Abstract
BackgroundAcute flaccid paralysis (AFP) surveillance was conducted as part of the World Health Organization’s strategy for completely eradicating poliomyelitis and leaving non-polio enteroviruses NPEVs as one of the main potential causes of AFP. We aimed to detect NPEV in association with AFP.MethodsWe used 459 isolates reported to be Negative Polio and some NPEVs by the World Health Organization Polio Regional Reference Laboratory (Thailand), which had been obtained during polio surveillance programmes conducted in Thailand in 2013–2014. Of 459 isolates, 35 belonged to the genus Enterovirus by RT-PCR and genotyping by DNA sequencing.ResultsThis study found 17 NPEV genotypes, with 3, 13 and 1 belonging to enterovirus (EV) species A (EV-A), EV-B, and EV-C, respectively. The EV-A types identified included coxsackievirus A2 (CA2), CA4, and EV71, typically associated with hand, foot and mouth diseases. EV-B is the most prevalent cause of AFP in Thailand, while CA21 was the only type of EV-C detected. The EV-B species (13/35; 76.5%) constituted the largest proportion of isolates, followed by EV-A (3/35; 17.6%) and EV-C (1/35; 5.9%). For the EV-B species, Echovirus (E) 30 and CVB were the most frequent isolates. E30, CVB, E14, and E6 were considered endemic strains.ConclusionNPEVs, e.g. CA4, are reported for the first time in Thailand. Despite some limitations to this study, this is the first report on the circulation patterns of NPEVs associated with AFP in Thailand. AFP surveillance has unearthed many unknown NPEVs and, the cases of death due to AFP occur annually. Therefore, it is important to study NPEVs in the wake of the eradication of poliovirus in the context of the continued incidence of paralysis.
Highlights
Acute flaccid paralysis (AFP) surveillance was conducted as part of the World Health Organization’s strategy for completely eradicating poliomyelitis and leaving non-polio enteroviruses Non-polio enteroviruses (NPEV) as one of the main potential causes of AFP
This study was not part of the routine surveillance programme based on the typing of all NPEV isolates; we identified EVs using universal pan-EV primers with Reverse-transcriptase polymerase chain reaction (RT-PCR) specific to the viral polyprotein 1 (VP1) region as universal primers of EV [27]
All 459 originally unidentified isolates isolated from RD cells and reported to be NPEVs were confirmed to be EVs by RT-PCR specific to the VP1 region
Summary
Acute flaccid paralysis (AFP) surveillance was conducted as part of the World Health Organization’s strategy for completely eradicating poliomyelitis and leaving non-polio enteroviruses NPEVs as one of the main potential causes of AFP. The AFP surveillance system available in each country can detect non polio enteroviruses some are rare types such as EVC95 EVC105 in Northern India, EVC99 and EVA120 in Nigeria [18, 19], so it is necessary to study the isolated enterovirus genotype as a source for further study in each country. We must be alert for NPEV in AFP cases Against this background, identifying the genotypes circulating in the country may improve our understanding of the epidemiology of EV infection; in the wider context of polio eradication, it may provide assurance that Poliovirus is not being overlooked. Laboratory data were analysed to provide an overview of the NPEV genotypes identified and their occurrence, diversity, and patterns of circulation in cases of AFP identified in Thailand in 2013 and 2014
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