Sheep - Neurological Problems

Neurological Diseases in Sheep

Diseases affecting the nervous system can lead to a number of different clinical syndromes – blindness, depression, nervousness, scratching, circling and difficulty walking or standing are just some of the symptoms which may be seen.  Sheep of all ages can be affected by a great number of different neurological diseases.

METABOLIC DISEASE is perhaps the most significant of the neurological disorders encountered and tends to affect adult sheep, particularly around lambing time.

• Pregnancy Toxaemia/Twin Lamb Disease occurs in late pregnancy in ewes carrying multiple lambs.  It usually affects thinner ewes that have not received enough concentrate.  Regular condition scoring during pregnancy can help avoid the condition.  The first sign is usually loss of appetite, followed by weakness and loss of vision.  Treatment should be immediate – drench with Twin Lamb Drench.
• Hypocalcaemia also tends to be seen in late pregnancy.  Ewes in any condition can be affected, particularly following stress such as gathering for housing or vaccination.  Ewes often lie down and may develop bloat.  The condition worsens over hours, resulting in death, so should be treated straight away with 50-100ml calcium 20% (blue top) under the skin – have treatment handy if ewes are likely to be at risk.
• Hypomagnesaemia nearly always occurs at peak lactation.  Lush grass is low in magnesium so ewes are particularly at risk when grazing this pasture.  Signs come on very rapidly: excitability, shaking and convulsions.  Death follows rapidly so ewes are often found dead.  If cases are found, give 50ml Magnesium Sulphate (black top) under the skin.  Watch the flock closely after moving onto lush pasture and have magnesium injection handy.  Magnesium supplementation can be given in high risk flocks.

If a ewe does not respond to treatment within a few hours, veterinary attention should be sought.

SCRAPIE is an infectious disease, a Transmissable Spongiform Encephalopathy (TSE), in the same bracket as BSE in cattle.  It is resistant to most disinfectants and can persist in the environment for years.  Cases tend to arise in older animals with only 1 or 2 individual sheep being affected at a time.  The condition is untreatable so the eventual outcome is death.

The different genetics of different sheep affects how likely an individual is to develop scrapie.  This can be assessed by a blood test.  By breeding only from the more resistant genotypes, the national flock will, over the years, become less at risk of this serious disease.  This is the concept behind the National Scrapie Plan (NSP).  The scheme is voluntary and is focussed on rams.  Government funding is currently under review and is likely to be altered from Spring 2008.  Up to date information is available via the DEFRA website at www.defra.gov.uk/nsp

OTHER DISEASES causing neurological symptoms are numerous, including Louping ill, Listeriosis, Gid cyst, Swayback, Border Disease (Hairy Shaker lambs), Cerebro-cortical Necrosis and Daft Lamb Disease.  The exact disease is not always obvious and it is worth seeking your vet’s opinion.  A diagnosis is often possible and treatment may well be successful, with prevention of further disease achieved for the future.