Bluetongue

What is Bluetongue?

Bluetongue (BT) 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 BT virus includes:

• domestic cattle;
• bison;
• deer; and
• goats and sheep.

BT can also affect wild animals such as:

• bighorn sheep;
• elk;
• mountain goats;
• mules;
• deer;
• pronghorn antelopes;
• white-tailed deer and most other even-toed hoofed animals.

Where is Bluetongue found?

BT can be found anywhere the midges that carry the virus are present. BT is commonly found in the U.S., Mexico, Australia, Africa, the Middle East, the Indian subcontinent and China. BT is also spreading northwards in Europe.

In Canada, the Canadian Food Inspection Agency (CFIA) has divided the country into five zones for BT, based on the presence or absence of BT transmitting midges. The midges that spread BT 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 BT in Canada, which are believed to be the result of wind-borne 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?

BT is transmitted from animal-to-animal by specific species of biting Culicoides midges that are limited geographically as described above and are at the northern limits of their habitat in the southern Prairies.

In Canada, the virus is usually restricted to late summer and early fall, since conditions must be warm enough for the BT virus to multiply within the midge (13°C to 35°C). Midge activity ceases with the first hard frost. There is no evidence that BT 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 BT has changed. However since February 21, 2007, import conditions were amended so that BT infected animals can now freely enter Canada from the U.S.

And as a result, an infected animal could become a seasonal source of the BT virus in the Okanagan Valley where midges exist and perhaps in the southern prairies.

Is Bluetongue a risk to human health?

No. There is no risk to human health associated with BT.

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.

BT 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 BT 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); and
• lameness.

How is Bluetongue diagnosed?

Tentative diagnosis of BT 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 BT virus.

How is Bluetongue treated?

There is no effective treatment for BT. 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 BT (serotype 8) which is emerging as a disease.

What roles and responsibilities exist to prevent Bluetongue?

Types of BT virus (BTV) present in the U.S. will be Immediately Notifiable under the Health of Animals Regulations once legislative changes associated with the lifting of BTV restrictions on U.S. imports in February 2007 are completed. Other exotic types of the virus remain Reportable under the Health of Animals Act. This means that all suspected cases, both U.S. or exotic, must be reported to the CFIA for immediate investigation by veterinary inspectors.

Any detection of the U.S. types of BT originating from the Okanagan Valley or the U.S. will not impact Canada's BT-free status outside the Okanagan Valley. Evidence of disease spread within Canada will affect Canada's BT-free status, but 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 occurred will lose the BT-free status.

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 BTV geographic zone and a detailed epidemiological investigation including tracing of all potentially infected animals as well as a recommendation for insect control measures during the biting fly season.

Should an exotic type of BT occur in Canada, the CFIA would respond in order to limit the impact of the disease to the geographic zone in which BT 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.

For more information

Contact your CFIA Area office:

• Atlantic Area: 506-851-7651
• Quebec Area: 514-283-8888
• Ontario Area: 519-837-9400
• Western Area: 403-292-4301

You can find your local CFIA District office on the CFIA Web site or by consulting the blue pages of your local phone directory.