The impact of temperature on canine Chagas disease transmission risk: A modeling study

Canine Chagas disease is a vector-borne parasitic disease caused by Trypanosoma cruzi. T. cruzi is transmitted by triatomine bugs (a.k.a. kissing bugs), an ectothermic host species. Understanding how temperature induces changes in vector traits such as fecundity, egg hatching, molting, and activity frequency is essential for developing predictive models for Chagas disease transmission.

A mechanistic model based on a Ross-MacDonald framework was developed to capture the temperature-dependent dynamics of T. cruzi transmission. Using empirical data on the impact of temperature on triatomine bugs' life traits, temperature-sensitive parameters were estimated using Bayesian inference approach. These parameters were used to compute a thermal suitability metric, S(T), as an indicator of transmission risk.

The model suggests that S(T) peaks at 21.8°C (95% CrI: 17.9-22.0°C) and declines to zero below 16.9°C (95% CrI: 15.3-18.2°C) and above 37.7°C (95% CrI: 36.7-38.6°C). Sensitivity analysis shows that triatomine fecundity, egg hatching, and molting rates exert minimal influence on the thermal optimum, while assuming that triatomine activity frequency is constant across temperature keeps S(T) constant between 16.9°C and 37.7°C. This indicates that the effect of temperature on the activity frequency of triatomine is a crucial factor affecting the thermal optimum. Spatial analysis of T. cruzi transmission risk across Texas indicates that the highest transmission risk is concentrated in South Texas and the Gulf Coast regions. Moreover, there is high seasonal variation in the transmission risk, with South Texas and the Gulf Coast experiencing higher risk during Spring, whereas elsewhere the risk is highest during Summer.

These findings underscore the critical role of temperature in shaping T. cruzi transmission dynamics. The study highlights the urgent need for more species-specific empirical research on how temperature affects vector life history traits. Such insights are essential to refine predictive models of Chagas disease and to develop more effective, targeted vector control strategies. These efforts will be crucial in advancing current initiatives aimed at mitigating the veterinary and public health impacts of canine Chagas disease.