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The Covid-19 pandemic has demonstrated the devastating impact of a zoonotic disease. While the way to avert such pandemics is to break the chain of transmission from wildlife to humans, such efforts do not always receive due attention nor are implemented with scientific rigour.
One such zoonotic illness where spillover events appear to have increased, resulting in recurring outbreaks, is Kyasanur forest disease (KFD) or monkey fever.
The illness, named after Kyasanur forest in the Western Ghats, where it originated, is a haemorrhagic fever borne by the tick, Haemaphysalis spinigera. It has a fatality rate of 3-5 per cent.
Researchers believe that the disease was for centuries endemic to the forests of the Western Ghats, circulating silently among primates and ticks. It was first identified in 1957 after an outbreak in a Kyasanur forest village in Shivamogga district of Karnataka.
Though outbreaks have remained largely confined to the area, the disease in the past few decades has begun to spread to other states, with Tamil Nadu and Kerala reporting KFD for the first time in 2013, followed by Goa in 2015 and Maharashtra in 2016.
Today, India records 400-500 cases a year, as per a 2019 study published in the journal GeoHealth. What’s worrying is that an article published in Reviews in Medical Virology in 2006 highlighted rising cases of KFD in Karnataka from January 1999 through January 2005, despite routine vaccination.
An often-cited reason for the increasing cases of KFD is the growing conflicts between humans and monkeys, particularly bonnet macaque (Macaca radiata) that is highly susceptible to KFD virus.
After Chamarajnagar district, Shivamogga is home to the highest population of bonnet macaque and reports some of the highest instances of monkey raids on agricultural fields and villages. Farmers regularly stage protests demanding that the state government either keep the macaques in check or compensate them for the losses.
In 2020-21, the government allocated Rs 6.25 crore to address the monkey menace. One of its plans was to set up “monkey parks” or rehabilitation centres in forests such as Nagavalli in Hosanagara taluka of Shivamogga.
The proposal faced opposition from communities and environmentalists alike, who feared that the move would trigger KFD in the surrounding areas. In 2022, taking a cue from Himachal Pradesh, the Karnataka forest department planned to sterilise the macaques.
The plan faces criticism from several quarters because of ethical concerns and is yet to be implemented. At places, communities are funding the capture of macaques from human settlements; the animals are then released into deep forests.
But such relocation efforts are not going to help. It might rather erode the macaques’ familiarity with natural habitat, and compel them to adapt to human-altered environments and depend on cultivated landscapes, resulting in never-ending conflicts and spread of KFD.
Between 2018 and 2022, researchers from the University of Trans-Disciplinary Health Sciences and Technology (TDU), Bengaluru, visited Shivamogga to identify the exact cause of the increase in KFD. The researchers found that villages in the district are surrounded by either monoculture plantations, degraded forests, or natural forests.
Almost 90 per cent of the 144 households interviewed said that conflicts with macaques are common in areas with mosaics of monoculture plantations, specifically acacia farms, or where agricultural land has increased in recent decades.
Some 60-70 per cent of the respondents reported that macaques started invading villages only with the decline in native fruit-bearing species in the forests.
In areas where natural forests are intact or where wildlife sanctuaries are around human settlements, no serious conflicts with macaques was reported. Instead, the respondents highlighted conflicts with other wildlife such as wild boar or Indian gaur.
Further analysis showed that the prevalence of KFD and density of ticks are highest in areas where forests are degraded. This shows that habitat loss is the root cause of the increase in human-macaque conflicts as well as KFD outbreaks.
For instance, since 1973, Shivamogga has witnessed a drastic decline in natural forest cover due to encroachment for agriculture, monoculture plantations, and development activities. The district tops the list of denotified forest lands by the government.
Over 70 per cent of forest land has been denotified for purposes like growing timber. In 1980, the forest department leased out for up to 40 years, some 28,000 ha in Shivamogga to the Mysore Paper Mill (MPM), which has established monoculture plantations of acacia, eucalyptus and pine. In 2020, the lease was extended until 2026, despite opposition from local communities and environmentalists.
Ecological restoration of such degraded forests seems to be the only sustainable and ethical solution to mitigate the situation. This may be attained by reconnecting wildlife corridors and forest fragments, which in turn will minimise human-wildlife conflict.
In plantations, mature trees can be periodically removed in patches and native fruit trees be planted to restore the habitat. With time, entire plantations can be converted into native forests, addressing the problems of macaque conflict and KFD.
Chetan H C and Samartha P are with The University of Trans-Disciplinary Health Sciences and Technology, Bengaluru; Ravi Ramalingam works with Ecorest Services Pvt Ltd, a think tank in Bengaluru
This was first published in the 1-15 April, 2023 print edition of Down To Earth