Host pregnancy influences the establishment of Trichinella zimbabwensis in Balb C mice

In order to determine the effect of host pregnancy in the establishment of Trichinella zimbabwensis, 120 female Balb C mice were divided into 4 groups of 30 mice each. Group 1 animals were orally infected with 50 T. zimbabwensis larvae per gram (LPG) of body weight on day 0; group 2 were mated on day 0 and not infected; group 3 were mated at day 0 and infected with 50 LPG at day 7 post-mating and Group 4 were control animals which were neither mated nor infected. Six animals from each group were sacrificed and the number of adult parasites in the intestines as well as larvae in the muscles were determined at day 0, 7, 14, 21 and 28 post-infection for group 1; 0, 7, 14, 21 and 28 post-mating for group 2 and days 7, 14, 21, 28 and 35 post-mating for group 3. In addition, levels of progesterone and cortisol were measured in all groups at the same intervals. Our results showed that pregnancy reduced the number of larvae establishing in muscles with progesterone levels significantly higher in pregnant than in non-pregnant Balb C mice (P < 0.05). There were no significant differences in cortisol levels between pregnant and non-pregnant mice. High progesterone level in pregnant mice was assumed to have parasiticidal effect on the new-born larvae (NBL). Further research is needed to determine the direct effect of progesterone on Trichinella NBL and how this can be exploited in designing remedies for preventing Trichinella infection in susceptible domestic animals and humans.