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Target Flies Before They Target Your Cattle!

Feel the force of dectospot fly control
As the temperature increases so too does the fly population resulting in misery for cattle across the UK. Are you aware though, that as well as causing a severe nuisance to cattle, flies can also be responsible for the spread of certain diseases?

At least 20 species of fly feed on cattle in the UK. Different species of flies feed on different secretions or tissues. Some pierce the skin and feed on blood; while others feed on secretions such as sweat, skin secretions, saliva, or tears. Some flies even feed on excretions such as urine or faeces.

There are two ways in which flies cause harm to cattle: 

  1. Nuisance
    Flies can cause severe nuisance, irritation and annoyance to cattle causing them to become aggravated leading to self-trauma and potentially injury to those handling them (e.g. kicking in the parlour). This is obviously detrimental to the welfare of these animals however it can also result in a drop in productivity due to reduced time feeding as the animals take evasive behaviour to try and alleviate the irritation.
  2. Disease Transmission
    Flies can act as vectors meaning that they have the ability to spread certain diseases between animals by biological or mechanical means.
    Biological transmission occurs when the fly is carrying the pathogen, usually from a blood meal - for example Bluetongue virus carried by the Culicoides midge.
    Mechanical transmission occurs when pathogens are passively transferred by the fly from one animal to the other. The spread of 'pink eye' bacteria from one animal to another demonstrates this form of transmission.

Vector Borne Diseases of Cattle

Summer Mastitis

Summer mastitis generally occurs in non-lactating animals during the summer months. It is a bacterial disease caused by a number of bacteria acting together. It is believed to be spread primarily by the fly the head fly (Hydrotea irritans). 

In cattle, large numbers of this fly cluster on the ventral abdomen and udder and the bacteria is mechanically transmitted from animal to animal.

The head fly lives in sheltered areas such as bushes/trees and only has the ability to fly in very calm, damp, humid conditions. As a result of this, the incidence of summer mastitis is highly variable and tends to be associated with 'problem fields' e.g. adjacent to woodland.

Disease may be present for up to a week before the animals appears systemically ill which is why it is important to check stock frequently during high risk periods. Be observant and look for swollen/enlarged teats - the consequences of summer mastitis are severe and animals may abort/die if untreated.

Infectious Bovine Keratoconjunctivitis

This disease often goes by 'New Forest Eye' or 'Pink eye'. It is a highly infectious disease caused by the bacteria Moraxella bovis. It can spread rapidly during the summer months and is more common in young stock. Head and nuisance flies act as mechanical vectors for the spread of this disease. The ocular lesions are very painful and disrupt grazing patterns resulting in poor performance and weight loss.

Blue Tongue and Schmallenberg in cattle

Both of these diseases have been shown to be transmitted by the Culicoides species of fly.

Bluetongue virus is generally not symptomatic in cattle. However, cattle act as reservoirs of infection which can be transmitted to sheep causing more severe disease. 

Schmallenberg rarely shows clinical disease in adult animals and often the first suspicion of disease occurs when a deformed calf is born. Where it does affect adult cattle, it causes milk drop, fever and diarrhoea.

Fly Control 

  1. Medicinal
    Medicinal products e.g. Deltamethrin pour-on are available which can help to control flies. Bimeda’s Dectospot 10mg/ml Spot On Solution for Cattle and Sheep (POM-VPS), is a great choice and
    • Can be used during pregnancy and lactation
    • Provides fly and lice control in cattle
    • Has zero milk withdrawal in cattle
    • Is available in a range of convenient pack sizes, including a 250ml, 1 litre, 2.5 litre and a 5 litre value pack, which is supplied with an applicator
    Before using any medicinal product, consult your vet or animal health advisor, about what is right for your herd.
  2. Target Larvae Development
    Manure, spilled feed or any moist, organic matter can act as larvae development sites. Either ensure the prompt removal of such matter or use an insecticide growth regulator, such as cyromazine. It works by preventing larvae from developing into flies, thus reducing the overall fly challenge in the environment.
  3. Environmental Control
    Avoid grazing ‘problem pastures’ at peak risk times where possible and consider the use of environmental approaches, such as fly paper of traps.

Your local vets and SQPs have a great deal of fly control knowledge so speak to them for advice and they can help you to design an appropriate strategy for your herd.


Use medicines responsibly. Noah.co.uk/responsible.

*Dectospot contains 10mg/ml deltamethrin and is a POM-VPS medicine.

The following active ingredients have indications for fly control in cattle: Deltamethrin, Alphacypermethrin, permethrin, cypermethrin cis 50: trans 50, moxidectin, doramectin, ivermectin.

Please consult your SQP or vet to determine which is the most appropriate for your herd and consult the SPC data sheets on the VMD website for further information on which species of fly are controlled and with which preparations. 


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