Research on midges carrying bluetongue and epizootic haemorrhagic disease viruses is useful in the face of the emergence of a new disease, Oropouche.
These still rare images, which will become more and more frequent: on October 8, a cattle breeder from Plouégat-Moysan (Finistère) vaccinated his herd, threatened by BTF (bluetongue) serotype 3, under the eye cameras.
In Brittany as in Occitanie, the problem is identical: “Since the summer of 2023, France has experienced two fronts of emergence of viruses transmitted by midges of the Culicoide genus to domestic and wild ruminants, bluetongue viruses, and epizootic hemorrhagic disease (EMD)”recall the scientists from CIRAD and INRAE.
And “third front”, with “an exotic strain of FCO” which circulated in northern Europe, opened in August 2024.
Risk area
A fourth and final front is becoming clearer with the emergence of a new serotype (No. 8) of FCO, adds Claire Garros, researcher at CIRAD in Montpellier, specialist in Culicoides.
Emergences for over thirty years
“For thirty years, European countries have been faced with emergence or re-emergence of diseases transmitted by these midges, our South is a risk zone. The economic impact is major, unprecedented today, including if the breeder decides to vaccinate his herd”, insists the scientist.
“The vaccine against FCO 3 is reimbursed but not the intervention of the veterinarian, and everything is the responsibility of the breeder for the vaccine against FCO 8. There is no vaccine against MHE”, specifies Claire Garros.
Sick, “the animals no longer gain weight and produce less milk, one to three liters less per animal per day with FCO 3”she recalls. And the animals are unsaleable: “From the moment an animal is infected, it must be declared to the World Organization for Animal Health, which closes the borders.” Without any impact on human health for FCO and MHE.
The Oropouche threat to human populations
This is not the case for another virus, Oropouche, also transmitted by Culicoides: “Until now, it caused flu-like symptoms in South America. For two or three years, the incidence has been increasing and the symptoms are getting worse. We have deaths, fetal damage which causes abortions and brain damage in fetus. A very big epidemic ends in Cuba.specifies Claire Garros.
Imported cases have also been detected “in France, Italy and the Scandinavian countries”.
Twenty-five years of animal health research is now proving valuable to scientists: “We were focused on breeding, we are facing a public health problem. We can be more responsive to this emergence”indicates Claire Garros.
To what extent could France, in its southernmost territories, such as Occitania, be on the front line? “The risk of transmission is secondary in Europe, we wonder about the risk of importing the virus. Culicoides are found everywhere on the planet. But for the virus to develop in insects, conditions are needed particular, it needs time and heat. We are interested in what climate change could modify, with a softening of autumns and winters, but also drier summers. underlines Claire Garros.
With a difficulty for scientists: “Culicoides are difficult animals to handle, five to ten species are capable of transmitting viruses, and we have relatively little funding.”
