2023-04-21 15:58:44
Six of the nine Anses laboratories, in the fields of animal health, food and hydrology, participated in the COVRIN project. The project was funded by the joint European One Health EJP program, coordinated by ANSES. Started in the midst of the Covid-19 pandemic, the project aimed to better understand factors for the emergence and spread of SARS-CoV-2 and to build models to better assess the conditions of virus transmission. It is coordinated by Wageningen Bioveterinary Research (WBVR), in the Netherlands, and the University of Surrey, in England.
Many coronaviruses in animals
Animal coronaviruses are good models for studying human coronaviruses. In fact, animals carry many viruses from this family, some of which have been known for a long time. “ The first coronavirus was discovered in poultry in the 1930s », recalls Paul Brown, from the Ploufragan-Plouzané-Niort laboratory. The presence of several coronaviruses in the same individual implies the possibility of recombination, i.e. of gene exchange between viruses. This faculty increases the risk of a new virus appearing, which might for example have a greater capacity to infect a new species or new characteristics which would affect the immune system of the infected animal or human. One of the objectives of the project was to evaluate the possibility of recombination between coronaviruses and to estimate the frequency of these events, taking coronaviruses present in pigs as a model.
Work on the ability of coronaviruses to pass from one species to another
Scientists from Ploufragan’s laboratory also studied whether coronaviruses usually detected in one species can infect closely related species. To do this, they based themselves on the three main coronaviruses which affect poultry: the avian infectious bronchitis virus, which mainly concerns chickens, the turkey coronavirus and the enteric guinea fowl coronavirus. These three viruses have a comparable genetic structure, except for the virus surface protein gene called “Spike” (S), which allows the virus to enter the host cell. To find out how this difference impacts their ability to infect, the scientists inoculated groups of chickens with the three viruses. They plan to do the same for guinea fowl and turkeys. Their results have not yet been published.
Still on the problem of the transition from one species to another, the rabies and wildlife laboratory in Nancy has undertaken to test the transmission of coronaviruses from one wild species to another. For this, the team took the hedgehog coronavirus as a model. “ It is a very common coronavirus, around 50% of hedgehogs collected in care centers carry it. », explains Élodie Monchatre-Leroy, director of the laboratory. First step: isolate the virus to test its ability to infect other animal species. This turned out to be easier said than done, as this coronavirus, found in the digestive tract and feces, is difficult to isolate and culture. Work is still underway to achieve this.
Improving the detection of coronaviruses in wildlife
As Covid-19 has shown, when viruses carried by wild animals are transmitted to humans, they are likely to cause epidemics. The detection of viruses circulating in wildlife is therefore essential to try to anticipate those presenting a risk of emergence. It is still necessary to be able to detect them reliably. Certain substances, such as blood or stools, contain inhibitors that prevent PCR tests from being carried out correctly. This complicates the detection of viruses from animal corpses. Evelyne Picard-Meyer, from the rabies and wildlife laboratory in Nancy, therefore improved the detection test by using “household genes”: “ These are genes present in all cells, she explains. If they are detected, the PCR analysis is valid. We can therefore conclude that if the virus detection test is negative, it means that the animal does not carry it. Otherwise, the sample is too damaged to be included in the monitoring statistics. ».
At the Anses Lyon laboratory, Viviane Hénaux was involved in the census of SARS-CoV-2 surveillance activities in companion, farmed and wild animals. The aim was to bring together surveillance data collected from April 2020 to December 2021 in each participating country. These data made it possible to build models of risk of transmission of the virus from animals to humans. The Rabies and Wildlife Lab provided data it had collected from some bats and pets as part of another project.
Study of deadly coronavirus in cats
Coronavirus is also common in cats, where it can cause a fatal disease, feline infectious peritonitis. The genetic sequences of circulating strains vary. The Virology mixed research unit, which brings together the ANSES animal health laboratory, the National Veterinary School of Alfort and Inrae, carried out a study on the variability of these sequences, in order to find out if some are linked to symptoms and higher mortality.
The unexpected abilities of SARS-CoV-2 to survive freezing
In addition to the risk of transmission by animals, the possibility of SARS-CoV-2 passing through contact with the environment or wastewater also arose. “ To consider these alternative entry routes, it is necessary demonstrate the presence of viruses capable of infecting a human on surfaces or in water », explains Sandra Martin-Latil. The food safety laboratory scientist was interested in plastic and stainless steel surfaces in contact with food. “ The problem arose when in the summer of 2020 cases were declared in China even though the country was free of the virus, she recalls. LThe hypothesis of contamination through contact with plastic packaging of imported frozen products has been raised. » This possibility had not previously been considered, enveloped viruses like the coronavirus usually being too sensitive to remain infectious for long on the surface of an object. We now know that we have to wait one week for the quantity of virus to decrease by 90% at 4°C and that it resists even longer at -20°C.
Spread of the virus through wastewater: an unresolved question
Regarding the contamination of water by SARS-CoV-2, we already know that the virus genome is detectable in wastewater and sewage sludge. This detection is also used to monitor the evolution of the pandemic within the population. However, as Ali Atoui, researcher at the Nancy Hydrology laboratory, recalls: Just because a fragment of the virus is detected does not mean it is infectious. To find out, we must succeed in isolating an entire virus. » The laboratory participated in the analysis of published studies on the issue. For the moment, none of them provided proof of the presence of infectious viruses in water or sludge from wastewater treatment plants. It should be noted that few studies on this subject have been carried out. This can be explained by the complexity of the methodologies to be implemented, which require to be supervised and carried out in a confined level 3 laboratory, which is not available to all scientific teams. Additionally, chemicals or microorganisms present in environmental samples can bias the results and therefore limit their relevance.
Not all the questions asked in the COVRIN project might be answered because the problem is so vast. Nevertheless, the project made it possible to consolidate or initiate collaborations between European specialists and exchange on study methods and protocols. The results of certain work should appear in the coming months. Research on SARS-CoV-2 and coronaviruses continues, in order to improve knowledge and detection methods, to better anticipate a future pandemic.
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