure or the very specific feeding habits of Culicoides midges and hippoboscid flies, the invertebrate vectors. Haemoproteus is considered nonpathogenic in most avian species.
Clinical Findings of Haemoproteus Infection in Poultry
Haemoproteus infections in birds are usually subclinical; however, Haemoproteus infection might have more of an impact than was previously thought, given the increase in reports documenting decreased host fitness, nestling deaths, decreased fledging success, and delayed recovery in infected birds versus uninfected birds.
Anemia, anorexia, weight loss, and depression have been reported with Haemoproteus infections. Rare cases progress to death. Clinical signs are usually attributed to anemia, the presence of megaloschizonts in the musculature, or host-cell destruction.
In poultry, infection with Haemoproteus lophortyx in bobwhite quail (in North America) can cause clinical signs and increased mortality rates, with as much as 20% flock loss. Usually, quail 5–10 weeks old are affected, and clinical signs include reluctance to move, prostration, and death. Gross lesions include splenic and hepatic congestion, plus hemorrhagic streaks in muscles. Histological examination has revealed myositis with megaloschizonts in the musculature, especially of the legs and back, as well as hemosiderin accumulation in splenic macrophages.
Haemoproteus meleagridis affects turkeys in North America. Experimental infection in turkeys with H meleagridis has resulted in lameness, diarrhea, anorexia, and depression. Histological lesions have been associated mainly with megaloschizont development in the musculature.
Infection in racing pigeons with Haemoproteus columbae or Haemoproteus saccharovi (called pigeon malaria) is commonly subclinical; however, it is often blamed for poor performance that is due to other diseases or to inadequate housing and management. Haemoproteus infection is usually subclinical in Columbiformes.
Diagnosis of Haemoproteus Infection in Poultry
Cytological evaluation
Histological evaluation
Haemoproteus is identified in stained blood smears from its large, pigmented gametocytes in mature RBCs that partially or, occasionally, completely encircle the nucleus without displacing it (see goose blood image). Merozoites do not occur in the peripheral blood.
Courtesy of Dr. L. A. Degernes.
Histopathological findings can include schizogony (asexual reproduction) within the endothelial cells of the lung, liver, and spleen. PCR tests for Haemoproteus have been developed.
Treatment and Control of Haemoproteus Infection in Poultry
Antimalarials
Control of invertebrate vectors
Little is known about effective treatment for Haemoproteus infections. No drug is approved for commercial use. Antimalarial drugs decrease the parasitemia but do not eliminate the parasite. Chloroquine, primaquine, quinacrine, and buparvaquone have been used in pigeons. Combinations of chloroquine and primaquine or of chloroquine and mefloquine have been used to treat owls.
For treatment purposes, it should be noted that a 500-mg tablet of chloroquine phosphate contains 300 mg of active chloroquine base, and a 26-mg primaquine phosphate tablet contains 15 mg of active primaquine base.
Treatment for Haemoproteus infection is not recommended in subclinically affected birds. Measures to control invertebrate vectors, such as screening of aviaries, help prevent transmission and heavy infections. Local guidelines must be followed for appropriate withdrawal times and residue avoidance in food-producing animals.
Key Points
Haemoproteus spp infection is usually subclinical.
Some species of Haemoproteus can cause clinical signs and, rarely, fatal disease in turkeys and quail.
Diagnosis is based on examination of blood smears, tissue cytological evaluation, histological examination, and/or PCR assay.
Drug treatment can decrease parasitemia but does not eliminate infection.
Limiting insect vectors helps control the disease in susceptible species.
For More Information
McDougald LR, Cervantes HM, Jenkins MC, Hess M, Beckstead R. Protozoal infections. In: Swayne DE, ed. Boulianne M, Logue CM, McDougald LR, Nair V, Suarez DL, associate eds. Diseases of Poultry. 14th ed. Wiley Blackwell; 2020: 1192-1254.
Atkinson CT. Haemoproteus. In: Atkinson CT, Thomas NJ, Hunter BD, eds. Parasitic Diseases of Wild Birds. Wiley-Blackwell; 2008:13-34.
