Bluetongue in Sheep | Can Bluetongue be treated?

Bluetongue in Sheep is a non-contagious, infectious, arthropod-borne disease of ruminants, particularly sheep. This disease was first reported in South Africa. Bluetongue can’t be transmitted between susceptible animals without a vector, so the distribution of vectors limits the spread of infection. If you don’t know about the blue tongue or sore muzzle then let’s have a look at Bluetongue in sheep.

Other names: Sore Muzzle, Pseudo Foot and Mouth Disease, Sore Disease

Cause of Blue tongue in Sheep:

BTV ( bluetongue virus ) is the causative agent of the blue tongue. This virus belongs to the genus Orbivirus in the family Reoviridae.

Some Characteristics of BTV:

• BTV is a double-stranded RNA virus.
• It is non enveloped and icosahedral in shape.
• There are 24 serotypes of this virus, out of which 6 have been identified in the U.S

Host Range:

The blue tongue is a disease of both domestic and wild ruminants. But this problem is more prevalent in sheep but it is also said that sometimes this disease can infect the cattle, goats, and antelope but they show no signs and symptoms.

Transmission of Blue tongue:

Bluetongue is not a contagious disease it means that direct transmission is not possible. So how this problem spreads? The answer is the biting midges. Let’s see an example of transmission.

Basically, the bluetongue virus doesn’t shed in body secretions and excretions. So when the midges particularly of genus Culicoides bite an infected host then the virus present in the blood of that host enters into the saliva of midges. When this virus-containing midge bites a healthy one then the virus transmits to that healthy animal. There are some cases reported that The BTV can be transmitted to the fetus in utero. and results in abortion or dumb newborns.

So long story short the major way of transmission of this disease is through the biting midges of genus Culicoides. In the U.S the most common midge responsible for causing the blue tongue is Culicoides variipennis var sonorensis. The sheep keds can also transmit the BTV.

Clinical Signs and Symptoms of Blue tongue:

Before listing the clinical signs, it must be necessary to mention that BTV has an affinity for RBCs so it causes greater damage to vascular endothelium. Due to damage in the endothelium of blood vessels, the permeability of vessels increases which leads to intravascular congestion, hemorrhage, and edema.

In peracute cases death occurs within 7–9 days, mostly as a result of severe pulmonary edema leading to dyspnea, frothing from the nostrils, and death by asphyxiation. In chronic cases, sheep may die 3–5 weeks after infection, mainly because of bacterial complications (especially pasteurellosis) and exhaustion.

The incubation period is around about 5-10 days and the clinical signs in sheep are:

Bluetongue in Sheep ( Clinical Signs)

• High fever (105°- 107° F)
• Edema of muzzle, nasal mucosa, face, lips, submandibular area and even eyelids
• Watery discharge from nostrils – initially then becomes mucoid and may dry to form crust
• Congestion and heamorrages in nasal mucosa ( if you observe closely)
• Excessive salivation
• Edema and cynaosis of tongue ( tongue color blue( thats why called bluetongue) tongue swell and even protude from mouth)
• At the junction of skin anf hooves the purple-red color ulcerations are present that leads to Coronitis and laminitis
• Superficial necrosis & infection of teats ( female sheep)
• Decrease in wool production and quality

Clinical signs of Bluetongue in Cattle | Antelope | Goats

The cattle are asymptomatic, mostly and the signs are just limited to fever, high respiratory rates, lesions on mouth and teats, etc. Goats have similar signs like cattle. Bluetongue overall in all susceptible hosts can cause abortion or the birth of malformed calves or lambs. The malformations include hydranencephaly or porencephaly, which results in ataxia and blindness at birth. White-tailed deer and pronghorn antelope develop severe hemorrhagic disease leading to sudden death.

Diagnosis of Blue tongue:

It is a well-renowned saying that ” forget the treatment, diagnosis is everything. ” Diagnosis of every disease revolves around 3 things

1- History

2- Clinical signs

3- lab test

So take some history from the owner of the animal and then look at the obvious clinical signs. It must be mentioned here that clinical signs are somewhat similar in different diseases so the best way of diagnosis is the confirmation by a lab test. But there are some signs that are specific in some diseases and those signs can help the veterinarian in the proper diagnosis of a suspected disease.

Bluetongue must be differentiated with FMD, Vesicular Stomatitis, PPR, etc

Treatment of Blue tongue in Sheep:

There is no specific treatment for animals with bluetongue apart from rest, provision of soft food, and good husbandry. Complicating and secondary infections should be treated appropriately during the recovery period.

Prevention of Buetongue in Sheep:

Control of bluetongue is different in the different geographical areas. During an outbreak, it may be possible that different serotypes are involved so the vaccination strategy depends on the suspected serotypes causing infection.

Note:

During the Culicoides season, it is highly recommended, not to use live, attenuated vaccines. Because these insects may transmit the vaccine viruses from vaccinated to nonvaccinated animals (eg, other ruminant species). The result may be reassortment of genetic material, giving rise to new viral strains.

Control of vectors by the use of insecticides or protection from vectors may lower the number of Culicoides bites and subsequently the risk of exposure to BTV infection.

Conclusion:

Bluetongue in sheep is viral, noncontagious disease of ruminants particularly sheep. It is transmitted by the bite of the midges. One of the diagnostic clinical signs in sheep is cyanosis and edema of the tongue etc, There is no specific treatment. By controlling the vectors and by vaccines we can prevent the incidence of blue tongue.