- Kyasanur Forest Disease, a tick-borne viral illness, continues to wreak havoc in the Malenadu region of Karnataka, spreading to neighbouring states along the Western Ghats at an alarming rate.
- Deficient rainfall and intense heat in southern states, conditions conducive to the proliferation of ticks, provide additional risks of the zoonotic disease this year.
- Deforestation and significant alterations in land use and ecological dynamics have brought the virus and its carriers into closer proximity to human populations.
- The sudden withdrawal of the KFD vaccine, the only defence against the disease, citing potency issues, has left the residents of hotspots and health workers in a lurch.
As temperatures rise in Karnataka’s Malenadu region, located along the Western Ghats, the residents remain on high alert due to the resurgence of a tick-borne illness endemic to India—Kyasanur Forest Disease (KFD). Locally known as monkey fever or mangana kayile in Kannada, this viral haemorrhagic disease, caused by a Flavivirus in the family of Flaviviridae, carries an estimated fatality rate of 3% to 15%. Dengue, in comparison, kills around 2.6% of the infected, according to an estimate.
The zoonotic disease follows a predictable annual cyclic pattern, emerging during the peak winter months of November and December, reaching its zenith in the summer, and then disappearing completely with the onset of monsoon, only to resurface with varying intensity the following year.
Since January this year, the region has already recorded 12 deaths, and more than 250 positive cases of KFD. The recent demise of a seven-year-old child in Uttara Kannada district due to KFD has heightened concerns. Highlighting the gravity of the situation, K.P. Sripal, a Shivamogga-based advocate and a member of the KFD Janajagruthi Okkoota, a civil society group advocating for better accountability and government protection against the disease, notes that this tragic incident marks the first child fatality from the disease in over 30 years. While we couldn’t verify the claim due to a lack of data, Dr K. J. Harshavardhan, deputy director of the government-run Virus Diagnostic Laboratory (VDL) in Shivamogga, says that a child’s death is a rare occurrence in KFD cases. “Young children do not go into the forest often and they also have better immunity against the virus. This death is a rare one,” he tells Mongabay-India.
Health officials also observe a broader trend wherein KFD cases peak approximately every four or five years, although no official study has been conducted to substantiate this claim. This trend could potentially be due to the four to five-year immunity the body builds against the virus after an attack, points out Shivamogga resident Darshan Narayan, a scientist with ATREE who has previously worked with the Indian Council of Medical Research (ICMR) and the state health department on the disease. Thus, 2024 holds particular significance, as the local residents and officials report that the last major outbreak in this region occurred in 2019.
A looming threat of deficient rainfall and intense heat, conditions conducive to the proliferation of ticks, provides additional risks this year. “The absence of customary December showers, which typically flush away ticks in their nymph stage—when they are most virulent—has been particularly concerning,” explains Harshavardhan. “While case numbers surged in January and February, there appears to be a promising downward trajectory in March,” he adds.
This Mongabay-India correspondent travelled to Kyasanur and Aralagodu villages, Shivamogga town, and surrounding areas to interview residents and officials at KFD’s hotspots.
How Kyasanur found its place in history
Kyasanur Forest Disease was first identified in 1957 within the Kyasanur forest range, adjacent to a village of the same name in Soraba taluk of Shivamogga. The sudden death of numerous monkeys, followed by fevers in individuals with a history of forest exposure, prompted the then government (the Government of Mysore) to initiate emergency measures such as free distribution of antibiotics for typhoid. Initially suspected to be typhoid and then yellow fever, subsequent investigations revealed ticks as carriers of an “unknown” virus. Interestingly, despite its name being associated interchangeably with the deadly disease, the village of Kyasanur never reported a death from the disease or has not had any positive KFD cases in the last 25 years, according to the records with VDL, as noted by Darshan.
Reflecting on the pivotal days when the disease first emerged, Huchappa, a nonagenarian from Kyasanur village, recounts guiding four forest officers in masks and gloves to the site of the deceased monkeys in the forest. “We spent a fortnight in the forest, returning with the dead monkeys in gunny bags and two live monkeys, caught using sugarcane as bait, in a cage.” He had a ringside view of the historical event unfolding as no other resident was willing to go into the forest with the officers. Huchappa hazily remembers those monkeys as bili manga or white monkeys, likely referring to Hanuman langurs.
Further laboratory analyses conducted on various tick specimens collected from monkeys, bovines, rodents, and humans, by the former Virus Research Centre in Pune, in collaboration with The Rockefeller Foundation, alongside state public health experts, led to the isolation and coding of the virus as P9605.
Is land use change responsible for KFD’s spread?
During the early stages of detection and research, it was speculated that the virus might have been transmitted via ticks carried by migratory birds. However, the prevailing theory now suggests that the virus is endemic, and likely circulating within the Malenadu forests from an earlier period. Due to the dense forest cover and minimal human activity within these regions, the virus remained relatively undisturbed. However, with deforestation and significant alterations in land use and ecological dynamics, the virus and its carriers were brought into closer proximity to human populations.
Sixteen tick species—most of them belonging to the genus Haemophysalis—out of 40 species of ticks recorded from KFD affected areas, have been found to be carrying the virus. The virus finds its maintenance and amplification within various host animals, each responding differently to infection. Humans, acting as dead-end hosts, typically encounter the virus accidentally and do not contribute to its natural cycle. Small mammals such as porcupines, squirrels, and rodents serve as reservoir hosts, crucial for sustaining the virus’s circulation between ticks and reservoir hosts. Although these animals become infected by the virus, they typically do not display symptoms of illness.
In contrast, primates such as Hanuman langurs (Semnopithecus entellus) and bonnet macaques (Macaca radiata), serve as amplifying hosts. The virus undergoes amplification within their bodies, leading to symptomatic infection similar to that seen in humans. The occurrence of monkey deaths serves as a significant indicator, acting as a “sentinel event,” signalling a potential epidemic in the area.
From 1957–1971, the disease was confined to Shivamogga district. It started spreading to the neighbouring district of Uttara Kannada in 1972 and eight years later, in 1980, cases were reported from Chikkamagaluru and from Dakshina Kannada in 1982. In 2012, the disease was reported from Chamarajanagara district and the Nilgiri district of Tamil Nadu. The following years saw it spread to neighbouring states of Kerala, Goa, and Maharashtra, as well as other districts of Karnataka like Belagavi, Gadag, Mysuru and Hassan.
Read more: Deforestation and disease: How natural habitat destruction can fuel zoonotic diseases