The Flies are Back!

Flies are a common problem in our cattle herds, having both welfare and financial implications. Nuisance and head flies spread the bacteria Moraxella bovis which can cause a severe infection of the eye and the surrounding tissues known as Infectious Bovine Keratoconjunctivitis (IBK) or ‘Pink Eye’. Along with flies, UV light, dusty environments and stress can all increase the risk of the disease.

Young animals are affected most commonly, but all ages can become infected. The earlier clinical signs are squinting of the eyes and tear staining of the face, quickly followed by reddening and swelling of the inner eyelids and ulceration of the surface of the eye.

Appetite may be reduced, leading to lethargy and longer term reduced growth rates. The disease can last between a few days to a few weeks. In the most severe cases blindness may occur. Infected animals should be isolated and kept in a shaded area. Oxytetracycline (Alamycin) is the antibiotic of choice and has equal success rates whether injected systemically or locally.

Flies also spread the bacteria causing summer mastitis, most commonly seen in dry cows and heifers between May and September. Large numbers of flies will be seen on the affected quarter, which will be hot and swollen, have an abnormally large teat and she will likely be kicking at it. She can then become sick, and so will go off her food, isolate herself and appear extremely agitated. Common events following summer mastitis are a loss of condition, permanently damaged quarter, abortion and even death. A vet should be called to any animal with suspected summer mastitis. Prevention of both of these diseases includes pour-on fly control, fly sprays and grazing cattle away from areas with high fly populations.

Head flies are also a major problem affecting UK sheep flocks during the summer months. The flies disrupt grazing, as animals will often spend their time itching and seeking shade. This distress has a huge impact on not only the animal’s welfare but also their body condition which, in turn, can lead to decreased fertility. Pour-on products containing deltamethrin or cypermethrin should start to be used around this time of year. Fly control is especially important in animals with wounds or have been tagged recently.

Fly strike cases are most commonly seen in the UK between May and September, but can be seen much later into winter depending on temperature. Therefore we need to keep an eye out for flystrike in any animals with open wounds or faeces around their back end. A recent survey found that 80% of UK flocks will see one or more cases of fly strike a year. The eggs hatch within twelve hours and the larvae eat away at the surrounding tissue. Usually the first signs you will see are restless animals and discolouration of the fleece, leading to extensive areas of traumatised tissue and can lead to death in untreated cases. Treatment involves clipping and applying a specific spot on to the affected area, anti-inflammatories and possibly antibiotics, depending of the severity of the lesion.

To reduce the risk of fly strike multiple measures can be implemented; these include good worm control, dagging, tail docking, fast disposal of carcasses and reducing the cases of footrot and scour. Chemical treatments can also be used as prevention, such as diazinon sheep dips and cypermethrin pour ons. Care must be taken to follow instructions on application and dosing.