Deforestation is a well known driver of climate change — reducing green spaces in the world and often replacing it with towns or land for agriculture to accommodate or feed an ever-growing population. Could it also be the case that deforestation is leaving the population more exposed to disease?
The two phenomena seem unlinked on the face of it, but such a notion is not without precedent. Rates of zoonotic diseases — those spread by animals — have shown a correlation with those living in areas close to fragmented forests. Lyme disease, spread by ticks, has shown to increase in areas associated with fragmented forests and deforestation in the US.
Ebola is another example of this concept. The disease is currently raging in the war-torn Democratic Republic of the Congo. It has been found that human activities in regions previously covered by forests favour the presence of some bat species — believed to be reservoirs of the Ebola virus. This has resulted in higher numbers of cases in areas where deforestation is rife.
In India, across the Western Ghats, deforestation is giving rise to higher rates of Kyasanur forest disease (KFD). KFD is caused by the Kyasanur forest disease virus (KFDV), which is spread to humans by tick bites or through contact with an infected animal, such as a monkey — hence the commonly used name “monkey fever”. The disease is endemic in south Asia and made headlines in Karnataka last year following a KFD outbreak. At the time, lapses in protocol on the part of the state health department concerning vaccination were flagged.
Vaccination against KFDV should take place within ten kilometres of any known infected person or infected animal. Reports suggested that this did not occur, instead only covering a short distance from each infection site, effectively allowing the infection to leapfrog from village to village.
Experts found through satellite imagery that areas prone to outbreaks coincided with those that were currently witnessing deforestation. This deforestation typically meant that human activity in the area increased, often bringing farm animals which could also potentially harbour the ticks.
The surge in disease cases often presents as a temporary issue. Another study published early in 2019, reported that in the 1983-84 cases, there was a massive outbreak of KFD with 2,589 cases. At the time of the outbreak a 1983 news article noted that 400 hectares of virgin forests in the Western Ghats were cleared to establish cashew plantations. An outbreak at this time is not unexpected, as during the forest clearing there would be increased interaction between workers and tick-prone areas.
Environmental destruction is too often thought of as just a contributor to climate change. While of dire importance of its own accord, for many this seems like a concern relegated to the far-future. Destruction of the environment can and has had a direct impact on human health in the short term as well, with these diseases highlighting this.