COMPARISON OF 4 MURINE EIMERIA SPECIES IN IMMUNOCOMPETENT AND IMMUNODEFICIENT MICE

Factors associated with immune-mediated protection against coccidial p arasites were examined in a series of experiments utilizing immunocomp romised scid/scid(SCID) and scid/scid. beige/beige (SCID/Bg) mice, as well as immunocompetent BALB/c mice. Number of oocysts produced per g feces each day and prepatent and patent periods were assessed for 4 ei merian parasites (Eimeria papillata, Eimeria vermiformis, Eimeria falc iformis, and Eimeria ferrisi) using the 3 murine strains. The number o f infections required to elicit a protective immune response was also determined for each coccidial species in BALB/c mice. We report the fi rst description of patent infections in inbred immunocompetent and imm unodeficient mice infected with E. papillata. Results indicate that du ring primary infections, parasite replication is under partial immunol ogical control for all Eimeria species. However, the control is mechan istically different for E. papillata because the adaptive immune respo nse does not contribute to the control of primary infections. Both coc cidial species infecting intestinal villar epithelial cells (E. papill ata and E. ferrisi) were affected by the beige mutation using parasite output as an indicator, whereas E. falciformis, which infects intesti nal crypt cells, is not. BALB/c mice were more resistant to challenge infections with upper intestinal parasites (E. papillata and E. vermif ormis) in comparison to challenge infections with lower intestinal and cecal parasites (E. falciformis and E. ferrisi).