Bluetongue is a viral disease of sheep, wild ruminants, and rarely cattle, goats, and carnivores. A vaccine is available to protect these animals against the disease.

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Bluetongue virus is the prototype virus of the genus Orbivirus , family Reoviridae. There are 24 serotypes worldwide, and 5 have been reported in the USA. The four serotypes currently found in the USA are 10, 11, 13, and 17. Serotype 2 was briefly reported in Florida and Alabama in the early 1980's. The distribution of the disease is limited by the culicoid insect vector that serves as the principal means of transmission between ruminant species. The viruses are biologically transmitted between ruminants by the biting midge Culicoides variipennis sonorensis , in the USA. This limits the regional distribution of the viruses to southern and western USA.

The usual incubation period in sheep is 5-10 days. In chronological sequence of appearance, clinical signs include dyspnea with panting; hyperemia of the lips, muzzle, and ears; pyrexia (reaching 107.5°F [42°C]); depression; and inflammation, erosions, and ulceration of the oral mucous membranes, particularly the dental pad. Other signs include swollen cyanotic tongue, lameness due to coronitis and widespread muscle necrosis, torticollis, vomiting, pneumonia, conjunctivitis, and alopecia. In sheep in the USA, mortality may range up to 30%.

In California, PHL produces vaccines to serotypes 10, 11, and 17 for use in sheep. Past surveys indicate that the predominant serotypes causing infection are 11 and 17. The modified live virus vaccines should not be used during the vector seasons because the culicoid vectors may pick up the vaccine virus and transmit it to other animals.  Pregnant ewes should not be vaccinated during the first 100 days of gestation; otherwise, fetal malformations may occur. Passive immunity in lambs may last 4-6 mo. In an outbreak, the decision to vaccinate depends on the viruses that are causing infection at the time.

BlueVac is a family of modified live virus vaccines recommended for immunization of healthy, non-pregnant sheep against bluetongue caused by virulent field strain virus.  There are currently 3 vaccines available for protection against the three strains of bluetongue virus present in California.  BlueVac-10 immunizes sheep against International Type 10 virus; similarly, BlueVac-11 immunizes against International Type 11 virus, and BlueVac-17 immunizes against International Type 17 virus.  Each vaccine strain will only promote immunity against its homologous field strain virus; there is no cross protection afforded.  If disease occurs in vaccinated sheep, it is important that laboratory assistance be obtained to identify the agent causing it.  Laboratory studies and field trials have demonstrated that the modified virus used in these products will not cause disease in vaccinated animals, but will produce a satisfactory strain-specific immunity.

BlueVac is sold through the California Wool Growers Association.  They can be reached at (916) 444-8122.  Their email address is cwga@gvn.net and their street address is California Wool Growers Association, 1225 H Street, Suite 101, Sacramento, California 95814-1910.  They have a web site at www.woolgrowers.org.