Warm weather increases parasite risk in sheep and cattle

NADIS and Merial Animal Health are warning sheep and cattle farmers that recent above average temperatures could lead to a rise in parasitic disease in growing animals this summer.

The timing of worm treatments for lambs during the grazing season will depend upon prevailing weather conditions, grazing history, levels of contamination and stocking density. Prolonged dry weather conditions during the spring may have delayed the larval challenge, but infectivity will increase once wetter weather returns and leave lambs susceptible to parasitic gastroenteritis (PGE).

Lambs on safe grazing at the start of turnout shouldn’t need worming until after they are weaned. Ideally lambs should be weaned onto silage or hay aftermaths that have not been grazed by sheep earlier in the year.

Lambs grazing permanent pastures will usually require worming to limit the build-up of infective larvae later in the season. Regular performance monitoring, or worm faecal egg counts (FEC) of lambs, from June onwards can be used to guide anthelmintic treatments. Treatment is generally recommended when FECs exceed 500-700 epg.

Parasite control in rams can sometimes be forgotten, and yet they often graze the same pasture year on year and may be at increased risk of parasite challenge as a result of this.

Sioned Timothy, Merial Animal Health’s veterinary advisor, said: “Rams are fully susceptible to PGE but are often forgotten in the farm’s parasite control strategy. To preserve fertility, rams must be in good condition with a target condition score of 3.5 at tupping in October/November.

“It can take at least two months of good grazing for rams to gain one unit of condition score and parasites can negatively impact weight gain. Assessing whether rams would benefit from a wormer treatment during the summer will help ensure they are fit to perform at tupping time.”

Dairy and beef cattle are at risk of husk, caused by infection with the cattle lungworm from June onwards. Unvaccinated calves, naïve adult cattle and those without an effective anthelmintic programme face the greatest threat.

Early signs of lungworm include coughing after periods of exertion and progress to more severe compromise, with coughing at rest, increased respiratory rate, and difficulty breathing. Prompt recognition and treatment is critical.

Ms Timothy added: “Early intervention significantly reduces costs and the impact on productivity. A diagnosis should be sought from the farm’s vet at the first sign of symptoms.”

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