Fly Problems in Livestock
Flies cause major economic production losses in livestock. They attack, irritate and feed on cattle and sheep; reducing feed intake, productivity and damaging hides and fleeces.
Their life cycles are completed very quickly, giving rise to very rapid population expansions, highlighting the need to apply fly control medicines early in the season.
Nuisance flies can spread disease such as ‘pink eye’ and summer mastitis amongst cattle. Midges add to these, spreading diseases such as the Schmallenberg virus.
During feeding, the head fly Hydrotaea irritans causes considerable irritation which may result in self trauma. This fly has also been implicated in the transmission of bacteria responsible for summer mastitis, a potentially serious disease leading to the loss of milk production and, in severe cases, the life of the animal.
Face flies such as Musca autumnalis feed on lachrymal secretions and have been implicated in the transmission of the causative bacteria for New Forest Eye.
The production loss caused by flies can be up to 0.3kg a day growth rate loss and up to 0.5l a day milk loss by fly worry.
Nuisance flies may disrupt grazing behaviour in sheep, but by far the most important fly infestations of sheep are those that result in blowfly strike. Primary blowflies are attracted to protein food sources for egg laying. These include the wool of sheep which is soiled with urine or faeces, or inflamed from prior parasite infestations (e.g. lice or mites). Maggots hatching at such sites can invade an existing wound or create a superficial wound as they feed.
Severe cases can end in death due to a combination of toxaemia from ammonia, which is the main excretory product of the larvae, and from bacterial septicaemia. The green bottle (Lucilia sericata) fly is the most common cause of blowfly strike in the UK.