Dietary relations between Moniliformis (Acanthocephala) and laboratory rats

Abstract

Aspects of the course of infection of Moniliformis dubius in male rats fed on four purified, isocaloric diets (A, B, C and D) were investigated. Diet A contained no digestible carbohydrate, diet B contained glycerol as a potential source of glucose, diet C contained 3.6% starch and diet D contained about 59% starch. After a rat had been adapted to one of the diets, it was infected orally with 20 cystacanths of Moniliformis and allowed to continue feeding on the same diet for periods varying from 1 to 18 weeks. A group of 4 rats was studied in this way on each of the diets for 11 weeks and on diets C and D for a further 7 weeks. The effects of the dietary treatments on the rats were studied by measuring their food intake, growth rate and liver glycogen. At the end of each experimental period, the rats were killed and the numbers, location, dry masses and state of reproduction of the worms were recorded. The composition of the diet appeared to have no effect on the establishment of Moniliformis in the small intestine and the populations of worms emigrated against the direction of gastrointestinal flow during the first month of the course of infection irrespective of the diet of the host. Worms from the rats fed on diets A and B hardly grew, their survival in their hosts did not appear to continue after 11 weeks and they showed no evidence of reproductive activity. Worms from rats fed on the low starch diet (C) did not grow as rapidly as those from rats fed on the high starch diet (D) during the first few weeks of the infection, but eventually they grew much larger and lived longer than worms from the hosts feeding on the high starch diet. Worms in the rats fed on diet C appeared to remain in a precise location in the anterior part of the small intestine from 4 weeks after infection of the host until the end of the experimental period. Worms in the rats fed on diet D had begun to move posteriorly in the small intestine from about 7 weeks after the infection of the host. The results of an experiment involving the transfer of rats with established infections of Moniliformis from a standard laboratory diet to diets A, B, C and D supported the conclusion that the survival, growth and reproduction of Moniliformis are dependent on the availability of glucose liberated during digestion in the host. Another experiment demonstrated that Moniliformis can survive periods of at least 14 days during which the host is deprived of an essential amino acid.