Bluetongue disease is a non-contagious, viral disease that primarily affects ruminants such as sheep, cattle, goats, and deer. It is caused by the Bluetongue virus (BTV), which belongs to the Orbivirus genus within the Reoviridae family. The virus is transmitted by biting midges of the Culicoides species, which act as biological vectors. The disease is named after one of its hallmark symptoms: swelling and cyanosis (blue discoloration) of the tongue in severely affected animals.
The clinical manifestations of Bluetongue vary among species. In sheep, particularly European breeds, the disease can be severe, leading to high fever, excessive salivation, facial and tongue swelling, nasal discharge, lameness, and weight loss. In some cases, mortality rates can reach up to 70%. Cattle and goats often experience milder or asymptomatic infections but can serve as reservoirs for the virus, allowing it to spread through midge vectors to more susceptible species. Deer and other wild ruminants can also be affected, sometimes experiencing high mortality rates.
Bluetongue has significant economic consequences due to trade restrictions, loss of livestock productivity, and costs associated with surveillance, vaccination, and vector control. The disease has historically been confined to tropical and subtropical regions, but climate change has expanded its range. Rising global temperatures and changes in precipitation patterns have facilitated the northward migration of Culicoides midges, leading to outbreaks in previously unaffected temperate regions such as Northern Europe. The emergence of new BTV serotypes has further complicated disease control.
Efforts to control Bluetongue focus on vaccination, vector control, and movement restrictions. Several inactivated and live attenuated vaccines exist, but their effectiveness depends on the circulating BTV serotype. Novel mRNA and recombinant vaccines are under development to provide broader protection. Vector control strategies include insecticide applications, habitat modifications, and midge repellents. Strict surveillance programs help detect and contain outbreaks, but challenges remain in regions with high midge populations and cross-border livestock trade.
Despite ongoing control measures, Bluetongue remains a major challenge for livestock industries worldwide. Continued research into climate-adaptive strategies, improved vaccines, and vector management is essential to mitigate its impact and protect animal health.
Bluetongue disease
