Smallholders must watch out for fly strike NOW! (From Smallholder)

Smallholders must watch out for fly strike NOW!

7:40am Tuesday 3rd July 2012 in Livestock

Henry Creagh finds out how one Shropshire-based smallholder protects her flock from blowfly strike and picks up some tips on preventing and treating other ectoparasites.

Lambing is almost finished when we catch up with Sally Mellor and she says it’s been a good year for the 60 Texel ewe flock, based on her 45-acre smallholding near Bishops Castle in Shropshire.

“Our lambing percentage this year is about 120% – some years it’s closer to 140%. But single lambs tend to be stronger, so I’m happy with this year’s crop.”

Lambing began in early February and continued through to mid March. And so far so good. But how does she protect her lambs and ewes from ectoparasites, like blowfly, as the grazing season progresses?

“Prevention is the key. I treat ewes and lambs routinely against blowfly strike – I use a pour-on product called CLiK® – and I haven’t seen a case for several years.”

Vet Thomas Tiley, from Novartis Animal Health, agrees that prevention is the key to avoiding fly strike.

“Experts agree that the blowfly season has become more intense and is starting earlier in the year. In 2011, for example, the first case of fly strike was recorded as early as the end of April,” he says.

“The blowfly lifecycle starts where the adults live and breed on the animal, lay their eggs, and the eggs hatch and develop into larvae that feed on the animal’s tissue. The feeding process is where the damage is done and is known as ‘fly strike’ or ‘myiasis’,” he explains.

“By this stage it can sometimes be too late to reverse the damage, and it can result in death of the animal, which is why prevention is a popular choice.”

He said popular blowfly preventatives among farmers in the UK are pour-on insect growth regulators (IGRs), such as CLiK or CLiKZiN® , which act to halt larval development thus preventing damage occurring. CLiK is a popular choice as it provides the longest duration protection, with CLiKZiN providing an alternative choice if medium duration protection and a short meat withhold period is required.

It is important to remember that as IGRs, CLiK and CLiKZiN are for prevention only and cannot be used to treat existing strike. If strike is detected, sheep should be treated with a product that kills maggots such as Crovect®, a synthetic pyrethroid. This product can also be used to effectively treat ticks, lice and headfly.

It is estimated that in an average year, around 75%1 of untreated flocks are affected by fly strike. “It is truly unpleasant when it happens and has a severe impact on the welfare of the animal. Within days of a blowfly laying its eggs, clinically normal sheep can be afflicted with flesh eating maggots,” says Thomas.

This is exactly why Sally doesn’t wait until she sees blowfly strike before she treats. “By then the damage has been done – I want to prevent it. I don’t like seeing maggots on my livestock.”

Sally adds that it’s quite easy to walk among the flock and spot if they have a problem, because Texel coats are not excessively woolly.

Texels are also a ‘clean’ breed as their fleeces are shorter – clean ewes means clean lambs. But still Sally doesn’t take any chances: “Why risk stock being struck down when treatment is so simple, easy and cost effective?”

She treats her lambs in mid May, when they’re between three and four months of age. “Using CLiK gives them 16 weeks of protection – enough to get them through the blowfly strike season – and that’s why I use that product rather than any other.”

The ewes are shorn at the end of May and then also treated with CLiK in early June, which again gives them protection for the rest of the summer. “One treatment should be enough to protect the ewes for the summer and early autumn. However, with the blowfly risk period getting longer, we may chose to retreat the ewe lambs we are going to use as breeding stock in September, this will ensure they are covered right up until the end of the season.

“It’s money well spent for peace of mind and a healthy flock,” adds Sally, who used to use a different product for blowfly strike prevention, but switched to CLiK five years ago due to its longer protection period. “I wouldn’t use anything else.”

IN A BOX Tips on preventing blowfly strike • For prevention, pour-on insect growth regulators (IGRs) are a popular and effective choice • If strike is detected, then the sheep can be treated with a synthetic pyrethroid • Dagging, prompt attention to wounds and effective worm control to minimize scours all reduce the risk of strike • If strike is suspected, it is always recommended to seek veterinary advice on treatment