Kyasanur forest disease
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Overview
Kyasanur forest disease is a tick-borne viral hemorrhagic fever endemic to South Asia. The disease is caused by a virus belonging to the family flaviviridae.
Historical Perspective
The disease was first reported from Kyasanur Forest of Karnataka in India in March 1957. The disease first manifested as an epizootic outbreak among monkeys killing several of them in the year 1957. Hence the disease is also locally known as Monkey Disease or Monkey Fever.[1] The similarity with Russian Spring-summer encephalitis was noted and the possibility of migratory birds carrying the disease was raised.[2] Studies began to look for the possible species that acted as reservoirs for the virus and the agents responsible for transmission. Subsequent studies failed to find any involvement of migratory birds although the possibility of their role in initial establishment was not ruled out. The virus was found to be quite distinctive and not closely related to the Russian virus strains. Antigenic relatedness is however close to many other strains including the Omsk hemorrhagic fever (OHF) and birds from Siberia have been found to show an antigenic response to KFD virus. Sequence based studies however note the distinctivenss of OHF.[3] Early studies in India were conducted in collaboration with the US Army Medical Research Unit and this led to controversy and conspiracy theories.[4][5]
Subsequent studies based on sequencing found that the Alkhurma virus, found in Saudi Arabia is closely related.[6] In 1989 a patient in Nanjianin, China was found with fever symptoms and in 2009 its viral gene sequence was found to exactly match with that of the KFD reference virus of 1957. This has however been questioned since the Indian virus shows variations in sequence over time and the exact match with the virus sequence of 1957 and the Chinese virus of 1989 is not expected. This study also found using immune response tests that birds and humans in the region appeared to have been exposed to the virus.[7] Another study has suggested that the virus is recent in origin dating the nearest common ancestor of it and related viruses to around 1942, based on the estimated rate of sequence substitutions. The study also raises the possibility of bird involvement in long-distance transfer.[8] It appears that these viruses diverged 700 years ago.[9]
Pathophysiology
Transmission
The main hosts of Kyasanur forest disease virus (KFDV) are small rodents, but shrews, bats, and monkeys may also carry the virus. KFD is transmitted from the bite of an infected tick (Haemaphysalis spinigera is the major vector). Humans can get these diseases from a tick bite or by contact with an infected animal, such as sick or recently dead monkey.
Larger animals such as goats, cows, and sheep may become infected with KFD, but they do not have a role in the transmission of the disease. Furthermore, there is no evidence of the disease being transmitted via the unpasteurized milk of any of these animals.
Epidemiology and Demographics
There are approximately 400-500 cases of KFD per year with a case fatality rate of 3% to 5%.
Risk Factors
People with recreational or occupational exposure to rural or outdoor settings (e.g., hunters, campers, forest workers, farmers) are potentially at risk for infection by contact with infected ticks.
Diagnosis
History and Symptoms
After an incubation period of 3-8 days, the symptoms of KFD begin suddenly with fever, headache, severe muscle pain, cough, dehydration, gastrointestinal symptoms and bleeding problems. Patients may experience abnormally low blood pressure. After 1-2 weeks of symptoms, some patients recover without complication. However, in most patients, the illness is biphasic and the patient begins experiencing a second wave of symptoms at the beginning of the third week. These symptoms include fever and signs of encephalitis (inflammation of the brain).
Laboratory Findings
The patients may have low platelet, red blood cell, and white blood cell counts. The diagnosis is made by virus isolation from blood or by serologic testing using enzyme-linked immunosorbent serologic assay (ELISA).
Treatment
There is no specific treatment for KFD, but supportive therapy is important. Supportive therapy includes the maintenance of hydration and the usual precautions for patients with bleeding disorders.
Prevention
Prophylaxis by vaccination, as well as preventive measures like protective clothing, tick control, and mosquito control are advised. An attenuated live vaccine is now available. Specific treatments are not available.
Sources
- CDC Kyasanur forest disease[2]
References
- ↑ Nichter, Mark (1987). "Kyasanur Forest Disease: An Ethnography of a Disease of Development". Medical Anthropology Quarterly, New Series. 1 (4): 406–423.
- ↑ Work, Telford H.; Roderiguez, FR; Bhatt, PN (1959). "Virological Epidemiology of the 1958 Epidemic of Kyasanur Forest Disease". American Journal of Public Health. 49 (7): 869–874. doi:10.2105/AJPH.49.7.869. PMC 1372906. PMID 13661478.
- ↑ Lin D, Li L, Dick D, Shope RE, Feldmann H, Barrett AD, Holbrook MR (2003). "Analysis of the complete genome of the tick-borne flavivirus Omsk hemorrhagic fever virus". Virology. 313 (1): 81–90. doi:10.1016/S0042-6822(03)00246-0. PMID 12951023.
- ↑ Harry Hoogstraal, Makram N. Kaiser, Melvin A. Traylor, Ezzat Guindy, and Sobhy Gaber (1963). "Ticks (Ixodidae) on birds migrating from Europe and Asia to Africa, 1959-61". Bulletin World Health Organ. 28 (2): 235–262. PMC 2554471. PMID 13961632.
- ↑ Lewis, Michael (2002). "Scientists or Spies? Ecology in a Climate of Cold War Suspicion". Economic and Political Weekly. 37 (24): 2324–2332.
- ↑ Charrel RN, Zaki AM, Attoui H, Fakeeh M, Billoir F, Yousef AI, de Chesse R, De Micco P, Gould EA, de Lamballerie X. (2001). "Complete coding sequence of the Alkhurma virus, a tick-borne flavivirus causing severe hemorrhagic fever in humans in Saudi Arabia". Biochem. Biophys Res. Commun. 287 (2): 455–61. doi:10.1006/bbrc.2001.5610. PMID 11554750.
- ↑ Jinglin Wang, Hailin Zhang, Shihong Fu, Huanyu Wang, Daxin Ni, Roger Nasci, Qing Tang, and Guodong Liang (2009). "Isolation of Kyasanur Forest Disease Virus from Febrile Patient, Yunnan, China". Emerg. Infect. Dis. 15 (2): 326–328. doi:10.3201/eid1502.080979. PMC 2657630. PMID 19193286.
- ↑ Rajeev Mehla, Sandeep R.P. Kumar, Pragya Yadav, Pradip V. Barde, Prasanna N. Yergolkar, Bobbie R. Erickson, Serena A. Carroll, Akhilesh C. Mishra, Stuart T. Nichol, and Devendra T. Mourya (2009). "Recent Ancestry of Kyasanur Forest Disease Virus". Emerging Infectious Diseases. 15 (9): 1431–1437. doi:10.3201/eid1509.080759. PMC 2819879. PMID 19788811.
- ↑ Dodd KA, Bird BH, Khristova ML, Albariño CG, Carroll SA, Comer JA, Erickson BR, Rollin PE, Nichol ST (2011) Ancient ancestry of KFDV and AHFV revealed by complete genome analyses of viruses isolated from ticks and mammalian hosts. PLoS Negl Trop Dis 5(10):e1352.