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Volume 17, Number 8–August 2011
Crimean-Congo Hemorrhagic Fever Virus in Hyalommid Ticks, Northeastern Kenya
Rosemary Sang, Comments to Author Joel Lutomiah, Hellen Koka, Albina Makio, Edith Chepkorir, Caroline Ochieng, Santos Yalwala, James Mutisya, Lilian Musila, Jason H. Richardson, Barry R. Miller, and David Schnabel
Author affiliations: Kenya Medical Research Institute, Nairobi, Kenya (R. Sang, J. Lutomiah, E. Chepkorir); US Army Medical Research Unit Nairobi (H. Koka, A. Makio, C. Ochieng, S. Yalwala, J. Mutisya, L. Musila, J.H. Richardson, D. Schnabel); and Centers for Disease Control and Prevention, Fort Collins, Colorado, USA (B.R. Miller)
Suggested citation for this article
As part of ongoing arbovirus surveillance, we screened ticks obtained from livestock in northeastern Kenya in 2008 to assess the risk for human exposure to tick-borne viruses. Of 1,144 pools of 8,600 Hyalomma spp. ticks screened for Congo-Crimean hemorrhagic fever virus by reverse transcription PCR, 23 pools were infected, demonstrating a potential for human exposure.
Crimean-Congo hemorrhagic fever virus (CCHFV), a member of the genus Nairovirus, family Bunyaviridae, causes hemorrhagic disease in humans with a >30% case-fatality rate. The virus was first described in 1944 in the Crimea in the former Soviet Union and later was found to be similar to a virus isolated in 1956 in the Belgian Congo (1).
Domestic ruminants are infected through tick bites and are able to infect more ticks to perpetuate the virus (2,3). The virus may be transmitted to humans by the bite of an infected tick or by contact with body fluids from an infected animal or person (4). The main vectors of CCHFV are ticks in the genus Hyalomma, family Ixodidae, with other ixodid ticks and ticks from the family Argasidae also contributing to transmission (2). The virus is transovarially transmitted among ticks (2,3); consequently, ticks are also reservoirs of CCHFV.
In Kenya, CCHFV has been detected on only 2 occasions: in Rhipicephalus pulchellus ticks collected in the 1970s from a dying sheep in a veterinary laboratory in the town of Kabete outside Nairobi (2) and from a person with Crimean-Congo hemorrhagic fever in western Kenya in October 2000 (5). Evidence of CCHFV activity in Kenya is limited, and although tick-borne arbovirus surveillance in Kenya has demonstrated circulation of a range of viruses, to our knowledge, detection of CCHFV has not been reported (6,7).
Crimean-Congo hemorrhagic fever is a substantial public health threat because of the associated high mortality rate (30%–60%), the potential for person-to-person transmission, the unavailability of a licensed vaccine, and the limited treatment options for infected persons (3,4). Entomologic surveillance is valuable for assessing the risk for human exposure and for identifying so-called hot spots for focused preventive action to minimize the effects of virus outbreaks. As part of ongoing entomologic arbovirus surveillance conducted by the United States Army Medical Research Unit in Kenya and the Kenya Medical Research Institute, ticks were collected from livestock in the semi-arid areas of Kenya, where intense pastoralist farming is practiced, to assess the risk to the community for tick-borne arbovirus exposure.
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Suggested Citation for this Article
Sang R, Lutomiah J, Koka H, Makio A, Chepkorir E, Ochieng C, et al. Crimean-Congo hemorrhagic fever virus in hyalommid ticks, northeastern Kenya. Emerg Infect Dis [serial on the Internet]. 2011 Aug [date cited]. http://www.cdc.gov/EID/content/17/8/102064.htm
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Rosemary Sang, Kenya Medical Research Institute, Centre for Virus Research, PO Box 54626, Nairobi 00200, Kenya; email: email@example.com