Bluetongue “bloutong” - Treatment and prevention tiips

·         Bluetongue is  an acute, insect-borne viral disease of sheep caused by an orbivirus,  transmitted by Culicoides midges, otherwise known as “muggies”. There are 24 known serotypes of blue tongue virus, of which 21 occur in South Africa. Cattle, goats and wild ruminants are also susceptible but clinical blue tongue is seldom seen in these species. 

·         This is a seasonal disease normally occurring  from mid-Summer until the frost in autumn. 

·         Sheep infected with the bluetongue virus develop a very high temperature and a severe inflammation of the band above the hoof.

·         In addition, affected sheep may have severe ulcer-lesions, and may refuse to walk because the feet are very painful.

·         An early clinical sign is excessive salivation, which occurs 3 to 4 days after the onset of the disease.

·         Although the disease is not usually fatal in adult sheep, they may die from secondary infections like pneumonia.

·         Lambs are severely affected by the disease and heavy losses can occur.

 Treatment

The animal's mouth and tongue are usually so sore that it cannot eat, and its hoofs are too painful for it to go and seek food. The first line of treatment is therefore to enclose the sheep in a small camp where shade, green feed and water are close at hand. They must be handled as little as possible. Antipyretics and analgesics (for example, aspirin) may be administered.

·         Since the insect breeds in the mud along the edges of slow moving streams and dams, efforts should be made to eliminate these as breeding sites.

·         Ideally flocks should be bedded on high ground.

·         The flock should be inoculated approximately 9 weeks before the start of the breeding season. 

·         Note that pregnant ewes should never be inoculated especially within the first 60 days of gestation.

·         This could result in the abortion or malformation of the lambs..

·         Animals should therefore be inoculated with the three vaccines A, B and C at three-week intervals. 

·         Antibiotics can only prevent secondary infections and are used to salvage affected sheep.

·         Maternal antibodies will protect lambs against the virus for the first three months of life and they should not be inoculated at this time.

·         They should however be vaccinated after the three months have passed.

·         If one vaccinates the lambs of vaccinated ewes before 3 months, maternal immunity may interfere with the response of the young sheep to the vaccine.

Prevention The inoculant can be administered as soon as the ewes have dropped their lambs. Lambs receive passive immunity through the colostrum of their dams and should preferably not be inoculated against bluetongue before the age of six months. Rams should receive the last inoculant two months before the mating season. Otherwise they must be inoculated after this period. Ewes should receive the last inoculant no later than three weeks before the mating season. Pregnant ewes should not be vaccinated. Should there be an outbreak of bluetongue without the sheep having been inoculated; ewes that have been in lamb for at least three months can be inoculated with reasonable safety.