Farmers are being warned to be on their guard against nematodirus this month, because changing weather patterns could produce a sudden surge  in worm numbers.

Farmers are being warned to be on their guard against nematodirus this month, because changing weather patterns could produce a sudden surge  in worm numbers.

Simon Harris, farm animal product manager for Novartis Animal Health, said the changing temperatures over the last few weeks had created the perfect conditions for nematodirus infection.

Nematodirus can strike without warning and have a devastating effect on lambs at certain stages of their development.He said: “We are asking farmers to be aware of the dangers of nematodirus, and to seek advice if they think their lambs might be at risk. Nematodirus can strike without warning and have a devastating effect on lambs at certain stages of their development.”

Lesley Stubbings of SCOPS (Sustainable Control of Parasites in Sheep), said that many lambs were in the critical stage of their development during May and June, so it is important for farmers to have a plan to deal with nematodirus infections.

She said: “Nematodirosis is a particularly nasty disease in lambs, causing a high number of mortalities and cases of stunted growth. Because of its lifecycle, nematodirus can strike very quickly, with little or no warning.

“Before they hatch, the nematodirus eggs have to undergo a period of cold weather followed by warmer temperatures above 10°C. If this change in conditions occurs over a short period of time it means lots of eggs hatching at once, creating a big challenge particularly if it coincides with lambs starting to take in significant amounts of grass. The result can be devastating.”

The main risk factors include:

  • lambs grazing pasture that carried lambs the previous spring;
  • a sudden late cold snap, followed by a period of warm weather;
  • lambs that are old enough to be eating significant amounts of grass (6-12 weeks old);
  • groups where there is likely to be challenge from coccidiosis; and
  • lambs that are under other stresses, eg triplets, fostered, on young or older ewes.

Ms Stubbings added: “We can’t afford to have a ‘wait and see’ policy, even faecal egg counting cannot be relied upon because the damage is done by immature larvae. Farmers must assess the risk to their lambs, and if they decide they need to act, SCOPS advises them to use a white (1-BZ) drench.”

Ms Stubbings also explained that the timing of a potential problem will vary from region to region: “In the south of England, for example, it is likely to occur earlier in May, while in Scotland and the north of England it may be early June.”

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