The lower than normal temperatures in recent weeks have reduced reports to date of blowfly strike/flystrike. Merchants report that sales of preventative products are slower to build as a result but there has been a gradual increase in recent days. The characteristic signs of sheep biting at infected areas are well-known by sheep farmers and it is a disease where an investment in a preventative treatment can be easily justified.

While weather has reduced the incidence of blowfly strike, the prolonged dry spell has increased reports of tick activity and tick-borne diseases at an earlier stage in the season. This is being reported in hill and more marginal areas, where the environment is conducive to sustaining a tick population.

Tick infestations

There are several tick-borne diseases, with the most common generally being tick-borne fever and louping ill.

Clinical symptoms of tick-borne fever include sheep being lethargic and stiff when moved, not eating and running a high temperature. Louping ill, on the other hand, causes neurological issues or a nervous disposition.

Issues are typically seen in young sheep that have developed no immunity and naïve sheep that have been brought on to the farm. Ticks go through three stages of development from larvae to nymph to adult.

For each stage of development, the tick requires a blood feed on a host such as a sheep.

It is during this stage that disease can spread rapidly, with the feeding period lasting anywhere from four to 14 days.

Heavy tick infestations can be such that you can see anaemia occur or occasional blood loss. In such cases, ticks will be very apparent on the inner legs and belly of lambs when they are turned over. Where there is a history of disease on the farm, preventative treatment is essential. It should also be noted that ticks pose a significant risk of disease to humans. May is an awareness month for Lyme disease and other tick-borne diseases.

Product selection

Table 1 (on the facing page) details preventative and treatment options currently available on the market taking blowfly strike as the main concern.

As can be seen, products differ significantly in the length of protection they offer, their withdrawal period and if they prevent and/or treat blowfly strike.

CLiK and CLiK Extra provide the longest period of protection for blowfly strike at up to 16 and 19 weeks, respectively. They also have the longest withdrawal period and this should be taken into account where treating lambs that are approaching slaughter weight.

Youngs Vector is the only pour-on product that has preventative properties for both blowfly strike and ticks. There are a number of spot-treatment products that provide protective cover for ticks, but these will only treat an established blowfly strike and provide no preventative cover in this regard.

Farmers carrying out plunge-dipping in Ireland have another option with the return of Cyperguard to the market. It is a non-organophosphate-based product and will treat and prevent blowfly strike, while it is also capable of treating and preventing tick infestations. It is not licensed for use in Northern Ireland and Britain.

Application procedure

The application procedure for plunge dips does not change depending on the parasite being targeted. The recommendation is to retain sheep in the solution for at least 60 seconds (head immersed fully once or twice), so that any scab present will be treated and resistance to scab mites will be avoided.

In terms of pour-ons, it is important to note that protection for products such as Ectofly and Youngs Vector will only be provided on the area of the fleece coming in contact with the product. It is therefore important to ensure accurate applications to the high-risk areas of the back, rump and tail-end.

Where animals have a dirty tail-end, dagging should occur before the product is applied. There is also a different type of nozzle required if applying product for blowfly strike and other parasites such as ticks/headflies.

Read the manufacturer’s guidelines carefully as recommendations can vary between products.