Crimean-Congo haemorrhagic fever virus in ticks collected from livestock in Balochistan, Pakistan

Abstract

Background: Crimean-Congo haemorrhagic fever virus (CCHFV) is a tick-borne zoonotic pathogen. It causes a fatal haemorrhagic disease in humans. Hard ticks, in particular Hyalomma spp., are considered to function as reservoir as well as vector for CCHFV.

Methods: A cross-sectional study was conducted in the province of Balochistan, Pakistan, from September to November 2017. Ticks were collected from cattle, sheep and goats in livestock farms. The ticks were morphologically identified, followed by confirmation with molecular methods (PCR and sequencing). Furthermore, ticks were examined for CCHFV genomes (S segment) by a one-step multiplex real-time RT-qPCR and positive samples were sequenced to determine the CCHFV genotype.

Results: In total, 525 of 529 livestock infesting adult ticks belonged to the genus Hyalomma, and 4 ticks to the genus Rhipicephalus (R. microplus 3×, R. turanicus 1×). In the genus Hyalomma, H. marginatum (28%), H. excavatum (26%), H. dromedarii (22%), H. anatolicum (16%) and H. scupense (8%) ticks were identified. Tick infestations were as follows: sheep 58%, goats 28% and cattle 14%. Four per cent (20/525) of ticks were CCHFV genome-positive, and all genomes clustered in CCHFV genotype Asia 1. Among CCHFV-positive ticks, 75% (15/20) were female and 25% (5/20) male. CCHFV genomes were most frequently detected in H. marginatum (30%, 6/20), followed by H. dromedarii (25%, 5/20), H. excavatum (20%, 4/20), H. anatolicum (20%, 4/20) and H. scupense (5%, 1/20). All CCHFV-positive ticks were found on sheep. The largest number of CCHFV-positive ticks were detected in the district of Kalat (60%, 12/20), followed by the districts of Quetta (30%, 6/20) and Killa Abdullah (10%, 2/20).

Conclusions: This study confirms the circulation of CCHFV in ticks in Balochistan, south-western Pakistan. It is imperative to take effective tick control measures in this area, especially to control livestock tick infestations to prevent CCHF infections in humans.

Keywords: Crimean-Congo haemorrhagic fever virus; Pakistan; cross-sectional study; livestock; ticks.