A model for Chagas disease with oral and congenital transmission.

This work presents a new mathematical model for the domestic transmission of Chagas disease, a parasitic disease affecting humans and other mammals throughout Central and South America. The model takes into account congenital transmission in both humans and domestic mammals as well as oral transmission in domestic mammals. The model has time-dependent coefficients to account for seasonality and consists of four nonlinear differential equations, one of which has a delay, for the populations of vectors, infected vectors, infected humans, and infected mammals in the domestic setting. Computer simulations show that congenital transmission has a modest effect on infection while oral transmission in domestic mammals substantially contributes to the spread of the disease. In particular, oral transmission provides an alternative to vector biting as an infection route for the domestic mammals, who are key to the infection cycle. This may lead to high infection rates in domestic mammals even when the vectors have a low preference for biting them, and ultimately results in high infection levels in humans

Populations at year 30 as functions of with .

<p>The number of infected humans, infected dogs, vectors, and infected vectors, all at year 30, as functions of . Here while all other parameters are set to the baseline values.</p

Infected humans at year 30 as a function of and .

<p>The number of infected humans at year 30 as a function of and , where and all other parameters are set to the baseline values.</p

The model parameters and the baseline simulation values.

<p>The model parameters and the baseline simulation values.</p

Infected humans at year 30 as a function of , , and .

<p>The number of infected humans at year 30 as a function of the vector consumption rate and congenital transmission probabilities (where ). All other parameters are the baseline values.</p

Higher initial conditions.

<p>Simulation results of the model with baseline parameters and higher initial conditions.</p

Populations at year 30 as functions of with .

<p>The number of infected humans, infected dogs, vectors, and infected vectors, all at year 30, as functions of . Here while all other parameters are set to the baseline values.</p

Infected humans at year 30 with different numbers of chickens and dogs.

<p>The figure shows the effects of changing the number of chickens and dogs on the number of infected humans in the village at year 30. Note that and all other parameters are set to their baseline values.</p

Vector growth and mortality coefficients.

<p>The vector growth rate coefficient in the baseline case and the vector mortality rate coefficient over one year.</p

Simulation results comparing models.

<p>Simulation results of the model in this work (black) and the model without both oral and congenital transmission (gray), from <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0067267#pone.0067267-Spagnuolo1" target="_blank">[21]</a>, in the baseline case using the parameters in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0067267#pone-0067267-t001" target="_blank">Table 1</a>.</p