Vector Consumption and Contact Process Saturation in Sylvatic Transmission of T. cruzi

Recent research in the transmission of the protozoan parasite Trypanosoma cruzi, some strains of which cause Chagas' disease, suggests that consumption of vectors by sylvatic hosts such as raccoons may play a role in maintaining the transmission cycle in the wild. As both hosts and vectors have been observed to invade new ecological niches, it is important to consider the effect vector consumption may have on vector density. For this reason a per individual contact rate is employed which rises roughly linearly for low vector densities and saturates for high densities. The model under study thus superimposes a predator-prey structure on a host-vector infection cycle (with first one, and then multiple, hosts). Outbreak behavior follows classical threshold behavior through the reproductive number R0, which allows evaluation of the importance of this transmission avenue relative to the traditional route. For sufficiently sharp contact rate saturation, two locally stable vector densities may exist.