Monitoring and learning about infectious diseases of horses in order to improve welfare and performance

Horse health raises specific issues, since these animals are mainly kept for recreation, sport and competition. Monitoring and detection of numerous equine infectious diseases is a mandatory step before they can be allowed to compete and breed.

ANSES is the reference laboratory for equine diseases at both national and European level. It is also an international reference laboratory for two diseases affecting horses: dourine and glanders.

France has more than one million Equidae according to the French Horse and Riding Institute (IFCE), putting it in second place in Europe. More than for other animal species, good horse health is of major economic importance: the equine sector accounts for more than ten billion euros in annual turnover, two thirds of which is linked to racing (source IFCE for 2019 (PDF)). In the field of equestrian sports, monitoring and detection of a number of infectious equine diseases must take place before the animals can compete, breed or travel to foreign countries.

Diseases subject to mandatory monitoring

Some equine diseases are regulated. They are monitored by France and the European Union, which means that their detection is compulsory. This is the case, for example, with glanders, a disease caused by a bacterium that is not found in Europe, but that infects horses in the Middle East, Asia and South America; or West Nile virus, a mosquito-borne disease affecting horses and humans that can have major consequences on the nervous system in the most serious cases. Equine infectious anaemia and African horse sickness are two other diseases whose detection in horses is mandatory.

Other diseases, especially those transmitted through reproduction, are regulated according to breed: positive cases are managed by breed associations, which make it mandatory to detect the disease before breeding or participating in a competition. These include contagious equine metritis, equine viral arteritis and dourine. 

ANSES's Laboratory for Animal Health is the national and European reference laboratory for equine infectious diseases: it is therefore responsible for providing scientific and technical support for controlling and monitoring these diseases. In particular, it trains veterinary testing laboratories in detection and confirms reported cases. The laboratory is also an international reference laboratory for the World Organisation for Animal Health (WOAH) on two equine diseases: dourine and glanders.

RESUMEQ: tracking the causes of horse mortality

ANSES also coordinates the RESUMEQ equine mortality surveillance network. It trains network stakeholders, and collects and analyses the results of autopsies carried out on horses in France. This monitoring provides information on the health status of the equine population and detects the appearance of emerging pathogens in France. It can also be used to raise alerts, particularly in the case of recurring food poisoning, and to detect the development of resistance to antiparasitics. The Laboratory for Animal Health also provides support to network players and veterinarians in the field in determining the causes of death of animals, when these are difficult to determine. Lastly, it offers its expertise to the judicial authorities when a horse's death is suspected to be of criminal origin. 

Research on equine diseases

Another component of the Laboratory for Animal Health's activities is research into equine diseases, which focuses on the development of new treatments, vaccines and innovative diagnostic tools. One research project, for example, is aiming to create a vaccine against Rhodococcus equi, which is the leading cause of death in foals. 

The equine sector is particularly prone to the emergence of antimicrobial resistance. ANSES develops new compounds against bacteria, viruses and parasites. It studies the mechanisms of resistance to treatments, in particular resistance to antiparasitics, which is a recent phenomenon. For example, it has drawn up recommendations on administering dewormers to limit the emergence of resistance.
Another subject of study is the interactions between viruses and horses. This work is carried out in partnership with specialists in human health, particularly at the Caen University Hospital and the Institut Pasteur. The viruses found in horses belong to the same families as those affecting humans. For example, the equine infectious anaemia virus, the first retrovirus discovered in the animal world, is similar to the AIDS virus, while the clinical respiratory signs associated with equine viral arteritis infection resemble those encountered in humans during infection with the SARS-CoV-2 virus, responsible for COVID-19. Partnerships with human health research organisations are also focusing on the development of diagnostic tools based on the latest generation of genome sequencing techniques, which allow pathogens to be identified more quickly and accurately. These examples of cooperation perfectly illustrate the "One Health" concept. 

Two sites on equine diseases

ANSES's Laboratory for Animal Health is located at two sites. The Normandy laboratory specialises in infectious reproductive diseases in horses and coordinates the surveillance network for causes of equine mortality, while the Maisons-Alfort site, in the Paris region, deals with diseases that can be transmitted from horses to humans, epidemics and emerging diseases transmitted by vectors such as insects and ticks.