Suppression of peripheral eosinophilia by the coccidium Eimeria nieschulzi (Apicomplexa: Eimeriidae) in experimentally infected rats

Four groups of 60 rats each were used to examine interspecific interactions between Eimeria nieschulzi and Nippostrongylus brasiliensis. Rats in group 1 served as uninoculated controls. Group 2 rats were each injected subcutaneously with 2.0 X 10(3) L3 larvae of N. brasiliensis. Group 3 rats were each inoculated per os with 2.5 X 10(5) sporulated oocysts of E. nieschulzi. Rats in group 4 were first infected with 2.0 X 10(3) larvae of N. brasiliensis and, at 8 days postinoculation, with 2.5 X 10(5) oocysts of E. nieschulzi. Ten animals from groups 1-3 were sacrificed at 4-day intervals postinoculation and group 4 rats were sacrificed at 4-day intervals beginning after the secondary infection. Blood smears were prepared from each animal to determine differential blood cell counts, bone marrow was examined at the times of peak infection for absolute and relative numbers of eosinophils, portions of the duodenum and jejunum were examined histologically for mast cells, and feces obtained from the cecum and large intestine were examined for ova/gram of feces. Results revealed that relative numbers of peripheral neutrophils and monocytes became elevated during the course of infection for all infected animals, and rats infected with the helminth only also had elevated eosinophil levels. However, rats infected singly with E. nieschulzi, or concurrently with the coccidium and helminth, had peripheral eosinophil levels that were not significantly different from controls.(ABSTRACT TRUNCATED AT 250 WORDS)