Técnica rápida de neutralização viral para a detecção de anticorpos contra o vírus da Diarréia Viral Bovina (BVDV) no leite

Abstract

The identification of bovine viral diarrhea virus (BVDV) positive herds through detection of antibodies in milk may viabilize large scale control/eradication programs. With this objective, the virus neutralization test (VN) was adapted to detect BVDV antibodies in milk. The adaptation consisted of a reduction in the time of incubation followed by detection of viral antigens in the indicator cells by immunofluorescence (IFA) and allowed readings at 24 hours. The rapid virus neutralization test (RVN) was initially tested in 1,335 serum samples, showing a 93.7% sensitivity and 91.1% agreement with the traditional VN. The RVN was also used to test 423 bovine sera that were toxic for cell culture in the traditional VN test, detecting 316 (74.7%) positive samples. Testing of matched serum and milk samples from BVDV seropositive cows showed that the VNR can detect antibodies in the milk of cows with serum neutralizing titers as low as 10. Anti-BVDV neutralizing activity was detected in milk of 97. 4% (191/196) of cows with serum titers ³320; in 92.9% (79/85) of cows with titers of 160; in 88% (59/67) of cows with serum titers of 80. The frequency of BVDV antibodies in milk was 76.9% (40/52) for cows with serum titers of 40; 61.3% (19/31) for cows with titers of 20 and 33.3% (10/30) for cows with serum titers of 20. These results demonstrate that the RVN test is adequate for detecting BVDV antibodies in milk, mainly in cows having moderate to high serum titers, and therefore may be used for testing bulk milk samples to identify herds with viral activity. The use of this test may viabilize large scale programs for control/eradication of BVDV infection. It allows to assay a large number of samples and identify positive herds through testing milk routinely submitted for somatic cell counts (SCC), reducing costs with individual sample collection, shipping and testing.

Seroprevalence and associated factors of infectious bovine rhinotracheitis and bovine viral diarrhea in dairy cows in the Caparaó region, Espírito Santo, Brazil

“…BVD is distributed worldwide, and its seroprevalence is estimated to range between 46% and 78% (RICHTER et al, 2019). In Brazil, several serological studies have demonstrated a wide distribution and high prevalence rate in several states, as follows: Bahia, 56% (NoRoNHA et al, 2001); Paraíba, 39% (FERNANDES et al, 2016); Goiás, 54% (BRITo et al, 2010); Minas Gerais, 61% (MINEo et al, 2006); São Paulo, 56% (SAMARA et al, 2004); Paraná, 61% (AlFIERI et al, 2004); and Rio Grande do Sul, 58% (SCHERER et al, 2002). However, until now, no data were reported for the state of Espírito Santo.…”