Non-Transmissibility in utero of Trichinosis in the Rat

Abstract

For several weeks after the maturation of ingested larvae of Trichinella spiralis in the intestine, those of the next generation enter the circulating blood of the host. Although the presence of migrating larvae in various organs, tissues and body fluids has been observed repeatedly, studies of pregnant hosts, such as the rat, guinea pig, rabbit, hog and man, have indicated that intrauterine transmission of trichinosis from mother to fetus does not occur. Roth, 1 however, recently reported the recovery by digestion of a few larvae in 2 out of 5 litters of guinea pigs born of mothers infected during pregnancy. Previous investigations have dealt with comparatively small groups of animals, and little importance has been attached to the stage of gestation at which mother animals have been infected.

Young adult white rats weighing from 180 to 280 gm. were fed by stomach tube the larvae of Trichinella spiralis obtained by digestion of infected rats in artificial gastric juice. 2 The time of inoculation varied from one day before, to 15 days after, copulation. The presence of infection in all mother rats was confirmed by subsequent microscopic examinations of their diaphragms and other skeletal muscles. Since migration of young larvae begins about one week after infection and usually continues for 2 weeks, larvae were migrating in various rats during all except the earliest stages in the maturation of the placenta and of fetal development of muscle. Attempts to obtain copulation of female rats 2 to 7 days after infection were unsuccessful. Twenty-one females were fed 15 larvae per gm. of body weight, an amount sufficient to cause an infection of moderate severity. To 2 groups of 3 rats each were fed 35 and 40 larvae respectively per gm. of body weight. Most of the offspring of rats fed 15 larvae per gm. were of usual size and weight, and developed normally.