Authors

Discussion

Given the ubiquity of endemic coinfection with epidemic infection in natural populations, determining the impacts the endemic parasites may have on epidemic parasite transmission is essential. During coinfection, interspecific parasite interactions, whether direct or indirect, could impact on the quality and quantity of parasite transmission stages. Using a model host (the German cockroach) its endemic gut protozoan (Gregarina blattarum) and the epidemic entomopathogenic nematode, Steinernema carpocapsae, we assessed the impact of varying levels of endemic infection upon the quality and quantity of the transmission stages of S. Carpocapsae. We hypothesized that the lipid resource, which we have previously shown mediates the interaction between the two parasites species, would decrease in S. carpocapsae in relation to the level of gregarine infection within the host impacting both the number and quality of emerging infective juveniles (IJs) of the nematode. We exposed specific parasite free cockroaches to different numbers of gregarine gametocysts (0 to 20) and subsequently exposed them to the epidemic S. carpocapsae. We then monitored, host time to death, number of emerging IJs with time and the lipid levels within the IJs.   Our results suggest that the level of endemic infection has substantial effects on transmission potential. We present these results and discuss their implication for epidemic transmission.