September 15, 2006

Research shows bluetongue less harmful than previously thought

Research by the UC Davis School of Veterinary Medicine suggests that parts of the US can eventually be declared free of "bluetongue," a viral disease that has long been the bane of the livestock industry.

A better understanding of the virus, through research has showed that animals can safely be moved from areas in which an infection occurred, thus limiting the economic impact of any outbreaks.

Bluetongue virus, which primarily affects sheep and wild ruminants, can cause expensive trade interruptions even though it rarely occurs in cattle. The USDA estimates that bluetongue costs cattle producers about US$125 million annually in trade restrictions and health-monitoring programmes.

Research conducted by UC Davis' School of Veterinary Medicine showed that the disease is only spread by midges and cattle may carry the virus but rarely show symptoms.

Infections in cattle normally do not last long and infected cases rise and fall with weather patterns.

The research also yielded diagnostic tests that can detect all strains of the bluetongue virus and a new vaccine against the disease. 

The bluetongue virus has not recently been transmitted through international trade of livestock, said Bennie Osburn, dean of the UC Davis School of Veterinary Medicine.

Instead, the virus exists throughout the world and specific strains have likely co-evolved with insects that transmit the infection.

In May 2005, the World Organization for Animal Health (OIE) amended the bluetongue section of its Terrestrial Animal Health Code to reflect the lower risk, causing other countries to ease bluetongue restrictions. Some, however, started at least a decade ago.

The researcher noted that global climate change poses the real threat as it expands the range of the insect carriers and causes the disease to spread to new places, a recent example being that of the disease migrating from southern Europe to northern Europe.