Kyasanur Forest Disease: Rise and spread of six-decade-old menace

Complacency in re-administration causes rise, as vaccine immunity lasts a year; 2022 to see peak, says scientist

Published: 24th April 2022 06:36 AM  |   Last Updated: 24th April 2022 06:36 AM   |  A+A-

Express News Service

BENGALURU: Kyasanur Forest Disease (KFD), aka Monkey Fever, a zoonotic viral disease transmitted to human beings through the bite of infected ticks, this year may see its peak in numbers as scientists predict that every three years the virus reaches its peak (parabolic wave). The last time it peaked was in 2019, with a maximum of 23 deaths and 343 cases in Shivamogga alone.

Dr Ranganath S, Scientist, Institute of Animal Health and Veterinary Biologicals, told The New Sunday Express, “This disease is directly related to the vaccination and immune status. Vaccines are given in one year and immunity lasts till the next year, and there would be a vaccine associated dip in cases. This makes people complacent and they don’t take the vaccine the following year, and cases peak during the third year.”


This six-decade-old disease has remained endemic due to various factors, mainly, man-animal interface. However, this indigenous disease was first highlighted in the Kyasanur forest range (hence the name) of Soraba taluk in Shivamogga district, and was confined to this zone.

Later, it spread to Sagar andHosanagar in the district, and is still active in these places. It then spread to Chikkamagaluru, Karwar and lately, Mysuru. In the past four years, it has spread to the neighbouring states of Goa, Maharashtra and Tamil Nadu.People, most often villagers, have close contact with nearby forest areas. Often, their houses are located inside forest areas, so human interaction with the forest ecosystem paves the way for monkey tick bites, resulting in the KFD.

The causal agent of this disease is from the virus family Flaviviridae, which is a member of the tick-borne encephalitis (TBE) complex. Haemaphysalis spinigera is the principal vector which settles on small rodents, monkeys and birds, which play a role in KFD transmission.

“It is no more limited to these areas. Even in cities like Bengaluru, when monkey deaths occur, a postmortem is done to. check for KFD. However, it is rare in such cities as the interface with ticks is less, and also immunity levels are high,” says Dr Ranganath.

The death of monkeys sends warning signals to health department officials, who then categorise the areas as high-risk, moderate and low-risk. The ticks bite the monkeys, leaving them dead.Dr Rajesh Suragihalli, District Health and Family Welfare Officer, Shivamogga, explains: “If monkey deaths are noted, health officials plunge into activities like sprinkling of Melathene powder in and around a 60- metre area and begin surveillance for early detection.”

He says outbreaks are normally in summer, as villagers visit nearby forest areas to collect firewood and dry leaves to save for the rainy season, and also let cattle into forests for grazing. “With this, the ticks enter the backyards of households, resulting in KFD,” he says.Usually, these ticks vanish with rain in the forests. So, with the onset of rain in May, the KFD infection lowers significantly.

In March 2019 , when the outbreak was severe with cases spreading from Karnataka to other states, the government formed a committee led by former Additional Chief Secretary M Madan Gopal and former Dean of Mandya Institute of Medical Sciences Dr Shivakumar Veeraiah, to enquire about gaps in efficient control of the outbreak, contain the spread and proper management of KFD patients, which needs to be properly implemented. However, although there are some efforts to follow recommendations and ensure the KFD cases are contained, experts feel the state reacts only when cases rise.

Health officials are expected to provide booster vaccines to villagers every year, between December and March. Annual rounds of vaccination using formalin inactivated tissue-culture vaccines have been conducted in the affected regions since 1990. The production of vaccines for the entire country happens in a lab in Bengaluru.

Dr Chandranaik, scientist in charge of KFD vaccination at the Institute of Animal Health and Veterinary Biologicals, says, “On an average, five lakh doses are produced every year and vaccines have a shelf life of one year from the date of production. It is from this lab that it goes to the health department and they dispose of it based on requests from other states.”

Though availability is not a concern any more, vaccinating people has been a challenge. Since the disease spreads among the labour class and the vaccine is painful with at least a day or two of fever, most of them don't volunteer for vaccination as their livelihoods are lost if they don't go for work, a health official says. He says the government needs to compensate the families for two days after vaccination to encourage them.

Health officials say cases are coming down in Sagar, Thirthahalli and other taluks due to the collective efforts of the health, forest and animal husbandry departments, and establishment of ‘fodder banks’ in the affected areas, preventing villagers from entering forest areas. However, they have not been able to contain the disease spread to other cities, districts and neighbouring states.
(With Subhashchandra NS & Ramachandra Gunari)

Shivamogga, Sagar and spread to adjoining areas in Chikkamagaluru, Udupi, Uttara Kannada, Dakshina Kannada and now spreading beyond the Western Ghats to Kerala, Tamil Nadu, Goa, Maharashtra and appears to be turning into an epidemic..

Scientists and public health experts working in the affected regions say in March 1957, there was an outbreak of Yellow Fever-like disease in Kyasanur forest in Shivamogga district. Renowned field entomologist Rajagopalan PK was called to investigate it.

The KFD virus Flaviviridae was isolated from a sick monkey and the viral samples of the insect collectors in the team were sent to Rockefeller Laboratory in New York, which confirmed that the virus was related to the one causing Omsk Hemorrhagic fever earlier found in Siberia, Russia, the reason being tick bites.

During this time, construction of Linganamakki dam over the Sharavathi river displaced nearly 22,698 families and submerged a lot of prime forest land. Ticks then moved from wild animals to cattle, as the displaced people were rehabilitated in other parts of Shivamogga. Landscape changes or replacing evergreen forests with plantations, are key to KFD spreading.

What is KFD?

KFD is a zoonotic viral disease identified more than six decades ago. It is transmitted to human beings by the bite of infected ticks. As it was first detected near Kyasanur forest area in Shivamogga district, the disease was named Kyasanur Forest Disease or monkey fever. It is not contagious from human to human, as with Covid-19.


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