Approaching equine infectious anemia in regions dominated by grade-working animals - a case of Pará, a state in the Brazilian Amazon.

Considering that control strategies for Equine Infectious Anemia, based on the serological diagnosis of equids and the removal of positive animals, may not be optimal for developing countries with an absolute predominance of grade working animals, this study aimed to address this issue based on the epidemiological situation of the disease in Pará, a state in the Brazilian Amazon. Pará was divided into five regions, and within each region a pre-established number of farms were randomly selected. Within each farm, a pre-set number of animals were randomly selected and submitted to Agar Gel Immunodiffusion test. A questionnaire was administered on the farms to identify risk factors for the disease. In total, 2,718 equids (horses, mules and donkeys) from 654 farms were tested. The prevalence at farms and animal level in the state was 34.5% (95% CI: 30.8-38.4) and 15.8% (95% CI: 14.4-17.4), with significant regional differences. Equids from farms with 11 or more equids (OR = 2.32 [95% CI: 1.38-3.92]) and those that shared water sources with other farms (OR = 1.76 [95% CI: 1.26-2.46]) were more likely to be infected. The average sensitivity of the surveillance system for detecting infected farms ranged from 0.92 to 1.14%, which is insufficient to disrupt the endemic balance of the disease in the state, demanding a reassessment. The key elements of this process, as well as the potential strategies to be implemented, have been discussed in the context of Pará and can be extended to regions with similar characteristics.