A stage-structured stochastic model of the population dynamics of Triatoma infestans, the main vector of Chagas disease

Abstract

We present a stage-structured mathematical model of the population dynamics of Triatoma infestans in a single house, as part of a more complex model incorporating domestic Trypanosoma cruzi transmission. Novel features of this model are a formulation in continuous time accounting for demographic stochasticity, temperature-dependent female fecundity and developmental times, and insect stage-dependent host irritability. The model assumes a closed domestic insect population regulated by insect density and stage-dependent host irritability depressing the insects’ feeding success and female fecundity. The model describes that the abundance of T. infestans insects fluctuates seasonally with only one peak in summer, whereas eggs show one peak in spring and another in the fall as a result of two peaks in female fecundity. The proportion of recently fed adult insects peaks in summer and falls close to zero in winter only when the intensity of host irritability differs markedly between small and large insect stages. In our model, the insect carrying capacity is the joint result of density-dependent access to hosts and density-independent mortality rates. Our hypothesis is that refuge quality in the house, not the absolute number of refuges, determined by construction features would translate into differential insect stage mortalities. The presence of only one hen brooding indoors during spring and summer increases insect numbers in a clearly detectable way. Sensitivity analysis showed strong effects on timed-averaged insect abundance of prolonged developmental time induced by low temperatures, the threshold insect density for host irritability, and mean female fecundity.