Submitted by Louise on Tue, 13/06/2017 - 08:23


The recent spell of warm humid weather has led to a mass hatch of blowflies. Prevention of blowfly strike is an integral part of the management of sheep during the summer months. Whilst chemical prophylaxis is important, management steps can also be taken to reduce the risk of flystrike.

Effective grazing and parasite management to prevent faecal staining of the perineum of both ewes and lambs will make them much less attractive to blowflies. Sheep that do get diarrhoea must be dagged to remove the dirty wool. Control footrot effectively to prevent lesions getting flystrike. Remove carcasses promptly as these attract large numbers of flies.

Which product is best for my flock?

There are three different types of product available to control blowflies. I have compared them in the table below to help with decision making. No product will be effective if the management strategy detailed above is not carried out in conjunction with treatment.

The method of application is VITAL to the product acting effectively. The manufacturers guidelines must be followed exactly. The correct applicator for the product must be used. Permethrin products are only effective on the parts of the body to which they are applied.

Product type

Duration of protection (blowfly)


Typical meat withdrawal (see individual product datasheets for full information)

Other information

Pyrethroid pour-ons

Up to 10 weeks (check individual datasheets)

Treatment and prevention

8-49 days

Also kills lice and ticks

Insect growth inhibitors

8 weeks

16 weeks


7 days

40 days


Organophosphate dips

6 weeks

Treatment and prevention

49-70 days

Also controls sheep scab, lice, ticks and keds

Must be used in accordance with current UK legislation





Flystrike treatment:

Should a case of flystrike occur the sheep must be treated straight away. Strike wounds become infected with bacteria very quickly, and toxins are released into the bloodstream that can make affected sheep very sick.

  • Shear wool from the fly struck area leaving at least a 5 cm shorn border around the wound

  • Clean the wound and ensure all maggots and blowfly eggs are removed. Ideally collect the maggots in a bag and dispose of them so they cannot hatch out into adult flies.

  • Apply a permethrin based product to the area that is licensed for blowfly treatment

  • Inject antibiotic (eg penicillin) daily for 5-7 days, inject non-steroidal eg Recocam (single dose)

  • Remove affected sheep from the flock, ideally house them, so they do not attract more blowflies to the rest of the group.

  • Treat the underlying cause eg dirty back end, foot rot.


It is at this time of year, when lambs are 6-12 weeks old, that we often see a significant rise in lamb coccidia counts when we are carrying out worm egg counts. However, there are 15 species of coccidia that can affect sheep in the UK and they all look the same under the microscope, but only 2 of those species are pathogenic – ie capable of causing severe gut damage to lambs. Therefore we recommend that you should regularly get samples checked to identify whether you have the pathogenic species of coccidia – Eimeria ovinoidalis and Eimeria crandalis present on your farm, and in what proportions. With this information, we can make much more informed decisions about the significance of coccidia counts in faecal samples. This test is called a coccidia speciation test, and needs to be carried out at a specialist laboratory. Please speak to Rachel if you would like more information regarding this test, and how to collect samples.

Coccidiosis can cause symptoms such as diarrhoea (often with mucus or blood), straining to pass faeces, abdominal pain and weight loss. Severe gut damage can occur, leading to chronic ill thrift and poor growth rates.

The lambs are initially exposed to coccidia via ewe’s faeces, the lambs then multiply up the coccidia as they pass through the intestines shedding huge numbers out onto the pasture. It is important to ensure feed and water troughs cannot be contaminated with faeces, and creep feeders should be regularly moved to prevent poaching and build up of infection. Adult sheep are immune to coccidiosis however they shed low numbers of the parasite all year, and this early exposure is vital. Lambs have initial protection via colostral immunity, and research has shown that if lambs are exposed to low numbers of coccidia before 4 weeks old, and they received sufficient colostrum, they will develop good immunity and not show clinical signs. However, if lambs are colostrum deprived, or if they do not receive this initial exposure to low levels of coccidia they will develop disease. This immunity may not be effective if lambs are suddenly exposed to a high level of coccidia, overwhelming the body’s immune system. Lambs that are particularly at risk include housed lambs that don’t get turned out to grass until they are over 4 weeks old, or turning young lambs out onto a pasture that has already been grazed by older lambs in the same season. The same is true for lambs that have been receiving either medicated creep feed or decoquinate buckets that is suddenly withdrawn at the end of the 28 day treatment period.

There is no cross protection between different strains of coccidia, so mixing sheep from different flocks, or moving sheep to graze a different pasture can trigger clinical symptoms. Stress due to cold wet weather or poor nutrition or a concurrent worm burden can exacerpate symptoms.

Several treatment options are available for both the prophylaxis and treatment of coccidiosis. They all have advantages and disadvantages, so please speak to one of our farm animal team for advice. We can also discuss with you appropriate prophylactic protocols for your flock.


Lamb Vaccinations

Colostral protection for clostridial diseases and Pasteurella will have waned by the time lambs are 6 weeks old. To ensure ongoing protection, the lambs themselves need to be vaccinated. A clostridial -only vaccination or combined clostridia /Pasteurella vaccines are available dependant upon the risks on your individual farm. Clinical cases of Pasteurella tend to be the tip of the iceberg, with many un-noticed subclinical infections that slow growth rates. Monitor your abattoir returns, if you are seeing cases of pleurisy or pleuropneumonia then Pasteurella is generally the cause, and vaccination could be warranted.

All lambs should be vaccinated against the clostridial diseases. His ubiquitous group of bacteria are found in soil and cause a wide range of different disaeses. However the outcome is always the same – the bacteria release toxins leading to sudden death. Treatment of affected animals (if you find them alive) is rarely successful.

It is vital to follow the vaccination protocol correctly, as per the manufacturers guidelines to ensure that maximum benefit can be gained from the vaccine. Stressed animals do not respond to vaccines well, so vaccination at the time of weaning is not recommended.