Louping Ill in Sheep
Summary written Hugh W Reid
Taken from Moredun Foundation Newsheet Volume 4 No. 3 (2004)
- Louping Ill is an acute virus disease which affects the brain and causes varying signs of in-coordination, paralysis, convulsions and death. The disease is primarily associated with sheep, but man, cattle, goats , pigs, horses, farmed red deer, llamas, dogs and (wild)red grouse can all be affected.
- The cause is a a tick-transmitted Arbovirus belonging to the tick-borne encephalitis (TBE) complex
- In areas where louping ill is endemic, it is most frequently diagnosed in lambs and yearlings. However, all ages of sheep can succumb - for example when susceptible sheep are moved into a louping ill area for the first time.
- Susceptible sheep suffering an infection with both the tick-borne-ferevr agent (Anaplasma phagocyophila) and loupnig ill virus may suffer mortality rates approaching 100%
- Diagnosis of louping-ill can be confirmed by looking for specific antibody in serum and by demonstrating the presence of virus in brains from dead animals.
- Transmission of louping-ill is dependent on the sheep tick (Ixodes ricinus) which requires a moist microclimate when it is on the ground and the availability of large mammals on which adult ticks feed. The tick is therefore largely restricted to upland sheep grazing and the distribution of louping-ill is restricted to favourable tick habitats.
- Ticks are inactive in the winter and only start questing for a host when the mean maximum weekly temperature exceeds 7oC. The incidence of louping-ill follows closely tick activity with losses occurring mostly in spring and autumn.
- Control of louping-ill may be achieved either by vaccinating sheep or by preventing them becoming infected by control of the tick.
- Vaccine is administered as a single subcutaneous injection. On infected farms it is commonplace to vaccinate ewe lambs that are to be retained for breeding either in the autumn or in the following spring before ticks become active. All purchased sheep should be vaccinated at least 28 days before exposure to tick-infested pastures. Where the disease occurs for the first time it may be prudent to vaccinate the whole breeding flock.
- Reduction in tick numbers can be achieved by a combination of strategic grazing and the use of acaricide dips or pour-ons.
- A combination of vaccination and tick suppression may also be appropriate but careful planning and a sustainable programme are essential for any louping-ill control strategy which should involve your vet and utilise the expertise and experience available from your local veterinary laboratory.
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