STRESS AND PARASITISM INTENSITY IN CAPYBARA (HYDROCHOERUSHYDROCHAERIS): AN EXPERIMENTAL STUDY

EBERHARDT, M. A,; COSTA, S. A.; GAGGIAMO, C.; TARRAGONA, E.; MAGNI, C.; WELSCHEN, N.; ROCHI, M.; PICASSO, J. P.; MORENO, P.; RACCA, A.; ROBLES, R.; BELDOMENICO, P.M.

Puerto Iguazú

Conferencia; 59th Annual International Conference of the Wildlife Disease Association.; 2010

Wildlife Disease Association

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 apybaras. Within each treatment,  however,  a  negative  association  was  found  between  measures  of  body ondition  and  coccidians,  Strongyloides  chapini  and  Viannainae.  Our  results  revealed  that  while parasite  loads were negatively associated with host condition,  their  relationship with nutrional 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.