Fact Sheet - Bluetongue
What is Bluetongue?
Bluetongue is a disease of domestic and wild ruminants that is spread by insects, particularly biting midges of the Culicoides species.
The range of domestic animals that can be infected with bluetongue virus includes:
- domestic cattle
- goats and sheep
Bluetongue can also affect wild animals such as:
- bighorn sheep
- mountain goats
- pronghorn antelopes
- white-tailed deer and most other even-toed hoofed animals
Where is bluetongue 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.
Most of Canada is currently free of the disease.
Over the past 30 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.
How is bluetongue transmitted 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 is able to 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.
Is bluetongue a risk to human health?
No. There is no risk to human health associated with bluetongue.
What are the clinical signs of bluetongue?
Signs of clinical disease vary among different species. Infection is inapparent in the vast majority of 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:
- 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)
How is bluetongue diagnosed?
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 taken into account. Laboratory tests are required to confirm the presence of the bluetongue virus.
How is bluetongue treated?
There is no effective treatment for bluetongue. Vaccines are available for certain types of the disease and are used in Africa and Asia.
What happens when bluetongue is found?
The types of bluetongue considered endemic in the U.S. (serotypes 2, 10, 11, 13 and 17) are immediately notifiable under the Health of Animals Regulations . Laboratories are required to report confirmed diagnoses to the CFIA. This enables prevalence verification and supports international reporting and certification requirements.
All remaining types of bluetongue, exotic to the U.S., are federally reportable under the Health of Animals Act . This means that all suspected or confirmed cases must be reported to the CFIA for immediate investigation by veterinary inspectors.
Should an exotic type of bluetongue occur in Canada, the CFIA would respond in order to limit the impact of the disease to the geographic zone in which the disease is found. The exact nature of the response would depend on a number of factors including the ability of the midges to exist and thrive in the season, and the zone where the outbreak is occurring.
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