Fact Sheet - Bluetongue
What is Bluetongue?
Bluetongue is a disease of domestic and wild ruminants that is only transmitted by insects known as midges.
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.
In Canada, the Canadian Food Inspection Agency (CFIA) has divided the country into five zones for bluetongue, based on the presence or absence of bluetongue-transmitting midges. The midges that spread bluetongue are only presently found in the Okanagan Valley of British Columbia, and in the southern parts of Alberta, Saskatchewan and Manitoba.
Most of Canada is currently free of the disease.
There have been five known occurrences of bluetongue in Canada, which are believed to be the result of wind-borne introduction of infected midges from the U.S. All occurrences have been in the Okanagan Valley in the past 30 years.
How is bluetongue transmitted and spread?
Bluetongue is transmitted from animal-to-animal by a specific species of biting Culicoides midge that is limited geographically as described above. These midges are currently at the northern limits of their habitat in the southern Prairies.
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.
Has the risk of bluetongue changed?
Yes, the risk of bluetongue has changed. However, since February 21, 2007, import conditions were amended so that no testing is required for bluetongue in the U.S. This means bluetongue-infected animals may now freely enter Canada from the U.S.
And as a result, an infected animal imported from the U.S. could become a seasonal source of the bluetongue virus in the pre-defined zones where midges exist.
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. Some countries in the European Union have implemented compulsory vaccination for a certain type of bluetongue, serotype 8, which has emerged as a more pathogenic form of the virus.
What roles and responsibilities exist to prevent Bluetongue?
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 . In general, there are no response programs for immediately notifiable diseases; however, laboratories are required to report confirmed diagnoses to the CFIA. This enables prevalence verification and supports international reporting and certification requirements.
Any detection of the U.S. types of bluetongue originating from the Okanagan Valley or the U.S. will not impact Canada's bluetongue-free status outside the Okanagan Valley. Evidence of disease spread within Canada will affect Canada's bluetongue-free status; however, it is hoped that trading partners will recognize the five ecologically distinct zones identified by the CFIA, so that only the zone where the detection occurs may be subject to possible trade restrictions.
Detection of infection and evidence of disease spread of U.S. types of bluetongue virus outside the Okanagan Valley would lead to a re-evaluation of the bluetongue geographic zone and a detailed epidemiological investigation. This would include tracing of all potentially infected animals, as well as a recommendation for insect control measures during the biting fly season.
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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