Host-sex Influences the Establishment of Trichinella zimbabwensis in Sprague-Dawley Rats

Males are usually more prone to parasite infections due to behavioural and ecological patterns as well as genetic and physiological differences between males and females. They have associated aggression, dispersal, and assemblage, which increase the chances of contact with both ectoand endoparasites. In order to determine the effect of host sex on the establishment and development of Trichinella zimbabwensis, 50 Sprague-Dawley rats aged 6 weeks and weighing between 130-150g were divided into two groups (25 males and 25 females), and orally infected with T. zimbabwensis. On days 5, 10, 15, 20, and 25 post-infection (PI), five randomly selected rats were sacrificed from each group, and the numbers of adult parasites in the intestine as well as larvae in muscles were determined. Results from the study showed a significantly higher amount of Trichinella adults and larvae (P < 0.05) in male than in female Sprague-Dawley rats (four times higher adult worms and two times higher in muscle larvae in males than in females). The mean number of female adult worms was significantly higher (P < 0.05) than male adult worms in male rats on day 5 PI. The mean number of gravid females recovered in male rats on day 5 PI was significantly higher (P < 0.05) than mean number of nongravid females. The female to male ratio of adult worms in male rats increased from 35:1 on day 5 PI to 6:1 on day 10 PI, whilst it was the reverse in female rats. The female to male ratio decreased at day 5 PI from 29:1 to 94:1 at day 10 post-infection. Our study concluded that there were significantly high establishment rates of T. zimbabwensis in the intestines and muscles of male SpragueDawley rats than in females, and the sexhormone-linked immunological characteristics could possibly explain these results.