Fatores de risco associados à prevalência de anticorpos contra brucelose em equídeos do Oeste do Pará, Brasil

Abstract

The state of Pará has one of the largest equine populations in Brazil, with more than 800,000 head. Most of these animals are found on farms (farm horses) with livestock farming and are used in the management of cattle and buffaloes. Furthermore, in urban areas of the state, horses are commonly used as a means of transport for transporting materials (cart horse) and in sports such as vaquejada, archery and barrel competitions and horseback riding (sport horse). Infectious diseases cause concern for equine breeders due to the damage to the animals' health, economic and public health impacts in the case of zoonoses. In this context, equine brucellosis stands out, a chronic, infectious, zoonotic disease caused by bacteria of the genus Brucella sp., especially in areas where bovine brucellosis is endemic. The disease requires mandatory notification to the Official Veterinary Service of Brazil when there is any suspected case according to the World Organization for Animal Health (WHO). Considering the significant equine herds and the lack of epidemiological studies in Pará, especially in the western region of the state, the objective was to determine the prevalence of antibodies against Brucellosis in horses raised in western Pará and identify possible risk factors associated with this disease in three diverse groups: farm, sport and cart horses. From a preliminary cross-sectional study with sampling at two levels per cluster for farm horses that included 75 properties in 14 municipalities and with convenience sampling to collect carriage and sport horses, a total of 1,059 equids were included in the study, being 1039 horses, 13 donkeys and 7 mules. Serum samples were obtained via jugular venipuncture using a sterile vacuum system with tubes without anticoagulant. The blood was centrifuged at 2000 x g for 10 min, and the serum was aliquoted and stored at -35°C for analysis. During sample collection, an epidemiological questionnaire was used to obtain information about animal characteristics, management and local conditions that may act as risk factors for the seroprevalence of the disease. To detect antibodies against equine brucellosis, the Buffered Acidified Antigen test (AAT) and Seroagglutination in Tubes with 2-mercaptoethanol (2-ME) were used as screening to confirm the results. Serological analyzes were carried out at the Animal Health Laboratory (LARSANA) of the Federal University of Western Pará. The data were tabulated to determine the frequency of seropositive and seronegative horses and the prevalence. Univariate analysis was performed using the Chi-square test to investigate the association between the prevalence of antibodies and possible risk factors associated with the diseases. A logit-type binary logistic regression with Backward elimination of terms including the risk factors considered. Variables with P<0.05 were maintained in the final model. The data were analyzed using Minitab 17 software. And the 95% confidence interval was calculated using Prism software. Of the 1,059 animals sampled, 44 (4.05% - 95% CI: 3-5.5) tested positive in the AAT test. Positive samples in the AAT test were confirmed using the 2-ME test and of these 11 animals were positive, 15 inconclusive and 18 negative. Considering only the results confirmed by 2-ME, the prevalence of equine brucellosis at animal level in horses in the western region of Pará was 1.03% (95% CI: 0.5-1.8). Among the factors considered, only the Southwest Mesoregion of Pará (P = 0.047) interfered with the prevalence of anti-Brucella sp antibodies. The presence of Brucellosis-positive animals was not associated with reproductive problems reported by animal owners. This is the first report of equids seropositive for Brucellosis in the region, which contributes to the knowledge of the epidemiology of the disease and confirms the potential risk of the equine species to public health since they are in direct contact with humans and other animals.