Download Epidemiology_Kyasanur Forest Disease

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 …….
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
- Uttara Kannada, Dakshina
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 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
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
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
 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
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
 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
Female tick laying eggs
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
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
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
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
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
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
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
Bio safety concerns
 One of the highest risk category pathogens
 Bio safety level 4
 One of the potential bioterrorist weapon