Bluetongue Disease in Animals - Symptoms and Prevention

Author: Peter Berry
Date Of Creation: 15 February 2021
Update Date: 18 May 2024
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Bluetongue virus of ruminants
Video: Bluetongue virus of ruminants

Content

Bluetongue disease or malignant bluetongue (MFC) is an infectious process, but not contagious among animals, as a mosquito to transmit. Animals susceptible to infection by the bluetongue virus are ruminants, but only sheep show clinical signs of the disease. Humans cannot be affected, so 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 damage to the endothelium of blood vessels. The diagnosis is laboratory-based and there is no treatment, as it is a mandatory notification disease in the list A of the World Organization for Animal Health.


Continue reading this PeritoAnimal article to learn all about Blue Tongue Disease - Symptoms and Prevention.

What is the blue tongue in animals?

Malignant bluetongue or bluetongue disease is a infectious but not contagious disease, which affects wild and domestic ruminant animals but causes clinical symptoms only in sheep.

Although the blue tongue may be present in cows or goats, they usually do not show clinical signs; however, cows are often the mosquito's preferred virus reservoir. In addition, the virus can remain in the blood for a month to a month and a half to be infective for the mosquitoes that transmit it, unlike sheep and goats where the high viremia (virus in the blood) lasts for no more than 15 days.


Therefore, bluetongue in cattle and goats is not symptomatically important, but it is important in the epidemiology of the disease, since they are considered viral reservoirs for the mosquito, especially cattle. Find out in this other article the most common diseases in cattle.

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

Malignant Bluetongue or Bluetongue Disease is a disease listed in the OIE Terrestrial Animal Health Code and must always be reported to the World Organization for Animal Health (OIE). It is a disease of great economic importance in endemic regions, as it produces direct economic losses due to decreased production and deaths, and indirect by the price of preventive measures and restrictions on animal trade.


Can malignant bluetongue be transmitted to humans?

No, the bluetongue disease it's not a zoonosis, is a disease that affects only ruminants, with or without symptoms. Furthermore, it is not directly transmissible between them, as it requires a transmitting vector, in case one, a mosquito.

Which virus causes bluetongue disease?

Bluetongue is a disease caused by the Bluetongue virus, a RNA virus belonging to the family Reoviridae and to gender Orbiviruses, transmitted by vectors. More specifically, they are mosquitoes of the genus Cullicoids:

  • Imicollicoides
  • Cullicoides obsolete
  • Cullicoides pulicaris
  • dewulfi Cullicoids

These mosquitoes have twilight and nocturnal activity, and are found in areas with mild temperatures, with high humidity in the environment and in the air. Thus, virus transmission occurs especially in periods of rain and hot temperatures.

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

In addition to contagion by females of these mosquitoes due to their habit of sucking blood, it has been observed to transplacental and semen transmission.

The virus that causes malignant bluetongue has more than 27 serotypes, but they are independent and do not cross-react, being mandatory vaccination specific for the serotype in question for each outbreak.

Bluetongue Symptoms in Animals

The bluetongue malignant fever virus or bluetongue disease 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 causes damage mainly to the endothelium of blood vessels, which can cause edema, vasculitis, hemorrhage, microthrombi and necrosis.

Bluetongue virus can also multiply in stimulated macrophages and lymphocytes. The injuries are more evident in the oral cavity, around the mouth and in the hooves.

Symptoms of a sheep with the bluetongue virus:

  • Fever 5-7 days after infection.
  • Serous to hemorrhagic nasal secretion.
  • Serous to hemorrhagic eye secretion.
  • Swelling of lips, tongue and jaw.
  • Psyalorrhea (hypersalivation).
  • Depression.
  • Anorexia.
  • Weakness.
  • Walking lame.
  • Wool fall.
  • Breathing difficulty.
  • Profuse diarrhea.
  • Vomiting.
  • Pneumonia.
  • Abortions.
  • Hyperemia in the coronary band of the hooves.
  • Edema on the face and neck.
  • Hemorrhages and erosions in the oral and nasal cavity.
  • Pulmonary artery bleeding.
  • Bleeding in the skin and connective tissue.
  • Muscle necrosis.
  • Lung edema.
  • Tongue swelling and cyanosis (blue tongue).

We emphasize that the bluetongue virus does not produce clinical signs in cows and goats, so we focused on symptoms in sheep.

To better understand the signs of a sick cow - signs of pain in cattle, don't miss this other PeritoAnimal article.

Bluetongue disease diagnosis

Given the aforementioned symptoms in sheep, the following diseases should be considered:

  • Bluetongue or malignant bluetongue.
  • Infectious Pododermatitis.
  • Ectima contagious.
  • Foot-and-mouth disease.
  • Small ruminant plague.
  • Rift Valley Fever.
  • Sheep smallpox.

In addition to the clinical symptoms that the sheep develop, it is necessary to confirm the diagnosis. taking samples and sending it to the laboratory for direct or indirect virus detection tests. You 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.

You indirect tests to look for antibodies to the virus in the serum of unvaccinated sheep are:

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

Bluetongue control in animals

There is no treatment for bluetongue or malignant bluetongue. Because it is a notifiable disease on the OIE List A and so devastating to sheep, the treatment is unfortunately prohibited. What the regulation requires is the euthanasia of the infected animals and the destruction of their bodies.

Since once infected animals cannot be treated, disease control is based on Preventive measures to prevent the virus and infection in case of suspicion or emergence of an outbreak.

Bluetongue prevention in animals

  • Establishment of a protection area and a surveillance area.
  • Ban on the movement of ruminants in the protected area.
  • Use of insecticides and mosquito repellents.
  • Entomological and serological controls in ruminants.
  • Vaccination of sheep with the specific outbreak serotype.
  • Control of animal transport and disinfection of used vehicles.
  • Declaration to authorities of all new cases that arise.

Properly preventing bluetongue disease or malignant bluetongue is vital to saving these animals' lives.

We also emphasize that it is important not to confuse bluetongue disease with bluetongue in dogs, which occurs for other reasons that are not related to any disease. Read our article on Bluetongued Dogs: Breeds and Traits to get to know them.

This article is for information purposes only, at PeritoAnimal.com.br we are not able to prescribe veterinary treatments or perform any type of diagnosis. We suggest that you take your pet to the veterinarian in case it has any type of condition or discomfort.

If you want to read more articles similar to Bluetongue Disease in Animals - Symptoms and Prevention, we recommend that you enter our section on Viral diseases.