HoBi-like pestivirus infection in an outbreak of bovine respiratory disease.

HoBi-like is an emerging pestivirus of the family Flaviviridae detected in cattle herds and biological products of bovine origin in many parts of the world, causing disease similar to that observed in bovine viral diarrhea virus (BVDV) infections. In this study we reported the detection of HoBi-like pestivirus in an outbreak of respiratory disease in calves from Brazil, seropositive for viruses of the bovine respiratory disease complex (BRDC). Thus, serum samples and nasal swabs were collected from calves up to one year old, presenting or not clinical signs of respiratory disease. Serum samples were submitted to virus neutralization test (VNT) for BVDV-1, BVDV-2, bovine herpesvirus-1 (BoHV-1), bovine respiratory syncytial virus (BRSV) and bovine parainfluenza-3 (BPIV-3). These samples were also tested for the presence of pestiviruses (BVDV-1, BVDV-2 and HoBi-like) and BoHV-1 by RT-PCR and PCR, respectively. Nasal swabs were analyzed by RT-PCR for pestiviruses, BRSV and BPIV-3. VNT results showed high serological prevalence and a wide range of antibodies titers, for all viruses studied, in calves of different age groups. The RT-PCR amplified the 5'UTR and E2 regions of pestiviruses of four calves, from both nasal swabs and serum samples, which sequencing identified the HoBi-like pestivirus. This is the first detection of HoBi-like in nasal secretions of calves in an outbreak of respiratory disease in Brazil, along with the serological detection of other respiratory viruses. We concluded that HoBi-like pestivirus should be considered as part of the BRDC, as a differential diagnosis, to take correct measures of control and prophylaxis.

Bovine respiratory syncytial virus seroprevalence and risk factors in non-vaccinated dairy cattle herds in Brazil.

BACKGROUND: The cattle industry is one of the most important Brazilian agribusiness sectors and is a strong contributor to the national economy. Annually about 44.6 million calves are bred, which makes the optimal management of these animals extremely important. Several diseases can affect the initial stages of the bovine production chain, being the bovine respiratory syncytial virus (BRSV) one of the most relevant pathogens. This study aimed to characterize the epidemiology of BRSV infection in dairy cattle herds of São Paulo State, Brazil, using serological and risk factors analyses. For that, 1243 blood samples were collected of animals from 26 farms and a questionnaire about possible risk factors for BRSV prevalence was performed. The obtained blood sera were analyzed using virus neutralization test (VNT). RESULTS: VNT results showed high BRSV prevalence in dairy cattle herds, reaching 79.5% of seropositivity. The BRSV seroprevalence among studied farms ranged from 40 to 100%. The analysis of risk factors indicated that the age group and the occurrence of coinfection with bovine herpesvirus 1 (BoHV-1) and bovine viral diarrhea virus 1 (BVDV-1) should be associated with a higher prevalence of BRSV, while natural suckling was considered a protective factor. CONCLUSIONS: The study showed that adult animals over 1 year old are an important risk factor for the high seroprevalence of BRSV in herds. The high BRSV prevalence associated with BoHV-1 and BVDV-1 suggests that biosecurity measures should be applied in order to reduce viral dissemination. Additionally, the natural suckling may be an important management to protect calves from high BRSV seroprevalence.

Comparação dos testes de virusneutralização contra os genótipos 1 e 2 do vírus da diarreia viral bovina (BVDV-1 e BVDV-2) em bovinos de rebanhos naturalmente infectados / Comparison of virusneutralization tests against genotypes 1 and 2 of the bovine viral diarrhoea virus (BVDV-1 and BVDV-2) in cattle of naturally infected herds

Os resultados dos testes de virusneutralização (VN) contra os genótipos do vírus da diarreia viral bovina (BVDV-1 e BVDV-2), bem como os respectivos títulos de anticorpos, foram comparados em 1.925 amostras de soro sanguíneo obtidas de rebanhos bovinos naturalmente infectados e não vacinados contra o BVDV, provenientes dos Estados de São Paulo e Minas Gerais. A proporção de amostras reagentes entre os genótipos foi analisada pelo Teste de McNemar, e os títulos de anticorpos das amostras reagentes ao BVDV-1 e ao BVDV-2 foram comparados pelo Teste de Wilcoxon. Não foi verificada discordância na proporção de bovinos reagentes ao BVDV-1 e ao BVDV-2 (P>0,05). No entanto, houve discordância entre os títulos de anticorpos detectados nos testes de VN contra os genótipos 1 e 2 do BVDV (P<0,0001). Embora a proporção de animais reagentes contra ambos os genótipos do BVDV tenha sido semelhante, resultados falso-negativos seriam obtidos se 67 amostras (3,5 por cento) tivessem sido submetidas apenas ao teste de VN, para o BVDV-1, e em 51 amostras (2,65 por cento), apenas para o BVDV-2. Alguns rebanhos apresentaram títulos de anticorpos superiores para o BVDV-1, enquanto outros para BVDV-2, demonstrando assim a ocorrência da infecção pelos diferentes genótipos do vírus entre os rebanhos analisados. Portanto, tais resultados demonstraram a necessidade da inclusão de ambos os genótipos do BVDV nos testes de VN.

The virusneutralization test (VN) results against bovine viral diarrhoea virus genotypes (BVDV-1 and BVDV-2), and the respective titers of antibodies, were compared in 1,925 serum samples collected from unvaccinated and naturally infected cattle herds, located in the states of São Paulo and Minas Gerais, Brazil. The proportion of reagent samples among the genotypes was evaluated by McNemar test and the antibody titers against BVDV-1 and BVDV-2 were compared by Wilcoxon test. There were no disagreement in the proportion of BVDV-1 and BVDV-2 reagent samples (P>0.05). However, there was a disagreement among titers of antibodies detected in the VN tests against BVDV genotypes (P<0.0001). Although the proportion of reagent animals to BVDV genotypes was similar, false negative results would be obtained if 67 samples (3.5 percent) had been submitted only to VN test against BVDV-1, and 51 samples (2.65 percent) only against BVDV-2. Some herds had higher titers of antibodies for BVDV-1, while others for BVDV-2, thus demonstrating the occurrence of infection by different virus genotypes among the analyzed herds. Therefore, these results demonstrated the need for inclusion of both BVDV genotypes in VN tests.