Strongyloides ratti: relative importance of maternal sources of infection

Abstract

Milk-borne infection is demonstrated for Strongyloides ratti in rats, accounting for 32% of the combined worm burden of non-immune mothers plus their offspring at a standard dose of 4000 L3. Migrating larvae are ‘switched’ to the mammary gland about 3 days prepartum in advance of the final events of lactogenesis in the host at 30 h prepartum. Larvae take between 24–48 h to reach the milk after injection.The ‘take’ in lactating rats was half that in virgin controls and pregnant animals before day 3 prepartum, but this discrepancy was not made up by the number of worms in the litter, the combined figure for mothers and offspring still being only 75% of the potential judged by the controls.Prenatal infection did not occur in these experiments, which involved carefully controlled cross-fostering between infected and uninfected mothers. Injections of larvae covered the period between 12 days to 20 h prepartum in different animals. This route is possible under other circumstances, although it is considered unlikely in non-immune females since there was no evidence of larval dormancy in maternal tissue.