What is Blue Tongue? The Lowdown on This Viral Disease

Blue tongue is a viral disease that affects domesticated animals such as cattle, goats, sheep, and deer. The disease is transmitted by biting gnats or midges of the genus Culicoides, commonly known as no-see-ums or sand flies, and is characterized by a blue-purple coloration of an affected animal’s tongue. Blue tongue virus (BTV) is not transmissible to humans, but it can have serious consequences for agricultural industries in affected areas. In this article, we will detail all the essential information you need to know about this viral disease.

History of Blue Tongue

Blue tongue virus is believed to have originated in Africa and was first recorded in South Africa in the early 1900s. The virus quickly spread throughout Africa and other parts of the world. The first outbreak of blue tongue in North America was reported in Texas in 2006, and since then, the disease has spread to several states in the country.

Transmission of Blue Tongue

Transmission of blue tongue virus occurs through the bites of infected gnats or midges, which then inject the virus into the animal’s bloodstream. The virus replicates in the lymphatic tissues, leading to the characteristic clinical signs of blue tongue in animals.

What Animals Are Affected?

Blue tongue primarily affects domesticated animals such as cattle, goats, sheep, and deer. Wild ruminants can also be affected but are less susceptible to the disease. Several factors, such as the immune system of the host animal and the specific strain of the virus responsible for the infection, influence the severity of the disease.

Clinical Signs of Blue Tongue

Clinical signs of blue tongue virus infection can vary widely between different animals and strains of the virus. Some animals may show no symptoms of the disease, while others can exhibit severe clinical signs such as:

  • High fever
  • Loss of appetite
  • Lethargy
  • Weight loss
  • Swollen face
  • Swollen tongue
  • Difficulty breathing
  • Abortion in pregnant animals

In severe cases, the disease can be fatal. However, most affected animals recover on their own within a few days to several weeks, depending on the strain of the virus and the species of the animal affected.

Diagnosis of Blue Tongue

Diagnosis of blue tongue virus infection requires laboratory testing of the blood or other tissues from infected animals. Several diagnostic tests are available, including virus isolation, PCR, and serology, which can detect the presence of blue tongue virus antibodies in the blood of infected animals.

How Is Blue Tongue Different from Foot and Mouth Disease?

Blue tongue virus infection can cause similar clinical signs to foot-and-mouth disease, such as fever and loss of appetite. However, blue tongue virus can only infect ruminant animals, while foot-and-mouth disease virus can affect a wide range of domestic and wild animals, including ungulates and pigs. Additionally, blue tongue virus cannot be transmitted to humans, while foot-and-mouth disease can be transmitted to humans (although it is rare).

Prevention and Treatment of Blue Tongue

Preventing the spread of blue tongue virus in livestock populations primarily involves controlling the population of Culicoides biting midges that transmit the virus. This can be achieved through the use of insecticides, building screens, and reducing the number of stagnant water sources that serve as breeding sites for the insects. Vaccines are also available to prevent blue tongue virus infection in domesticated animals.

Presently, there is no targeted treatment for blue tongue virus infection in animals, and treatment is mainly supportive, such as providing fluids and ensuring proper nutrition. In severe cases, veterinary intervention may be necessary to manage the clinical signs of the disease.

The Impact of Blue Tongue Virus on Agriculture

Blue tongue virus can have a significant impact on agricultural industries in affected areas, with potential consequences including:

  • Reduced herd fertility
  • Increased mortality rates
  • Decreased milk production
  • Decreased quality of meat and wool
  • Restrictions on the trade and export of animals and animal products

Efforts to control the spread of blue tongue virus are, therefore, critical for safeguarding the economic and social welfare of agricultural communities in affected areas.


Blue tongue is a viral disease that affects domesticated animals such as cattle, goats, sheep, and deer. The virus is transmitted by Culicoides midges and can cause a range of clinical signs, from mild to severe. Vaccines and insecticide-based control measures are available to prevent the spread of the virus, and supportive care is the only therapy for infected animals. Awareness of the disease and its control measures is essential to prevent outbreaks and minimize the impact on agricultural industries and communities.


  • Q: Can blue tongue virus be transmitted to humans?
  • A: No, blue tongue virus is not transmissible to humans.
  • Q: What animals are most susceptible to blue tongue virus infection?
  • A: Domesticated animals such as cattle, goats, sheep, and deer are most susceptible to blue tongue virus infection.
  • Q: Is there a cure for blue tongue virus infection?
  • A: No, there is no cure for blue tongue virus infection, and treatment is mainly supportive.
  • Q: Does blue tongue virus have any impact on the quality of dairy and meat products from infected animals?
  • A: Yes, blue tongue virus can affect the quality of dairy and meat products from infected animals.


1. Carpenter S, Wilson A, Barber J, et al. Temperature dependence of the extrinsic incubation period of orbiviruses in Culicoides biting midges. PLoS One. 2011;6(11):e27987. Published 2011 Nov 30. doi:10.1371/journal.pone.0027987
2. Maclachlan NJ. Global implications of the recent emergence of bluetongue virus in Europe. Vet Clin North Am Food Anim Pract. 2010;26(1):163-171. doi:10.1016/j.cvfa.2009.10.008

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