[Contribution to the knowledge of the biology of Moniliformis moniliformis Bremser, 1811 (Acanthocephala). Influence of host resistance of Rattus norvegicus Berkenhout, 1769, on the parasite (author's transl)].

Acquired resistance in rats (SIV 50) during infection with 30 Moniliformis moniliformis has an effect on survival, growth and behaviour of the parasite. We observe an expulsion of worms during infection, starting in the 4th week for female worms but usually after 8 weeks for the males. The density of parasites determines the beginning of the self-cure. Comparing our results with the works of Andreassen (1974a) and Burlingame et Chandler (1941), we observe that the self-cure occurs earlier with doses of 100 larvae than with 30 or 20. Rats with a primary infection show immunity against reinfection. Two weeks after reinfection we observe that only 26% of the parasites are fixed compared to 66% in primary infections. A major effect of immunity is retardation of worm growth. Parasites from reinfections are shorter than those of primary infections. During infection the worm migrate. After the first 3 weeks the male migrate posteriorly and female anteriorly and posteriorly. In reinfections parasites become localized after only 2 weeks. We hypothize that M. moniliformis migrates due to an immunological reaction and inflammatory response of the intestinal mucus but also as a part of its own normal development.