Proliferative visceral Isospora (atoxoplasmosis) with morbid impact on the Israeli sparrow Passer domesticus biblicus Hartert, 1904.

House sparrows (Passer domesticus biblicus Hartert, 1904) caught in the Jordan valley, the coastal plain, and the desert region in Southern Israel were found massively infected with extraintestinal proliferative stages of Isospora, previously named Atoxoplasma. Infection coincided with Isospora spp. infections in the digestive tract. Prevalence of infection reached 70% among sparrows of all three regions; however, only in the Jordan valley did the severity of the sparrows compromised their survival. Healthy appearing captured birds showed symptoms of "going light" syndrome -- diarrhea, emaciation, and death. Birds succumbed within 48 h to 15 days after confinement to cages. Merozoites accumulated predominantly in the spleen but were rarely found in the peripheral blood. The parasite stages in the visceral leukocytes propagated by merogony and yielded single large waiting-stage merozoites. Visceral infections resulted in multifocal necrosis. Proliferative visceral Isospora infection (atoxoplasmosis) is one of the more severe causes of mortality among captive birds, free-ranging birds appear to coexist with the infection but succumb under capture stress.

Leucocytozoonosis in the Israeli sparrow, Passer domesticus biblicus Hartert 1904.

Among the 91 house sparrows (Passer domesticus biblicus Hartert, 1904) examined and caught in the Jordan valley, Israel, 79% were found to be infected with Leucocytozoon fringillinarum Woodcock 1910. In the coastal plain of Israel (South of Tel Aviv), Leucocytozoon infection was found in only 3 out of 43 examined sparrows. In the birds examined, Leucocytozoon gametocytes were present, often in large numbers, in the circulating blood of the visceral organs, whereas they were only sporadic or even absent in the peripheral blood. Gametocytes were seen in the brain capillaries in only a few birds. Only one of the heavily infected sparrows was anemic. Leucocytozoon merozoites were present in the liver and kidneys in only a few infected birds. Merogonic infections did not induce any severe pathological changes, while the gametocyte congestion caused dilation of the blood vessels and sinuses. Tissue damage by the gametocyte parasitemia was most evident in the liver and kidneys. Leucocyte infiltration developed alongside the affected vessels; diffuse necrosis developed in the infiltrated areas. In the kidneys, many tubules were degenerated. Leucocytozoon gametocyte infection in sparrows is unique in that it appears to be confined, for most of its duration, to the visceral circulation, resulting in clinical consequences. Geographically, it is confined to habitats presumably supporting vectors.