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Kyasanur Forest Disease – Epidemiology and Prevention

Kyasanur Forest Disease – Epidemiology and Prevention. History …. Heavy mortality in two species of monkey (Langur & Red faced bonnet ) in 1955 in forests of Shimoga Mortality in monkeys was followed by acute febrile prostrating illness among villagers and few human deaths. History …….

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Kyasanur Forest Disease – Epidemiology and Prevention

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  1. Kyasanur Forest Disease – Epidemiology and Prevention

  2. History ….. • Heavy mortality in two species of monkey (Langur & Red faced bonnet ) in 1955 in forests of Shimoga • Mortality in monkeys was followed by acute febrile prostrating illness among villagers and few human deaths

  3. History ……. Autopsy on monkeys Place of reporting of First monkey death in march 1957

  4. Kyasanur forest disease • Found in India • Limited originally to Shimoga district in Karnataka (800 sq km) • Newer foci in 3 more districts - Uttara Kannada, Dakshina Kannada and Chikmangaluru (6000 sq km) • Serosurveys reveal KFD in Kutch & Saurashthra

  5. Problem statement • The outbreak during 1983-1984 is the largest with 2167 cases and 69 deaths. • In 1997, the cases came down to 75 and deaths to 4. • The number of human deaths varied between 4-15% of the cases • Few hundreds of cases and some deaths are reported even today

  6. Agent factors • Febrile disease associated with hemorrhages caused by an arbovirus, flavivirus • KFD virus is a member of group B togaviruses • Belongs to Russian spring summer encephalitis (RSSE) group of viruses

  7. Host factors • Age : Majority between 20 and 40 years • Sex: Males • Occupation: Cultivators who visit forest with cattle or cutting wood • Epidemic correlates with peak human activity in forests i.e between January and June

  8. Natural hosts & reservoirs • Small mammals - rats, squirrels, shrews and bats are the main reservoirs • Neutralizing antibodies have also been found in cattle, buffaloes, goats and porcupines • Monkeys - amplifying hosts

  9. Natural cycle • In enzootic states the infection is maintained in small mammals and also in ticks • When monkeys come in contact with infected ticks , they get infected , amplify and disseminate the infection in “hot spots ”of infection • Humans in these hot spots are infected by bite of infected anthrophilic ticks like H. spinigera

  10. VECTORS Female tick laying eggs • Hard tick species of the genus Haemophysalis particularly H.spinigera and H.turtura • Ticks act as both as vectors and reservoirs of infection in KFD

  11. Vector bionomics and seasonal transmission • Adult Ticks become active after few monsoon rains in June • Adult population reaches peak during July & August and gradually declines in September • Larval activity builds in post monsoon Oct-Dec • Nymphal activity high from January to May

  12. Vector bionomics and seasonal transmission of KFD • Epidemics coincide with nymphal activity • Nymph most important stage for human transmission of infection as viraemia is significant in nymphs • Adults ticks feed on cattle and viraemia is not significant

  13. Environmental factors • Tropical evergreen, deciduous forests • Clearing of forests for cultivation and other developmental activities leads to change in tick flaura and fauna

  14. MODE OF TRANSMISSION • By the bite of infective ticks (nymphal stage) • Humans are dead end in the natural cycle • No evidence of man to man transmission • Transtadial transmission is common in ticks but transovarial transmission is absent except in Ixodides species

  15. CLINICAL FEATURES • Acute phase with sudden onset of fever, headache, severe myalgia with prostation lasting for 2 weeks • GI disturbances and hemorrhagic manifestations in severe cases • Second phase characterized by mild meningoencephalitis after an afebrile period of 7-21 days • Case fatality varies between 4-16%

  16. Treatment Conservative • Antipyretics • Analgesics • Supportive therapy

  17. Diagnosis • Diagnosis by suspicion by clinical signs and symptoms • H/O occupation/travel in forests • Detecting the presence of virus in blood • Serological evidence by haemagglutination and immunofloresence

  18. CONTROL Personal protection • Adequate clothing • Insect repellants such as DMP, DEET provide 90-100% protection against tick bites • Examine themselves for ticks and promptly remove them • Health education

  19. CONTROL OF TICKS • By aircraft mounted equipment to dispense lindane, cabaryl fenthion at 2.24 kg/ hectare at forest floor • Spraying carried out within 50m around hot spots • Restriction of cattle movement brings reduction in vector population

  20. CONTROL Vaccination • Inactivated chick embryo tissue culture vaccine developed by NIV, Pune • Neutralizing antibodies in 70% of vaccinated persons • Vaccinating at risk population i.e villagers living near forests , forest workers , occupational personnel concerned with forests

  21. Bio safety concerns • One of the highest risk category pathogens • Bio safety level 4 • One of the potential bioterrorist weapon

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