We all look forward to long warm summer days but they inevitably mean the arrival of dreaded flies! These annoying critters are not just a nuisance – they can have real health implication for our horses too. All are annoying; but some congregate in the corner of horse’s eyes and other sensitive areas to drink the fluid, and some bite, piercing the horse’s skin to feed on its blood.
So, which are the most common flies that affect horses in the UK and what can we do to manage the impact they may have?
The midge (Culicoide)
Midges are 1mm-3mm long and hover in swarms at dawn and dusk. They can cause the skin condition sweet itch; an allergic reaction to midge bites. Typically, sweet itch causes the mane and tail hairs to be rubbed away, causing skin lesions aggravated by the horse rubbing them. In some cases, itching along the legs and under the belly causes areas of sore, open, broken skin, which tend to bleed.
Midges lay their eggs on ponds, standing water, and damp vegetation, so try to avoid turnout for your horse near water courses or ponds and sheltered areas close to woodland. You can stable your horse at dawn and dusk which are prime midge-feeding times. Keep your horse’s skin covered using an ear to tail rug designed to help prevent the condition. A good midge repellent is essential — your vet will be able to guide you on this, although choosing one with an oil base will act as a protective barrier. Some oils used on their own or benzyl benzoate also have the same effect. Anecdotal evidence suggests some feed supplements can help but it’s best to seek advice from your vet.
Prevention is better than cure but if your horse is affected then it is vital that any treatment combats the sores as well as offering the horse relief from the itch and that it is carried out daily, otherwise the midges will start to bite which triggers the itch/scratch cycle.
The horse fly (Tabanus)
These have a brown/black body and are 0.5cm to 2.5cm in size. They are normally alone and near wooded areas in June and July and are most active on warm days. Horse flies feed on blood and can give a nasty bite. They tend to feed on the horse’s underbelly, legs, neck and withers. The bites are painful and appear as small lumps with a central ulcer.
If possible, keep your horse away from wooded areas and apply an effective, long-lasting insect repellent. Fly masks and rugs can help and horse flies will rarely venture into dark areas, so stabling can offer some protection. Treat bites with a mild antiseptic wash or cream.
The bot fly (Gastrophilus intestinalis)
Adult bots have yellow and dark striped bodies. The female lays her yellow eggs on the horses forelegs, shoulders, neck and mane; these hatch when the horse licks or bites them. The larvae then burrow into the horse’s tongue and gums before making their way into the stomach. They attach to the stomach lining until spring, when they are passed out through the faeces and onto the soil to develop into adults. The cycle takes nine months in total.
In summer, comb the eggs off your horse and use fly spray to discourage the female from laying more eggs and use an appropriate wormer in early winter, which will the kill bot larvae inside the horse’s mouth and stomach.
The deer fly (Chrysops)
The deer fly has brown lacey wings and is the cousin of the horse fly. It is smaller but just as vicious as it tends to feed in groups and will even give chase. An effective fly spray is usually the best advice. Give your horse a good covering before hacking out.
The stable fly
These flies are found in stables as they lay their eggs in moist, rotting vegetation. Keep stable hygiene good and make sure the muck heap is well away from your horse’s stable. Stable flies feed on horses’ legs and abdomens, and bites typically appear as itchy or painful wheals. Good hygiene is the best defence, but repellents can also be used.
The house fly (Musca domestica)
This a nuisance fly, it laps instead of bites. These flies are iridescent blue/black and buzzy! They will congregate mainly around your horse’s eyes and nose. Fly fringes and masks can help to keep the flies away from your horse’s face. Turning your horse out with a field companion means they can keep the flies off each other. House flies breed in fresh horse manure, so make sure you pick up the droppings from your paddocks daily if possible.
Black flies (Simuliidae)
These are small and breed in rapidly moving water. High-risk times are dawn and dusk during spring and early summer when they feed around the face – particularly inside the ears. Here they can trigger allergic skin reactions to their saliva. Bites form as painful lumps, often with pin-prick areas of bleeding and crusting. Fly sprays can act as a deterrent, as well as ear nets and oil-based products. Petroleum jelly applied inside the ears may prevent the insects biting and stabling at key times may be helpful.
Top tips for managing your horse’s fly problem:
- Use anti-midge/fly turn-out rugs and neck covers, fringes, veils and nose nets. If your horse hasn’t worn one before introduce it gradually, and remember to watch out for rubbing.
- Long manes and tails are a natural fly defence.
- Apply a long-lasting fly repellent.
- Turn horses out together where possible, as they can flick flies away from one another with their tails.
- Remove droppings from your paddock and wet bedding from your horse’s stable on a daily basis and keep the muck heap a good distance away from your horse’s stable.
- Be aware of where and when midges are most active and try to reduce your horse’s exposure.
- Spray your horse’s stable walls thoroughly with an insecticide. This will help to discourage stable flies from lingering there.
- Put up fly papers in your horse’s stable.
- Worm your horse against bots after the first frost.
- Some people choose to make their own fly repellents; citronella, lavender oil, cider vinegar and tea tree oil are just some of the commonly used ingredients.
Check out Blue Cross’s article on caring for horses in the summer, it’s one of our most popular reads! If you want further information on horses, we have plenty of information onsite; you can also check out the Blue Cross website for further advice.