Kyasanur Forest Disease (KFD) is a zoonotic disease associated with sudden onset of high-grade fever, prostration, nausea, vomiting, diarrhea, and occasionally neurological & hemorrhagic manifestations.

It derives its name from the forest range where the virus was first isolated. It is also known as “monkey disease/monkey fever” because of its association with monkey deaths.

Incidence in India

The disease was first reported in 1957 from Shimoga district, Karnataka, which is a primitive sylvan territory in Western Ghats of India, subsequently spread centripetally to other districts of Karnataka viz., Chikkamagalore, Uttara Kannada, Dakshina Kannada, and Udupi districts and to Chamarajanagar district in 2012 and Belagavi district in 2016.

2013, KFDV was detected in autopsy material of dead monkeys in the Nilgiris district of Tamil Nadu state. Monkey deaths and human cases have now been reported from three neighboring states bordering Karnataka viz., Wayanad (2013) and Malappuram districts of Kerala (2014), North Goa district of Goa state (2015) and Sindhudurg district of Maharashtra (2016). Recent incidence has been reported from Wayanad district, Kerala.

Mode of transmission

KFDV is transmitted by an infected tick, especially nymphal stage ticks. The wild monkeys Semnopithecus entellus and Macaca radiata get the disease through the bites of infected ticks. The infection causes severe febrile illness in most of the monkeys. When infected monkeys die, the ticks drop from their body, thereby generating “hot spots” of infectious ticks that further spread the disease. Humans can get the disease from an infected tick bite or by contact with an infected animal, such as a sick or recently dead monkey. Available epidemiological data do not suggest any human-to-human transmission. However, human cases have been reported in the past while working on this virus in the laboratory.

The epidemic period usually begins in October or November and peaks from January to April, then declines by May and June. The epidemic/ outbreaks relate to the activity of nymphs, which is very high during November to May.

Symptoms

Incubation period: Estimated to be between 3 – 8 days after the bite of an infective tick.

(KFD) usually presents with sudden onset of high-grade fever with chills, intense frontal headache, severe myalgia, and body aches. Muscle tenderness, photophobia, nausea, vomiting, and diarrhea are usually seen. Respiratory symptoms like a persistent cough may be present in some cases. The temperature may be as high as 104 0 F/40 0 C, and last for 5 – 12 days and there is intense prostration. In a few cases, hemorrhagic symptoms may occur in the early stage in the form of bleeding from the nose, gums, and intestines as evidenced by hematemesis or fresh blood in the stools. Some patients have a persistent cough, blood-tinged sputum, and occasionally substantial hemoptysis but generally, resolve soon.

In severe cases, neurological symptoms like neck stiffness, mental disturbance, coarse tremors, giddiness, and abnormality of reflexes are noted.

he second phase of the illness occurs after the febrile phase, on an average, from day 8 onwards. This phase is initiated by headache, severe prostration progressing to signs and symptoms of central nervous system involvement in very few cases presenting as meningoencephalitis.

Case fatality is 2 – 10%. Fatality is higher in the elderly and in patients with co-morbid conditions like – liver diseases (alcoholic) etc.

Treatment

No specific treatment for KFD is available; however, prompt symptomatic and supportive therapy including maintenance of hydration, hemodynamic stability, and management of neurological symptoms decreases morbidity and mortality.

Prevention and control

Surveillance:

KFD surveillance consists of three major components :

1. Human surveillance: Early detection of patients, prompt laboratory diagnosis and proper management of patients are very important. Passive routine surveillance and routine review of the surveillance data to be done under IDSP to detect impending outbreaks of KFD. Event-based surveillance of unusual suspected KFD cases/deaths to be done in the control and containment.
2. Monkey surveillance: The surveillance on the death of monkey/ monkeys in non-endemic as well as endemic areas of KFD to be carried out regularly in a real-time manner in collaboration with Forest and Veterinary Department. Human cases can be suspected in case of unusual monkey death.
3. Tick surveillance: Tick surveillance and tick mapping for identifying hotspots and tick incrimination studies in KFD prone areas for monitoring tick positivity for KFD to be carried out regularly on a periodic basis.

Personal protection

Application of repellants such as Dimethyl phthalate (DMP), NN-Diethyl-m-Tolumaide (DEET) and certain other proprietary preparations having these or similar chemicals, e.g. Mylol on the exposed parts is effective from one to a few hours. If the duration of stay inside the forest is longer, more than one application may be necessary.

People living in the forest or visiting forest areas should strictly use tick repellents along with personal protection measures (long clothes by covering the neck, chest, back, and legs) before going to the forest.

Vaccination

There is limited availability of information on the KFD vaccine for human use in India. State Government of Karnataka is following the KFD vaccination policy in the KFD endemic area.

Tick control

1. Source reduction: The spraying of insecticide may be carried out in areas where monkey deaths have been reported within a radius of 50 meters around the spot of the monkey death. It is also effective in forest tracks frequently visited by people for various activities.
2. Vector control: Vector control may be done by dusting with insecticides or by spraying with pyrethroids. Repellents may be used on body/exposed parts during a venture into forests. The application of insecticide on cattle can prevent the transportation of ticks from forests to dwelling premises.
3. Physical control: Controlled burning of the dry leaves and bushes in the forest boundaries, premises of human habitats.

Important points to remember

Do’s

1. Report monkey deaths to Animal husbandry/forest officials and /or Health Department OR Health Authority.
2. Persons, who are visiting/working in the forest, should cover the body with full clothes.
3. Apply tick repellents like DMP oil to the exposed parts before going to the forest.
4. Wash the clothes and body with hot water and soap after returning from the forest.
5. Report on the incidence of the disease/deaths, which occurs as a high fever with severe headache and body aches to the nearest health facility.
6. Educate the villagers to avoid the forest areas where monkeys have died.
7. Bring to the notice of the Health Department or Department Hospitals or Private Hospitals, regarding any serious cases in the villages or from KFD affected areas, which require immediate symptomatic treatment.
8. Ectoparasite (tick) control in cattle and domestic animals will help in reducing the density of tick’s population