Summary written by Peter Nettleton MSc BVMS, PhD, MRCVS
Taken from Moredun Foundation Newsheet Volume 4 No. 8 (2005)
- Border diseases was first described in the region of the English/Welsh border. It is also called 'hairy shaker' or 'fuzzy lamb' disease, and has been recognised in most sheep-rearing areas of the world.
- It is a congenital disorder of lambs characterised by low birth weight and viability, poor condition, tremor and an excessively hairy birth coat in normally smooth-coated breeds. Other features of the disease include barren ewes, abortion and stillbirths.
- The disease is caused by infection of the fetus in early pregnancy with border disease virus (BDV), a pestivirus which can also infect other ruminants and pigs. Other species, including man, are not susceptible.
- The causal virus is closely related to bovine virus diarrhoea virus (BVDV) which causes a comparable cogenital disease in cattle.
- Acute infections of susceptible sheep are transient, usually subclinical and result in a good immunity to future infection.
- When susceptible ewes in early pregnancy are infected the virus crosses the placenta and invades the fetus. The ewe shows no disease but the fetus is infected.
- Infected fetuses may die and be resorbed quickly or an be aborted at any stage of gestation or be stillborn.
- Some fetuses will survive, and all those infected in the first half of gestation will be persisently infected (PI) with BDV. Such PI sheep will excrete the virus particularly fro the nose and mouth, continously for the rest of their lives.
- PI sheep can mature normally and are a constant dangerous source of infection.
- Autumn purchase of PI replacement female sheep is the commonest way for the disease to be introduced into a flock with the disease being recognised the following spring.
- No vaccine is currently available in the UK. Control of the disease has to be acheived by good management and is aimed at preventing the exposure of pregnant ewes to PI carrier sheep.
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