Investigation of Seroprevalence and the Risk Factors of Ehrlichia and Anaplasma Species Along the Texas–Mexico Border

Background: Ehrlichiosis and anaplasmosis are emerging tick-borne bacterial zoonotic diseases resulting from infections with Ehrlichia and Anaplasma species, respectively, within the family Anaplasmataceae . These tick-borne pathogens represent a growing public health problem in the United States. Materials and Methods: To assess their seroprevalence and risk factors for infection along the Texas–Mexico border, we conducted a cross-sectional seroprevalence study using plasma samples obtained from 616 adults residing in Starr County, Texas. Plasma samples were screened for IgG reactivity to Ehrlichia and Anaplasma antigens using a dual-spot indirect immunofluorescent assay. Ticks were also collected from this region and tested for Anaplasmataceae DNA. Results: Seroprevalence was higher for cases of Anaplasma spp. (10.4%) than Ehrlichia spp. (4.8%) and Anaplasmataceae unspecified (6.9%). Age and gender were both significantly associated with seropositivity. PCR testing of the collected ticks revealed a 12.4% (12/97) positivity for Ehrlichia canis, all detected in Rhipicephalus sanguineus (Brown dog) ticks, but none were positive for Anaplasma species. Conclusion: These findings suggested that Ehrlichia and Anaplasma species are endemic in the region and highlighted the need for ongoing surveillance and public health interventions.