Abstract

Background:
Equine habronemiasis is a neglected parasitic disease of horses caused by the gastric nematodes Draschia megastoma, Habronema muscae, and Habronema microstoma. Transmission depends on synanthropic muscid flies and climate, but their environmental suitability in Mexico is poorly defined.

Aim:
To estimate the potential distributions of these nematodes in Mexico, identify major environmental drivers, and quantify spatial overlap to highlight areas of increased coinfection risk.

Methods:
We compiled georeferenced occurrences from GBIF and field surveys, cleaned and spatially thinned records at 1 km, and linked them to 19 WorldClim bioclimatic variables. Correlated predictors were removed and at most eight variables per species were retained. Species distribution models were calibrated in R using a maximum entropy framework, evaluated with AUC and TSS, and thresholded (maxSSS) to obtain binary suitability and overlap maps.

Results:
Models showed discrimination (AUC 0.817–0.924). Draschia megastoma had the broadest suitable area (19.4% of Mexico), Habronema muscae an intermediate range (29.6%), and Habronema microstoma was highly restricted (0.07%). Temperature- and precipitation-related variables, especially annual mean temperature, maximum temperature of the warmest month, and precipitation seasonality, were consistently influential. Spatial overlap was concentrated in central and northeastern Mexico, with no grid cell predicted to be suitable for all three species simultaneously.

Conclusion:
Ecological niche models reveal contrasting niche breadth and partial climatic niche partitioning among equine gastric nematodes in Mexico, delineating hotspots where overlapping suitability may increase coinfection risk and guide targeted diagnosis, surveillance, and integrated fly and anthelmintic control strategies.

Key words: Draschia megastoma; Ecological niche modelling; Habronema microstoma; Habronema muscae; Spirurid nematodes.