Heligmosomoides polygyrus: time of anthelmintic treatment and infection parameters in mice exposed to increasing doses of larvae.

D Kerboeuf, G Jolivet

Index: Exp. Parasitol. 57(3) , 307-15, (1984)

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Abstract

Mice were multiply infected with increasing doses of Heligmosomoides polygyrus larvae. On Day 9 or on Day 30 after the beginning of infections, an anthelmintic treatment was administered and its effect on reinfections and egg production was studied. The time of treatment was found to be an important factor, since early treatment produced marked resistance to subsequent infection, whereas a similar effect was not observed for the late treatment. Most immunity appeared after a lag time of about 3 weeks following treatment. Mice placed in direct contact with high doses of larvae had massive infections, and large quantities of worm eggs were recovered in the faeces. After larval doses were no longer given, there was a decrease of the worm burden in both treated and untreated animals. Studies of egg laying showed that the increased resistance induced by the treatment was also responsible for a reduced egg production. The relationship between fertility of H. polygyrus females and the size of young parasite populations was positive, but was negative for older populations. The slope of the regression line of this relationship was steeper in treated than in untreated mice. Egg production by a female worm was depressed to a certain extent by the resistance reactions of the host, but did not decrease below a threshold value of 100 eggs per female per day.