Epidemiological modeling of < i > Trypanosoma cruzi < /i > : Low stercorarian transmission and failure of host adaptive immunity explain the frequency of mixed infections in humans

by Nicol ás Tomasini, Paula Gabriela Ragone, Sébastien Gourbière, Juan Pablo Aparicio, Patricio Diosque People living in areas with active vector-borne transmission of Chagas disease have multiple contacts with its causative agent,Trypanosoma cruzi. Reinfections byT.cruzi are possible at least in animal models leading to lower or even hardly detectable parasitaemia. In humans, although reinfections are thought to have major public health implications by increasing the risk of chronic manifestations of the disease, there is little quantitative knowledge about their frequency and the timing of parasite re-inoculation in the course of the disease. Here, we implemented stochastic agent-based models i) to estimate the rate of re-inoculation in humans and ii) to assess how frequent are reinfections during the acute and chronic stages of the disease according to alternative hypotheses on the adaptive immune response following a primary infection. By using a hybrid genetic algorithm, the models were fitted to epidemiological data of Argentinean rural villages where mixed infections by different genotypes ofT.cruzi reach 56% in humans. To explain this percentage, the best model predicted 0.032 (0.008 –0.042) annual reinfections per individual with 98.4% of them occurring in the chronic phase. In addition, the parasite escapes to the adaptive immune response mounted after the primary infection in at least 20% of the events of re-inoculation. With these low annual rates, the risks...
Source: PLoS Computational Biology - Category: Biology Authors: Source Type: research