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Molecular characterization and phylogenetic relationship of wild type 1 poliovirus strains circulating across Pakistan and Afghanistan bordering areas during 2010-2012.

ABSTRACT: Pakistan and Afghanistan share a long uncontrolled border with extensive population movement on both sides. Wild poliovirus transmission has never been interrupted in this block due to war against terrorism, poor public health infrastructure, misconceptions about polio vaccines and inadequate immunization activities. All these issues complicate the eradication operations and reinforce the complexity of wiping out poliomyelitis from this region. This study illustrates the origins and routes of cross-border wild poliovirus type 1 (WPV1) transmission during 2010-2012 between Pakistan and Afghanistan. Sequence analyses were conducted based on complete VP1 capsid protein sequences for WPV1 study strains to determine the origin of poliovirus genetic lineages and their evolutionary relationships. Phylogenetic tree was constructed from VP1 gene sequences applying Maximum Likelihood method using Kimura 2- parameter model in MEGA program v 5.0. A total of 72 (14.3%) out of 502 wild-type 1 polioviruses were found circulating in border areas of both countries during 2010-2012. Molecular phylogenetic analysis classified these strains in to two sub-genotypes with four clusters and 18 lineages. Genetic data confirmed that the most of WPV1 lineages (12; 66.6%) were transmitted from Pakistan to Afghanistan. However, the genetic diversity was significantly reduced during 2012 as most of the lineages were completely eliminated. In conclusion, Pakistan-Afghanistan block has emerged as a single poliovirus reservoir sharing the multiple poliovirus lineages due to uncontrolled movement of people across the borders between two countries. If it is neglected, it can jeopardize the extensive global efforts done so-far to eradicate the poliovirus infection. Our data will be helpful to devise the preventive strategies for effective control of wild poliovirus transmission in this region.

SUBMITTER: Shaukat S

PROVIDER: S-EPMC4168008 | biostudies-literature | 2014

REPOSITORIES: biostudies-literature

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Molecular characterization and phylogenetic relationship of wild type 1 poliovirus strains circulating across Pakistan and Afghanistan bordering areas during 2010-2012.

Shaukat Shahzad S Angez Mehar M Alam Muhammad Masroor MM Sharif Salmaan S Khurshid Adnan A Malik Farzana F Rehman Lubna L Zaidi Syed Sohail Zahoor SS

PloS one 20140917 9

Pakistan and Afghanistan share a long uncontrolled border with extensive population movement on both sides. Wild poliovirus transmission has never been interrupted in this block due to war against terrorism, poor public health infrastructure, misconceptions about polio vaccines and inadequate immunization activities. All these issues complicate the eradication operations and reinforce the complexity of wiping out poliomyelitis from this region. This study illustrates the origins and routes of cr ...[more]

PMID: 25229826

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Project description:BACKGROUND:Afghanistan remains among the three countries with endemic wild poliovirus transmission, and high population immunity levels are required to interrupt transmission and prevent outbreaks. Surveillance and vaccination of children in Afghanistan have been challenging due to security issues limiting accessibility in certain areas. METHODS:A serosurvey was conducted in 2013 within accessible enumeration areas (EAs) among children aged <5?years using samples collected for a national micronutrient assessment survey to assess poliovirus immunity in Afghanistan. Of 21194 total EAs in Afghanistan, 107 were inaccessible and therefore were excluded from the sampling frame. RESULTS:Population immunity was high overall but varied for the poliovirus serotypes, and was lowest for type 3 (95% [95% CI: 93%, 96%]) compared to type 1 (99% [95% CI:97%, 99%]) and type 2 (98% [95% CI:96%, 99%]). The proportion of the population immune to all three types was 93% (95% CI: 91%, 95%), and the proportion seronegative for all three types was 0.5% (95% CI: 0.2%, 1.7%). CONCLUSION:Except for regional differences in immunity to type 3 virus, there were no other apparent differences in seroprevalence by region or by any of the demographic or nutritional characteristics assessed in this study. The study was not powered to provide provincial level seroprevalence estimates, but Paktika Province, in the South region, had the largest proportion of seronegative specimens for type 1 (4 seronegative of 17 serum specimens compared to 14 seronegative of 673 for the remainder of the areas). Among accessible children in Afghanistan, seroprevalence of antibodies to poliovirus was high, with most seroprevalence reported at 95% or greater. Despite high seroprevalence in areas assessed in this study, the continued detection of poliovirus cases in the South and East regions indicate that overall regional vaccination coverage and performance is not sufficient to stop polio transmission.

Project description:BACKGROUND: Pakistan and Afghanistan are two of the three remaining countries yet to interrupt wild-type poliovirus transmission. The increasing incidence of poliomyelitis in these countries during 2010-11 led the Executive Board of WHO in January, 2012, to declare polio eradication a "programmatic emergency for global public health". We aimed to establish why incidence is rising in these countries despite programme innovations including the introduction of new vaccines. METHODS: We did a matched case-control analysis based on a database of 46,977 children aged 0-14 years with onset of acute flaccid paralysis between Jan 1, 2001, and Dec 31, 2011. The vaccination history of children with poliomyelitis was compared with that of children with acute flaccid paralysis due to other causes to estimate the clinical effectiveness of oral poliovirus vaccines (OPVs) in Afghanistan and Pakistan by conditional logistic regression. We estimated vaccine coverage and serotype-specific vaccine-induced population immunity in children aged 0-2 years and assessed their association with the incidence of poliomyelitis over time in seven regions of Afghanistan and Pakistan. FINDINGS: Between Jan 1, 2001, and Dec 31, 2011, there were 883 cases of serotype 1 poliomyelitis (710 in Pakistan and 173 in Afghanistan) and 272 cases of poliomyelitis serotype 3 (216 in Pakistan and 56 in Afghanistan). The estimated clinical effectiveness of a dose of trivalent OPV against serotype 1 poliomyelitis was 12·5% (95% CI 5·6-18·8) compared with 34·5% (16·1-48·9) for monovalent OPV (p=0·007) and 23·4% (10·4-34·6) for bivalent OPV (p=0·067). Bivalent OPV was non-inferior compared with monovalent OPV (p=0·21). Vaccination coverage decreased during 2006-11 in the Federally Administered Tribal Areas (FATA), Balochistan, and Khyber Pakhtunkhwa in Pakistan and in southern Afghanistan. Although partially mitigated by the use of more effective vaccines, these decreases in coverage resulted in lower vaccine-induced population immunity to poliovirus serotype 1 in FATA and Balochistan and associated increases in the incidence of poliomyelitis. INTERPRETATION: The effectiveness of bivalent OPV is comparable with monovalent OPV and can therefore be used in eradicating serotype 1 poliomyelitis whilst minimising the risks of serotype 3 outbreaks. However, decreases in vaccination coverage in parts of Pakistan and southern Afghanistan have severely limited the effect of this vaccine. FUNDING: Poliovirus Research subcommittee of WHO, Royal Society, and Medical Research Council.

Dataset Information

Molecular characterization and phylogenetic relationship of wild type 1 poliovirus strains circulating across Pakistan and Afghanistan bordering areas during 2010-2012.

Publications

Molecular characterization and phylogenetic relationship of wild type 1 poliovirus strains circulating across Pakistan and Afghanistan bordering areas during 2010-2012.

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