Parasitoid mediated effect on host behavior: impacts on infection risk by other pathogens

The parasitoid wasp Microplitis demolitor carries the polydnavirus Microplitis demolitor Baculovirus (MdBV) to facilitate parasitism of the larval stages of the moth Chrysodeixis includens. Prior studies established that MdBV infection globally suppresses host immunity, which raised the question of whether parasitized hosts are more vulnerable to infection by other pathogens. I assessed whether parasitism altered host growth and development by measuring body weight, head capsule width, frass, and locomotor activity. I then tested host susceptibility and risk of infection by the pathogens Bacillus thuringiensis and Autographa californica multicapsid nucleopolyhedrovirus (AcMNPV). Results indicated that parasitism suppressed host feeding behavior, which caused stunted host growth and development. Parasitized and non-parasitized hosts were equally as susceptible to AcMNPV and Bt when force fed. In contrast, when third instars fed naturally on AcMNPV containing diet parasitized hosts exhibited significantly lower levels of mortality, but Bt spread diet exhibited no significant mortality difference.