Increased intestinal muscle contractility and worm expulsion in nematode-infected mice.

Intestinal nematode infections are accompanied by mucosal inflammation and an increase in propulsive motor activity that may contribute to parasite eviction from the gut. To examine whether differences in worm expulsion correspond to the increased intestinal muscle contractility that accompanies nematode infection, we studied mice with genetically determined differences in their ability to expel the nematode parasite Trichinella spiralis. Specifically, we examined isometric contraction of longitudinal muscle, worm counts, and inflammation, as measured by myeloperoxidase activity, in two strains of mice infected with T. spiralis. The strong responder strain, NIH Swiss, expelled the parasites by day 16 postinfection, whereas the poorer responding B10.BR strain was still heavily infected by day 21 postinfection. However, both strains developed similar increases in jejunal myeloperoxidase activity. Both strains demonstrated increased isometric tension development after infection, but peak tension occurred earlier in NIH Swiss mice (day 8 vs. day 12 postinfection) and was of significantly greater magnitude than in B10.BR mice. We conclude that the ability to expel T. spiralis from the small bowel is not related to the degree of granulocyte-dependent mucosal inflammation but is reflected in the magnitude of the accompanying increase in force generation by intestinal smooth muscle.