Borrelia burgdorferi sensu stricto is the main etiological agent of Lyme disease (LD) in the USA. In Brazil, it is believed that a similar spirochete is the causal agent of the Baggio-Yoshinari syndrome (BYS), a zoonosis also transmitted by ticks, whose clinical manifestations are similar to those of LD. Despite the epidemiological importance, there are no studies reporting the presence and the prevalence of B. burgdorferi among horses in Mato Grosso State. The aim of this study was to detect and measure the frequency of IgG antibodies anti-B. burgdorferi American strain G39/40 in horses in the municipality of Sinop, MT-Brazil, using the indirect enzyme-linked immunosorbent assay (ELISA) for serological diagnosis. Blood samples from 367 horses were collected in 81 farms. An epidemiological questionnaire was applied during the visits to obtain information related to the animals and the farms. From the 367 horses, 214 were positive for B. burgdorferi sensu stricto according to the results of the ELISA test, representing an apparent prevalence of 54.04% [CI = 0.4548051-0.6237234]. Concomitantly, 89 blood samples were taken for molecular analysis by nested polymerase chain reaction (PCR). According to the PCR test results, none of the samples were reactive, although 53 of these samples were reactive according to ELISA. Seventy five farms (92.59%) had at least one reactive horse for B. burgdorferi. Our results support the hypothesis of the presence of anti-Borrelia spp. antibodies in horses in Mato Grosso, reaching a high animal prevalence. Besides that, leisure/sport purposes proved to be a risk factor, with an odds ratio of 3.16. These findings clearly indicate the need of borreliosis control in Sinop and make a significant contribution to the knowledge of the disease in Mato Grosso.

A brucelose é uma importante enfermidade na pecuária nacional. Dentre os agentes causadores desta enfermidade, destaca-se a espécie Brucella abortus. Sendo assim, objetivou- se com este estudo a realização de inquérito sorológico para diagnosticar a sorprevalência de anticorpos anti- Brucella abortus em ovinos da região médio-norte do estado de Mato Grosso, pela detecção de anticorpos anti-Brucella abortus em 255 ovinos, pela técnica do Antígeno Acidificado Tamponado. De acordo com os resultados obtidos, foi verificada frequência de 3,53% ovinos sororreagentes, sendo 3,72% nas fêmeas e 2,5% nos machos. Esta pesquisa revelou elevada ocorrência de anticorpos anti-Brucella abortus em ovinos no Estado do Mato Grosso. Diante disso, o sucesso do Programa Nacional de Controle e Erradicação da Brucelose (PNCEBT) no estado pode ser prejudicado, uma vez que é comum a criação consorciada de pequenos ruminantes e bovinos nessa região, além do considerável risco à Saúde Pública.