Spatial Distribution of Equid Exposure tospp. in Goiás State, Midwestern Brazil.

Abstract

This study sought to investigate the presence of anti-spp. antibodies in georeferenced serum samples from equids across all regions of the state of Goiás, while also presenting variables that indicate risk factors for the circulation of rickettsiae, and evaluating the presence of rickettsial DNA in ticks collected from equids and the surrounding environment in the municipalities of Uruaçu and Porangatu, located in the northern region of the state. A total of 1156 equid serum samples provided by the Goiás Agricultural Defense Agency (Agrodefesa) were analyzed for antibodies against 4antigens. Additionally, 39 blood samples were collected from equids during a 3-day field expedition in January 2024, alongside 938 ticks collected from both animals and the environment. In total, 297 adult ticks were randomly selected for molecular analysis and tested by qPCR targeting the rickettsialA gene. Positive samples were further analyzed using cPCR to target theA andA genes. Results revealed that 9.6% (111/1156) of the serum samples were seroreactive to at least oneantigen. Among these, 36% had antibodies against, 18.9% against, 69.4% against, and 14.4% against. Furthermore, the possible antigen responsible for a homologous reaction was found in 3.6% of equids for, and in the same proportion for, while 23.4% of animals showed antibodies for, and none exhibited a homologous reaction to. Meanwhile, 28.2% of the serum samples collected during the field expedition had antibodies against, with 72.7% identifyingas the antigen involved in the homologous reaction. In the logistic regression analysis, the variables of education level, altitude below 500 m, and presence of female mules demonstrated a positive effect on seropositivity. Ticks from animals were identified assensu lato,,, and, while environmental ticks were identified ass.l.,, and. In the qPCR assays, two specimens ofs.l., one of, and one ofamplified a fragment of theA gene. Of these, ones.l. specimen amplified a fragment of both theA andA genes, and onespecimen amplified a fragment of theA gene through conventional PCR. Sequencing confirmed the detection of. These findings highlight the presence of anti-spp. antibodies in equid serum samples from all regions of the state of Goiás, emphasizing the important role of equids as sentinels forspp. To our knowledge, this study represents the largest effort to detect anti-spp. antibodies in equid serum samples in Brazil. Additionally, it is the first nationwide investigation of its kind conducted in collaboration with the Agricultural Defense Agency (Agrodefesa), serving as a significant example of the One Health approach.