NATURAL SCHISTOSOMA-MANSONI INFECTION IN WILD RATS FROM GUADELOUPE - PARASITOLOGICAL AND IMMUNOLOGICAL ASPECTS

Rattus rattus is the predominant rodent in the mangrove area of Guadel oupe. Between 1990 and 1991 we found 73 R. rattus and five R. norvegic us. Among the infected rats with Schistosoma mansoni, 59% for R. rattu s and 80% for R. norvegicus, the comparison of the median of the worm load was not statistically different. Both species of infected rats sh owed adult worms and eggs in the lungs and 20% of them showed, at the same time, two and even three generations of worms. Neither adults nor eggs were seen in the intestinal wall or stools of R, norvegicus, ins tead R. rattus had eggs in the liver, in the intestinal wall and the s tools. Therefore, R. norvegicus gets infection as well as R. rattus, b ut does not participate in the transmission of the schistosomiasis. In order to elucidate this difference, we looked at the humoral recognit ion of these two rats, to the molecular antigens of the three stages o f the parasite: cercaria, adult worm (AWA) and egg (SEA). In general, R. norvegicus recognized cercarial antigens more frequently than R. ra ttus, 73, 81 and 172 kDa being statistically different. Regarding AWA, molecules 82, 86, 117 and 150 kDa were recognized more often by R. ra ttus as compared to R. norvegicus. The reverse was true for the Ig, 33 and 61 kDa. Only the differences between 61 and 150 kDa molecules wer e statistically significant. With respect to SEA, R. norvegicus recogn ized more 28, 45, 47, 49, 63 and 92 kDa molecules than R. rattus, but the latter recognized the 140 kDa molecules of SEE to a higher degree (95 and 140 kDa were significantly different). It is plausible that th e immune response to cercarial invasion is more effective in R, norveg icus in allowing the parasites to reach adulthood, but it does not let them live in the mesenteric veins and therefore to lay their eggs in the intestinal wall and feces. (C) 1997 Elsevier B.V.