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Control of External Parasites in Sheep

19 May 2020
Type Media Article

Martina Donnelly, Drystock Adviser Teagasc, Athenry

While we as a nation are adapting to a new way of life during the current COVID restrictions, farming activities are in full swing as we enter into the summer months. 

External parasites in sheep can start to become a problem as the weather conditions improve. The main external parasite we are familiar with and associate with this time of the year is flystrike but ticks, lice (biting and sucking) and scab can also have a significant effect on the animal health, welfare and the overall profit on a sheep enterprise.  Managing and control of these external parasites is now an essential task that must be carried out on sheep farms regularly.

The wool and skin of the sheep is the area where these external parasites inhabit. Examination of the flock on a regular basis and ensuring that sheep are kept as clean as possible through dagging and shearing will reduce the risk of flystrike but will also give you a good indication if there are any other external parasites present such as lice, scab or ticks.

In addition to this, ensuring sheep handling facilities, yards and trailers are kept as clean as possible so as to further reduce the risk of spread of external parasites. It is reported that scab and lice can survive off the sheep for 17 days, and still infest other sheep. Where sheep are purchased, it is advised to treat and keep them away from the home flock for up to a three week period. After sheep are treated, try to get them out to grass as soon as possible.

Good management practices on farms can help delay the outbreak of external parasites and even the severity of an outbreak, most farms will require some use of chemical control to ensure to maintain the health and productivity of the flock.

There is increasing awareness now about the correct use of animal health products so as to reduce resistance. It is important to follow the guidelines of using the right product in the right amounts at the right time and used and administered the right way. The withdrawal periods of any product used on farm is another important consideration when choosing a product so that it does not impact future slaughter dates.

There is a range of preventative treatments to combat the various external parasites available to farmers. The availability of labour and the layout of your handling facilities will also dictate the type of product that you will use. These products are expensive so if in doubt about what you are treating and the best way to administer this consult your vet for advice. As with any treatment given to animals, record the product, dates given, amounts and the withdrawal period.

The chemical products available are administered via plunge dipping and pour-ons. The use of pour-ons for the treatment of external parasites has become popular due to the ease of application. There are various types of pour-on products available. Again it is important to use the correct product so that product will work to the best efficacy.

Treating lambs now with a long lasting pour-ons will ensure season long protection and will also make sure that withdrawal periods are completed before the first lambs are ready for sale. This makes the treatment per lamb more cost effective while also reducing the amount of product type required as it is governed by bodyweight. Where lambs are near to slaughter age, treat with a short cover product which has a short withdrawal period.

For flystrike prevention ensure the correct pour-on applicator nozzle is used and spray along the back and around the tail of the sheep at the recommended rates. These products contain chemicals that prevent the blowfly eggs from hatching and the maggots from developing.

The plunge dipping of sheep occurs less now than years ago due to the high labour requirement. Dipping products will prevent and treat for flystrike as well as giving good control for other external parasites. Pour on products are also available to control lice and ticks if an issue arises.

Good health and safety measures should be in place when administering any animal products. The products used to control external parasites on sheep contain chemicals that can be harmful to humans. Protective clothing, rubber gloves, face shield, rubber boots and apron are essential when sheep dip is being handled in its concentrated form. It is important to take care of both your own health and that of those assisting on your farm.

Spent containers of pour-on should be disposed of correctly and it is important that you take five minutes to read the instructions carefully, so that you can take appropriate precautions and ensure that, at the same time, the job is done properly.

Teagasc Facebook and Teagasc Ovicast have excellent videos giving technical updates for sheep farmers.