Developing speed of human civilization has geared- up with the advert of technology, energy, and booming market economy in the last decades resulting number of human and natural calamities including several infectious diseases spreading around the globe. Over the past two decades, the outbreaks of novel diseases have been increasing steadily. Most of these disease outbreaks are due to the different modes of contact with new pathogens especially carried by animals which are also known as zoonotic diseases.

Changes occurring in nature such as biodiversity loss, climate change as the consequences of anthropogenic activities are the prime factor of zoonotic diseases. Anthropogenic activities like commercial wildlife trade, logging and deforestation, expansion of agriculture into previously undisturbed areas, and loss of habitat alter the delicate balance of the ecosystem which results in disturbance to flora and fauna in a broad spectrum. Habitat of animals residing in that area is not the only thing being disturbed but also the overall wellbeing of animals. The stress may result in breaking the immunity barrier of animals which leads to reservoir spillover causing novel diseases. Also, the migration and movement of animals have a greater chance of proximity with other animals and people and share pathogens imploding new diseases to humans or other life forms which may result in the pandemic. Similarly, bush meat hunting, large livestock farms, consumption, and import/export of exotic animals also serve as a source for spillover of infections from animals to people and will suddenly create epidemic outbreaks with risks of pandemic.

 

                  (Photo credit: Amnat/alamy)

Zoonotic diseases have a major impact on global health, accounting for three out of four newly emerging diseases. According to the World Economic Forum, the world has lost 60 percent of all wildlife in the last 50 years while a number of new infectious diseases have quadrupled in the last 60 years. Research shows that serious diseases have been spilled over from animals to humans in a period of time.

The Ebola outbreak in West Africa initially spread to humans by fruit bats as the result of deforestation, leading to interaction between humans and wildlife. The Nipah virus in East Asia resulted from the intense pig farming done in the encroached habitat of infected fruit bats. Likewise, Hendra virus in Australia, Swine flu (H1N1), West Nile virus, Middle East Respiratory Syndrome (MERS), and Sudden Acute Respiratory Syndrome (SARS) were all because of anthropogenic disturbance to wildlife. All of these zoonotic disease outbreaks can be traced back to the inter-linkage between humans and beast. Correspondingly, the still prevailing coronavirus disease (COVID 19) caused by (SARS-CoV-2) is a novel infectious disease arising due to human encroachment in nature.

This disease has become a pandemic, causing havoc and has made the whole global population kneel down on knees. Multiple studies show that the virus of COVID-19 initially came from bats to humans through an intermediary animal. Pangolin the most illegally traded mammal in the world is thought to be an intermediary host between bats and humans. The patient zero (first case) of COVID-19 was reported in Hubei province of China near a seafood market center where a profuse number of animals are poached, killed and sold as delicacies and traditional medicines. Now the disease has spread all over the globe and bought it at peril. Such an incident of an interaction between wildlife and human has resulted in many pandemics in the past and may cause in the near future too.

Apart from this, climate change is also a major factor that plays a vital role in shaping the frequency of pandemics. Shifting of climatic patterns force species to change their habitat into an area where humans are prevalent with new opportunities for pandemics to evolve. It also alters and accelerates the imparting patterns of pathogens modifying the frequency, genetic makeup, habit, and survival of the species reflecting the inevitability of outbreaks and epidemics. Research shows that nearly one- third of emerging infectious diseases over the past 10 years were vector-borne (diseases like malaria, dengue fever) as a result of unusual change in climate. It even brings old viruses back from dead, thawing Zombie contagions like anthrax released from a frozen reindeer in 2016, which can come down from arctic and haunt us from the past.

Biodiversity threat and climate change aggravate each other. The extinction of species and habitats is correlated with climate disruption which ultimately contributes to the rise of pandemics. Study shows that the potential for future pandemics are likely to occur more frequently and spreading more rapidly.

According to IPBES, as many as 1.7 m unidentified viruses of the type known to infect people still exist in mammals and birds and probably even more disruptive and fatal than COVID -19. Thus, there is an urgent need for constructive strategies to minimize human effects on the environment, reducing the risk of pathogens which induce zoonotic disease outbreaks.

(Bhattarai is currently a B.sc Third year student at Institute of Forestry, Pokhara campus, Nepal)