KYASANUR FOREST DISEASE : A TICK-BORNE VIRAL ZOONOTIC DISEASE 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. In 2013, KFDV was detected in autopsy material of dead monkeys in Nilgiris district of Tamil Nadu state. Monkey deaths and human cases have now been reported from three neighbouring 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.
Transmission cycle and seasonal risk period for KFD
KFD, also referred to as Monkey Fever, is a tick-borne viral haemorrhagic disease, which can be fatal to humans and other primates. The causal agent, Kyasanur Forest Disease Virus (family Flaviviridae, genus Flavivirus), is a member of the tick-borne encephalitis (TBE) complex. It is transmitted by a range of tick species, with Haemophysalis spinigera being considered the principal vector. A wide range of small rodents, monkeys and birds are thought to play a role in Kyasanur Forest Disease Virus (KFDV) transmission. Cattle are probably important hosts for adult H. spinigera ticks but develop neutralising antibodies against KFDV which suppress virus amplification.
Humans, who contract KFD virus when bitten by an infected tick or by coming in contact with an infected animal, are considered dead-end hosts. This is because they cannot infect ticks nor other people with the virus and hence do not play a role in the onward transmission of KFDV.
Who is affected?
KFD first emerged in Kyasanur Forest in the Indian state of Karnataka in the 1957, after this forest ecosystem became increasingly degraded by human activities. Since 2012, Kyasanur Forest Disease has spread to new districts and states within India, and human cases have increased significantly to around 500 each year. Between 5 and 10% of people who are known to be affected by KFD develop haemorrhagic symptoms and die. There have been at least 340 confirmed deaths from the disease over the last five years.
People most affected by Kyasanur Forest Disease live in low-income forest communities and include:
- resident and migratory farmers who graze animals (largely cattle) in the forest year-round to produce manure for plantations
- tribal forest-dwellers who harvest fuel wood and non-timber forest products, such as honey, nuts, and dry leaves
- day labourers in plantations or for State Forest departments
Livelihoods are impaired by when people avoid the forest due to the risk of Kyasanur Forest Disease or due to death and sickness of family members that principally generate household income. Although KFD is managed through vaccination, information campaigns and tick protection measures, lack of awareness about the disease and poor vaccine uptake can prolong and exacerbate epidemics.
Why is KFD risk higher in degraded and fragmented forest?
The risk of contracting Kyasanur Forest Disease is thought to be higher in fragmented and degraded forests because KFD first appeared when forests were cleared for mining, road building and agriculture in the 1950s.
Many tick, wild rodent, bird and primate species are thought to have a potential role in transmission of the KFD virus. But crucially, it is not known how these potential host and vector species are linked to forest types, and which ones are key in transmitting KFD to people as forests become more degraded or open due to human activities.
Similarly, work is urgently needed to understand how the specific activities of local communities in the forest increase their risk of contracting the disease, and whether and how such activities could be avoided without harming their health and livelihoods.
Mode of transmission
KFDV is transmitted by an infected tick, especially nymphal stage ticks. The wild monkeys Semnopithecus entellus and Macaca radiata, gets the disease through the bites of infected ticks. 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 form an infected tick bite or by contact with an infected animal, such as sick or recently dead monkey. Available epidemiological data does 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 relates 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 persistent cough, may be present in some cases. Temperature may be as high as 104 0 F/40 0 C, and last for 5 – 12 days and there is intense prostration. In few cases hemorrhagic symptoms may occur in 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 persistent cough, with 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 meningo-encephalitis.
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 :
- Human surveillance: Early detection of patients, prompt laboratory diagnosis and proper management of patients is 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 unu sual suspected KFD cases/deaths to be done in the control and containment.
- Monkey surveillance: The surveillance on death of monkey/ monkeys in non-endemic as well as endemic areas of KFD to be carried out regularly in real time manner in collaboration with Forest and Veterinary Department. Human cases can be suspected in case of unusual monkey death.
- 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 periodic basis.
Personal protection
Application of repellants such as Dimethylphthalate (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 neck, chest, back, and legs) before going to the forest.
Vaccination
There is limited availability of information on KFD vaccine for human use in India. State Government of Karnataka is following KFD vaccination policy in the KFD endemic area.
Tick control
- 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.
- 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 venture into forests. Application of insecticide on cattle can prevent transportation of ticks from forests to dwelling premises.
- Physical control: Controlled burning of the dry leaves and bushes in the forest boundaries, premises of human habitats.
Important points to remember
Do’s
- Report monkey deaths to Animal husbandry/forest officials and /or Health Department OR Health Authority.
- Persons, who are visiting/working in the forest, should cover body with full clothes.
- Apply tick repellents like DMP oil to the exposed parts before going to forest.
- Wash the clothes and body with hot water and soap after returning from the forest.
- Report of incidence of the disease/deaths, which occurs as high fever with severe head ache and body ache to nearest health facility.
- Educate the villagers to avoid the forests areas where monkeys have died.
- 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.
- Ectoparasite (tick) control in cattle and domestic animals will help in reducing the density of tick’s population.
Don’ts
- Don’t bring the leaves of trees from KFD infected area to the village for cattle bedding material.
- Don’t visit the area where recent monkey death is been reported, especially an area where case of KFD has been reported in the past.
- Don’t handle the infected monkey carcass by bare hand without personal protective equipment.
Source : CD Alert – NCDC, Directorate General of Health services
Compiled & Shared by- Team, LITD (Livestock Institute of Training & Development)
Image-Courtesy-Google
Reference-On Request.
