Response of Immunized, Parenterally Nourished Rats to Challenge Infection with the Nematode, Trichinella spiralis

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Abstract
Experiments were designed to test the hypothesis that structural and chemical changes in the small intestine associated with total parenteral nutrition (TPN) alter relationships between hosts and enteric parasites. Parenteral feeding of rats immunized to Trichinella spiralis (nematoda) led to a decrease in gut mass. This was reflected by a significant drop in gut wet weight and reductions in mucosal dry weight, DNA, protein, carbohydrate and lipid. These changes were accompanied also by lowered brush border enzyme activity. When challenged orally with 8 × 103T. spiralis larvae and switched immediately to oral feeding, more worms became established in the small intestines of these rats than in rats given similar doses of larvae, but maintained by oral feeding throughout the experiment. Despite the significant difference in initial worm burden, both enterally fed and parenterally fed rats completely expelled their parasites by 7 and 8 days postinfection, respectively. Results indicated that factors involved in preventing establishment of T. spiralis in immunized rats were suppressed by the prolonged absence of food from the GI tract, whereas factors responsible for expelling worms that were able to gain residence in the mucosa appeared to be unaltered or at least functionally reversible.