As the Covid-19 virus (Coronavirus SARS-CoV-2) continues to spread worldwide and claims to be infected, its source remains unknown. Each scientific community puts forward its own theory, with some suggesting that the virus may have leaked from the laboratory.
Another theory, based on recent research in China’s Wuhan Wet Market, among others in Cambodia, Laos, Japan, China, and Thailand, suggests that an ancestor virus in rhinophilus bats was caused by infecting wild and / or domesticated animals. In humans, in fact, in these various studies, several viruses, including genetic sequences such as SARS-CoV-2, were isolated in these bats.
A missing link
Although it has been shown that some species of bats naturally host these coronaviruses, wild or domestic animals (or animals) that acted as a bridge between them and humans – the missing link – remain unknown. The Pangolins were initially suspected, but now appear to have been bailed out instead of one of the most talked about missing links. A coronavirus genome sequence detected in pangolins was actually related to SARS-CoV-2, but the rest of the genome was genetically far from it to support the hypothesis.
In addition, viruses within the pangolin host that were genetically close to SARS-CoV-2 were mostly seized in the live animal market at the end of the supply chain. As a result, they were in close contact with other animal species. Most likely they were infected with this supply chain instead of their natural environment. Mink firms were also suspected of being intermediate hosts in China.
After all, pangolins and rhinolofas bats do not share the same habitat, making it less likely that the two species would communicate with each other as the virus spread from one species to another. Civet and raccoon dogs, on the other hand, may be an intermediate source of SARS-CoV-1). Rats or primates can also carry pathogens with zoonotic potential, such as Hantavirus – which can cause hemorrhagic fever with renal syndrome – or Philovirus, which contains the Ebola virus. The latter is transmitted to humans by wild animals, especially bats, antelopes, and primates such as chimpanzees and gorillas, then spreads among humans, mainly through direct contact with infected human blood, secretions, and other bodily fluids. The average mortality rate is about 50%.
In 2013, the earliest cases of the disease were identified from the Ebola virus in West Africa. The increase in cases has killed more than 10,000 people, mainly in Guinea, Liberia and Sierra Leone.
Risky habit of eating bush meat
Activities such as hunting, animal-handling or eating wild animal meat therefore create the conditions for viruses to spread from animals to humans – a potentially devastating phenomenon called “spillover”.
The ZooCov project seeks to define and measure this risk in Cambodia. For almost two years – and since the onset of the epidemic – it has adopted a “one-stop-shop” approach to detecting – and how – pathogens such as coronaviruses can be transmitted from wild animals to humans.
In fact, in Southeast Asia, wildlife is regularly traded and bushmeat is traditionally eaten. These eating habits are often opportunistic. In some communities, it is a low-protein dietary supplement. It can also be frequent and targeted. In Cambodia, 77% of the 107 families interviewed on the ZooCov project said they ate bushmeat last month.
It is also widely used for medicinal purposes. In Vietnam, between 2016 and 2020, the Vietnamese authorities seized 1,342 living pangolins (6,330 kg), 759 dead pangolins or pangolin carcasses (3,305 kg, found 934 kg) and 024 in the analysis of pangolin and related byproduct records.
Yet there is a cultural and social dimension to this enjoyment that is still not properly understood. Among the affluent – and often in the big cities – people sometimes eat the flesh of shrubs for the sake of social status, and a belief that eating it enriches the physical or physiological features of their animals. They eat bushmeat to reject meat produced in industries that are sometimes considered unhealthy. Animals are widely reared to meet this demand and the demand for fur production.
In Cambodia’s Stong Trang and Mandalkiri provinces, where protected forests remain, researchers surveyed more than 900 people living on the edge of the forest to determine the structure of the illegal bushmut business. Statistical analysis is underway to identify the people most at risk of exposure to wildlife with such pathogens. We already know that those who have been exposed are mostly young middle-class men, and some communities are more open than others. Sociological studies have helped to better understand today’s context: the legal framework, the profile of players in the trade, their purpose and barriers to wildlife trade and consumption, and how the context has changed with each different health crisis (bird flu, Ebola), SARS-CoV-1, Etc.).
Which population is most at risk?
These ongoing crises seem to have rarely affected the habits of these communities. In addition to eating regular bush meat, a quarter of households surveyed said they still hunt or trap wild animals, and 11% claimed to sell bushmats or wild animals. Furthermore, in the same field of study, more than 2,000 samples were taken from wild animals that have been trafficked or eaten for livelihood – bats, rats, turtles, monkeys, birds, wild boars, etc. – analyzed. Some of these samples have been tested positive for coronavirus, and scientists at the Institute Pasteur du Cambos (IPC) are currently sequencing their genomes to learn more about their origin, evolution and zoonotic potential. Finally, researchers collected blood samples from more than 900 people in the same region to find out if they had been exposed to the coronavirus or coronavirus. These analyzes are still ongoing, but what we do know is that these people were not exposed to SARS-CoV-2 when the survey was conducted.
If the covid crisis has taught us anything, then it is important to identify such emergencies early on to eradicate the pathogens in the buds. While there are many questions about how cases are raised, there are just as many questions about monitoring systems for tracking them. The results of the ZooCov project will be used primarily to create a system for the detection of spillovers of zoonotic viruses, especially by strengthening the system for wildlife health monitoring already in place in Cambodia, which was established by the Wildlife Conservation Society (WCS). . Other large-scale research and development projects will help us understand, identify, and prevent these phenomena of emerging cases.
The authors would like to thank the Cambodian Ministry of Health, its Ministry of Agriculture, Forest and Fisheries and its Ministry of Environment, as well as all the project partners: the Institute Pasteur du Cambos (IPC), the Wildlife Conservation Society (WCS), Flora and Fauna International (INF). Recherche Por Le Development (IRD), University of Hong Kong (HKU), Greece Network, International Development Enterprise (IDE), World Wildlife Fund (WWF), Elephant Livelihood (ENLI).
Translated from French by Thomas Young for Fast Forward.
Veronica Chevalier, Veterinarian Epidemiologist, CIRAD; Francois Rogers, Regional Director for Southeast Asia, Veterinarian and Epidemiologist, CIRAD, and Julia Guilleboud, Research Engineer, Institute Pasteur
This article has been republished from Conversations under a Creative Commons license. Read the original article.