CRIMEAN-CONGO HAEMORRHAGIC FEVER
ANNA MEREDITH
Royol (Dick) School ofVeterinory Studies, University of Edinburgh, Scotland, UK
Crimean-Congo hemorrhagic fever (CCHF) virus is a member of the genus Nairovirus in the family Bunyaviri- dae.
CCHF is one of the severe forms of human haemorrhagic fever that is endemic in Africa, Asia, Eastern Europe and the Middle East and is invariably fatal. CCHF virus is an enveloped, spherical, single-stranded RNA virus consisting of three RNA segments, small (S), medium (M) and large (L), which encode the nucleocapsid protein, glycoproteins and viral polymerase, respectively. The virus is tick- borne, and its distribution correlates with that of the Hyalomma tick, which is the main vector, although other ixodid species may also be infected. The virus circulates in an enzootic tick—vertebrate—tick cycle, and a wide range of domestic and wild species may act as a reservoir. Antibodies to CCHF virus have been detected in numerous small wild mammals, including European brown hare (Lepus europaeus), hedgehog (Erinaceus europaeus) and house mouse (Mus musculus). These smaller species that harbour immature ticks are believed to act as amplifying hosts and maintain the virus, and mature ticks can then transmit the infection to larger species, including domestic and wild ruminants, horses and pigs. Ticks have both trans-stadial and transovarial transmission of virus, and humans are generally infected by tick bites, although infection by percutaneous or permucosal routes by contact with animal blood or tissue or drinking unpasteurized milk is also possible.Clinical disease has only been described in humans, and the recent emergence or re-emergence of CCHF in several Balkan countries, Turkey, southwestern Russia, the Ukraine, northern Greece and Spain has highlighted CCHF disease as a significant zoonotic threat in Europe. Reasons for re-emergence may include climate change and anthropogenic factors such as changes in land use, agricultural practices or hunting activities, and movement of livestock that may influence vector competence and hosttick—virus dynamics.
The role of migrating wild birds, particularly ground- dwelling species that are more likely to harbour infected ticks, is unclear but is also considered as a potential route of incursion into new regions in Europe.REFERENCES
1. WHO. Haemorrhagic fever with renal syndrome: memorandum from a WHO meeting. Bulletin of the World Health Organization. 1983;61: 269—75.
2. Heyman, P, Vaheri, A., Lundkvist, A. & Avsic-Zupanc, T. Hantavirus infections in Europe: from virus carriers to a major public- health problem. Expert Review Anti Infective Therapy. 2009;7:205-17.
3. Tersago, K., Schreurs, A., Linard, C., Verhagen, R., Van Dongen, S. & Leirs. H. Population, environmental, and community effects on local bank vole (Myodes glareolus) Puumala virus infection in an area with low human incidence. Vector Borne and Zoonotic Diseases. 2008;8:235- 44.
4. Tersago, K., Verhagen, R., Servais, A., Heyman, P, Ducoffre, G. & Leirs, H. Hantavirus disease (nephropathia epidemica) in Belgium: effects of tree seed production and climate. Epidemiology and Infection. 2009;137:250-6.
5. Carey, D.E., Reuben, R., Panicker, K.N., Shope, R.E. & Myers, R.M. Thottapalayam virus: a presumptive arbovirus isolated from a shrew in India. Indian Journal Medical Research. 1971;59:1758-60.
6. Lee, H.W, Baek, L.J. & Johnson, K.M. Isolation of Hantaan virus, the etiologic agent of Korean hemorrhagic fever, from wild urban rats. Jounal of Infectious Diseases. 1982;146:638^4.
7. Suzan, G., Marce, E., Giermakowski, J.T. et al. Experimental evidence for reduced rodent diversity causing increased hantavirus prevalence. PLoS One. 2009;4:e5461.
8. Yanagihara, R., Amyx, H.L., Lee, PW, Asher, D.M., Gibbs, C.J., Jr. & Gajdusek, D.C. Experimental hantavirus infection in nonhuman primates. Archives of Virology. 1988;101:125-30.
9. Leighton, F.A., Artsob, H.A., Chu, M.C. & Olson, J.G. Aserological survey of rural dogs and cats on the southwestern Canadian prairie for zoonotic pathogens.
Canadian Journal of Public Health. 2001;92: 67-71.10. Malecki, T.M., Jillson, G.P, Thilsted, J.P, Elrod, J., Torrez-Martinez, N. & Hjelle, B. Serologic survey for hantavirus infection in domestic animals and coyotes from New Mexico and northeastern Arizona. Journal American Veterinary Medicine Assocociation. 1998;212:970-3.
11. Escutenaire, S.PP, Sjolander, K.B., Heyman, P, Brochier, B. & Lun- dkvist, A. Evidence of Puumala Hantavirus infection in red foxes (Vulpes vulpes) in Belgium. Veterinary Record. 2000;147:365-6.
12. Ahlm, C., Wallin, K., Lundkvist, A. et al. Serologic evidence of Puumala virus infection in wild moose in northern Sweden. American Journal of Tropical Medicine and Hygiene. 2000;62:106-11.
13. Jay, M., Ascher, M.S., Chomel, B.B. et al. Seroepidemiologic studies of hantavirus infection among wild rodents in California. Emerging Infectious Diseases. 1997;3:183-90.
14. Slonova, R.A., Tkachenko, E.A., Kushnarev, E.L., Dzagurova, T.K. & Astakova, T.I. Hantavirus isolation from birds. Acta Virologica. 1992;36:493.
15. Mollaret, H.H. L'infection a bacille de Malassez et Vignal. World Health OrganizationlZoonoses. 1967;67(9).
16. Hardestam, J., Karlsson, M., Falk, K.I., Olsson, G., Klingstrom, J. & Lundkvist, A. Puumala hantavirus excretion kinetics in bank voles (Myodes glareolus). Emerging Infectious Diseases. 2008;14:1209-15.
17. Bird, B.H., Ksiazek, T.G., Nichol, S.T & MacLachlan, N.J. RiftValley fever virus. Journal American Veterinary Medical Association. 2009;234:883-93.
18. Evans, A., Gakuya, F., Paweska, J.T. et al. Prevalence of antibodies against Rift Valley fever virus in Kenyan wildlife. Epidemiology and Infection. 2008;136:1261-9.