Interspecific Interactions between Nippostrongylus brasiliensis and Eimeria nieschulzi in the Rat

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Abstract
Interspecific interactions between N. brasiliensis and E. nieschulzi were studied by measuring parasite fecundity and patency in rats concurrently infected with both species. Nine groups of 5 rats each were inoculated with either 4 .times. 103 N. brasiliensis larvae or 2.6 .times. 105 E. nieschulzi sporulated oocysts or both. Groups 1 and 2 served as singly-infected controls. Group 3 rats were infected simultaneously with both parasites. Rats in groups 4 to 8 were infected first with N. brasiliensis and later with E. nieschulzi on days 3, 4, 8, 9 and 14 post infection. Rats in group 9 were infected with E. nieschulzi and then with N. brasiliensis 2 days later. Patency of N. brasiliensis infections was extended significantly (P .ltoreq. 0.05) beyond singly-infected controls in all groups with concurrent infections except group 3, whereas ova production was significantly greater than that in singly-infected controls only when both parasites were administered simultaneously (group 3). Patency of E. nieschulzi was significantly shorter in group 7 rats and longer in group 9 rats compared to that of singly-infected controls. Total oocyst production was unaltered except for groups 5 and 7, in which there was a significant reduction. Apparently the endogenous stages of E. nieschulzi increased N. brasiliensis longevity.