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SAC Vets Warn of Lamb Disease Threat in May

SAC News Release Ref. No: 11N46
Published: 18 Apr 2011

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With spring temperatures slow to rise SAC Vets anticipate that in early May, all over Scotland, Nematodirus will threaten lambs as young as six weeks old. It is at this age lambs begin to eat more grass and also swallow Nematodirus battus worms. The worms can cause sudden deaths, with watery diarrhoea, while those that survive are left sickly and weak. There can be further losses from a parasite causing Coccidiosis with kidney damage causing renal failure.

The risk of losses increases when a cold period in the spring is followed by a warm spell leading to a mass hatch of eggs on pasture. As that fits this year’s pattern it is anticipated that a simultaneous hatch of N battus larvae will occur from election day onwards.

There is a particular risk on heavily stocked low ground pastures and any grazing with a history of the disease. If the Nematodirus hatch continues into June, hill lambs on improved pastures, which are relatively heavily stocked, may also be affected.

According to Ayr based SAC Vet Dr. George Mitchell,

“It is important to remember that the parasite can kill lambs before eggs appear in faeces, so if any unexplained deaths occur in lambs it would be wise to send freshly dead lambs for post mortem examination to an SAC Disease Surveillance Centre (DSC). That way the disease can be diagnosed or ruled out”.

Where the risk factors apply then farmer should begin treatment once the lambs reach 6 weeks of age.

“If the risk is high then don’t wait for signs of scouring, but treat with a wormer effective against Nematodirus, but remember to check the data sheet before you buy”, says George Mitchell. “If in doubt dung samples should be checked for worm eggs 7-16 days after treatment depending on the product used. You should find no eggs if the drench was effective. However anticoccidial treatment may also be required”.
 
As the rise in worm numbers on the pasture is extremely rapid Dr. Mitchell recommends two doses at 7-10 day intervals for most situations. Where there is a particularly severe problem the best solution may be to move the ewes and lambs to low risk pasture (eg reseeded pasture) if it is available.

While cattle don’t develop clinical Nematodirus disease, if young calves graze with sheep they can become infected and increase the build-up of larvae on the pasture. It is good practice to have faeces samples from all young stock checked regularly for evidence of worm eggs, not only to ensure animal welfare when challenge is high, but also to prevent needless dosing and decrease the risk of the development of resistant worms.

A secondary hatch of eggs of Nematodirus has been recorded in some areas in autumn following wet weather. Casualty animals and/or dung samples should be submitted to check for this possibility.

SAC offers a Wormscan service on bulk faeces samples to reduce cost – further details are available from your local SAC Veterinary Centre.

Dr. George Mitchell can be contacted via the details below.

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News Release Contacts

SAC Contact

Dr George Mitchell
Veterinary Investigation Officer
SAC (Scottish Agricultural College) Work Disease Surveillance Centre, Auchincruive,
Ayr
KA6 5AE
TelWork 01292 520318
Fax 01292 521069

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News Release Issued By

Mr Ken Rundle
Senior Communications Officer
SAC (Scottish Agricultural College) Work SAC, King's Buildings, West Mains Road,
Edinburgh
EH9 3JG
TelWork 0131 535 4196

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