Licensed merchants, veterinary establishments and pharmacists dispensing antiparasitic veterinary medicine products report sales of blowfly control products slow to kick off this season.
There has been a small increase in recent days with some flocks tying in blowfly protection with other tasks such as nematodirus treatment or clostridial disease vaccination.
But, by and large, the lower temperatures have pushed this task down the list of priority actions up to now.
While lower temperatures have suppressed the risk of blowfly strike, there are some reports of tick infestations on lambs with the characteristic season for tickborne diseases generally occurring at an earlier stage of the season in recent years.
Hill farms face the greatest challenge but more marginal lands with an environment conducive to sustaining a tick population are also at risk.
Therefore, it is important for farmers to be cognisant of these risks and tailor their external parasite control programme appropriately.
Table 1 details external parasite control options taking blowfly strike as the main concern. It includes products available for plunge dipping in the first section of the table while the second section includes pour-on products.
Product characteristics included in the table have been collated from the Summary of Product Characteristics (SPC) published by the Health Products Regulatory Authority (HPRA) and, where listed, from the Veterinary Medicines Directorate (VMD) product information database.
As is quickly evident, the products differ significantly in terms of the range of external parasites they target, whether or not they will treat or prevent the different ailments and the length of protection offered.
There is also significant variance between withdrawal dates, which is important at this stage of the year when lambs may be approaching slaughter.
Withdrawal dates are especially relevant to CLiK and CLiK Extra. These products provide the longest period of protection for blowfly strike at up to 16 and 19 weeks, respectively, but they also have the longest withdrawal period (40 days) of pour-on products majoring on blowfly prevention.
These products are relatively expensive but are popular among lowland farmers due to the length of protection offered.
It is important, however, to highlight one aspect which crops up regularly each year– the CLiK range of products do not treat an established strike and therefore if an established strike is present at the time of application you will need to address this separately.
Youngs Vector is common among hill sheep farmers as it is the the only pour-on product that has preventative properties for both blowfly strike and ticks.
The table also lists a number of spot-on type products, which provide protective cover for ticks, with these all capable of treating an established blowfly strike without providing any preventative capabilities.
These products offer a period of protection for up to eight weeks
Ectoflits, CLikZin and Youngs Vector are common options for farmers with aged lambs as they have a much shorter withdrawal period of seven to eight days.
Plunge dipping as a means of controlling and preventing blowfly strike often gets some flack due to a shorter window of protection with farmers comparing it to pour-on products with the longest duration of cover.
It is important to note that these products offer a period of protection for up to eight weeks and therefore strategic use as the season progresses or to treat a range of external parasites is often the best option.
Plunge dipping cannot be equalled in terms of suitability for the control of sheep scab.
The application procedure also has a massive influence on the cover provided. The mode of action in products such as CLiK are insect growth regulators (IGRs), which essentially stifle any development, while products such as Ectofly are pyrethroids and work by disrupting an insect nervous system eventually leading to death.
Whatever the product, both should be applied to a dry fleece which avoids any contact with rain for at least six to 12 hours post-application.
Protection in most products will also only be provided on the area of the fleece coming in contact with the product. Therefore, it is important to carefully read the manufacturer’s guidelines and use the appropriate nozzle or spray head to apply the product.
The cleanliness of the fleece will also have an influence and any daggings present should be removed for optimum protection.
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.