# Endemic and zoonotic cycles of cutaneous leishmaniasis depend on vector feeding preferences: An epidemiological model for Southeastern Mexico

## TL;DR

This study uses a mathematical model to show how two sand fly species contribute differently to the spread of cutaneous leishmaniasis in Southeastern Mexico.

## Contribution

The novelty is modeling CL transmission dynamics with vector feeding preferences to identify distinct roles of two sand fly species.

## Key findings

- Lutzomyia cruciata prefers human blood and contributes to zoonotic transmission.
- Bichromomyia olmeca is more rodent-associated and maintains reservoir infections.
- Vector feeding preferences and transmission rates are critical for CL dynamics.

## Abstract

Cutaneous leishmaniasis (CL) is a neglected tropical disease caused by Leishmania spp. parasites. It poses significant public health challenges among economically marginalized communities in endemic regions like Southeastern Mexico. Here, we developed a mathematical model to describe the transmission dynamics of CL in the Yucatan Peninsula region, focusing on two key sand fly vectors: Lutzomyia cruciata and Bichromomyia olmeca.

Transmission was modelled as frequency dependent with Susceptible-Infected dynamics for vectors and rodents, and Susceptible-Exposed-Infected-Susceptible for humans, and accounts for the impact of available blood meals on vector populations. The model was parameterized from published literature for vector and reservoir growth rates and carrying capacities, transmission efficiency, and vector feeding preferences.

The simulations highlight the importance of both vector species in CL transmission, with Lu. cruciata showing a higher preference for human blood, while Bi. olmeca is more frequently associated with rodents. Sensitivity and scenario analyses reveal that the system is highly sensitive to transmission rates and vector feeding preferences, suggesting that Bi. olmeca is necessary to maintain infection among reservoirs, while Lu. cruciata contributes to zoonotic transmission.

Overall, we emphasize that vector species have different roles on leishmaniasis epidemiology due to feeding preferences. Therefore, roviding funding to improve basic knowledge into the epidemiology of this disease, will improve our understanding of its dynamics. Once achieved, policymakers can develop targeted interventions to reduce CL incidence in affected regions to improve the outcomes of public health interventions.

Cutaneous leishmaniasis (CL) is a skin disease caused by parasites and spread by the bites of infected sand flies. It affects vulnerable populations in rural and marginalized communities, such as those in Southeastern Mexico. Although it can cause long-lasting skin sores and social stigma, many aspects of how this disease spreads in the region remain poorly understood. We developed a mathematical model to better understand the transmission of CL in the Yucatan Peninsula, focusing on two sand fly species that feed, at different degrees, on both humans and wild animals. Our results show that the two sand fly species play different roles in disease transmission: one species maintains wild animal infection, while the other transmits the disease to humans. These results derive from data scattered across the study region, which carries significant uncertainty, and represent important information gaps. These limitations highlight the need for further research on how local sand fly populations interact with human and animal hosts, thus improving modelling efforts for disease control.