Last September, reports appeared in the mainstream media of the diagnosis of the first cases of bluetongue in some cattle in Ticino. This disease, also known as bluetongue, can have major repercussions for livestock farmers, as it has in the past in other countries. The most up-to-date data provided by the Federal Office of Food and Veterinary Safety indicates that from 08/28/2024 until 03/31/2025, 2,976 herds across Switzerland were affected by the disease.
Its spread is due to an insect, smaller than common mosquitoes. In Ticino, its presence and spread is the focus of monitoring by SUPSI, coordinated by Eva Veronesi senior researcher at the Institute of Microbiology.
First, what is blue tongue and what consequences can it have?
Blue tongue disease is a noncontagious disease caused by the bluetongue virus transmitted through the bite of midges of the genus Culicoides (Diptera: Ceratopogonidae). These insects, about one-third the size of mosquitoes (1-3 mm), are active from April to November, a couple of hours before sunset and a couple of hours after sunrise. Only a few species are able to transmit the virus, remaining infected throughout their lifespan.
The virus does not cause any disease in humans, but causes very serious and lethal damage in sheep and cattle, while other ruminants (goats, deer, fallow deer) can become infected but more mildly. The name of the disease comes from the name taken on the animal's tongue, which can become cyanotic. Common symptoms include high fever, pulmonary edema, respiratory distress, oral mucosal lesions, conjunctivitis, lameness, abortion, and decreased milk production.
To date, 27 different serotypes of the virus have been identified with different epidemiological and pathological characteristics. There is no cure, but prevention is possible through vaccines.
How far and how widespread is it?
The spread of the disease is linked to the presence of species that can transmit the virus and by the presence of animals susceptible to the infection, which can become sick once bitten by an infected insect. The presence of bluetongue has not been reported in territories hostile to these insects such as Antarctica, some Pacific islands and other Arctic regions. Usually, more severe symptoms are observed in the second year of the disease outbreak.
Although Ticino has only recently been touched, the disease already has a long history.
Blue tongue virus was first identified in South Africa (1902) and later spread to the American, Asian and Australian continents. It was first discovered in Europe in 1943 (Cyprus) with sporadic appearances until the 1970s in other countries on the continent (Spain, Portugal, Turkey, Greece).
From the late 1990s to 2005, the spread of the disease exploded in Mediterranean countries, affecting at least 16 nations including France, Italy, Bulgaria, Macedonia, Albania, Croatia, Bosnia and others (except Switzerland) causing the death of more than one million sheep. By the end of 2005, five serotypes (BTV-1, 2, 4, 9, and 16) were circulating in Europe.
In 2006, a new strain of the virus (BTV-8) was identified in the Netherlands initially spreading to Belgium, France, Portugal, Italy, and Germany, before spreading the following year to the rest of northern Europe (Spain, Switzerland, England, Denmark, Austria, Romania). In 2007, Belgium alone had more than 25,000 sheep that had died between July and October, and by the end of 2007 more than 50,000 farms in Europe were infected with the virus, causing economic damage of more than 170 million euros. Bluetongue continued to spread with new cases overwhelmingly and with serious economic consequences through 2011 pushing into countries adjacent to the 2006-07 core infection, to include more than 20 European countries.
A lack of timely and preventive vaccination, as happened during the great outbreak of 2006, promotes a very rapid spread of the virus spreads throughout the period of activity of these insects (approximately April to November).
What are you doing at the institute level to monitor this phenomenon?
In August last year, Switzerland was hit by a new wave of bluetongue serotype 8 and, for the first time ever, with serotype 3 already reported in 2023 in other European countries. This serotype is much more aggressive than BTV-8, with a mortality of up to 20-25% in sheep, 1-5% in cattle.
SUPSI's Institute of Microbiology, with the support of the Federal Food and Veterinary Safety Office, is working to estimate the potential presence of these insects even during the colder months (January-March) in order to assess the risk of spreading the virus. Specifically, Culicoides traps have been placed on several farms affected by blue tongue in 2024. The captured insects are taken to the laboratory to determine the species.
What solutions are available to farmers?
There are two approaches: prevent infection through vaccination of animals at risk (sheep and cattle); prevent proliferation of vector insects (removal of Culicoides breeding areas: manure, organic material) and exposure of animals to them.
Vaccines for both serotypes (8 and 3) are currently available, so farmers can contact their veterinarian to proceed with vaccination of livestock as soon as possible. It is very important that vaccination take place before Culicoides begin to bite. The vaccine does not preclude an animal from getting sick, but symptoms will be milder and recovery faster. Protection begins from the third week post vaccination.
As with other diseases, there is a specific vaccine for each serotype, and usually the production or marketing of a vaccine is linked to the prevalence of a particular serotype in the relevant territory. This can lead to delays in distribution when an outbreak is caused by a serotype first found.
Bluetongue disease will be the focus of an information morning open to farmers, ranchers, veterinarians and anyone interested in learning about and helping to prevent its spread. The appointment is for April 30 from 9 a.m. to 1 p.m. in the Multipurpose Hall of the SUPSI Campus in Mendrisio.