STUDIES ON THE REPRODUCTIVE CAPACITY OF ECHINOSTOMA-CAPRONI (TREMATODA) IN HAMSTERS AND JIRDS

Total egg output per infective stage inoculated was used as a measurem ent of the reproductive capacity in Echinostoma caproni infections in hamsters and jirds. Egg production per adult E. caproni recovered was comparable in the hamster and in the jird, but the reproductive capaci ty of E. caproni in infections with 6 metacercariae in the hamster mar kedly exceeded that in the jird. This was due mainly to the expulsion of worms from the jird. Eggs per gram faeces produced was shown to be an invalid parameter in comparing the reproductive capacity in E. capr oni infections in jirds and hamsters due to differences in amounts of faeces produced, and evidence was obtained that uterine egg counts may not be a useful parameter in assessment of overall reproductive poten tials. In the hamster, the reproductive capacity of infections with 25 or 6 metacercariae of E. caproni was comparable. This reflected a den sity independent recovery and egg production of the adult worms. The r eproductive capacity, being an expression of the importance of a parti cular host species for the reproduction of a parasite population, is s uggested as a convenient and useful quantitative parameter in the esta blishment of standardized criteria for evaluating host-parasite relati onships in definitive host models.