The identification of the immunological mechanisms affecting concomitant infections is increasingly recognized to be crucial for the understanding of the host mediated responses to parasite transmission and the epidemiology of co-infections. I shall present results on the dynamics of helminth-bacteria co-infections from laboratory experiments of rabbits challenged with two gastrointestinal nematodes and a respiratory bacterium, and discuss the results in relation to the long term dynamics of these co-infections in a natural rabbit population. Immune-parasitological analyses were performed on samples (blood, tissues, parasites) collected regularly over time and from different organs.

Results/Conclusions

Results suggested that the host acquired immune response modulated these infections by affecting bacteria replication and nematode development and fecundity. The intensity and kinetic of the immune response changed with the type and number of co-infections, which then affected parasites intensity and long term persistence. Surprisingly, host acquired immune response strongly affected bacteria but not nematode shedding rate. The relevance of changes in host immunity during co-infections and the non-linearity between immune response and parasite shedding are discussed in relation to the persistence and transmission of chronic infections.