HOST-PARASITE RELATIONSHIPS IN INFECTIONS WITH 2 KENYAN ISOLATES OF SCHISTOSOMA-MANSONI IN NMRI MICE

To relate the marked differences observed in morbidity due to Schistos oma mansoni infection in the Kangundo and Kibwezi areas of Machakos Di strict, Kenya with possible parasite-related differences in pathobiolo gical characteristics, a quantitative comparison of the host-parasite relationship in infections in NMRI mice with S. mansoni isolates from the 2 areas was conducted. One hundred and 20 cercariae were used per mouse, and necropsy took place between 35 and 94 days following infect ion. Parameters assessed comprised worm establishment, tissue egg coun ts, fecal egg excretion, egg production/worm pair, and weights of live r and spleen. Central findings included a higher worm establishment an d a lower egg production/worm pair in Kangundo infections than in Kibw ezi infections, comparable total tissue schistosome egg counts, and a higher liver/intestinal tissue schistosome egg ratio in Kibwezi infect ed mice than in the Kangundo infected mice. In addition, a much higher fecal egg excretion, expressed as eggs/g feces and eggs/g feces/worm pair, was observed in mice infected with the Kangundo isolate of S. ma nsoni than in mice infected with the isolate from Kibwezi. Although po ssible limitations in the use of mouse models need be realized, the re sults provide some support to the hypothesis that parasite-related dif ferences in pathobiological characteristics may at least contribute to the marked difference observed in S. mansoni-induced morbidity betwee n the Kangundo and Kibwezi areas.