Characterization of the Non-Polio Enterovirus Infections Associated with Acute Flaccid Paralysis in South-Western India

Non-polio enteroviruses (NPEVs) have been reported frequently in association with acute flaccid paralysis (AFP) cases during Polio Surveillance Programs (PSPs) worldwide. However, there is limited understanding on the attributes of their infections. This study reports characteristics of NPEVs isolated from AFP cases, investigated during PSPs held in 2009–2010, in Karnataka and Kerala states of south-western India having varied climatic conditions. NPEV cell culture isolates derived from stool specimens that were collected from 422 of 2186 AFP cases (<1–14 years age) and 17 of 41 asymptomatic contacts; and details of all AFP cases/contacts were obtained from National Polio Laboratory, Bangalore. The distribution of NPEV infections among AFP cases and circulation pattern of NPEV strains were determined by statistical analysis of the data. Genotyping of all NPEV isolates was carried out by partial VP1 gene sequencing and phylogenetic analysis. NPEV positive AFP cases were significantly higher in children aged <2 years; with residual paralysis; in summer months; and in regions with relatively hot climate. Genotyping of NPEVs identified predominance of human enteroviruses (HEV)-B species [81.9%—Echoviruses (E): 57.3%; coxsackieviruses (CV) B: 15%; numbered EVs: 8.9%; CVA9: 0.7%] and low levels of HEV-A [14.5%—CVA: 6%; numbered EVs: 8.5%] and HEV-C [3.6%—CVA: 2.6%; numbered EVs: 1%] species, encompassing 63 genotypes. EV76 (6.3%) and each of E3, CVB3 and E9 (4.97%) were found frequently during 2009 while E11 (6.7%), CVB1 (6.1%), E7 (5.1%) and E20 (5.1%) were detected commonly in 2010. A marked proportion of AFP cases from children aged <2 years; presenting with fever; and from north and south interior parts of Karnataka state was detected with E/numbered EVs than that found with CVA/CVB. This study highlights the extensive genetic diversity and diverse circulation patterns of NPEV strains in AFP cases from different populations and climatic conditions.

全球范围内的脊髓灰质炎监测项目（Polio Surveillance Programs, PSPs）中，频繁有非脊髓灰质炎肠道病毒（Non-polio enteroviruses, NPEVs）与急性弛缓性麻痹（acute flaccid paralysis, AFP）病例相关的报道，但目前学界对其感染特征的认知仍较为有限。本研究针对印度西南部气候条件各异的卡纳塔克邦与喀拉拉邦2009-2010年脊髓灰质炎监测项目中排查的AFP病例，分析了分离得到的非脊髓灰质炎肠道病毒的相关特征。研究纳入的毒株来自2186例AFP病例（年龄介于<1岁至14岁）中的422例粪便标本，以及41名无症状接触者中的17名粪便标本的细胞培养分离物；所有AFP病例及接触者的相关信息均取自班加罗尔国家脊髓灰质炎实验室。通过对数据进行统计学分析，明确了非脊髓灰质炎肠道病毒感染在AFP病例中的分布特征，以及病毒株的流行模式；同时通过VP1基因部分测序与系统发育分析，完成了所有非脊髓灰质炎肠道病毒分离株的基因分型。统计分析显示，<2岁的儿童、存在残留麻痹症状的病例、夏季以及气候相对炎热的地区，非脊髓灰质炎肠道病毒阳性的AFP病例占比显著更高。基因分型结果表明，人类肠道病毒（Human enteroviruses, HEV）B组占绝对优势[81.9%——其中埃可病毒（Echoviruses, E）57.3%、柯萨奇病毒B组（coxsackieviruses, CV B）15%、编号肠道病毒8.9%、柯萨奇病毒A9型0.7%]，人类肠道病毒A组（HEV-A）占比为14.5%[柯萨奇病毒A型6%、编号肠道病毒8.5%]，人类肠道病毒C组（HEV-C）占比3.6%[柯萨奇病毒A型2.6%、编号肠道病毒1%]，共涵盖63个基因型。2009年检出频率较高的毒株为EV76（6.3%），以及E3、CVB3与E9（均为4.97%）；2010年则以E11（6.7%）、CVB1（6.1%）、E7（5.1%）与E20（5.1%）为主要流行株。相较于柯萨奇病毒A型/柯萨奇病毒B组，卡纳塔克邦北部与南部内陆地区、<2岁儿童以及伴有发热症状的AFP病例中，埃可病毒/编号肠道病毒的检出占比显著更高。本研究揭示了不同人群与气候条件下，急性弛缓性麻痹病例中非脊髓灰质炎肠道病毒株广泛的遗传多样性与多样化的流行模式。