Several tons of dead bodies floating in a pond or lake. This is the consequence of carp sleeping sickness. Caused by the carp edema virusthe disease only affects carp, whether ornamental or common. Up to 80% of the population of a pond can be wiped out by the virus. First detected in Japan in the 1970s, the virus has since spread to several continents. The World Organization for Animal Health (OMSA) recently defined carp sleeping sickness as an emerging disease that must be declared.
She is present in France for ten years and concerns bodies of water of all sizes throughout the territory. The disease is most common in late winter when the waters warm up, but outbreaks have been observed year-round.
There is no cure for the disease, so it is important to detect to put in place measures to prevent its spread, such as a ban on fishing and the transfer of fish from contaminated ponds. To enable this detection, the Fish Virology, Immunology and Ecotoxicology Unit (VIMEP) of ANSES’s Ploufragan-Plouzané-Niort laboratory adapted a PCR test developed in Great Britain. He transferred it to three departmental laboratories for voluntary veterinary analysis, which carry out the analyzes in the event of suspicion of the disease (see box). These tests allow diagnose the presence of the virusthe symptoms of the disease can be confused with those of other infectious diseases.
Searching for disease-promoting factors
The unit also participates, alongside another unit of the Ploufragan-Plouzané-Niort laboratory, the Health and Well-Being Epidemiology Unit (EPISABE), in an ongoing research project, called CEVIRAL. This is financed by the European Maritime Affairs and Fisheries Fund (EMFF) and coordinated by the technical institute for poultry, rabbit and fish farming (ITAVI). It aims to better understand the disease, in particular the factors favoring its spread, such as water temperature, and to trace the origin of contamination. ” For example, we were able to show by viral DNA sequencing that three lakes in the Tarn had been contaminated in 2022 by the same strain, following the introduction of carp from the same batch of fish.. “, illustrates one of the authors of the study. The project also aims to inform those involved in fish farming and fishing who are still unaware of the disease. They are encouraged to participate in research by collecting observations and sending samples for analysis if the disease is suspected.