Zoonosis and reverse Zoonosis – the human agent
The total area of forests in India is 802,088 sq. Km as per the latest India State of Forest Report (ISFR -2019), while that of tiger reserves including core and buffer areas stands at 71,027 sq. Km; these figures subject to the ambiguous definition of Forest.
With an exploding population and shrinking of forests, humans are inevitably interacting with wild animals, directly or indirectly, more so than ever before. A majority of emerging diseases in the last 30 years are said to have originated from wild animals.
In the wake of Coronavirus, a zoonotic disease originating in horseshoe bats and probably infecting humans via Pangolins, the world has been jolted out of sleep, to the circumstances of contracting diseases from wild animals.
In fact, the increasing porous boundaries of forests and linear development projects have increased the two-way interactions between humans and wild animals. While this increased the scope of zoonosis, there is also the issue of the lesser known (to common man) reverse zoonosis or zooanthroponosis (which is wild animals contracting diseases from humans or human related activities).
While AIDS, SARS, MERS and plethora of zoonotic diseases including the SARS-COV2 (Covid-19) have taken the world by storm, reverse zoonotic diseases are spreading even to the remotest corners of the world, through the obvious agent, humans. For example, scientists have found the presence of human-origin bacteria salmonella and campylobacter in Polar fauna. It is theorised that these strains could have a devastating effect ranging from collapsing of local populations to extinction of the sensitive species in Antarctica.
Probably, a few months ago, this article wouldn’t have raised too many brows. But, today, we are seeing the impact of the Coronavirus SARS-COV2 in humans, and so it is high time we need to understand, act on reducing our interaction with wildlife to reduce the occurrence of zoonotic and reverse zoonotic diseases. An emergent virus in humans could be treatable or have a reduced spread, but a similar virus in animals could wipe local populations and cause extinction.
Porous Boundaries
With an increased human population, particularly in fringe areas and villages located inside forests, it is not just the rise in human-animal conflict that is worrying but also the human activity inside or along the fringes. Human activity includes open defecation, cattle grazing, collection of forest products such as firewood, honey, Tendu leaves (wrapper for beedis), Mahua (locals use it to make wine) etc, poaching, encroachment and trespassing.
Since there is no particular demographic measure of people living inside and outside the forests, I am forced to consider the rural population numbers. In 1901, the rural population of India stood at 200 million approx. By 1951, the number rose to 300 million and by 2011, the number exploded to 892 million by 2018 (which is four times that of the population a century ago).
One of the most troubling aspects in rural areas is defecation in open. 36.5% of this rural population practices open defecation (as per data from World Bank) which is around 325 million people which causes various diseases for humans such as diarrhoea and intestinal worm infections, typhoid, cholera, hepatitis, polio that can seep into wild populations.
The extent of human encroachment and activity in and around Forests can be understood from Sariska, one of the heavily strained Tiger Reserves. The 900 sq. Km reserve (of which 800 sq. Km is ear-marked as Critical Tiger Habitat) is surrounded by more than 3000 villages. It was recommended to relocate more than 29 villages, of which only 3 have been relocated, to this date. 40% of the reserve is encroached upon by cattle and grazers. In addition, illegal mining has been a rampant issue, despite a Supreme Court ban on the same.
Poaching already wiped the tigers of Sariska more than 15 years ago. Tigers were reintroduced from Ranthambore, but the reserve is challenged by not only poaching but also electrocution and poisoning. The male to female ration stands at an alarming 1:8 which increases the dangers of a genetic bottleneck.
Barring a handful of tiger reserves (the total area is approx. 2% of India), most of the other reserves are overrun by humans, and are heavily fragmented. The forests are no longer contiguous and are engulfed in a matrix of agricultural fields. Tiger forests are one of the most protected forests in India, and if this is the case in the most protected areas, it is not hard to imagine the condition of the rest of the forests, which is around 22% of geographic area of India.
The subsistence of indigenous tribal populations on the naturally available forest resources has become unsustainable that it is forcing them to abandon their traditional livelihoods and take up farming or cattle rearing, which in turn is causing irreparable damage to forests.
While, this figure may be less than the rural and fringe population depending on forests, but both are causing an increase in cattle population along with a rapid increase in feral dog numbers.
Feral dogs have been observed to enter the forests and even hunting deer in packs. They are known to mate with wild Jackals (and possibly other canines) to produce hybrid species. Jackals being scavengers subsist in fringes of villages.
Feral dogs are known to harbour deadly diseases such as Canine Distemper Virus (CDV) and Canine Parvo Virus (CPV). In Africa, these diseases from dogs have wiped out local populations of Lions in Serengeti National Park. In 1994, CDV wiped out around 1000 lions in Tanzania. African Wild dogs and Ethiopian Wolf populations too suffered irreparable damage. At the Great Indian Bustard Sanctuary, Nannaj, Maharashtra, a team of scientists tested around 80 dogs and found that 75 of these dogs had high levels of CDV and CPV. In end of 2018, in the last known lair of Asiatic Lions in Gujarat, a Canine Distemper Virus (and babesiosis, a zoonotic tick infection) has killed around 30 lions.
Even in Cattle, there are more than tens of diseases with zoonotic and reverse zoonotic potential, such as anthrax, rabies, ringworm, salmonellosis etc.
Given the increase in wild animal and human conflict, it is not hard to comprehend the increasing interaction and crossing paths which can have detrimental effects on wild animals (and humans alike).
The government needs to move an excess population from forests and fringes and provide them with an alternate means of living.
Linear Development Projects
While rural population increase is one worry, the development or growth of cities has created another problem. In 1951, there were 5 cities with a million-plus population, and by 2011, there were 53 such cities. With an increase in number of cities, there is an industrial growth and to move people and goods, linear infra needs to be developed.
New road ways and railways are constructed through forests. Existing ones are expanded on a war-footing, with scant regard for forests and natural ecosystems. Telecommunication, electric and pipelines (oil and water) are laid, water canals are dug, fences are erected blocking the natural wildlife corridors.
The recent NH 44 Pench highway expansion through Pench forests, the Gaduli-Santalpur road in Rann of Kutch Gujarat that runs through the only Flamingo breeding ground in Asia, the Ken-Betwa interlinking project submerging 89 sq. Km of Pench Tiger Reserve, the North Koel dam submerging 119 sq. Km of Palamu Tiger Reserve etc., are blatant examples of the preferential treatment to linear development, over ecosystems.
Through a forest, a road or a railway line is not only damaging and polluting the sensitive ecosystems but also leading to littering along the path.
Many species of monkeys such as macaques and langurs are seen congregating along the roads or even tracks to pick up the food thrown away intentionally (for feeding) or unintentionally. This not only affects the foraging capabilities of these human ancestors but also increases the scope of reverse zoonosis. It is said that monkeys and apes are highly susceptible to human diseases. They thus become vectors or carriers of the human diseases into the wild.
This in addition to getting humans in close proximity to animals; the more the roads, the more will the public travel, often getting them in reach of the previously inaccessible forests. This aides in more porosity along the roads and also is responsible for an increase in poaching.
Studies show that there is a two-fold increase in extraction area of bush-meat, when roads pass through forests. Even in India, consumption of animals such as wild boars, monitor lizards, monkeys, deer and even pangolins and flying foxes is rampant and the demand is increasing. We shouldn’t be surprised if there is a Wuhan-like incident in India.
Until and unless our interaction with the wild animals is reduced, one or the other species will suffer to the extent of local extinctions. Coronavirus might have raised awareness about zoonotic diseases, but the need to protect wild animals due to reverse zoonosis should also be a top priority – and to do so, we need to rethink on our ever-increasing population and mindless development.