Genetic diversity of bovine Picobirnavirus, Brazil.

Picobirnaviruses (PBVs) are emerging and opportunistic viruses with possible zoonotic potential. In this study, we present the detection, molecular characterization, and genotypic differentiation of PBVs from genogroup I in bovine stool samples from different Brazilian regions. A high proportion of PCR-positive samples (23.4%) was detected in a total of 77 analyzed. Nucleotide identity, alignment, and phylogenetic analyses revealed high diversity among the studied sequences. The results obtained indicate, for the first time, the circulation of bovine PBVs belonging to genogroup I in different Brazilian states, with heterogeneous phylogenetic-clustering profiles.

Longitudinal study of bovine rotavirus group A in newborn calves from vaccinated and unvaccinated dairy herds.

Reports of rotavirus excretion in calves usually result from cross-sectional studies, and in face of the conflicting results regarding protection of calves born to vaccinated dams against diarrhea, the aim of the present study was to evaluate rotavirus excretion in dairy calves born to vaccinated or unvaccinated dams, to identify the genotypes of bovine rotavirus group A (RVA) strains isolated from these animals as well as to investigate characteristics of the disease in naturally occurring circumstances throughout the first month of life. Five hundred fifty-two fecal samples were taken from 56 calves, 28 from each farm and, in the vaccinated herd, 11/281 samples (3.91%) taken from six different calves tested positive for RVA while in the unvaccinated herd, 3/271 samples (1.11%) taken from 3 different calves tested positive. The genotyping of the VP7 genes showed 91.2% nucleotide sequence identity to G6 genotype (NCDV strain), and for the VP4 gene, strains from the vaccinated herd were 96.6% related to B223 strain, while strains from the unvaccinated herd were 88% related to P[5] genotype (UK strain). Genotypes found in this study were G6P[11] in the vaccinated herd and G6P[5] in the unvaccinated herd. All calves infected with rotavirus presented an episode of diarrhea in the first month of life, and the discrepancy between the genotypes found in the commercial vaccine (G6P[1] and G10P[11]) and the rotavirus strains circulating in both vaccinated and unvaccinated herds show the importance of keeping constant surveillance in order to avoid potential causes of vaccination failure.

Molecular detection and phylogenetic analysis of bovine astrovirus in Brazil.

Bovine astrovirus (BoAstV) is associated with gastroenterical disorders such as diarrhea, particularly in neonates and immunocompromised animals. Its prevalence is >60 % in the first five weeks of the animal's life. The aim of this study was to detect and perform a phylogenetic analysis of BoAstV in Brazilian cattle. A prevalence of 14.3 % of BoAstV in fecal samples from 272 head of cattle from different Brazilian states was detected, and 11 samples were analyzed by nucleotide sequencing. The majority of positive samples were obtained from diarrheic animals (p < 0.01). Phylogenetic analysis revealed that Brazilian samples were grouped in clades along with other BoAstV isolates. There was 74.3 %-96.5 % amino acid sequence similarity between the samples in this study and >74.8 % when compared with reference samples for enteric BoAstV. Our results indicate, for the first time, the occurrence of BoAstV circulation in cattle from different regions of Brazil, prevalently in diarrheic calves.

Long-term stability studies on protection against Newcastle disease by commercial live vaccine used in Brazil.

The thermostability (TS) and efficacy offered by live vaccines against Newcastle disease strains B1, La Sota, VG-GA and Ulster, produced or imported by four Brazilian laboratories, were evaluated during their validity period. Kinetic profiles were obtained from samples conserved in refrigerators during 0, 4, 8, 12, 16, 20 and 24 months after their manufacturing. The statistical analysis of the vaccine titre effect obtained by the fresh air (FA) method showed that the vaccine profiles were parallel and coincident, presenting a significant descending trend. The vaccine titres and efficiency proofs at the end of the validity period were above the level of legislation requirements and showed an average loss in titre of 0.40 and 0.66 log(10,) within the first and second validity years, respectively. The titre obtained by TS, within the month after manufacturing, had no significant difference from the titre obtained by FA within 24 months after manufacturing, being their pairs of observations positively correlated (r=0.49, p=0.0003), showing that the TS method, which anticipates the vaccines' performance at the end of the validity period, can substitute the FA method 24 months after manufacturing.

Isolation of bovine coronavirus (BCoV) in monolayers of HmLu-1 cells

A partir de 20 amostras fecais de bezerros, com quadro clínico de diarréia, positivas para BCoV por hemaglutinacão/inibicão da hemaglutinacão (HA/HI), procedeu-se o isolamento viral em monocamadas de células da linhagem HmLu-1. Até a quinta passagem seriada, 13 apresentaram efeito citopático do tipo sincicial, semelhante à amostra padrão Kakegawa de BCoV. Ao serem submetidas a uma reacão de soroneutralizacão com gamaglobulina anti-coronavírus bovino, 8 delas foram consideradas positivas, uma vez que o efeito citopático foi neutralizado. Ao serem tituladas e submetidas à reacão de soroneutralizacão em microplacas, apenas 3 delas puderam ser confirmadas como positivas. As células da linhagem HmLu-1 mostraram-se permissivas para o isolamento de BCoV, todavia a baixa intensidade na replicacão viral demonstrou ser necessário o desenvolvimento de novas metodologias para se poder alcancar esse intuito e a confirmacão do isolamento por soroneutralizacão.

Implicações técnicas da vacinação na resposta imune contra o vírus da febre aftosa / Techinical implications of the vaccination in the immune response against the foot-and-mouth disease virus

Na bovinocultura brasileira, a vacinação contra o vírus da Febre Aftosa (FA) é fundamental para a fase inicial de erradicação da enfermidade. Mesmo a qualidade da vacina tendo controle rígido feito pelos órgãos oficiais, restam variáveis técnicas ainda não monitoradas como manipulação, transporte e conservação pelo consumidor, dose, local e forma de aplicação que interferem na resposta imune, preocupações essas, que direcionam o presente estudo. Assim, pela pesquisa de anticorpos neutralizantes do vírus da FA em placas de microtitulação com cultivo de células BHK-21, foram determinados os títulos, calculados em logaritmo decimal (SN), em soros sanguíneos de bovinos vacinados conforme o protocolo apresentado. No primeiro grupo com 25 animais, a média de SN foi igual a 2,37 e 2,19, respectivamente, 30 e 180 dias após a vacinação, cuja vacina foi manejada por especialista com todos os cuidados técnicos recomendados. Outro grupo com 140 bovinos, distribuídos em 5 fazendas distintas, apresentou média de SN igual a 1,66 e 1,5l depois de 30 e 180 dias após a vacinação, cuja vacina foi manejada sem acompanhamento técnico e por indivíduos não especializados. Finalmente um terceiro grupo com 10 animais, que ficaram sem vacinação, apresentou média de SN igual a 0,82 e 0,81, também 30 e 180 dias após a aplicação do placebo. Assim, só os cuidados com a qualidade da vacina são insuficientes para proporcionar títulos satisfatórios que determinam proteção dos rebanhos contra o vírus da FA, uma vez que a literatura pertinente considera rebanhos com 1,52 de média do SN como tendo 50% dos animais protegidos, e com 1,70 como tendo mais de 70% de proteção, no período de até 7 meses.