Did you know that significant damage can occur as a result of blowfly strike in as little as 36 hours?
By the time strike is visibly spotted, a considerable amount of damage has already happened and the majority of economic loss will have already occurred.
If untreated, strike can kill or adversely affect the welfare of infested sheep
Farmers, as registered keepers of animals, have a responsibility to prevent or treat infestations within their flocks. Failure to do so can result in prosecution for animal cruelty.
4 ways in which blowflies can undermine sheep productivity:
- Downgrading wool clip
- Reducing reproductive potential and lamb crops
- Increasing time to market for lambs
- Reducing leather quality
Blowfly strike can be a devastating and deadly disease in Ireland. It has serious welfare implications for affected animals, and carries significant economic costs for affected flocks.
Using published data on strike risk and fly abundance patterns in the UK, with no prophylactic treatment applied, in a moderate risk area, a 250-ewe flock with an output of 1.5 live lambs per ewe might expect 19 ewe strikes with one death and 23 lamb strikes with two deaths over the entire season.
Price modelling indicates the costs of not treating are £200 and £160 for ewe and lamb deaths, respectively, £437 for labour and reactive treatment and £230 in lamb production losses, giving a total cost of £1027 or €1,350*.
Blowfly Strike
It has been shown that every year 80% of flocks will have one or more cases of flystrike.
With the blowfly season having the potential to lasting longer and starting earlier than in previous years, it is no wonder that management of fly strike is changing.
For instance, 2014 saw, anecdotally, one of the worst years for blowfly strike. The weather was warm and wet, leading to a high blowfly challenge.
This highlighted any weaknesses in blowfly control strategies, whether that was in the timing of product use, or in the application of the product.
In comparison, the 2015 season, started much later, but continued later as well, with anecdotal reports of blowfly strike in early November.
Irrespective of the start or end of the season, one thing is clear, putting a strategy in place to manage blowflies is an essential requirement for sheep farmers.
Time it right
Overwintered larvae start developing into adult blowfly when soil temperatures reach 9C. The rapidly changing Irish weather means this might happen earlier than expected, catching farmers off guard. It’s farmers consider early prevention as the safest option.
From an animal health retailers point of view, farmers will be regularly coming into stores to purchase supplies during/May, providing an ideal opportunity to advise on a blowfly preventative strategy.
Why prevention is always the best option?
1. Resistance
While it’s tempting for farmers to use a product that treats a broad range of parasites, this is how resistance develops.
Farmers should be encouraged to use a narrow-spectrum product when they are trying to treat one specific parasite, in accordance with industry recommendations.
Therefore, using an IGR for blowfly prevention will ensure farmers are using a targeted product for the parasite they are looking to control and then can switch to an SP or OP dip in autumn and winter when other parasites are prevalent.
2. Cost savings of prevention
Many farmers will take a ‘wait and see’ approach, only treating for blowfly later in the season due to perceived savings in treatment cost.
However, having to treat strike rather than preventing it can be far more costly, not only financially but also in terms of time and effort. The emotional impact and disruption of flock management should not be underestimated.
The costs of not preventing using a simple example like the one below can encourage farmers to take a proactive approach.
This example, as detailed above, applies to a moderate risk area and a 250-ewe flock, and shows an estimate of the annual cost of not treating blowfly strike*.
- Ewe deaths €250
- Lamb deaths €200
- Labour and reactive treatment €546
- Lamb production losses €287
1. Reactive vs proactive
If farmers haven’t prevented and have already suffered strike, they will need a product that treats the disease as well as continuing their preventative blowfly control.
In cases of strike, an SP pour on, such as cypermethrin (Vector®) can be used for treatment, whilst IGRs offer long-term protection for the rest of the flock.
2. Correct application
It’s important to ensure the chosen product is easy, quick and applied safely. Correct application is crucial in getting the most out of the investment and ensuring it isn’t wasted.
*Blowfly strike: biology, epidemiology and control. Richard Wall and Fiona Lovatt, In Practice 2015 37: 181-188.
