ESTABLISHMENT AND USE OF ALTERNATIVE DEFINITIVE HOSTS FOR ECHINOCOCCUS

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An alternative definitive host model for echinococcus multilocularis was established following the successful recovery of gravid adult cestode from the small intesine of prednisolone-treated Mongolian gerbil and golden hamster after oral inoculation of protoscoleces. This paves the way for maintaining the complete life-cycle of the cestode in laboratory using rodents alone. The interspecies range of such "host permissiveness", that is, the ability to serve as alternative definitive host, for the cestode was examined using 10 species of wild rodents belonging to the family Heteromydae and sub-family Hesperomynae from the north American continent. Immature cestode were recovered from the Kangaroo rat and also from the pocket mouse. Of the 5 inbred strains of hamster evaluated, the AN strain was the most susceptible. Intestinal epithelial mucus was thought to prevent the initial establishment of the cestode in the mice, hamster and Mongilian gerbil. Differences in the number of mucosal mast cells between prednisolone-treated and non-treated animals suggest the defensive role of the cell against the parasite. Acquired immunity to reinfection of the cestode was also observed in hamster. Biliary cholesterol concentration of prednisolone-treated hamster might be an indicator for susceptibility to the cestode. In experiments involving E. granulosus infection in cortisone- treated hosts such as hamster, Mongolian gerbil, Akodon and Oryzomys, immature cestodes could be recovered only up to day 10 postinfection. By using the alternative definitive host model system and experimentally infected dogs, we have developed a reliable immunodiagnositic test for Echinococcus infection in dogs. The test involves the detection of heat- stable coproantigen by sandwich ELISA using a monoclonal antibody.