Equine Sarcoids and Fly Control

Sarcoids are tumours which appear most often on the horse’s head, around the groin and the axilla areas and sometimes within wounds or anywhere on the skin. According to the Royal Veterinary College, sarcoids can account for around 40% of all equine cancers.

They are estimated to be more prevalent in the UK than in Europe and vets believe that one of the reasons for this may be associated with biting flies. Although a link between fly infestation and sarcoids has not been proven most experts point to the fact of the virus DNA and protein, although not the whole virus, appearing on flies. Another point of view comes from Dr Derek Knottenbelt, an equine vet and one of the world’s leading authorities on sarcoids. He believes that sarcoids are caused by the bovine papilloma virus (BPV) however many horses which become infected with this virus do not go on to develop sarcoids. It is also true that where there are several horses together one horse may develop sarcoids but the others don’t. Experts are also looking into whether there could be a genetic susceptibility or resistance to sarcoids and it is thought that genetically susceptible horses can develop sarcoids following exposure to BPV.

Problem is worse in Summer

There’s no doubting that there are more cases of sarcoids during the summer months when the fly populations are at their highest and for this reason, Dr Knottenbelt believes that this, together with the known distribution of sarcoid cases, would indicate a strong link between flies and sarcoids. He also acknowledges that there is still little understanding of the disease and specifically the complex issue of horse to horse transmission but is confident in the assumption that flies are indeed responsible.

Are Sarcoids Contagious?

This is obviously of great concern to horse owners but as yet there is no proof or evidence that sarcoids can transmit contagiously between horses either directly or indirectly, or between horses and cattle. Sarcoids can affect horses of all ages and breeds, and both males and females, and they are usually not painful or itchy. If your horse is showing signs of pain or itching then the likelihood is that any lesions or lumps are due to allergies or infection and not sarcoids. An affected horse will often develop multiple sarcoids simultaneously or else repeatedly.

What do sarcoids Look Like?

They can vary in appearance and in aggression levels, needing different treatments according to the type. There are three kinds:

  • Verrucose are flat and scaly and resemble scars or ringworm. These are the least aggressive.
  • Nodular are spherical in appearance with a wide, flat base and may be ulcerated or covered in normal skin.
  • Fibroblastic are the most aggressive ones and often have an irregular appearance, clustering together with variable sizes and shapes.
  • There can sometimes be a mix of all the above types of sarcoid on one horse.

Treatments For Sarcoids

Sarcoids do not ‘self-cure’ and the wrong treatment, or no treatment at all, can make things worse. There have been worrying tales of owners failing to see the seriousness of sarcoids and trawling the internet for suggestions. These can often be useless at best, harmful at worst. One such suggestion – that applying toothpaste to a sarcoid will cure it – is dangerous nonsense as this could cause the sarcoid to flare up and become worse. At the very least, toothpaste will not help! When you consider that, depending on the type of sarcoid, treatments can include chemotherapy or laser surgery, it’s clear that relying on random internet searches or friends’ ‘advice’ may not be beneficial.

Other treatments can include radiotherapy, cryosurgery and complex medicinal treatments. The whole issue of sarcoids is complex due to their behaviour, appearance and position on the horse which means that there is often no single or universal treatment. For this reason, it is always best to seek veterinary advice to obtain the correct assessment and treatment options. Your vet can also advise on whether a sarcoid can be left alone and simply monitored to look for changes or irritation by rugs or tack.

How You Can Lessen The Odds

Be vigilant in ensuring that there is as little opportunity for contact between flies and your horse as possible. A good fly rug is the first line of defence for horses and ponies and for a horse with sarcoids it is absolutely essential.

When choosing a fly rug it’s important to distinguish its purpose, whether it will be for guarding against flies generally or whether you want something to guard against sweet itch specifically. If you are combating sweet itch you’ll need a close-fitting rug that has a very close-weave construction to keep out the tiny Culicoides midge whose saliva is the cause of sweet itch.

Black flies (Simuliidae) can plague the horse’s face, eyes and ears. Anywhere on a horse that is moist will be attractive to flies and the eyes are especially vulnerable to irritation so a properly fitted fly mask or hood can prevent this.

Stable flies (Stomoxys) are attracted to soiled and moist bedding and apart from causing infection can carry stomach worms (Habronema) and eye worms (Thelazia). Keeping stable areas and yards as clean and dry as possible will help greatly in preventing fly infestations.

Ticks will look for areas on a horse like inside the ears, around the muzzle and nostrils, under the forelock and mane and around the fetlocks and dock. Aside from the irritation caused, a tick can carry Lyme disease which in horses can have serious consequences including dermatitis, lameness and arthritis not to mention a general feeling of ill-health. Incidentall,y Lyme disease can also affect humans and can have long-term consequences here too. Never attempt to remove ticks by burning them or coating them with petroleum jelly or ice cubes. These ‘old wives tales’ will not remove them fully. The mouth parts could be left in and the ticks may in the process regurgitate their stomach contents; this could lead to infection. Remove them with a specialist tick removal tool as soon as possible. If you’re unsure how to do this your vet or veterinary nurse will be only too happy to show you.

Repellents and Insecticides

Make these useful sprays a vital part of your armoury against flies but be sure you understand the purpose of each.

A repellent is designed to make the horse a less attractive target for flies. Citronella is said to be an effective insect repellent as are eucalyptus, tea tree and lavender.

Insecticides are designed to kill flies and insects on or soon after contact. Because some of these can contain strong, toxic chemicals they are often meant to be diluted and used around stable areas. There are some available that can be used directly onto an animal’s skin. It is important that you obtain advice first before deciding which repellents and insecticides to buy as various ingredients may be suitable for some instances and not others. Pay special attention to the ingredients of those that you use.

Above all, by far the most effective way to fight flies and prevent serious conditions like sarcoids from occurring is to ensure that your horse, his stable and bedding and all tack and rugs are kept as clean as possible at all times. Be vigilant, check your horse regularly and call your vet for advice if you see anything that could cause a problem.

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