Summer parasite control in lambs highlighted by NADIS forecast

Parasite control in weaned lambs should be high on sheep farmers’ priority list in July
Parasite control in weaned lambs should be high on sheep farmers’ priority list in July

Parasite control in weaned lambs should be high on sheep farmers’ priority list in July, along with preparing for the risk of blowfly strike; while cattle farmers should be alert for lungworm infection, according to the NADIS parasite forecast sponsored by Merial Animal Health.

"In lambs the aim is for sustainable parasite control which achieves acceptable growth rates while managing the parasite burden and reducing clinical disease," says Sioned Timothy, Veterinary Adviser for Merial Animal Health.

"No sheep can ever be kept parasite-free and this is not an achievable target."

Where weaned lambs are concerned, peak pasture larval contamination occurs in July and August as the result of an increasing build-up of eggs passed by lambs earlier in the season.

Ms Timothy says: "This larval challenge can be avoided by moving lambs to silage aftermath not grazed by sheep this year, and preferably to pasture not grazed by sheep last year.

"The value of such clean grazing is critical on most sheep farms, but is often in short supply."

There are three main strategies for controlling PGE (parasitic gastroenteritis) this grazing season:

• Targeted anthelmintic treatment based upon liveweight gain

• Whole group anthelmintic treatment based upon lamb faecal worm eggs counts.

• Whole group anthelmintic treatment at regular intervals; this is not sustainable and not recommended)

Blowfly strike in sheep is a major threat from June onwards and NADIS points out that PGE control is key to reducing the risk, alongside the use of an appropriate topical treatment.

The latest NADIS reports points to the correct predictions earlier this year of high levels of nematodirosis in lambs, with above average number of outbreaks reported in many regions.

Pasture management will now be critical to reduce infection risk rates next year.

Where possible farmers should be planning grazing management to ensure that next year’s lambs are not turned out onto pasture grazed by those born this spring.

'High levels' of anthelmintic resistance

Recent findings from the WAARD Project (Wales Against Anthelmintic Resistance Development) have shown that there are high levels of anthelmintic resistance among sheep on Welsh farms.

On 47 Welsh farms tested during 2014 and 2015 resistance levels included 94% to Benzimidazole (1-BZ), 68% to Levamisole (2-LV) drenches, and 51% Ivermectin (3-ML) drench, while 43% of farms demonstrated triple wormer resistance.

"Given these results it is essential that advice on anthelmintic use is farm-specific and that wormer efficacy is assessed as part of the process.

"SCOPS advise that group 4-AD and group 5-SI anthelmintics should be used strategically and only where necessary, but they should not be left in reserve for when all other groups have failed on a farm.

"It is clear that farmers and vets need to work much more closely on planning year-round parasite control," says Ms Timothy.

According to the NADIS forecast for cattle, there is a risk of lungworm disease occuring from June onwards in unvaccinated calves, those cattle not protected by a strategic wormer treatment, and naïve adults.

Early signs of lungworm include coughing, initially during activity but then at rest as the disease progresses, and an increased respiratory rate.

Affected cattle rapidly lose weight and body condition, and dairy cows will often show a sudden drop in milk production.

"Prompt anthelmintic treatment is essential in order to minimise the impact of the parasite,” says Ms Timothy.

"Beef cattle and dairy youngstock can be treated with Ivomec Classic®, while Eprinexâ is suitable for use in lactating dairy cows.

"These products provide persistent activity for up to 4 weeks, and so prevent re-infection during this period, A further important benefit of Eprinexâ in dairy cattle is its zero milk withhold, which means it can be used during lactation without the need to discard milk."