Haemoproteus spp is the most common blood parasite in birds, especially nondomestic birds. More than 120 species have been reported. Pigeons, doves, and raptors are frequently infected. Species are found in free-living ducks, quail, and turkeys but are rare to absent in commercial flocks probably because of very specific feeding habits of Culicoides spp and hippoboscid flies, the invertebrate vectors. Haemoproteus is considered nonpathogenic in most avian species, although anemia, anorexia, weight loss, and depression have been reported occasionally. Experimental infection in turkeys and Muscovy ducks resulted respectively in lameness, diarrhea, anorexia, and depression; or lameness, dyspnea, and sudden death. Infection in racing pigeons (called pigeon malaria) is commonly asymptomatic but often blamed for poor performances that are due to other diseases or inadequate housing and management.

Diagnosis is made by examination of stained blood smears and observation of large, pigmented gametocytes in mature RBC that partially or occasionally completely encircle the nucleus without displacing it. Merozoites are not observed in the peripheral blood. Little is known about effective treatment. Antimalarial drugs reduce the parasitemia but do not eliminate the parasite. Chloroquine, primaquine, quinacrine, and buparvaquone have been used in pigeons. Combinations of chloroquine and primaquine or chloroquine and mefloquine have been used to treat owls. Treatment is not recommended in asymptomatic birds. Measures to control invertebrate vectors, such as screening of aviaries, help prevent transmission and heavy infections.

Last full review/revision March 2012 by Arnaud J. Van Wettere, DVM, MS, DACVP