CONICET | Buscador de Institutos y Recursos Humanos

It is now broadly accepted that parasites influence wildlife population dynamics. In turn, hosts may influence parasite dynamics, as parasitism intensity is dependent on the intrinsic susceptibility of the host. Our goal was to evaluate experimentally if induced stress increases the gastrointestinal parasitism intensity in capybaras. Twenty-six young captive-bred females were randomly allocated into 6 enclosures and received either of three treatments: two groups were fed a restricted diet (40% less), other two groups were frequently physically restrained, and the remainder two groups served as controls. After three months, all animals were euthanized and multiple samples and measurements were collected. Growth and body condition were substantially affected by both treatments, especially in the food-restricted group. However, blood cell counts and lymphoid tissue weight did not differ across groups. Coccidian intensity was significantly higher in treated animals than in controls, especially in the food-restricted groups. Nematodes, however, did not show such difference. Moreover, the subfamily Viannainae was found at higher loads in controls than in physically restrained ones, and the difference was similar and almost significant with foot-restricted capybaras. Within each treatment, however, a negative association was found between measures of body condition and coccidians, Strongyloides chapini and Viannainae. Our results revealed that while parasite loads were negatively associated with host condition, their relationship with nutritional and psychophysical stress in capybaras differed depending on the parasite species. Further studies should explore if such differences are a consequence of differential allocation of resources in the physiological economy (e.g. trade-offs between somatic effort and immunity), or, rather, differential parasite uptake.

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