Print PageDuring a parasite infection the response of the host can range from either tolerance of the parasites, by limiting the damage they cause and allowing the infection to persist, or resistance, by mounting an immune response that reduces parasite burdens and eventually develops into some level of protection. The extent of this response along the tolerance-resistance spectrum will be shaped by both on the host and the parasite. Our goal was to identify the mechanisms that generated such distinct phenotypes in a population of rabbits infected with two common gastrointestinal parasites and monitored monthly for seven years. Parasite intensity was quantified in every rabbits, parasite development and fertility measured using a digitalized system, peripheral antobodies quantified with ELISA and host characteristics (age, sex, abdominat fat mass, foetus mass) recorded. The relationships between level of infection and host health, fitness and immune response were examined.
Results/Conclusions
Results showed that the ability to tolerate the infections was a function of the level of infection, however, above a threshold the first parasite species was expelled by an effective immune response while the second parasite continued to be well tolerated by the host but numbers decreased because of parasite density-dependent processes. Fitness showed a tendency to be higher when associated to the tolerant than the resistant parasite. Consistently with this results parasite life history traits (development and fertility) were modulated by host immunity for the first parasite and density dependence for the second. The consequences of tolerance and resistance phenotypes are discussed in relation to strategies of parasite transmission and persistence of infections.
