Field study of fecal excretion as a decision support tool in response to silent reintroduction of wild-type poliovirus 1 into Israel

doi:10.1016/j.jcv.2015.03.005

Journal of Clinical Virology

Volume 66, May 2015, Pages 51-55

https://doi.org/10.1016/j.jcv.2015.03.005 Get rights and content

Highlights

•
Silent reintroduction of wild type poliovirus 1 into Israel occurred in early 2013.
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A field survey was performed in order to assess risk and support decision-making.
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Field testing utilized screening by a novel direct molecular assay.
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Testing identified the main population cohorts contributing to virus circulation.
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Study results informed the decision on supplemental immunization.

Abstract

Background

Israel has used an inactivated polio vaccine (IPV)-only schedule since 2005 (95% coverage). Silent reintroduction of wild type poliovirus 1 (WPV1) into Israel in early 2013 was detected in Southern Israel via routine environmental surveillance without clinical cases.

Objectives

To estimate the rate of WPV1 excretion by age and residence and inform decision-making regarding supplemental immunization with OPV.

Study design

A convenience sample of Bedouin and Jewish residential areas in the epicenter of the incident, focusing on under 8 year-olds who not previously given OPV. Fecal samples were directly tested for WPV1 RNA using a novel qRT-PCR assay. Positive samples were confirmed by gold standard cell culture and subject to genotyping.

Results

Overall, 2196 non-duplicate fecal samples were collected and analyzed. WPV1 was detected in 61 samples (2.8%), 55 of which (90.2%) were from Bedouins. WPV1 excretion rates were 5.4% among Bedouins and 0.6% among Jewish individuals. Respective age-specific rates among Bedouin and Jewish children were 4.9% and 0.2% for 0–2 years and 7.2% and 1.7% for 2–8 years. Molecular testing had 89.5% sensitivity (higher than culture) and 100% specificity.

Conclusion

The rapid performance of a field study to evaluate WPV1 excretion unequivocally demonstrated substantial WPV1 infection rates among children under 8 years in Southern Israel, thus informing the decision to vaccinate this age group with bOPV and risk communication to both healthcare personnel and the public. Rapid development and implementation of molecular screening can thus underpin risk assessment and management in complex epidemiological situations.

Section snippets

Background

Israel had been free of wild poliovirus (WPV) since 1988 based on ongoing acute flaccid paralysis (AFP) and environmental surveillance [1]. Routine immunization in Israel has involved inactivated polio vaccine (IPV) only since 2005. In 2013, WPV1 was discovered into Southern Israel [2] and found in sewage samples obtained from Rahat and Beer-Sheva [3]. Molecular analysis determined the strain to be closely related to the South Asia type 1 lineage (WPV1-SOAS) endemic in Afghanistan and Pakistan

Objectives

In the framework of Israel's response to this unprecedented silent reintroduction (WPV1 transmission lacking clinical cases in a population immunized with IPV only), data regarding the force of infection in the community were needed in order to determine the most appropriate supplementary immunization activity (SIA). An urgent field survey of WPV1 excretion was thus carried out.

Study design

The study involved a convenience sample of the population of Southern Israel in July 2013. The primary goal was to estimate the rate of WPV1 excretion and secondary goals were to estimate excretion rates by age group and residence. Our assumption was that children <9 years old, representing birth cohorts not given oral polio vaccine (OPV) were the main source of transmission. Since prevalence was unknown, sampling efforts were concentrated in the Bedouin and Jewish populations at the epicenter

Results

Of 2395 collected samples, 2196 non-duplicate samples were initially analyzed (49% from Bedouin, 51% from Jewish residents). Of 2065 samples with age data, 1576 (76.3%) were obtained from <8 year-olds (OPV-naive), 40 (1.94%) from 8–10 year-olds (transition between vaccine schedules), 122 (5.91%) from 10–22 year-olds (cohorts given OPV and IPV) and 327 (15.84%) from >22 year-olds (cohorts given OPV only).

Sixty-one subjects excreted WPV1-SOAS (2.77%), of whom 55 were Bedouin (90.16%). Among 59

Discussion

The detection of silent introduction of WPV1 into Israel via environmental surveillance created challenges for risk assessment (magnitude of virus circulation and correlation between environmental findings and human excretion), risk management (data needed to support the decision-making regarding a vaccination campaign and target population), and risk communication (generate evidence to facilitate acceptance of a live vaccine campaign) [10]. The development of a novel molecular assay specific

Funding

None.

Conflicts of interest

None.

Ethical approval

The study was approved by the Institutional Review Board of Sheba Medical Center (SMC-0774-13) and the CDC.

Authors’ contribution

All authors have contributed to this work and qualify for authorship.

Acknowledgements

The authors would like to thank the following: Southern District Health Office personnel for collection of specimens and data; The clinical laboratory services of three Israeli HMO's: South District laboratories of Clalit Health Services (D Amichay, E. Fuchs and staff), Central laboratories of Maccabbi Health Services (B. Sheinberg, M. Parizade, D.Taran and staff) and Leumit Health Services (Y. Dickstein, N. Ben Horin and staff); Laboratory personnel at the Central Virology Laboratory, Israel

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During 2013/14, Israel witnessed the silent reintroduction and sustained transmission of wild poliovirus type 1 (WPV1) detected through routine environmental surveillance performed on sewage samples. The public health response to silent poliovirus transmission in a population with high inactivated polio vaccine (IPV) coverage poses an emerging challenge towards the ‘End Game’ of global poliovirus eradication. This paper reviews the risk assessment, risk management and risk communication aspects of this poliovirus incident. Special emphasis is placed on the use of scientific data generated in the risk assessment phase to inform the public health response. Reintroducing a live vaccine in supplemental immunization activities in response to transmission of WPV or vaccine-derived poliovirus should be considered close to the ‘End Game’ of polio eradication, especially if targeting the population at risk is feasible. Such circumstances require a comprehensive contingency plan that will support the generation of important public health evidence at the risk assessment stage, thereby allowing to tailor the risk management approaches and underpin appropriate risk communication.
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Article preview

Journal of Clinical Virology

Highlights

Abstract

Background

Objectives

Study design

Results

Conclusion

Section snippets

Background

Objectives

Study design

Results

Discussion

Funding

Conflicts of interest

Ethical approval

Authors’ contribution

Acknowledgements

References (12)

Poliovirus serotype-specific VP1 sequencing primers

J. Virol. Methods

Advanced environmental surveillance and molecular analyses indicate separate importations rather than endemic circulation of wild type 1 poliovirus in Gaza district in 2002

Appl. Environ. Microbiol.

Insidious reintroduction of wild poliovirus into Israel, 2013

Euro Surveill.

Intensified environmental surveillance supporting the response to wild poliovirus type 1 silent circulation in Israel, 2013

Euro Surveill.

Cited by (11)

Polio endgame: Lessons for the global rotavirus vaccination program

Public health response to the silent reintroduction of wild poliovirus to Israel, 2013–2014

Primary and booster vaccination with an inactivated poliovirus vaccine (IPV) is immunogenic and well-tolerated in infants and toddlers in China

Time Taken to Detect and Respond to Polio Outbreaks in Africa and the Potential Impact of Direct Molecular Detection and Nanopore Sequencing

The role of time-varying viral shedding in modelling environmental surveillance for public health: Revisiting the 2013 poliovirus outbreak in Israel

Inferring numbers of wild poliovirus excretors using quantitative environmental surveillance

Short communicationField study of fecal excretion as a decision support tool in response to silent reintroduction of wild-type poliovirus 1 into Israel

Highlights

Abstract

Background

Objectives

Study design

Results

Conclusion

Section snippets

Background

Objectives

Study design

Results

Discussion

Funding

Conflicts of interest

Ethical approval

Authors’ contribution

Acknowledgements

J. Virol. Methods

Advanced environmental surveillance and molecular analyses indicate separate importations rather than endemic circulation of wild type 1 poliovirus in Gaza district in 2002

Appl. Environ. Microbiol.

Insidious reintroduction of wild poliovirus into Israel, 2013

Euro Surveill.

Intensified environmental surveillance supporting the response to wild poliovirus type 1 silent circulation in Israel, 2013

Euro Surveill.

Short communication
Field study of fecal excretion as a decision support tool in response to silent reintroduction of wild-type poliovirus 1 into Israel