What are coronaviruses?
Coronaviruses are a family of many viruses. IThey affect many species of mammals and birds, some can be transmitted to humans or be specific to them. The diseases they cause are varied but mainly affect respiratory and digestive systems. They have in common the particularity of being highly transmissible. In terms of animal health, many coronaviruses are known, whether in dogs, cats, pigs, ruminants, horses, camels, birds or wildlife, especially bats.
What diseases do they cause?
The severity of the infections caused is highly variable. In veterinary medicine, infections with these viruses are common. They can have a significant economic impact, particularly in breeding young ruminants, pigs or chickens and turkeys. Poultry, for example, can be contaminated with the infectious bronchitis coronavirus, while turkeys and guinea fowl also have coronaviruses that specifically infect them at the digestive level. Pigs are prone to porcine epidemic diarrhea virus, transmissible gastroenteritis or porcine respiratory coronavirus. Cats can contract the deadly feline infectious peritonitis virus, while young horses and young cattle suffer from digestive disorders. Finally, the impact of infecting wildlife (bats, hedgehogs, rodents, etc.) is unknown.
How are coronaviruses transmitted from one species to another?
The Covid-19 epidemic reminds us that mutations in coronaviruses can sometimes allow them to change host. Indeed, these viruses have the ability to evolve rapidly through changes in their genetic material, which mutates frequently. They can also recombiner, i.e. exchanging portions of the genome, which can occur if two different coronaviruses co-infect the same host cell. This evolution may give them the ability to reach new target organs or adapt to new host species. These new viruses can be particularly pathogenic because the new host species is not used to it, it does not have the immune defenses necessary to respond effectively to this new infection. However, if these events have been detected quite frequently in the recent past (the Covid-19 virus is the third coronavirus to pass from animals to humans in regarding twenty years), the phenomenon is not new: one of the viruses responsible for the common cold in humans, the OC43 coronavirus, is believed to have evolved from the transmission of the bovine coronavirus to humans at the end of the 19th century.
What is ANSES doing regarding coronaviruses?
ANSES is carrying out various studies on coronaviruses in poultry, pigs, cats and wildlife. The occurrence of the Covid-19 epidemic has strengthened its work on the subject, in particular on the possibility of inter-species transmission and treatment and diagnostic techniques according to approaches that might be interesting in a comparative virology approach. here are some examples :
Know the viruses circulating in animals
The three ANSES laboratories for Rabies and Wildlife in Nancy, Animal Health in Maisons Alfort and Ploufragan-Plouzané-Niort took part in the ANR project Epicurean from 2014 to 2018. Coordinated by the University Hospital Center of Caen, this work has made it possible to highlight the significant diversity of coronaviruses circulating within domestic and wild animal populations in France and Europe. New viral species have been described in humans and in domestic and wild fauna. In parallel, the researchers followed the evolution of a Betacoronavirus, sister group of Sars-CoV within a colony of bats. This section provided an understanding of the evolutionary dynamics of the virus within a host population.
Currently, the Alfort animal health laboratory coordinates the European MuseCov project, in which two other ANSES laboratories also participate (the ANSES laboratory in Ploufragan-Plouzané-Niort and the Nancy laboratory). It aims to better understand the diversity of coronavirus strains circulating in animal populations, including SARS-CoV2. The objective is to better understand the dynamics of coronavirus infections in various animal populations and to rapidly detect the emergence of particularly pathogenic variants.
Finally, the ANSES laboratory in Ploufragan-Plouzané-Niort is interested in mutations and molecular mechanisms that accompany the transmission of coronaviruses avians in the different poultry species or which allow genetic rearrangements in porcine coronaviruses.
Better understand the mechanisms of inter-species transmission
The Joint Virology Research Unit (EnvA-Inrae-Anses) of the Animal Health Laboratory in Maisons-Alfort is carrying out, in conjunction with an Inserm team, a research project on molecular determinants of feline coronavirus pathogenicity. This virus can cause a fatal disease in cats called feline infectious peritonitis. The mechanisms that promote crossing the inter-species barrier are studied. This work is carried out in collaboration with the rabies and wildlife laboratory in Nancy, on possible interactions with coronaviruses present in wildlife, and that of Ploufragan-Plouzané-Niort, on avian coronaviruses.
Developing diagnostic and treatment techniques
The Ploufragan-Plouzané-Niort laboratory develops molecular diagnostic methods or serological avian and porcine coronaviruses. A project, started at the end of 2019, aims to develop a serological test (ELISA), making it possible to detect antibodies produced in response to infection with the European strain of turkey coronavirus (Tcov), which does not currently exist.
The rabies and wildlife laboratory has developed molecular and serological diagnostic methods for Sars-CoV-2 infection in mink to carry out the first survey on French farms. This made it possible to detect one of the four farms as contaminated with more than 90% of the animals having a positive serological response.
On the side of treatmentsthe Rabies and Wildlife Laboratory took part in the project Timing, funded by ANR and coordinated by INRAE. He studied the beneficial or harmful effect of type I interferons. These are small proteins produced naturally in the body in response to a viral infection. Many studies have shown that a defect in the production of these interferons by the body would be associated with development of severe forms of COVID-19. However, type I interferons are not always beneficial because they can cause excessive inflammation. The Timing project made it possible to show in animal models that only very early administration of interferon (before infection or just following) was beneficial and that, contrary to the hypothesis, late administration was not harmful.
Understanding the genetic evolution of coronaviruses
Furthermore, coronaviruses have a strong potential for evolution, through events of mutation, even recombination, then selection. Since 2018, the Ploufragan-Plouzané-Niort laboratory has been studying the genetic evolution of chicken (IBV) and turkey (TCoV) coronaviruses. Since 2018, the unit has studied in particular the genetic evolution of avian coronaviruses in the presence of vaccination or not. The results showed that the genetic evolution of an avian coronavirus is very rapid (from the first passage in unvaccinated subjects) and different in vaccinated and unvaccinated subjects. These results make it possible to better understand the evolution of coronavirus in the presence of vaccine immunity.
Assessing the transmissibility of Covid-19 from animals to humans
The Agency was also asked to give opinions on the risk of transmission of the SARS-Cov-2 virus from animals to humans. She thus determined that, even if certain species, such as cats, ferrets, minks and hamsters were susceptible to Covid-19, domestic animals and wild animals play no role in the maintenance and spread of SARS-CoV-2 in France, where the spread of the virus is the result of human-to-human transmission through the respiratory route. However, the there is a risk of an animal reservoir forming. ANSES therefore recommends being particularly vigilant during contact between humans and species capable of harboring the virus (cats, mink, etc.), in the event of a high density of animals, and animal-human promiscuity, particularly in a closed or confined environment.
A reference mandate for the monitoring of SARS-CoV-2 in wastewater and sludge from treatment plants
Since the end of 2021, the Hydrology Laboratory has been the national reference laboratory for monitoring SARS-CoV-2 in wastewater and sludge from wastewater treatment plants. This surveillance aims to supplement the tools already available, particularly in a context of low viral circulation, to detect early (re)emergence of the virus in the population. The laboratory is notably responsible for harmonizing the methods used to detect the virus and for evaluating the capacities of the laboratories responsible for carrying out the analyses.
Avoiding exposure to coronavirus in the workplace
As part of its occupational health missions, ANSES has also issued recommendations on measures to adopt to avoid contamination in the workplace other than care and health. She is also leading a research project, SACADA, aimed at identifying how the virus circulates in meat preparation workshops and to propose appropriate preventive measures. Due to their characteristics, in particular cold, humidity and the need to make physical efforts, these professional environments are indeed favorable to the spread of the virus between workers.
Photo : Centers for Disease Control and Prevention
