What is Bluetongue?
Bluetongue (BT) is a non-contagious, viral disease affecting domestic and wild ruminants (primarily sheep and including cattle, goats, buffalo, antelope, deer, elk and camels) that is transmitted by insects, particularly biting midges of the Culicoides species.
Transmission and spread
The insect vector is the key to transmission of BT virus between animals. Vectors are infected with BT virus after ingesting blood from infected animals. Without the vector, the disease cannot spread from animal to animal.
Public Health Risk
There is no public health risk associated with BT.
Clinical Signs
In infected sheep, clinical signs vary and can include:
- fever;
- hemorrhages and ulcerations of the oral and nasal tissue;
- excessive salivation, and nasal discharge and swelling of lips, tongue, and jaw;
- inflammation of the coronary band (above the hoof) and lameness;
- weakness, depression, weight loss;
- profuse diarrhea, vomiting, pneumonia;
- ‘blue’ tongue as a result of cyanosis (rare);
- pregnant ewes may abort;
- may have ‘break’ in wool growth in recovering sheep resulting in partial or complete loss of wool.
Diagnostic
BT may be suspected based on typical clinical signs, prevalence of required insect vectors and particularly in areas where the disease is endemic. are required to confirm the diagnosis. (OIE Terrestrial Animal Health Code and OIE Manual of Diagnostic Tests and Vaccines for Terrestrial Animals).
Prevention And Control
In endemic areas, sentinel monitoring programs actively sample animals in sentinel herds to monitor for presence of the virus. In combination with active surveillance programs to identify location, distribution and prevalence of insect vectors in an area, control measures can be implemented in a timely fashion such as:
- identification, surveillance and tracing of susceptible and potentially infected animals;
- quarantine and/or movement restrictions during insect activity period;
- identification of specified zones;
- vaccination; and
- insect control measures.
Geographical Distribution
BT has a significant global distribution in regions where the insect vector (i.e. biting midges species Culicoides) is present, including Africa, Asia, Australia, Europe, North America and several islands in the tropics and subtropics. The virus is maintained in areas where the climate will allow biting midges to survive over winter.
Ranking of importance in the United States
Bluetongue is not a major economic threat to the US livestock industry, but it can cause significant losses to individual producers. The disease is most prevalent in the southeastern and southwestern United States, where the climate is favorable for the insect vector.
Important Points To Note About Bluetongue in the United States
There is no cure for bluetongue, so prevention is key.
Vaccination is the most effective way to prevent bluetongue. There are vaccines available for all serotypes of the virus.
Insect control measures can also help to reduce the risk of bluetongue transmission. These measures can include using insecticide sprays, traps, and nets.
If you suspect that your animals may have bluetongue, it is important to contact your veterinarian immediately.
