Sheep can be affected by a number of ectoparasites that inhabit their skin or fleece. Ectoparasites can have a significant effect on sheep productivity by downgrading the wool quality, reducing reproductive potential leading to a poor lamb crop, and by reducing meat production. More importantly ectoparasites can adversely affect the welfare of infested sheep. Untreated infestations of scab or blowfly strike can be fatal whilst ticks can carry other sheep diseases as well as human infections.

Sheep scratchingThe “summer” that has passed us by has had one benefit in terms of reduced fly levels and subsequently less blowfly strike than normal. It is vital however that the responsible advisor does not forget the importance of good ectoparasite control advise to the farmer. Maggots can often raise their head well into September, due to mild weather and parasitic scours being a suitable bed of infestation. It is therefore prudent to be vigilant and to advise appropriate preventative and curative treatment for blowfly and other ectoparasites.

Traditionally All Sheep received their traditional Summer and Winter Dip which gave good control againist the external parasites of sheep. Nowadays there is a myriad of options available to the farmer including dipping with cypermethrin dips, traditional organophosphorus based dips, and various pour on formulations with various active ingredients such as Cypermethrin, Dicyclanil and Cyromazine.

The various options available to farmers mean that there can be confusion relating to the activity of different active ingredients and the different formulations available. This has led to increased risks of ectoparasitic outbreaks and indeed there are reports of increased incidences of Sheep Scab and lice in sheep in recent years. This is because while dipping gave control and treatment of all external parasites, many pour ons are geared toward one specific purpose and other parasites can multiply unhindered.

It is vitally important for the responsible person to know the indications, modes of action and limitations of the treatments so that they can give correct and timely advise to the farmer. Firstly however, it is vitally important for the farmer to get an accurate diagnosis of the problem so that he can get an appropriate product from his supplier. I have recently heard a farmer complaining about a product he claimed was not working. He had treated his sheep unsuccessfully after he incorrectly diagnosed the sheep as having lice when in fact they had the highly contagious, severely dehabiliting and notifiable sheep scab. Such a delay in diagnosis and appropriate treatment can be difference between a mild infestation and a severe flock outbreak.

My advice to the farmer would be to consult a vet if there is any doubt about the causal agent of any outbreak of ectoparasitic disease. The vet can use his professional judgement or can take samples for fast and cost effective microscopic laboratory examination to confirm a diagnosis. The appropriate product can then be decided on and treatment initiated.

Click image for more detailsWhen dipping sheep it is important to realise first of all that safety instructions on the products should be paid attention to in full. Particular attention should be paid to preparing and handling the dips, wearing appropriate protecting clothing and disposal of the dips safely on land afterwards. To ensure efficacy of the dip it is vital that the dip be diluted to the recommended concentration and equally it is important that the dip tank is topped up with dip and water at the recommended intervals.

There are reports of increased post – dipping lameness in UK dipped sheep this summer. Post –dipping lameness in sheep is caused by infection with Erysipelothrix rhusiopathiae after dipping in insecticidal solutions which do not contain a bactericidal agent. This increased incidence is down to the fact that due to the unusual amounts of rain falling, sheep holding facilities are dirtier than normal which is leading to increased levels of contamination in the dipping tank. I have not heard of increased incidences of post dipping lameness in Ireland this August but it has to be a consideration as weather conditions here are far from optimum.

To avoid post dipping lameness ensure the tank is thoroughly cleaned before use and only fill the clean tank with water on the actual day of dipping. Also ensure minimal faecal contamination by not dipping the sheep on full stomachs. Post dipping lameness may occur when the sheep are dipped in dirty wash, or wash which has been allowed to stand in the bath overnight or longer. This is why it is important that the dip bath should be emptied and thoroughly cleaned at the end of each day’s dipping or earlier if it becomes excessively dirty during the days dipping.

Click image for more detailsDipping is my preferred method for scab treatment and control. Both traditional OP dips such as Ectoflits and non-OP dips such as Cyperguard have good activity againist the scab mite Psoroptes ovis. For the purposes of dipping against sheep scab, sheep must be totally immersed in a sheep bath of an approved sheep dip, and all parts of the sheep except the head and ears must remain immersed in the bath for a period which shall in no case be less than one minute.

When applying sheep pour ons, first and foremost the product must be used in the correct manner and for the correct purpose. Dicyclanil containing pour ons while effective at blowfly prevention cannot be used for any other form of ectoparasite treatment or control. To clarify, these products have no efficacy at blow fly treatment, lice ticks, keds or scab control.

Another class of commonly used pour ons in sheep, high- cis Cypermethrins can be used for blowfly treatment and blowfly strike prevention, as well as having efficacy againist lice, ticks and headflies. These Cypermethrins should be used according to the manufacturer’s recommendations to achieve required control of the particular parasite in question. These cypermethrin products are useful because of their wide range of indications and also tend to have short meat withdrawal periods which are useful when treating fattening labs at this time of year.

Overall there were never as many options for the farmer in for ectoparasite control. It is therefore important that those in the trade are well informed so that they can give the best advice possible and ensure ectoparasitic control is optimum. This well informed advice will help ensure maximum productivity and minimal ectoparasitic disease on Irish Sheep farms.

For an example of good dipping practice Click Here