Blue tongue disease in animals - Symptoms and prevention

Bluetongue disease is an infectious process, but it is not contagious among animals because they need a mosquito for its transmission. The animals susceptible to being infected by the bluetongue virus are ruminants, but only sheep will show the clinical signs of the disease. Humans cannot be affected, it is not a zoonosis. Cows are the best reservoirs of the virus due to their long viremia. In the pathogenesis of the disease, the virus causes its damage to the endothelium of blood vessels. The diagnosis is laboratory and has no treatment as it is a notifiable disease on list A of the World Organization for Animal Health.

Keep reading this AnimalWised article to learn all about the blue tongue disease, your symptoms and treatment.

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  1. What is blue tongue in animals?
  2. What virus causes bluetongue disease?
  3. Blue tongue symptoms in animals
  4. Diagnosis of blue tongue disease
  5. Control of blue tongue in animals

What is blue tongue in animals?

The blue tongue is a infectious but not contagious disease, affecting wild and domestic ruminant animals, but causing clinical symptoms only in sheep.

Although bluetongue may be present in cows or goats, they generally show no clinical signs, however, cows are often the mosquito's preferred virus reservoirs. In addition, the virus in the blood can remain from a month to a month and a half to be infectious for the mosquitoes that transmit it, unlike sheep and goats in which the high viremia (virus in blood) does not last more than 15 days. Therefore, bluetongue in cattle and goats is not symptomatologically important, but it is important in the epidemiology of the disease as it is considered viral reservoirs for the mosquito, especially cattle. Discover in this other article the most common diseases of cattle.

In the sheep the disease can become very serious, with average mortality from 2% to 30%, although it can reach 70%.

Bluetongue is a disease of the OIE Terrestrial Animal Health Code and must always be notified to the World Organization for Animal Health (OIE). It is a disease of great economic importance in endemic regions because it produces direct economic losses due to decreased production and deaths, and indirect ones due to the price of preventive measures and restrictions on the trade of animals..

¿The blue tongue is transmitted to humans?

Do not, it is not a zoonosis, it is a disease that affects only ruminants with or without symptoms. In addition, it is not directly transmissible between them, since they require a transmitting vector, in this case a mosquito..

What virus causes bluetongue disease?

Bluetongue is a disease caused by the bluetongue virus, a RNA virus belonging to the Reoviridae family and the Orbivirus genus, vector-borne. Specifically, they are mosquitoes of the genus Cullicoides:

  • Cullicoides imicola
  • Cullicoides obsoletus
  • Cullicoides pulicaris
  • Cullicoides dewulfi

These mosquitoes have a twilight and night activity and are found in areas with warm temperatures, high humidity in the environment and without air. Hence, the transmission of the virus occurs especially in periods of rain and warm temperatures (late spring or early autumn).

Due to the need for exclusive transmission by a vector mosquito, the disease areas coincide with the vector regions, specifically Europe, North America, Africa, Asia, Australia and several islands in the tropics and subtropics.

In addition to the contagion by females of these mosquitoes due to their hematophagous habits, transplacental transmission and by semen have been seen.

The virus has more than 27 serotypes, but they are independent and there are no cross-reactions, and specific vaccination for the serotype in question is mandatory for each outbreak..

Blue tongue symptoms in animals

The virus replicates early in infection in the vascular epithelium and regional lymph nodes. From there, it spreads through the blood to other lymph nodes and lungs protected by invaginations in the red blood cells. The virus mainly causes damage to the endothelium of blood vessels, which can lead to edema, vasculitis, hemorrhage, microthrombi and necrosis.

Bluetongue virus can also multiply in stimulated macrophages and lymphocytes. Lesions are most evident in the oral cavity, around the mouth, and on the hooves. Specifically, the symptomatology of a sheep with the bluetongue virus it can include:

  • Fever 5-7 days after infection.
  • Serous to hemorrhagic nasal discharge.
  • Serous to hemorrhagic ocular discharge.
  • Swelling of the lips, tongue, and jaw.
  • Psialorrhea (hypersalivation).
  • Depression.
  • Anorexy.
  • Soft spot.
  • Limp.
  • Wool fall.
  • Shortness of breath.
  • Profuse diarrhea.
  • Vomiting.
  • Pneumonia.
  • Abortions.
  • Hyperemia in the coronary band of the hooves.
  • Edema in the face and neck.
  • Hemorrhages and erosions in the oral and nasal cavity.
  • Pulmonary artery hemorrhage.
  • Hemorrhages in skin and connective tissue.
  • Muscular necrosis.
  • Lung edema.
  • Swelling and cyanosis of the tongue (blue tongue).

Remember that the blue tongue virus in cows and goats does not produce clinical signs, which is why we focus on the symptoms in sheep.

Diagnosis of blue tongue disease

Given this symptomatology in sheep, the following diseases should be considered:

  • Bluetongue.
  • Pedero.
  • Contagious ecthyma.
  • Aphtose fever.
  • Peste des petits ruminants.
  • Rift Valley fever.
  • Sheep pox.

In addition to the clinical signs that the sheep develops, it is necessary to confirm the diagnosis by Sampling and its sending to the laboratory for direct or indirect tests to detect the virus. The direct tests that detect the virus in blood and serum with EDTA, tongue, nasal mucosa, spleen, lung, lymph nodes or heart are:

  • Antigen capture ELISA.
  • Direct immunofluorescence.
  • RT-PCR.
  • Seroneutralization.

The indirect evidence to look for virus antibodies in serum of unvaccinated sheep are:

  • Competition Elisa.
  • Indirect ELISA.
  • Agar gel immunodiffusion.
  • Seroneutralization.
  • Attachment of the Complement.

Control of blue tongue in animals

There is no treatment for blue tongue. Because it is a notifiable disease on OIE List A and so devastating for sheep, treatment is unfortunately prohibited. What the regulation requires is to slaughter the infected animals and destroy the bodies.

Since once infected animals cannot be treated, control of this disease is based on preventive measures to avoid the virus and infection in the event of a suspected or outbreak, consisting of:

  • Establishment of a protection zone and a surveillance zone.
  • Prohibition of movements of ruminants within the protection zone.
  • Use of insecticides and repellants for mosquitoes.
  • Entomological and serological controls in ruminants.
  • Vaccination of sheep with the specific serotype of the outbreak.
  • Control of animal transport and disinsection of used vehicles.
  • Declaration to the authorities of all new cases that may appear.

Carrying out a correct prevention of the disease of the blue tongue is vital to save the lives of these animals.

This article is merely informative, at we do not have the power to prescribe veterinary treatments or make any type of diagnosis. We invite you to take your pet to the vet in the event that it presents any type of condition or discomfort.

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