Uncommon Bloodborne Organisms in Poultry

Trypanosomes have been described in several avian species, including chickens, but rarely, if ever, do they cause disease. Trypanosomes are more commonly identified in organ smears, especially bone marrow, than in peripheral blood, and they can be cultured. Invertebrate hosts of trypanosomes are thought to be any of several bloodsucking insects. Treatment of infection by trypanosomes is not warranted.

Borrelia spp are tickborne (Argas spp) spirochetes that can cause fatal systemic disease in a wide range of bird species, including chickens, turkeys, and waterfowl (see Avian Spirochetosis). Penicillins, tetracyclines, tylosin, and tick control are used for prevention and treatment.

Babesia spp are uncommon, nonpigmented, piriform, erythrocytic protozoal parasites of birds. Natural infections of penguins, falcons, cranes, and several other avian species occur. Infection in poultry has not been reported. Ticks are considered to be the invertebrate hosts.

V, X, or fan shapes characterize dividing forms of Babesia. Knowledge regarding their importance, treatment, or control in birds is limited. Only Babesia shortti, which rarely occurs in Falconiformes, has been reported to be pathogenic. Imidocarb diproprionate has been reported for treatment of infected falcons.

Local guidance must be followed in the administration of all medications to food-producing animals, observing appropriate withdrawal times and residue avoidance.

Hepatozoon is a protozoal parasite infrequently identified in wild birds. Its prevalence in wild birds is 2–5%. It produces relatively large, nonpigmented, elongated gametocytes with rounded ends that can be found in WBCs (see turkey vulture blood image).

Hepatozoon, photomicrograph, blood, turkey vulture

Image

Courtesy of Dr. D. E. Scott.

Hepatozoon gametocytes are usually not located within an indentation of the nucleus, whereas Isospora is oval and partially encircled by the nucleus. The Hepatozoon life cycle in birds is uncertain; however, argasid ticks and fleas have been identified as probable vectors for Hepatozoon spp that infect swallows. Ixodes ticks, mites, and other arthropods can also be involved. Hepatozoon spp are not known to be pathogenic.

Isosporiasis (atoxoplasmosis) is a disease of passerine birds caused by infection with coccidian protozoa in the genus Isospora. Canaries, finches, sparrows, and species of the Sturnidae family (starlings, mynahs) are the most commonly affected. Very rare cases of infection have also been reported in raptors. Poultry are not known to be affected. In affected birds, hepatomegaly and splenomegaly, sometimes with pinpoint foci of necrosis, are observed at necropsy.

Diagnosis of isosporiasis is based on fecal flotation tests, buffy coat smears, liver and spleen impression smears, histological examination, and/or PCR assay. Decreased mortality rates and oocyte shedding have been achieved by oral administration of sulfachlorpyridazine, toltrazuril, and diclazuril. Prevention is critical to control the disease.

Zoites of other sporozoa (eg, Toxoplasma, Sarcocystis) and organisms normally in the digestive tract (eg, trichomonads, coccidia, histomonads) can be transiently found in blood. Histomoniasis often also produces liver lesions in poultry, especially in turkeys.

• Grainer EC. Isospora, Atoxoplasma, and Sarcocystis. In: Atkinson CT, Thomas NJ, Hunter BD, eds. Parasitic Diseases of Wild Birds. Wiley-Blackwell; 2008:108-119.