11-04-2014 02:05 AM | Animal Health, News, Sheep, Veterinary News

Experts warn sheep farmers of Nematodirus risk



Lesley Stubblings
Lesley Stubblings
Farmers are being warned by sheep experts to act now to protect vulnerable lambs against Nematodirus. The vast majority of cases occur in the spring putting young lambs at great risk. However, changing weather patterns mean that this particularly nasty disease can now also be seen in the autumn.

Experts warn sheep farmers of Nematodirus risk


The disease is caused by the immature stages of the worm Nematodirus battus, which can strike very quickly and with little warning.

“Before hatching, nematodirus eggs have to undergo a period of cold weather followed by warmer temperatures above 10°C,” explains Matt Colston, Veterinary Surgeon for Novartis Animal Health. “So a sudden rise in temperature, as we can have at this time of year, following on from a prolonged ‘cold snap’ can trigger a mass hatching of eggs, creating a big challenge. This is particularly dangerous for lambs, especially those at six to 12 weeks old that are starting to take in significant amounts of grass. At such a critical development stage they are at high risk and can suffer varying degrees of gut damage, causing diarrhoea, weight loss and death.”

Nematodirus symptoms include profuse watery diarrhoea, ill thrift, weight loss and sudden death, particularly of growing lambs

In a recent study, common gastrointestinal parasites were found to cost the UK sheep industry £84 million per year1. Farmers need to be prepared and seek advice if they think their lambs might be at risk of nematodirus.

“Because this disease strikes so quickly, we can’t afford to have a ‘wait and see’ policy with Nematodirus,” says Lesley Stubbings of Sustainable Control of Parasites in Sheep (SCOPS). “The damage is done by large numbers of immature larvae that are not producing eggs so Faecal Eggs Counts (FECs) are also not reliable. If farmers feel their lambs are at risk, and they need to treat for Nematodirus, then SCOPS advises the use of a white (1-BZ) drench* which is effective against this parasite and suitable for young lambs.”

“The SCOPS Nematodirus warning map will be live on the SCOPS website from early April,” advises Mrs Stubbings. “It is sensible for sheep farmers to visit the forecast leading up to and through the risk period.”

Nematodirus battus also has a slower, more extended life-cycle than most worms, and eggs deposited during one spring or summer generally do not hatch until the following spring. This allows infection to pass from a lamb crop in one year to the lambs born the following year, again, increasing the risk of mass hatchings.

“For this reason, if it is possible, moving lambs to fields that were not grazed by lambs in the spring and summer of the previous year will significantly reduce their risk of contracting clinical Nematodirus,” adds Mr Colston.

With the limited options for stock and pasture rotation using the correct choice of wormer, containing benzimidazole a group1 white drench, is vital for successful lamb production in the face of Nematodirus.

Nematodirus, Coccidiosis or both?

Coccidia and nematodirus are both gut parasites affecting young lambs. Symptoms are similar, but treatment is not, so diagnosis must be early and accurate.

· Both cause severe diarrhoea, even death

· Lambs can have nematodirus and coccidiosis at the same time.

· Treatment for nematodirus will not treat coccidiosis and vice versa

· Treatment must be accurate and early

· Diagnose coccidiosis by identifying oocysts in dung.

· Suspect nematodirus if young lambs are scouring in the spring or early summer and there is no evidence of coccidiosis (Both can be confirmed by post mortem examination)

· Regular dung samples can identify rising oocyst counts, allowing treatment before lambs suffer a growth check

· Treat coccidiosis with anti coccidial drench containing toltrazuril or diclazuril

· Treat nematodirus with a group1 white drench wormer

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