Evolutionary study of potentially zoonotic hepatitis E virus genotype 3 from swine in Northeast Brazil

Hepatitis E virus (HEV), an emerging virus associated with acute hepatic disease, leads to thousands of deaths worldwide. HEV has already been reported in Brazil; however, there is a lack of epidemiological and molecular information on the genetic variability, taxonomy, and evolution of HEV. It is thus unclear whether hepatitis E is a neglected disease in Brazil or it has low relevance for public health in this country. Here, for the first time, we report the presence of HEV in Northeast Brazil. A total of 119 swine faecal samples were screened for the presence of HEV RNA using real-time polymerase chain reaction (RT-PCR) and further confirmed by conventional RT-PCR; among these, two samples were identified as positive. Molecular evolution analyses based on capsid sequences revealed that the samples had close proximities to HEV sequences belonging to genotype 3 and were genetically related to subtype 3f isolated in humans. Parsimony ancestral states analysis indicated gene flow events from HEV cross-species infection, suggesting an important role of pig hosts in viral spillover. HEV’s ability for zoonotic transmission by inter-species host switching as well as its possible adaptation to new animal species remain important issues for human health.

戊型肝炎病毒（Hepatitis E virus, HEV）是一种与急性肝病相关的新发病毒，在全球范围内造成数千人死亡。巴西此前已有戊型肝炎病毒的相关报道，但目前仍缺乏关于该病毒遗传变异、分类学及演化的流行病学与分子生物学数据。因此目前尚不清楚，在巴西境内戊型肝炎是否属于被忽视的传染病，亦或是对该国公共卫生的影响程度较低。本研究首次报道了巴西东北部地区存在戊型肝炎病毒。本研究共纳入119份猪粪便样本，采用实时聚合酶链反应（real-time polymerase chain reaction, RT-PCR）筛查戊型肝炎病毒RNA，并通过常规逆转录聚合酶链反应（conventional RT-PCR）进一步验证，最终检出2份阳性样本。基于衣壳序列的分子演化分析显示，本次检出的阳性样本与属于基因型3的戊型肝炎病毒序列高度相似，且与从人体分离得到的3f亚型毒株具有密切的遗传亲缘关系。简约祖先状态分析结果表明，戊型肝炎病毒存在跨物种感染的基因流事件，提示猪宿主在病毒溢出过程中发挥了关键作用。戊型肝炎病毒通过跨物种宿主切换实现人畜共患传播的能力，以及其对新动物宿主的潜在适应性，仍是关乎人类健康的重要公共卫生议题。