CONICET | Buscador de Institutos y Recursos Humanos

A simulation model was developed to represent the population dynamics of two bugs (Triatoma infestans and Rhodnius prolixus), which are the main vector species of Chagas´ Disease in some Latin American countries. The model includes the infection process of bugs with the parasite causing the disease (Trypanosoma cruzi). Human and animal hosts for bugs (with a preference factor for each) were considered; bug migration between houses and between houses and the wild environment was also modelled; the three types of houses most common in rural areas were considered, The bugs´ population regulation mechanisms were modelled acting over natality and mortality. The population parameters of the two bug species that had no independent actual estimation were calibrated with a field series available only for R. prolixus. Populations of both species showed sustained oscillations under certain conditions, with about two cycles per year for T. infestans and about four cycles per year for R. prolixus, and proportional to the length of each species´ development time. Development-stage class distribution alternations are associated with these oscillations; adults are most abundant when population size is at its minimum. The symmetry of the fluctuation seems to be affected by female fecundity. Sensitivity analyses show that the main parameters affecting the stability behavior of the vector populations were: (a) the threshold nymphal density at which irritation of the host starts, (b) female fecundity, (c) number of hosts available, and (d) the emigration rate. The threshold nymphal density at which irritation of the host starts, combined with female fecundity, proved critical in producing a change in the stability behavior of the population, from a stable point equilibrium to a limit cycle. These results, if incorporated into transmission control models, can be used to optimize control strategies.

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