Hymenolepis diminuta: changes in intestinal morphology and the enterochromaffin cell population associated with infection in male C57 mice.

Mean villus height, crypt depth and the number of 5-HT-positive enterochromaffin (EC) cells have been examined in two regions of the small intestine (20-30% and 60-70% distance from the pylorus) of male, 6 to 8-week-old, C57 mice following a 5-cysticercoid infection of the rat tapeworm, Hymenolepis diminuta. Test mice and sham-infected controls were autopsied 0, 4, 8, 10, 14 and 28 days post-primary infection (p-1 degree-i) and 2, 4, 5, 7 and 14 days post-secondary infection (p-2 degrees-i), administered 28 days p-1 degree-i. Morphometric analysis revealed a statistically significant increase in crypt depth in the 60-70% intestine region in infected mice during both primary and secondary infections; no significant deviation from the control was observed for villus height in infected mice. Statistical analysis showed a significant increase in the number of 5-HT-positive EC cells in infected mice. This response occurred in the lower portion of the intestine on days 10-p-1 degree-i and 5-p-2 degrees-i, and was not due to increased mucosal surface area in this region. Results are discussed with reference to murine cestode rejection and the possible involvement therein of the neuroendocrine system.