Animais persistentes infectados pelos vírus da Diarreia Viral Bovina em rebanhos leiteiros não vacinados criados em regime semi-intensivo: freqüência, fatores de risco e georreferenciamento de focos

Abstract

The Bovine Viral Diarrhea (BVD) is a major infectious disease of cattle. Persistently infected (PI) animals by bovine virus diarrhea virus (BVDV) have great importance in the epidemiology of the disease, due to the elimination of high virus titers in all their secretions and excretions, serving as reservoirs of the virus, and constant source of infection for susceptible animals. In this way, the research aimed to identify persistently infected animals in dairy cattle not vaccinated, raised in semi-intensive system in the state of Maranhão. The study was realized in 92 dairy herds, belonging to 23 districts located in the regions of Açailândia, Bacabal, Ilha de São Luis, Imperatriz and Pedreiras. 920 dairy females stratified according to age band (< 3 years, between 3-7 years and > 7 years) were sampled. Serum samples were analysed through the AcELISA and AgELISA techniques for the identification of PI animals and it was applied an epidemiological questionnaire during the sample collect to research the factors that could be associated to persistent infection. From the 920 serum analysed samples, 0.86% (8/920) were positive to AgELISA e not reagent for AcELISA, thus classified as persistently infected animals. Only the regions of Imperatriz and Bacabal had PI animals, they obtained frequency of 2.14% (6/280) and 1% (2/200), respectively. In the 23 studied 12 (52.17%) had PI animals, with 17.39% (16/92) of the herds as at least one animal with viremia. The highest frequency (1.08% - 3/276) of PI animals was observed in the category of animals under the age of three years and the lowest (0.72% - 2/276) in females over the age of seven years. Among the variables considered risk factors, contact with fomites and animals from neighboring herds were statistically significant (P <0.05) associated with the presence of PI animals. The spatial study demonstrated that BVDV infection is widely distributed in the dairy regions of the state of Maranhão. These results demonstrate the significant spread of BVDV in the study regional characterized by the identification of animals PI.