The migration of Hymenolepis diminuta in the rat's intestine during normal development and following surgical transplantation

Abstract

The normal position of attachment of the scolex of H. diminuta from day 6 to day 27 in single worm infections in male Wistar rats was determined. A migration forward from a position of attachment 30–40% down the length of the small intestine to the 10–20% region during day 7 to day 14 was confirmed. A concomitant and slightly faster movement backwards of the posterior of the worm led to the mid-point of the strobila changing from 35 to 50% down the intestine. By day 18 the worms were mature and occupied the whole small intestine except the anterior 10% and the posterior 5–10%. The worms weighed approximately 350 mg dry weight (= 1550 mg fresh weight) at maturity, no significant weight increase occurred thereafter.6½ and 7½ day-old worms were transplanted from donor rats into the duodenum or posterior ileum. Nearly 100% recovery of the single worm transplants in recipient rats was obtained. Both anterior and posterior implanted worms returned to the region of the intestine from which they had been removed. Migration was measured over periods of 13–72 h and was found to be complete within 24 h. Worms transplanted into the duodenum continued to grow at nearly the normal rate but worm transplants into the posterior ileum lost nearly a day's growth. The significance of this point is discussed.Opium was found to prevent migration of the tapeworm, but ligation of the bile duct did not prevent the tapeworm migrating forward from a point of insertion near the ileo-caecal junction.The evidence confirms the concept that a tapeworm is a dynamic organism capable of recognizing a specific region of the intestine, of detecting when it is not in this region, of being able to interpret one or more stimuli to indicate direction and of having a motor system sufficiently coordinated to overcome peristalsis.We gratefully acknowledge financial support by the Medical Research Council (London) and technical assistance from Miss Helen Stallard, B.Sc., Miss Pat Grant and Miss Gillian Moore. One of us (Trond Braten) wishes also to thank the University of Glasgow for the award of a Visiting Fellowship.