Effectiveness of fluralaner treatment regimens for the control of canine Chagas disease: A mathematical modeling study

Author summaryChagas disease- caused by the protozoan parasite Trypanosoma cruzi and vectored by triatomine insects- poses a serious threat to human and dog health, as infection may go undetected and cause heart disease. Systemic insecticide treatment of dogs is one proposed One Health intervention to reduce T. cruzi transmission for both dogs and humans, given that dogs are parasite reservoirs. Fluralaner, a systemic insecticide commonly administered to dogs to prevent ectoparasites such as fleas and ticks, induces mortality of triatomines in laboratory settings. We investigated the efficacy of different fluralaner treatment regimens in three endemic peridomestic transmission environments (high, medium, and low) for lowering triatomine density, T. cruzi infection prevalence, and incidence among dogs using mathematical models. Our simulations suggest that fluralaner treatment is an effective method of reducing T. cruzi transmission to dogs, and the ideal frequency to treat dogs with fluralaner depends on the transmission environment. Given the intervention may increase the abundance of dead vectors in the dog's environment, empirical data are needed on the duration of parasite viability within dead vectors and frequency of canine consumption of dead vectors for a more comprehensive evaluation of the intervention. BackgroundCanine Chagas disease is caused by the protozoan parasite Trypanosoma cruzi and transmitted by insect triatomine vectors known as kissing bugs. The agent can cause cardiac damage and long-term heart disease and death in humans, dogs, and other mammals. In laboratory settings, treatment of dogs with systemic insecticides has been shown to be highly efficacious at killing triatomines that feed on treated dogs. MethodWe developed compartmental vector-host models of T. cruzi transmission between the triatomine and dog population accounting for the impact of seasonality and triatomine migration on disease transmission dynamics. We considered a single vector-host model without seasonality, and model with seasonality, and a spatially coupled model. We used the models to evaluate the effectiveness of the insecticide fluralaner with different durations of treatment regimens for reducing T. cruzi infection in different transmission settings. ResultsIn low and medium transmission settings, our model showed a marginal difference between the 3-month and 6-month regimens for reducing T. cruzi infection among dogs. The difference increases in the presence of seasonality and triatomine migration from a sylvatic transmission setting. In high transmission settings, the 3-month regimen was substantially more effective in reducing T. cruzi infections in dogs than the other regimens. Our model showed that increased migration rate reduces fluralaner effectiveness in all treatment regimens, but the relative reduction in effectiveness is minimal during the first years of treatment. However, if an additional 10% or more of triatomines killed by dog treatment were eaten by dogs, treatment could increase T. cruzi infections in the dog population at least during the first year of treatment. ConclusionOur analysis shows that treating all peridomestic dogs every three to six months for at least five years could be an effective measure to reduce T. cruzi infections in dogs and triatomines in peridomestic transmission settings. However, further studies at the local scale are needed to better understand the potential impact of routine use of fluralaner treatment on increasing dogs' consumption of dead triatomines.

Automated summary

The author investigated the efficacy of systemic insecticide treatment of dogs in reducing T. cruzi transmission and found that the frequency of treatment can effectively lower the infection in both dogs and triatomines. However, further research is needed on the impact of treatment on dogs' consumption of dead triatomines.