Fritzen Juliana T T, Lorenzetti Elis, Oliveira Marcos V, Bon Vinicius R, Ayres Henderson, Alfieri Alice F, Alfieri Amauri Alcindo
Laboratory of Animal Virology, Department of Veterinary Preventive Medicine, Universidade Estadual de Londrina, Rodovia Celso Garcia Cid - Campus Universitário, PO Box 10011, Londrina, Paraná, 86057-970, Brazil.
MSD Animal Health, São Paulo, Brazil.
Trop Anim Health Prod. 2019 May;51(4):887-892. doi: 10.1007/s11250-018-1769-2. Epub 2018 Dec 8.
Neonatal diarrhea is the main cause of morbidity and mortality in calves up to 30 days old, and rotavirus A (RVA) is the main viral etiology. RVA vaccines are one of the main tools for diarrhea control in neonates. The aim of this cross-sectional study was to monitor by RT-PCR the G and P genotypes of RVA strains identified in dairy cattle herds regularly vaccinated with the RVA UK strain (G6P[5]). Of the 14 randomly selected herds, two were excluded because no calf was diagnosed with diarrhea on the day of fecal collection. Another six herds were also excluded from the study because all 20 diarrheic fecal samples evaluated were RT-PCR-negative. In the remaining six herds, 17 (25.4%) of the 67 diarrheic samples were RVA-positive. One G and P amplicon from each herd were selected for nucleotide sequencing. In the phylogenetic analysis, five RVA strains presented the G6P[11] genotype, and one presented the G10P[11] genotype. The G6 genotype present in all RVA field strains clustered into a distinct phylogenetic arrangement (lineage III) of the UK vaccine strain (lineage IV), characterizing the emergence of a phylogenetically distant G6 strain. In addition, we observed the emergence of strains with G10 and P[11] genotypes characterizing failure in heterologous immune protection. These results show the epidemiological importance of constant monitoring of RVA strains in vaccinated cattle herds and the low frequencies of diarrhea and diagnosis of RVA suggest that a regular vaccination program reduces the frequency and severity of RVA diarrhea in suckling calves.
新生犊牛腹泻是30日龄以内犊牛发病和死亡的主要原因，而A组轮状病毒（RVA）是主要的病毒病原。RVA疫苗是控制新生犊牛腹泻的主要工具之一。本横断面研究的目的是通过逆转录聚合酶链反应（RT-PCR）监测在定期接种RVA英国株（G6P[5]）的奶牛群中鉴定出的RVA毒株的G和P基因型。在随机选择的14个牛群中，有2个被排除，因为在粪便采集当天没有犊牛被诊断出腹泻。另外6个牛群也被排除在研究之外，因为所评估的20份腹泻粪便样本的RT-PCR检测均为阴性。在其余6个牛群中，67份腹泻样本中有17份（25.4%）RVA呈阳性。从每个牛群中选择一个G和P扩增子进行核苷酸测序。在系统发育分析中，5株RVA毒株呈现G6P[11]基因型，1株呈现G10P[11]基因型。所有RVA野毒株中存在的G6基因型聚集成英国疫苗株（谱系IV）的一个独特的系统发育排列（谱系III），这表明出现了一个系统发育距离较远的G6毒株。此外，我们观察到具有G10和P[11]基因型的毒株的出现，这表明异源免疫保护失败。这些结果表明，持续监测接种疫苗牛群中的RVA毒株具有流行病学重要性，而腹泻和RVA诊断的低频率表明，常规疫苗接种计划可降低哺乳犊牛RVA腹泻的频率和严重程度。
