Prioritizing Environment Is Tantamount To Safeguarding Your Own Health

The once in a life time pandemic generated the conversations about various diseases, not only their transmission and impact on health but also their origin and linkages with the ongoing environmental changes. In this article, we talk about some examples where the starting point for the outbreak is the breaching of species barrier by the causative agents due to environmental disruptions which have been exacerbated by the human activities.

Louis Pasteur's and Robert Koch's Germ Theory of disease presented evidences that 'germs' (microorganisms as viruses, bacteria, protozoa, fungi etc.) are responsible for the disease causation. These germs have to come in contact with the humans to make them susceptible to cause disease.

Over 300 new diseases have emerged in humans worldwide

The microbes remain active in sylvatic cycles (animal to animal transmission) till they breach the species barrier due to close proximity with the humans to become zoonotic (animal to human and vice versa transmission). From 1940 to 2004, over 300 new diseases have emerged in humans worldwide , out of which 70% are of zoonotic origin.

The environmental disturbances as biodiversity loss, climate change augmented by the anthropogenic activities as deforestation, changes in the land use patterns, wild life trade etc. increase the chances of humans contracting the infection from these otherwise naturally sanitized microbial reservoirs.
It is a well-known fact that climate change has led to global warming with an increase in droughts, floods, changes in habitats, rise in sea level, melting of glaciers, high precipitation etc.

The physiology, like reproduction, growth, mortality rate and habitat; survival and transmission of the pathogens largely depend on these environmental factors. These changes can be beneficial for the propagation and spread of many pathogens.

178 million hectares of forest have been deforested

This study describes that dormant artic virus can jump to a new host because of the increased temperatures in the region! The rise in resistant vectors and vector borne diseases as malaria and dengue due to increased precipitation or water-logged land masses is a well-known fact. 178 million hectares of forest have been cut in the last 30 years around the world.

Clearing up of lands for agriculture, forest resources as timber and urbanization has led to a lot of adverse effects like reduction in carbon sequestration, climate change, habitat and biodiversity loss and exposure of pathogens.

How Biodiversity richness protects humans

Anthropogenic activities like deforestation, rapid industrialization, monoculture acceleration and use of harmful chemicals in agriculture and industries has led to substantial biodiversity loss. In the last 50 years about 30% of the world's biodiversity has been lost. Apart from this a lot of species have become critically endangered and vulnerable. 33% of corals, 32% of amphibians, 12% of birds and 23% of mammals are facing the threat of extinction. Biodiversity richness protects humans from exposure to pathogens. Biodiversity loss decreases the number of natural hosts available for the pathogens, rendering increased chances of exposure to humans.

These anthropogenic drivers of the diseases are interconnecting and often overlapping. Following few examples elaborate the linkages of the environmental factors with spread of some of the epidemics and pandemics.

How dreaded diseases originate

The dreaded Acquired Immunodeficiency Syndrome (AIDS) disease caused by the Human Immunodeficiency Virus (HIV) started in 1981 and is an ongoing epidemic. Originated in non-human primates, the mutated SIV (Simian immunodeficiency virus) jumped the species barrier to infect humans. Rapid urbanization was the turning point that allowed the pandemic to start. The natural habitats of the monkey and ape populations that originally sustained the SIV, ancestor of HIV-1 were decimated by deforestation.

The virus that circulated almost exclusively among non-human primates was forced to adapt and spread to humans which were the abundant alternative host for it's survival.
The 2014-2016 Ebola Virus Disease (EVD) outbreak in West Africa is the largest Ebola outbreak since the virus was first discovered in 1976.

WHO's report

World Health Organization's report validated the hypothesis that deforestation helped spread the virus. Rampant deforestation in the region for the rapid agricultural development were major environmental disruptions that caused the epidemic. The longstanding poverty in the region exacerbated by a woefully inadequate medical response by the international health community further aided to spiraling it out of control.

Nipah virus encephalitis (NVE) spread in Malaysia and Singapore in 1999 is attributed to the pigs being exposed to and infected by Nipah virus (NiV). It spread like wildfire because of crowding and close proximity in animal husbandry. NiV spread in India was caused by fruit bats ousted from their natural habitats due to deforestation.

Cholera's connection with environment

Cholera has been with humans for centuries. It spreads in the absence or shortage of safe water and of proper sanitation and poor waste management. The causative agent is an aquatic bacteria Vibrio cholerae, which lives naturally with shellfish/crabs or other aquatic crustaceans by attaching itself to their chitin exoskeleton. The relationship between cholera outbreaks and climate and environmental changes is well established. Otherwise dormant bacteria becomes viable in higher temperatures ranging up to 30 degrees.

COVID-19 is of zoonotic origin and so are the very new Monkey pox and Marburg virus disease (MVD) outbreak in Ghana. We have also suffered swine flu and plague outbreaks in the past, which too are zoonotic. More examples of emergence and spread of diseases can be quoted to validate the fact that the degradation in the environment by anthropogenic activities is directly responsible for decimating human health. High time to preserve and conserve our ecosystems and environmental health to safeguard our own health!

About Author: Prof. Shweta Rana, Associate Professor-Environmental Studies, FLAME University
Devanshi Parekh, EVS Major, Alumna, FLAME University.