KYASANUR FOREST DISEASE

It is a febrile disease associated with hemorrhages caused by an arbovirus flavivirus.

Transmitted to man by bite of infective ticks.

History :KFD 1st recognized in 1957 in Shimoga district of

Karnataka state in South India.Local habitants called the disease “ monkeys disease”

because of its association with dead monkeys. The disease was later named “ Kyasanur forest” – from

where the virus was 1st isolated.

Problem statement:The disease was 1st found to be limited to an area

around the original focus (Shimoga district) covering about 800 sq.km.

The disease is now restricted to four districts ( Shimoga, North Kannada, South Kannada, Chikamagaloor) in Karnataka state in India covering over 6000 sq. km.

Serological surveys in different parts of India revealed antibodies to KFD or a closely related virus in human & animals, particularly in cattle in Kutch & Saurashtra.

According to the reports, the disease continues to be active in its endemic foci.

The outbreak during 1983-84 seems to be the largest with 2,167 cases & 69 deaths, as against 571 cases & 15 deaths during 1981

The Karnataka government has established a surveillance system which monitors the occurrence of KFD in humans & mortality in monkeys in known epidemic areas, as well as neighboring areas.

Deaths of monkeys are considered as heralders of this disease in endemic area.

The reported number of cases & deaths due to Kyasanur forest disease from Karnataka state in 1999-2004.

Year Cases Deaths

1999 10 0

2000 30 3

2001 59 2

2002 98 6

2003 306 11

2004 112 2

Epidemiological determinants Agent: The agent KFD virus is a member of group B toga

viruses (flavivirus)It is antigenically related to other tick borne flavivirus,

particularly the Far Eastern tick-borne encephalitis & Omsk hemorrhagic fever.

KFD has a prolonged viraemia in man for about 10 days or more.

Natural hosts & reservoirs: Small mammals particularly rats & squirrels are the

main reservoir of the virus.Birds & bats are less important hosts.

The monkeys are amplifying hosts for the virus- they are not effective maintenance hosts because most of them die from KFD infection.

Cattle provide Haemaphysalis ticks with a plentiful source of blood meals, which in turn leads to a population explosion among ticks, thus cattle's are very important in maintaining tick populations but play no part in virus maintenance.

Man is an incidental or dead-end host, and plays no part in virus transmission.

Vectors :The virus has a complex life cycle involving a wide

variety of tick species.15 species of hard ticks of the genus Haemaphysalis,

particularly H. spinigera & H. turtura are known to transmit the disease.

KFD has also been isolated from soft ticksThe highest number of human & monkey infection

occurs during drier months (January - June) – period coincides with the peak nymphal activity of ticks.

Host factors :

Age: Majority of cases affected were between 20 to 40 years.

Sex : Attack rate was greater in male than in femaleOccupation : The attacked people were mostly

cultivators who visited forests accompanying their cattle’s or cutting woods.

Human activity: The epidemic period correlates with the period of greatest human activity in the forest i.e., from January until the onset of rains in June.

Mode of transmission :The transmission cycle involves mainly monkeys &

ticks.The disease is transmitted by the bite of infective

ticks, especially nymphal stages. There is no evidence of man to man transmission

Mode of transmission:Estimated to be between 3 and 8 days

Clinical features: Acute phase lasts for 2 weeks. Sudden onset of feverHeadacheSevere myalgia with prostrationGastrointestinal disturbanceHemorrhages from nose, gums, stomach & intestine ,

occur in severe cases.Second phase:Mild meningoencephalitis after an afebrile period of 7 to

21 days.Manifested by a return of fever, severe headache

followed by neck stiffness, coarse tremors, abnormal reflexes and mental disturbances

The case fatality rate has been estimated to be 5 to 10 %

Diagnosis is established only after detecting the presence of virus in the blood and /or serological evidence

Control measures:Control of ticks: For control of ticks in forests, application can be made

by power equipment or by aircraft-mounted equipment to dispense carbaryl, fenthion, naled or propoxur at 2.24kg of active ingredient per hectare

The spraying must be carried out in “hot spots” i.e., in areas where monkeys deaths have been reported, within 50 meters around the spots of monkey deth, beside endemic foci.

Heavy tick population in the forest area is attributed partly to the free roaming cattle, restriction of cattle movement is thought to bring about a reduction in vector population

Vaccination: The population at risk should be immunized with killed

KFD vaccine.Personal protection:Protection of individuals exposed to the risk of infection

by adequate clothing & insect repellent such as dimethyl phthalate (DMP, DEET) should be encouraged.

They should examine their bodies at the end of each day for ticks & remove them promptly.

The habit of sitting or lying down on the ground should be discouraged through health education.