Expert Speak Health Express
Published on May 04, 2020
Inter-species spillover of viruses: Understanding zoonosis and India’s future concern

Opening wet markets as cause of concern

As China emerges from almost 80days of lock down with diminishing cases of COVID-19, a number of the wet markets of Wuhan region, (except for the Huanan Seafood Wholesale Market around which the primary cluster occurred) are coming back to business. Now, wet markets are very common features especially so for the South Asian countries where fresh, perishable items like fish, meat etc. can be acquired. In Chinese wet markets, along with items found conventionally worldwide, exotic creatures like bats and pangolins are also sold for meat. For China, they are a very essential part of their daily life. Unfortunately, around September 2019, one of those  exotic creatures, most probably a bat, or a pangolin that came in contact with food mixed with bat saliva, carried a deadly virus that went through a inter-species spillover and started infecting human beings and very rapidly so. Now, as those wet markets start business once again, the whole world asks in horror, will this make way for another inter-species spillover of a new virus in future?

Understanding zoonosis

When a virus changes its infectable species from an animal to a human host, the process is called ‘zoonosis’. Zoonosis has happened before and is bound to happen in future also. Close contact with cattle and domestic animals caused zoonosis of strains of avian influenza and anthrax. Zoonotic infection through food, especially meat is quite common. For example, Salmonella infection through contamination of meat can cause Typhoid or Para-typhoid. Zoonotic infections from insects are also common.

But, some of the recent zoonosis of deadly new or ‘novel’ viruses came from what can only be described as human being’s intention of going into the unknown, into previously undisturbed forests. Encountering new plants, animals, and by default, a huge store house of new pathogens. In last century viruses of HIV and Ebola started infecting human beings via zoonosis. Both of these viruses started spilling over from animals (chimpanzees and bats, respectively) to humans in the jungles of African continent and can be linked to the consumption of ‘Bush Meat’. Bush meat is the meat of hunted wild life used for human consumption. This practice still goes on in a number of forested regions in tropical Africa, Asia, Central and South America. The Bush Meat trade grew during 1990s and caused the demise of a large number of chimpanzees and other primates, bats, toads and rodents. Around 2005, commercial harvesting and trade of bush meat was acknowledged as a threat to biodiversity. As the growing population result in declining forested areas and increasing demand for meat, the hunters are going into previously unexplored forests increasing the chance of encounter with new pathogen infected animals and inter-species spillover of novel viruses.

The zoonosis of HIV (Human Immunodeficiency Virus) is famously known as the Cut Hunter Hypothesis. The HIV is very similar to SIV or Simian Immunodeficiency Virus found in the Chimpanzees. It is presumed in the first half of twentieth century, while preparing the meat of a chimpanzee infected with SIV, the hunter had an open wound through which the virus entered his body. It would take the virus half of a century of mutation though to reach its present form of HIV. And it’s still mutating. The Ebola Virus follows almost the same trajectory of zoonosis like HIV. And, as mentioned before, it is being presumed that, SARS-CoV-2, the virus responsible for present Covid – 19 pandemic went through a similar inter-species spillover.

Controlling zoonosis: How is it possible?

The existence of exotic wild animal meats in the wet markets of China has been under fire after the COVID-19 outbreak. The wild animal section of the Huanan market, the assumed epicentre of the outbreak, sold live and slaughtered species of snakes, beavers, porcupines, and baby crocodiles and many other animals like bats and pangolins. And these markets should be under surveillance for sure. World Health Organization (WHO) has instructions on how a healthy food market should operate. The document has a full annexure on avoiding avian influenza from wet markets. It gave high priority to clean cages, hygienic butchering  environment, personal protective equipment (PPE) for sellers and handlers, market zoning to stop contamination of different types of meat, hand washing and sanitizing, education and awareness regarding wet market practices and monitoring of the market as a whole. Instructions, if properly followed, might have been able to stop the global crisis we are facing now.

But, blaming a single country or controlling wet markets only in that country might not be the proper preventive measures to control or restrict future zoonosis. Because, as mentioned before, wet markets are common phenomena in a number of developing countries, including India. And, butchering of wild life for food is a common practice in a number of countries. There are complex reasons behind these practices ranging from traditional food habits to sheer poverty.

Zoonosis a result of disturbed forests

In 2014, Smith et al. published their work on how the rate of zoonosis has escalated since the 1980s. Jones et al. described zoonosis from wildlife as ‘the most significant, growing threat to global health’. Some experts (like David Quammen) have the opinion that the increased zoonosis might have a relationship with the deforestation, pressure on forest ecosystem and increased human-wildlife interactions. An ecosystem, when functioning and healthy, (for example, a healthy pristine forest) provides some benefits to human kind. They support nutrient cycles, soil formation, primary production that in terms help to provide provisioning, regulating and cultural services. One of those regulating services of the forest is controlling diseases. One of the processes of doing so is by containing pathogen carrying organisms within its depths and away from human contact. But, when the forest ecosystem is disturbed, it causes behavioural changes in animals increasing their encounter with human beings and domestic animals making way for inter-species spillover of new viruses. For example, the habitat destruction forced the wild fruit bats to shift to fruit trees around human habitat. This increased their encounters with domestic animals which ultimately resulted in the inter-species spillover of Nipah and Hendra viruses.

Why India should be concerned

A significant part of India (including parts of West Bengal, North Eastern states and Kerala) fall under the high risk zone of zoonosis from wildlife. India like any other country of South Asia has a number of wet markets. And in some of these wet markets (like those in the North Eastern states) a number of exotic animals are sold for meat (although some of them are supposed to be vulnerable and protected under wildlife laws). This, unfortunately, creates a favourable situation for a similar zoonosis that is presumed to have happened in the case of the novel corona virus responsible for the present pandemic.

What can be done

While the whole world will slowly but surely emerge from the present crisis in near future, any country with wet markets and disturbed forests, any country where eating exotic animals and bush meat is a practice, should keep in mind that the next outbreak of a new zoonotic pathogen might just be around the corner. This pandemic is not going to be the last one. Zoonosis or the emergence of new pathogens from animal origin is a natural process. It cannot be totally avoided. But, can be slowed down or controlled through proper precautions. Only increasing awareness of the process and dangers of zoonosis, monitoring wet markets following WHO guidelines, influencing policy induced positive changes in the food habits of the communities dependant on bush meat, restricting wild life trade seems to be the way ahead to tackle future possible threats.

While these practices are necessary all over the world, India can become a pioneer by adopting a strict code to control possibilities of future zoonosis just after this lockdown is over. After all, controlling and monitoring a few practices is a far more convenient process than locking down a whole country for a couple of months when a new zoonosis happens and a new pandemic breaks out.

The views expressed above belong to the author(s). ORF research and analyses now available on Telegram! Click here to access our curated content — blogs, longforms and interviews.


Jaya Thakur

Jaya Thakur

Jaya Thakur was a Junior Fellow at ORF Kolkata. Worked with the Economy and Development Programme at ORF Kolkata. Her specialization is Environmental Issues in ...

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