Blue Tongue Disease in Cattle and Sheep Goats

BTV causes an acute disease with high morbidity and mortality.  BTV also infects goats, cattle, and other domestic animals as well as wild ruminants.

Major signs are :

high fever, 

excessive salivation

swelling of the face and tongue and 

cyanosis of the tongue

Swelling of the lips and tongue gives the tongue its typical blue appearance, though this sign is confined to a minority of animals. Nasal signs may be prominent, with nasal discharge and stertorous respiration. Some animals also develop foot lesions, beginning with coronets, with consequent lameness. 

In sheep, this can lead to knee-walking.  In cattle, constant changing of position of the feet gives bluetongue the nickname The Dancing Disease.  Torsion of the neck (opisthotonos or torticollis) is observed in severely affected animals. Not all animals develop signs, but all those that do lose condition rapidly, and the sickest die within a week. 

For affected animals that do not die, recovery is very slow, lasting several months. The incubation period is 5–20 days, and all signs usually develop within a month.  The mortality rate is normally low, but it is high in susceptible breeds of sheep.

Treatment and Control of Bluetongue in Ruminants

Supportive care

Prevention

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

Prophylactic immunization of sheep remains the most effective and practical control measure against bluetongue in endemic regions. Attenuated and inactivated vaccines against BTV are commercially available in some countries. Three polyvalent vaccines, each comprising five BTV serotypes, are widely used in southern Africa and elsewhere. A monovalent (BTV type 10) modified live virus vaccine is available for use in sheep in the US.