Blood and Tissue Protozoa of the English Sparrow (Passer domesticus domesticus) in Galveston,Texas*

SYNOPSIS. The 42% incidence of Plasmodium in blood films of English sparrows reported here is the highest on record for surveys of blood parasites of birds in the United States. The only Plasmodium species identified in the sparrows was P. relictum. Adult birds were almost universally infected and tended to experience the highest degree of parasitemia in the spring months, while young birds had a higher blood positivity in the summer months. The lowest incidence of Plasmodium positive blood films occurred in fall and winter in the Galveston area. Overwintering birds had a decrease in parasitemia corresponding to reported minimal gonadal activity in sparrows. The 20% incidence of Lankesterella (avian Toxoplasma) in the blood of these sparrows was also higher than has been reported in other blood film surveys in this country. Incidence of this parasite in blood films was highest in the summer months, corresponding with highest average temperature for the year. Lankesterella could be found in 95% of sparrows whose tissues were examined after autopsy. Ducks and pigeons in the immediate vicinity of the survey sparrows had neither Plasmodium nor Lankesterella in blood films. Resident wild birds from adjacent rural areas, including redwinged blackbirds, boat-tailed grackles, laughing gulls and meadowlarks, had fewer Plasmodium and Lankesterella than the sparrows. A few Lankesterella were found in the liver or spleen of young redwinged blackbirds, and only 2 of 79 wild birds had the organisms in their heart blood. Plasmodium was found only in meadowlarks and included P. hexamerium and elongatum as well as relictum.