As the Covid-19 virus (SARS-CoV-2 coronavirus) continues to spread and infect victims worldwide, its origin remains unknown. Each scientific community puts forward its own theory, with some suggesting that the virus could have leaked out of the lab.

Another theory, based on recent studies of the Wuhan wet market in China, along with others conducted in Cambodia, Laos, Japan, China and Thailand, argues that the ancestral virus in rhinoloph bats came from infecting wild and / or domestic animals. to people. Indeed, in these various studies, several viruses with genetic sequences very similar to SARS-CoV-2 were isolated in these bats.

Missing link

Although some species of bats have been shown to take these coronaviruses naturally, wild or domestic animals (or animals) that acted as a bridge between them and humans – the missing link – remain unidentified. At first, the Pangalins were suspected, but now it seems that they have become casualties, not one of these missing links, about which much is said. The coronavirus genome sequence found in lizards was indeed related to the SARS-CoV-2 sequence, but the rest of the genome was too distant from it genetically to support the hypothesis.

Moreover, lizard owners in whom viruses genetically close to SARS-CoV-2 were found were mostly confiscated from livestock markets at the end of the supply chain. As a result, they continued to come into contact with other species. It is very likely that they were infected along this supply chain and not in the wild. In China, suspected as an intermediate host of the mink.

Finally, lizards and rhinoceroses do not have the same habitat, making it very unlikely that there was any contact between the two species in which the virus jumped from one to the other. On the other hand, civets and raccoon dogs may be an intermediate source of SARS-CoV-1). Rodents or primates can also carry pathogens with zoonotic potential, such as hantaviruses – which can cause hemorrhagic fever with renal syndrome – or filaviruses, which include the Ebola virus. The latter is transmitted to humans through wild animals, particularly bats, antelopes and primates such as chimpanzees and gorillas, then spreads to humans, mainly through direct contact with blood, secretions and other body fluids from infected humans. The average mortality rate is about 50%.

In 2013, the first cases of the Ebola virus were detected in West Africa. The increase in these cases has led to more than 10,000 deaths, mostly in Guinea, Liberia and Sierra Leone.

A risky habit of eating meat

Thus, activities such as hunting, animal husbandry or eating wild animal meat create the conditions for the spread of viruses from animals to humans – a potentially destructive phenomenon called “transmission”.

The ZooCov project sought to identify and quantify this risk in Cambodia. For almost two years – and since the beginning of the pandemic – it has adopted a One Health approach to study whether and how pathogens such as coronaviruses can be transmitted to humans from wild animals that are hunted and eaten.

Indeed, in Southeast Asia, wildlife is regularly traded, and wild meat is commonly eaten. This eating habit is often opportunistic. In some communities, it complements a low-protein diet. It can also be frequent and focused. In Cambodia, 77% of the 107 families surveyed by the ZooCov project said they had eaten wild boar meat in the past month.

Widespread and use for therapeutic purposes. In Vietnam, an analysis of records of confiscations by the Vietnamese authorities of pangolins and related by-products between 2016 and 2020 reported 1,342 live lizards (6,330 kg), 759 dead lizards or carcass lizards (3,305 kg) and 43 kg of pangolins , 902 kg.

However, this consumption also has a cultural and social dimension that is still not properly understood. Among the affluent – and often in large cities – people sometimes eat wild boar meat out of a desire for social status and out of a belief that eating it endows them with the physical or physiological properties of the animal. They also sometimes eat wild boar meat due to the abandonment of industrially produced meat, which is considered harmful to health. Animals are widely bred to meet this demand and the demand for fur production.

In the provinces of Stung Treng and Mandolkir in Cambodia, where protected forest areas have been preserved, researchers surveyed more than 900 people living on the edge of these forests to determine the pattern of illegal wildlife meat trade. Statistical analysis is conducted to determine the people most at risk of contact with wildlife, thus with such pathogens. We already know that mostly young middle-class people are exposed, and that some communities are exposed more than others. Sociological research has also helped to better understand the current context: the legal framework, profiles of trade players, their motives and disincentives in wildlife trade and consumption, and how the context has changed with each health crisis (bird flu, Ebola, SARS-CoV- 1, etc.).

Which population groups are most at risk?

These subsequent crises seem to have had little effect on the habits of these communities. In addition to regular consumption of wild boar meat, a quarter of households surveyed said they still hunt or trap wildlife, and 11% say they sell wild boar or wildlife meat. In addition, in the same areas of research, more than 2,000 samples were analyzed from wild animals that are traded or eaten for subsistence – bats, rodents, turtles, monkeys, birds, wild boars, etc. Some of these samples have tested positive for coronaviruses, and scientists from the Institut Pasteur du Cambodia (IPC) are now sequencing their genomes to learn more about their origins, evolution and zoonotic potential. Finally, researchers collected blood samples from more than 900 people from the same region to find out if they had come in contact with a coronavirus or coronaviruses. These tests are still ongoing, but we know 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 detect such phenomena in time to destroy pathogens in the embryo. While there are still many questions about how cases occur, there are as many questions about the monitoring systems that need to be set up to track them. The results of the ZooCov project will be used to develop a system for early detection of zoonotic viruses, in particular by strengthening the wildlife health monitoring system already in place in Cambodia, which was established by the Wildlife Society (WCS). . Other large-scale research and development projects will help us understand, detect and prevent these occurrences.


The authors thank the Ministry of Health of Cambodia, the Ministry of Agriculture, Forestry and Fisheries and the Ministry of the Environment, as well as all project partners: the Pasteur Institute of Cambodia (IPC), the Wildlife Society (WCS), Flora and Fauna International (FFI) , Institut de Recherche pour le Développement (IRD), University of Hong Kong (HKU), GREASE network, International Development Enterprise (iDE), World Wildlife Fund (WWF), Elephant Livelihood Initiative Environment (ELIE). ), BirdLife International, Jahoo and World Hope International.

Translated from French by Thomas Young for Fast ForWord.

Veronica Chevalier, Veterinary Epidemiologist, Sirad; Francois Roger, Regional Director of Southeast Asia, Veterinary and Epidemiologist, Sirad and Julia Gileba, Research Engineering, Pasteur Institute

This article is republished with The Conversation under a Creative Commons license. Read the original article.

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