Kyasanur Forest DiseaseDr Gautham MS LecturerDept of Community Medicine M S Ramaiah Medical College

History ….. Heavy mortality in two species of monkey ( Langur & Red faced bonnet ) in 1955 in forests of

Shimoga led to the discovery of KFD

Mortality in monkeys was followed by acute febrile prostrating illness among villagers and few human deaths

History …….Autopsy on monkeys

Place of reporting of First monkey death in march 1957

Kyasanur forest disease Found in India Limited originally to

Shimoga district in Karnataka (800 sq km

Newer foci in 3 more districts namely U.kannada,D. Kannada and Chikmangaluru

( 6000 sq km ) Serosurveys reveal KFD in

Kutch & Saurashthra

Problem statement The outbreak during 1983-1984 is the largest with

2167 cases and 69 deaths.

In 1997 the cases came down to75 and deaths to 4.

The number of human deaths varied between 4-15% of the cases

Even today few hundreds of cases and some deaths are reported

Agent factors .. Kyasanur forest disease (KFD) is a 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

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

Natural hosts & reservoirs Circulates in small mammals rats, squirrels, shrews

and bats are the main reservoirs .

Neutralizing antibodies have also been found in cattle, buffaloes, goats and porcupines

Maintenance hosts – maintain the infection in nature

Natural hosts & reservoirs

Monkeys are the amplifying hosts for the virus.

Amplifying hosts --- multiplication of the virus takes place at very high levels such that the intensity of infection is very high.

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

VECTORS Female tick laying eggs Virus has been isolated from 16

species of ticks but Hard tick species of the genus Haemophysalis particularly H.spinigera and H.turtura are the main vectors

Ticks act as both as vectors and reservoirs of infection in KFD

Vector bionomics and seasonal transmission of KFD

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

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

Environmental factors Tropical evergreen,

deciduous forests

Clearing of forests for cultivation and other developmental activities leads to change in tick flaura and fauna and is an important determinant for outbreaks

MODE OF TRANSMISSION

By the bite of infective ticks.(nymphal stage ) Human is dead end in the natural cycle There is no evidence of man to man transmission Transtadial transmission is common in ticks but

transovarial transmission is absent except in Ixodides species

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%

Treatment Conservative

Antipyretics Analgesics Supportive therapy

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

CONTROL Timely control decreases morbidity and mortality in

humans 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

CONTROLPersonal 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

CONTROLVaccination 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

Bio safety concerns One of the highest risk category pathogens Bio safety level 4

One of the potential bioterrorist weapon

THANK YOU