Herpesvírus bovino em complexos cumulus-oócitos e fluido folicular em vacas sorologicamente positivas

Abstract

The bovine herpesvirus type 1 (BoHV-1) is a highly prevalent virus in cattle herds, promoting productive and economic losses. The increase demand of the use to assisted reproductive technologies in bovine females is a reality in the global agribusiness. Brazil is the most important in vitro (IVP) embryos producer in the world. However, there is a concern of disease transmission from gametes and embryos, thus this subject becomes very important for research so it is very important to have a better knowledge about the presence of BoHV-1 in oocyte cumulus-complexes (COC) and follicular fluid (FF). The aim of this study was to investigate the presence of the BoHV-1 in serologically positive COCs donors, and the presence of viral DNA in nasal and vaginal mucosal, COCs and FF on the reliable conditions of Brazilian dairy cattle producing management. A protocol of immunosuppression with dexamethasone was used to inducing viral recrudescence and the acute phase of the disease in naturally BoHV-1 infected animals. Therefore, 18 serologically positive and not to be vaccinated COCs donors (n = 18) were used. A dexamethasone protocol (0.1 mg / kg / bw) was administered in 12 animals for five consecutive days, the treated group (GT). The remaining animals received saline solution at the same moment of GT, composing the untreated group (GNT). The groups were divided in two subgroups (GT1, n = 6; GT2, n = 6; GNT1, n = 3; GNT2, n = 3) to permit the OPU in four-days intervals for each subgroup during 20 days . The GT1 and GNT1 groups were evaluated on days 0, 4, 8, 12, 16, 20 and GT2 and GNT2 groups were evaluated on days 2, 6, 10, 14, 18 . Parallel to the OPU, clinical exams were performed, as well as collection of blood samples for serum neutralization and leukocyte evaluation, nasal and vaginal swabs for real time PCR and virus isolation. COCs and FF samples were send to real-time PCR. The results show that there was a viral recrudescence in both experimental groups. In GT the neutralizing antibody titres increased more four folds. Herpes characteristic lesions of were also observed in nasal and vaginal mucosa and it was more frequent in GT than in GNT. The results of real-time PCR of nasal and vaginal swabs demonstrated more presence of viral DNA that the GT. But the CCOs and the FF of GT showed higher amount of viral DNA that the GNT, however with peak viral detection on similar moments. A high correlation between the nasal swab and the FF was observed, indicating a possible viremia. The research of BoHV-1 in nasal swabs of COCs donors may be a possible strategy for a sanitary donor selection. The study also showed that despite of the manifestation of clinical signs or increased antibody titre from positive animals for BoHV-1 are sources of contamination for herds livestock and the virus can be spread through CCOs and FF.