Studies on In vitro Larvaposition by Adult Trichinella spiralis

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Abstract
The effects of several components of the in vivo and in vitro incubation environment of T. spiralis on in vitro larviposition by adult worms were examined. Migratory larvae were not released in great numbers from dead adult worms. The numbers of migratory larvae shed in vitro by adult worms was independent of the number of female worms (5, 25, 50, 100 or 200 worms) present in equal volumes of incubation medium. Adult female worms deposited similar numbers of migratory larvae in vitro in the presence and in the absence of adult male worms in the incubation medium. Larviposition by adult worms was similar during the last five 4 h segments of a 24 h period of in vitro incubation, but was reduced during the first 4 h. Adult worms recovered from mice starved for 12 h or from the posterior half of the small intestine of the mouse deposited fewer larvae than did worms isolated from mice fed ad lib or isolated from the anterior half of the small intestine of the mouse host, respectively. Female worms recovered from female mice produced fewer migratory larvae than did those isolated from male mice regardless of the age of the host (3-4, 6-8 and 8-10 wk old mice). Although host age did not affect larviposition of adult worms isolated from female mice, those recovered from younger male mice (3-4 and 6-8 wk old) produced more larvae than did those isolated from older male mice (8-10 and 40-48 wk old). Adult worms incubated at temperatures above and below 37.degree. C (26.1.degree., 30.degree., 40.degree., 42.degree. and 45.degree. C) shed fewer migratory larvae than did those incubated at 37.degree. C. As the level of infection in mice increased, the numbers of migratory larvae shed in vitro by adult worms decreased.