A population model for Triatoma infestans in chicken coops

Abstract

Despite the strenuous efforts devoted to its elimination, Chagas disease is still prevalent in large regions of Latin America. Its main vector, Triatoma infestans (kissing bug), feeds on people and domestic animals and finds refuge in the peripheral structures of rural and semi-rural houses. Here we propose a mathematical model based on discrete-time equations that describe the evolution of the populations of all the stages of T. infestans residing in a chicken coop, a typical bug reservoir in non-urban habitats. The chicken coop has also been used as a suitable location for observations of T. infestans populations under realistic, controlled conditions. The variables that govern the model are the time of the year, the temperature, and the blood intake by the triatomines. Using the available data, we design fitting functions, such as maximum blood intake, development time, mortality rate, egg fertility, etc., for each population group. Then, we validate our model using D. Gorla's experimental work on T. infestans populations. Finally, we analyze the minimum conditions of temperature and food availability necessary for the survival of T. infestans, showing that average daily temperatures below 12 °C or average yearly temperatures below 16 °C or above 32 °C lead to colony extinction. Feeding also regulates the colony size, and we find that if a few triatomines (5% of the colony) are well fed, and the rest occasionally get a meager meal, the colony size can be, on average, constant over the years. By quantifying what happens in structures crucial to the species survival, our model is an important step forward towards the formulation of a general population model for T. infestans in the Grand Chaco under current conditions.