Bluetongue is a disease of domestic and wild ruminants that is spread by insects, particularly biting midges (small flies) of the Culicoides species.
The range of domestic animals that can be infected with bluetongue virus includes:
- domestic cattle
- bison
- deer
- goats and sheep
- llamas and alpacas
Bluetongue can also affect wild animals such as:
- bighorn sheep
- elk
- mountain goats
- mule deer
- pronghorn antelopes
- white-tailed deer and most other even-toed hoofed animals
Bluetongue is caused by a virus with a number of serotypes that vary in their ability to cause disease in animals. Bluetongue serotypes 2, 10, 11, 13 and 17 are immediately notifiable under the Health of Animals Regulations . Laboratories are required to contact us regarding the suspicion or confirmation of this disease. This enables prevalence verification and supports international reporting and certification requirements. There are occasional serological detections, mostly in cattle imported from the U.S.
All remaining types of bluetongue are federally reportable under the Health of Animals Act. This means that all suspected or confirmed cases must be reported to us.
On this page
- Risk to human health
- Signs
- Where it is found
- Transmission and spread
- Diagnosis
- Treatment
- Additional information
Risk to human health
There is no risk to human health associated with bluetongue.
Signs
Signs of clinical disease vary among different species. Infection is inapparent in many species. Cattle, goats and elk, for example, are affected by a very mild, self-limiting infection.
Bluetongue can cause serious illness and death in sheep as well as deer and potentially other wildlife. There is no cure and death may occur within seven days. In sheep, the symptoms of bluetongue include:
- fever
- reddening of the lining of the mouth and nose
- swelling of the lips, tongue and gums
- difficulty swallowing and breathing
- a swollen, purple-coloured tongue (hence, the name bluetongue)
- lameness
Where it is found
Bluetongue can be found anywhere the midges that transmit the virus are present. It is commonly found in the U.S., Mexico, Australia, Africa, the Middle East, the Indian subcontinent and China. Bluetongue is also spreading northwards in Europe including England, France, Wales and the Netherlands.
Bluetongue disease is absent in most of Canada.
Over the past 40 years, there have been occurrences of bluetongue in the Okanagan Valley, British Columbia, which are believed to be the result of wind-borne introduction of infected midges from the U.S. In September 2015, bluetongue was confirmed in southwestern Ontario.
Transmission and spread
Bluetongue is transmitted from animal-to-animal by a specific species of biting Culicoides midge. In Canada, the presence of the virus is usually restricted to late summer and early fall, since conditions must be warm enough for the bluetongue virus to multiply within the midge (13°C to 35°C). Midge activity ceases with the first hard frost. There is no evidence that bluetongue can survive winter in Canada.
The virus does not survive in the environment outside a midge or its animal host. It cannot be spread through contact with animal carcasses and products such as meat and wool.
Diagnosis
Tentative diagnosis of bluetongue in sheep can be made based on the appearance of clinical signs and lesions. The presence of midge vectors is also considered. Laboratory tests are required to confirm the serotype of and presence of the bluetongue virus.
Treatment
There is no effective treatment for bluetongue. Vaccines are available for certain types of the disease and are used in Africa, Asia and parts of Europe. There currently is no licensed vaccine available for use in Canada.