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Year : 2016  |  Volume : 34  |  Issue : 1  |  Page : 22--26

Non-polio Enteroviruses in Karnataka, India: Virological surveillance of acute flaccid paralysis cases (July 1997–2013)

H Hanumaiah1, CG Raut1, DP Sinha1, PN Yergolkar2,  
1 National Institute of Virology, Bengaluru Unit, Bengaluru - 560 029, Karnataka, India
2 Immunization and Vaccine Development Unit, SEARO, New Delhi, India

Correspondence Address:
C G Raut
National Institute of Virology, Bengaluru Unit, Bengaluru - 560 029, Karnataka
India

Abstract

Background and Objectives: Since 1997 National Institute of Virology, Bangalore Unit involved in WHO's Acute flaccid paralysis paediatric cases surveillance programme to isolate and detect polioviruses. Stool samples yielded not only polioviruses but also Non-Polio enteroviruses. This report is an overview of non-polio Enterovirus (NPEV) epidemiology in Karnataka state, India for the period of 16-years and 6 months from July 1997–2013. Methods: A total of 19,410 clinical samples were processed for virus isolation as a part of acute flaccid paralysis (AFP) surveillance for Global Polio Eradication Programme in India at National Polio Laboratory, at Bengaluru. NPEV detection was performed by virus isolation on cell culture according to World Health Organisation recommended protocols. Results: A total of 4152 NPEV isolates were obtained. The NPEV isolation rate varied from year to year but with a total NPEV rate of 21.39%. Conclusion: A seasonal variation was noted with high transmission period between April and October with peaks in June–July. The male to female ratio was 1:1.2. The isolation of NPEV decreased significantly with the increase in age. Epidemiology of NPEVs from AFP cases in Karnataka is described.

How to cite this article:
Hanumaiah H, Raut C G, Sinha D P, Yergolkar P N. Non-polio Enteroviruses in Karnataka, India: Virological surveillance of acute flaccid paralysis cases (July 1997–2013).Indian J Med Microbiol 2016;34:22-26

How to cite this URL:
Hanumaiah H, Raut C G, Sinha D P, Yergolkar P N. Non-polio Enteroviruses in Karnataka, India: Virological surveillance of acute flaccid paralysis cases (July 1997–2013). Indian J Med Microbiol [serial online] 2016 [cited 2020 Oct 27 ];34:22-26
Available from: https://www.ijmm.org/text.asp?2016/34/1/22/174115

Full Text

 Introduction



Acute flaccid paralysis (AFP) is defined as acute or sudden onset of weakness or paralysis of a limb characterised as flaccid (reduced tone) in a child <15 years of age.[1] The surveillance of AFP is the detection, investigation of flaccid paralysis onset in children under 15 years or any other suspected poliomyelitis case in a person of any age as followed for Global Poliomyelitis Eradication Initiative (GPEI) of the Government of India and the World Health Organisation (WHO).

AFP can be caused by some bacteria, parasites, insects and various viruses such as Enteroviruses, mumps virus, rabies virus, some arboviruses such as Togavirus, Japanese encephalitis virus, Human Immunodeficiency Virus, West Nile virus, herpes simplex virus, cytomegalovirus, varicella-zoster virus and Epstein-Barr virus. There are no unique clinical symptoms to differentiate between different cases of AFP caused by different agents.[2]

Non-polio Enterovirus's (NPEV) is a group of viruses belonging to the Picornaviridae family that contain a positive strand RNA covered by an icosahedral capsid. They are one of the main factors of AFP in children, transmitted through the faecal-oral route and respiratory droplets and can replicate in gastrointestinal tracts and Nasopharynx.[3] Historically, poliovirus serotypes 1, 2 and 3 were the most significant members of Enteroviruses causing AFP and residual paralysis by infecting the motor neurons which lead to irreversible weakness of lower limb and respiratory muscles.[4] Mass vaccination against poliovirus with the Sabin vaccine or the oral poliovirus vaccine started in 1989[5] and has decreased the number of poliomyelitis cases globally.

AFP surveillance is considered as the most efficient method for evaluating the GPEI. Two stool specimens are collected 24 hrs apart within 14 days of onset of paralysis, and specimens are transported to the designated polio laboratory ensuring reverse cold chain. All cases are followed up for 60 days to determine the presence of residual paralysis. It endeavours to report all flaccid paralysis including Guillain-Barre syndrome and excluding trauma in children below 15 years.[6],[7],[8]

Although the rate of poliomyelitis has been declined through the mass vaccination program, AFP and residual paralysis cases are reported continuously. The cases occur all around the world, even in the poliovirus eradicated countries.[8],[9],[10] This situation has made scientists to study on different agents of AFP in children. As NPEV's are capable of replication in motor neurons, they could be considered as a probable cause of this huge prevalence of AFP.[8],[9]

 Methods



Acute flaccid paralysis surveillance for Global Poliomyelitis Eradication Initiative in Karnataka (July 1997–2013)

A total of 19,410 stool specimens were collected from 9698 AFP cases (n = 19,410, most of the cases had two stool specimens collected at an interval of 24–48 hrs), during the 16½ years period between July 1997 and December 2013, in Karnataka, India supported by Department of Health, Government of Karnataka and National Polio Surveillance Project and virological investigations were performed at National Polio Laboratory, National Institute of Virology (NIV), Bengaluru Unit.

Virus isolation

The stool samples were processed according to the WHO protocols accepted for the program. It was inoculated in human rhabdomyosarcoma (RD) and human poliovirus receptor-CD155 expressing recombinant murine (L20B) cell lines. The stool specimens producing a cytopathic effect (CPE) in RD cells are passed on to L20B cells, if CPE is not produced, then they are considered as NPEVs. The infected cells were harvested and kept frozen (−20°C).

 Results



A total of 4152 NPEV's were isolated from 19,410 samples from 30 districts of Karnataka during the period.

Annual and seasonal non-polio Enterovirus isolation rate

The NPEV isolation rate varied from year to year and from 14.85% to 30.58% with an average of 21.45%, suggesting a relatively high prevalence [Figure 1].{Figure 1}

In 1997, AFP surveillance specimens were received from July and NPEV rate obtained from 1998 onwards it was the annual rate. Though NPEV positive AFP cases were detected throughout the year some seasonal specificity is observed: A low period of transmission was observed during the months of January to March and November and December months with a high period of transmission from April to October with a peak in Monsoon (July–September) [Figure 2]. The monthly prevalence of NPEV for the corresponding years can be well determined as shown in [Figure 3].{Figure 2}{Figure 3}

District wise

Karnataka state investigated in the study has been divided into three zones as North Karnataka (NK), South Karnataka (SK) and Coastal Karnataka (CK) based on meteorological parameters.[3] NPEV positivity (The 4152 NPEV isolates positives) in AFP cases was found to be significantly higher in NK than in SK, Gulbarga district followed by Raichur of NK region shows highest NPEV rate in the state. However, lower rates were seen in CK region [Figure 4].{Figure 4}

Gender and age wise

Gender and Age wise data of NPEV positivity among AFP cases were determined for the period of 14 years from 2000 to 2013. NPEV infections were detected in both males and females. The infection rate was slightly higher in female than male.

The male to female ratio was found to be 1:1.2. The highest NPEV isolation rate was observed among the children aged 1–2 years followed by 3–5 years and least was among 11–15 years [Figure 5]. The isolation of NPEV decreased significantly with the increase in age.{Figure 5}

Details of contacts received during the study period

To increase the sensitivity of detection of wild poliovirus in cases when adequate stool specimens cannot be collected from hot AFP case, contact stool collection is made from those children who have the closest contact with the index case, e.g., siblings, playing together and living in same household, etc., (during the final stages of polio eradication it becomes increasingly important to identify AFP cases that appear likely to be polio, so that immediate follow-up action can be taken. All such cases, which in the opinion of DIO/SMO, after examination, look like polio, are labelled as 'hot cases'). Contact stool specimens collected from all 'hot' AFP cases with the inadequate specimen.[11]

No contact samples received during 1997–2000. From 2001 to 2013, contacts samples were collected for 46 index cases/hot cases. The number of samples collected varied from 5 to 9 samples per index case. Of 46 contacts, 37 (80.43%) were positive for NPEV. Ninety-nine (41.59%) samples were positive for NPEVs from 238 samples collected from 46 contacts [Table 1]. Among the 46 Index cases, samples were available for only 14 cases, out of which 10 (71.42%) were positive for NPEVs.{Table 1}

 Discussion



The primary objective of AFP surveillance is to detect, investigate, report, disseminate and promptly implement control measures for wild poliovirus cases. The isolation rate of NPEV in most tropical countries typically exceeds 10%[12] and varies geographically.

Karnataka being a state in a tropical country of India, the NPEV isolation rate was 21.39% of total AFP specimens during 16½ years of the period (July 1997–2013). The findings are in accordance with other Indian studies reported NPEV isolation rate between 20% and 34%.[13],[14] No wild poliovirus has been reported in India since January 2011, whereas in Karnataka since November 2007,[15] from 2007 the NPEV isolation average rate was almost constant of about 20% till 2012 and is decreased to 14.97% in 2013.

Millions of NPEV infections occur globally exhibiting a peak in summer and autumn and are caused by more than 65 NPEV serotypes, including Coxsackie A viruses, Coxsackie B viruses, Echo viruses and numbered Enteroviruses.[16] In this study, the initial high transmission was observed in summer and reached a peak in Monsoon. The highest percentage of NPEV isolation rate was during June–July (13%), May and August (10%), September–October (9%) and April (8%) the lowest percentage was during January, February, March and December (5%) followed by November (6%). The activity of NPEVs recorded in this study was found to be closer to that described in earlier studies from northern India and America.[3],[17],[18]

We evaluate the age distribution of AFP cases, which is also a risk factor. Of the five age categories of 1-year, 1–2 years, 3–5 years, 6–10 years and 11–15 years, the NPEV proportion of AFP cases 32.81% recorded in children aged 5 years and below was lower than the 90% that reported in India.[19] Similar studies report lower prevalence among this age group of children.[20],[21] Our findings supports with Enterovirus infections are more prevalent in children than in adults and the isolation decreased with increased in age.[22],[23]

We evaluated the non-polio AFP rate with respect to meteorological zones.[3] NK being hot and dry climate region shows 60.62%, whereas SK (moderate) and CK (wet and hot) regions show 35.25% and 4.14%, respectively. Hence, the climatic factors also play a role in the transmission and infection rates of NPEVs.[3],[17],[24]

Some studies have reported that the non-polio AFP rate was not associated with population density.[3],[25] Though we noted remarkably high NPEV isolation rate in AFP cases in NK known to have lower population densities,[26] as compared to that of densely populated SK.[3] Further, a significant high percentage of NPEV isolation rate was observed at Bengaluru rural and urban, which is densely populated area in SK region and lowest percentage was seen in CK region with higher population than NK.

 Conclusion



As we head towards global eradication of poliomyelitis, attention towards detection of NPEV infection causing AFP to be studied in depth. The present study suggests that after the eradication of poliomyelitis, AFP cases negative for wild poliovirus but positive for NPEV with residual paralysis may continue to be detected. The results of this study can be used for further characterisation of NPEV isolates for better understanding of the epidemiology of NPEV causing paralysis and long-term outcome of these cases. This overview study would also help in understanding the NPEV prevalence in the AFP children in Karnataka and the need for further studies in depth for the role of NPEVs.

Acknowledgements

Authors are thankful to Dr. DT Mourya, Director, NIV, Pune for sustained scientific encouragement and constant focused support. Authors thank Mr. Thippeswamy B, Dharani Devi, Mr. SuriyaPrakash and Mr. Madhav Rao for technical works. Authors also thank the entire team of personnel involved in the network of AFP surveillance and laboratory investigations for Polio Eradication Initiative in India and all technical staff of NIV Bengaluru-unit for providing data on AFP cases and NPEV isolates.

Financial support and sponsorship

World Health Organization-National Polio Surveillance Project, India.

Conflicts of interest

There are no conflicts of interest.

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