Tapeworm infection decreases intestinal transit and enteric aerobic bacterial populations.

Intestinal myoelectric patterns in rats are altered after chronic luminal infection with the tapeworm Hymenolepis diminuta. This study evaluates whether these altered patterns were associated with changes in intestinal fluid transit and endogenous enteric microbe levels. Luminal transit, measured throughout the small intestine during the interdigestive state, was significantly decreased during tapeworm infection. Reduced transit was regional, occurring in the same location as that of the tapeworm and maximal myoelectric alterations. In other experimental systems, aerobic and anaerobic bacterial overgrowth is associated with decreased transit; however, reduced transit during tapeworm infection was unexpectedly associated with decreased numbers of aerobic bacteria, whereas anaerobic bacterial populations remained unchanged. The lack of overgrowing endogenous microflora suggests that overgrowth is not responsible for tapeworm-stimulated alterations in host myoelectric patterns. We speculate that a tapeworm secretion could be responsible for both transit and motility changes while delayed intestinal transit could prevent tapeworm expulsion, aid the tapeworms' migration, and contribute to the digestion and absorption of nutrients by hosts and/or parasites.