Predicting present and future suitable habitat of Ixodes scapularis, vector of Lyme disease, in the Texas-Mexico border

Background/Question/Methods

Ticks transmit more pathogen species than any other group of blood-feeding arthropods worldwide, affecting humans, livestock and companion animals. The major impact of tick-borne pathogens on the general public in North America and Europe first became evident with the detection of Borrelia burgdorferi as the causative agent of Lyme disease in the 1980’s. The Ixodes species, e.g., Ixodes scapularis, are competent vectors for B. burgdorferi. Lyme disease is the most prevalent arthropod-borne disease in the US and Europe. Recently the number of reports of infected humans has increased, making Lyme disease acquire a new category as an emergent infectious disease. Lyme disease risk maps have been developed in the US, mainly focusing in the Northeast and Midwest regions of the country. The causative agent, vector, and mammalian reservoirs are distributed throughout the region between the US and Mexico. Nevertheless, no major studies of risk for Lyme disease or evaluation of climate change effects on the spatial or temporal distribution of the vector Ixodes have been conducted in these areas. Maps for present and future suitable habitat distribution (2050; under climate change) in the USA-Mexico border were developed for Ixodes scapularis using a maximum entropy algorithm by correlating the known distribution of the species with climatic variables. Maps were evaluated using the AUC in a ROC plot.

Results/Conclusions

Our findings indicate that I. scapularis is potentially widely distributed in the Texas-northeast Mexico region with a higher probability of occurrence along the Gulf of Mexico coast and with a stable area of distribution of approximately 592,240 Km² that will remain stable for the most part until 2050. Additionally, B. burgdorferi infection was documented in I. scapularis from the US-Mexico border region. Projections of the models for vector distribution and disease risk highlight the relevance of the US-Mexico border as a region of shared ecological risk for Lyme disease. Forecasting based on climate trends provides a tool to adapt strategies in the near future to mitigate the impact of Lyme disease related to its distribution and risk for transmission to human populations in the eastern sector of the Mexico-US region.