CCHF virus variants in Pakistan and Afghanistan: Emerging diversity and epidemiology

https://doi.org/10.1016/j.jcv.2015.03.021Get rights and content

Highlights

  • CCHF is endemic in Pakistan and its neighboring areas of Afghanistan.

  • Multiple genetic variants of CCHF Asia-1 genotype co-circulate in this region.

  • Active surveillance coupled with laboratory investigations should be implemented.

Abstract

Background

Crimean Congo hemorrhagic fever (CCHF) has been reported from more than 30 countries in Africa, Asia, Eastern Europe and Middle East. The disease is considered endemic in Pakistan and neighboring countries like Iran and Afghanistan.

Objectives

This study aimed to explore the genetic diversity of CCHF virus (CCHFV) detected in Pakistan and Afghanistan based on analysis of partial S-segment sequences.

Study design

During 2011, one hundred samples satisfying the CCHF case definition were tested by (ELISA) and RT-PCR for detection of IgM antibodies and viral RNA, respectively. Phylogenetic analysis was carried out on partial S-segment nucleotide sequences using MEGA 5.0.

Results

Out of one hundred collected during 2011, 49 (49%) were positive for CCHF either by ELISA/RT-PCR or both. The mean age of the CCHFV positive cases was 30.32 years (range 18–56 years) and overall mortality rate was 20.4%. All CCHF virus isolates from this study clustered with strains previously reported from Pakistan, Iran and Afghanistan within the Asia-1 genogroup. Four distinct sub-clades were found circulating within Asia-1 genogroup. Six CCHFV strains found in Pakistan and Afghanistan grouped into a new sub-clade-D.

Conclusions

Data from this study shows that endemic foci of CCHFV span the international border between Pakistan and Afghanistan with genetically diverse variants circulating in this region. Our findings emphasize to establish a laboratory based surveillance program and devise health policy measures to control CCHF infection especially in Baluchistan.

Section snippets

Background

Crimean Congo hemorrhagic fever virus (CCHFV) belongs to the genus Nairovirus within the family Bunyaviridae [1]. It contains single stranded, three negative sense RNA segments known as small (S), medium (M) and large (L) which encode nucleocapsid protein, glycoproteins (Gn and Gc) and viral RNA polymerase, respectively [2], [3], [4]. Based on geographical origin and phylogenetic analyses of S gene segment, CCHFVs has been classified into seven distinct genetic groups; African group 1 comprises

Objectives

The purpose of the current study was to understand the genetic diversity of CCHF viruses from Pakistan and Afghanistan at a molecular level through analyses of partial S-segment sequence.

Sample selection and collection

The study was carried out from January to December 2011 at the National Institute of Health in Islamabad, Pakistan. One hundred blood samples were collected from suspected patients of CCHF. The case definition used for identification of CCHF patients included fever, malaise, myalgia, bleeding from various orifices and low platelet count. CCHF was confirmed by reaction of IgM antibody using ELISA kit (Biological Diagnostic Supplies Limited, BDSL®) in accordance with the manufacturer’s

Results

Out of one hundred blood samples collected from suspected cases of CCHF during 2011, 49 (49%) samples tested positive for CCHF either by ELISA/RT-PCR or both. Out of 49, ten samples were positive for IgM antibodies on ELISA, fourteen for CCHF virus RNA by PCR while twenty five were found positive for both IgM antibodies and RNA (Table 2). Positive samples were received from five districts of Baluchistan province (Killa Abdullah, Loralai, Pishin, Quetta, and Zhob) and Afghanistan (Kandahar) (

Discussion

Pakistan is an agricultural country where a large proportion of population resides in villages and towns. There is an extensive variety of entomological disease vectors and endemic pathogens across the country resulting in a large potential for human exposure. The causality of vector borne diseases is often directly associated with social upheaval and economic status of people living in rural areas [14]. Baluchistan being the largest province of country covers almost 43% of the country’s

Funding

No current external funding sources for this study.

Competing interests

None declared by any co-author.

Ethical approval

The study was approved by the ethical committee of National Institute of Health, Islamabad, Pakistan. Additionally, none of the identities related to patients have been disclosed at any stage.

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