Blowfly strike: Take action before it sets in

The next headache for sheep farmers over the coming months is the threat of blowfly strike in their flocks. The blowfly season seems to be starting earlier and lasting longer year-on-year.

Blowfly is an external parasite that commonly appears over the summer months; however, due to ever-changing weather patterns, it is not uncommon to hear cases of it earlier and later on in the year.

More often than not, most farmers will have or come across blowfly strike in their flock, so it is important that action is taken now before it sets in.

In late spring coming into the summer months, the population of flies increases rapidly. This, along with the onset of warm, humid weather and rainfall, are the main contributing factors to the prevalence of flystrike.

Sheep that have a soiled fleece are most at risk of being struck down with flystrike. The most common areas that sheep are affected is around the tail or rump region. However, they can also become infected on the shoulder, along the back or where a cut has occurred on the skin.

Blowfly strike occurs when flies become attracted by a foul-smelling, soiled fleece and deposit many hundreds of eggs onto affected sheep. These eggs will then hatch into larvae and begin to feed on the sheep’s skin – causing wounds.

Within a matter of days, if action is not taken, more and more sheep will become infected.

Obvious symptoms that sheep have been struck down with flystrike include: foot-stamping; vigorous shaking; gnawing or rubbing of the tail; restlessness; wool loss; and a loss of body condition. If sheep aren’t treated it will result in death.

Early treatment before the population of flies increases substantially will give farmers the best chance of controlling the outbreak of flystrike.

The good news is farmers have options when it comes to controlling and preventing the outbreak of flystrike.

At this time of the year, farmers may favour the use of pour-ons as a method of providing protection and wait until later in the season before dipping.

It’s important to note that there are significant differences with pour-ons, with some only providing protection against certain parasites. As well as that, some products will treat and prevent against a parasite, while others will only prevent against. So, both of these factors need to be taken into account when purchasing a product.

Pour-ons will provide protection against flystrike for generally up to 10 weeks or so; however, there are some products that provide protection for up to 19 weeks.

It is important to be mindful of the withdrawal periods associated with pour-on products. Withdrawal periods can vary from seven days up to 40 days.

For farmers with ewes or lambs coming close to slaughter, it is essential that the withdrawal periods are adhered to.

A short-term solution is to dag dirty tail ends, which will significantly help with early cases of flystrike.

Finally, care should be taken when using products that are being used to treat against flystrike. Protective clothing, gloves and a respiratory mask should be worn.

When treating for flystrike, it is important that farmers keep the following points in mind.

  • Apply in dry weather;
  • Apply to clean, dry wool – crutch excessively dirty sheep;
  • Treat lambs early before flystrike is anticipated;
  • Consider withdrawal periods when selecting a treatment;
  • When using a pour-on product, make sure to apply it from the neck down to the rump area.

So, from now on, watch out for any sheep showing signs of restlessness, tail wagging or attempts at biting or scratching. Move quickly if you see a problem. If showery weather occurs and the days are humid, then take action to protect your flock.

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