Anticorpos contra vírus do grupo da língua azul em caprinos e ovinos do sertão de Pernambuco e inferências sobre sua epidemiologia em regiões semi-áridas

Abstract

The Bluetongue is a non-contagious, infectious disease of ruminants, caused by the Bluetongue virus (BTV), transmitted by insects of the Culicoides genus. The gravity of the clinical signs of the Bluetongue varies according to the species, being the ovine the most severely affected. Serological survey carried out in Brazil indicate that the BT virus is widely diffused among bovine and bubaline; in caprine and ovine, there are few reports of serological survey and two outbreaks with clinical cases. Most publications discuss the epidemiology of the BT in temperate areas that suffer periodic outbreaks. This work was conducted with the objective of estimating the prevalence of antibodies against the BTV in caprine and ovine in the semi-arid region in the State of Pernambuco and to evaluate, preliminarily, the conditions for the maintenance of the Culicoides in semi-arid tropical environments. The serological survey was conducted by probabilistic sampling in two mesoregions of the State of Pernambuco (Semi-arid of Pernambuco and the São Francisco Semi-arid), where sampleswere collected from 41 caprine (n=410) and 40 (n=400) herds. Besides this, information was acquired about the main climate variables (pluviometric precipitation, maximum and minimum temperatures) which interfere in the dynamics of the population and competence of Culicoides to transmit the BTV. Seropositive animals to immunodiffusion in agar gel (IDGA) for the BT were found in 24.39% (11.25≤p≤37.54) of the caprine herds and in 27.5% (13.66≤p≤41.34) of ovines distributed in the mesoregions of Semi-arid region of Pernambuco, which presented 4.84% (2.53≤p≤7.47) of caprine and 4.14% (1.85≤p≤6.43) of seropositive ovine and of the São Francisco of Pernambuco area, 1.00% (0.00≤p≤2.95) of caprine and 4.55% (0.65≤p≤8.44) of seropositive ovine. The estimated prevalence was of 3.90% (2.03≤p≤5.78) and 4,25% (2.27≤p≤6.23) for caprine and ovine, respectively. It was observed that among caprine, positive results were registered in 4.18% (1.87≤p≤6.50) of the sources, 4.88% (0≤p≤11.47) of the reproducers and 2.44% (0≤p≤5.78) of the young animals, while among the ovine 4.29% (1.91≤p≤6.66) of the sources, 5.00% (0≤p≤11.75) of the reproducersand 3.75% (0≤p≤7.91) of the young animals presented positive serology for the BT. No significant differences were reported between positivity for the BT and the mesoregion, species and animal category (χ2; P>0.05). Based on the climatic variables, a rainy period waswell characterized, from December to May, and a dry period, from June to November. The evidence of the presence of antibodies for virus of the BT group distributed equally between herds and mesoregions, indicates that there are epidemiologic conditions for the maintenance of an arboviruses in the semi-arid region, which are discussed in this article.