Factsheets

Horses


Overview
Horses are part of an ever growing industry, with over 600,000 horses in the UK, 1.4 million riders and 5 million people with an active interest in the equine industry*. Most people acquire a horse out of choice, so if you make this decision you should think carefully before going ahead. A horse needs lots of love and care, including regular worming, vaccinations and dental care. Owning a horse is time consuming and can be costly; not only will you will need to consider where you will keep your horse, you must also consider the ongoing costs of owning a horse which include accommodation, bedding, feed and healthcare.

In the unlikely event that your horse goes missing it is going to be very difficult for anyone to know who it belongs to, unless your horse carries some form of permanent identification. It is wise to get your horse microchipped or freezemarked, this will avoid heartache in the long run, should your horse go missing or is stolen.

Horses are herd animals, and thrive on being together with other horses. Don’t forget that your horse will need somewhere to graze, a stable for warmth in the winter time, a constant supply of water, feeding daily and regular exercise. It can cost hundreds of pounds a month to care for a horse, including accommodation, food, veterinary care and insurance; there will be other costs, including buying tack and rugs and extra livery charges when you go on holiday.

Horses can live into their thirties, over this time your horse will need lots of care and attention. Being able to provide all of this will ensure you and your horse make the most of your time together.

* Research conducted in 2004 by the Henley Centre for DEFRA and the British Horse Industry Confederation.

Melanoma - skin tumour

There are numerous different causes of skin lumps in horses. One of the most common nodular skin diseases is melanoma, found predominantly in grey horses. It is uncommon in non-grey horses. Although often considered a benign tumour in horses, melanoma has malignant potential and can be locally invasive; early intervention to remove/treat any tumour is advised. Treatment is much more difficult in advanced cases. It is important to call your vet to examine any new or growing lumps you notice on your horse, particularly grey horses.

What is melanoma?

Melanoma is a very common tumour in horses that predominantly affects the skin. Common sites include the groin, lips, eyelids and perineal skin. It is also frequently found in the parotid salivary gland, lymph nodes of that region and guttural pouches.

Grey horses, usually over 8-10 years of age and rarely under 6 years, are most commonly affected, although melanomas can occur in younger and non-grey horses. Although often considered benign, it is thought that melanoma in horses can become malignant and spread locally or even to internal organs in up to two thirds of horses.

How will I know if my horse has melanoma?

Grey horses often present initially with single, small, raised nodules on the perineum. The nodules are firm, non-mobile spherical/ovoid dark brown/black masses within the skin.
 
Most commonly affected sites over the body are under the tail, the perianal region and also the vulva and sheath, but any area of skin can be affected. The nodules can spread to local lymph nodes and grow in chains. They may also present as lumps in the throat lash region due to growth within the parotid lymph nodes and salivary glands.
 
Growth of nodules is usually slow, and they may remain static for years with no apparent clinical problems. However, when enlarged, they can affect the horse and cause discomfort/interfere with tack. For example, melanomas in the throat lash region can prevent fitting of the bridle/headcollar and limit flexing of the head; perianal tumours can limit the passage of droppings and become ulcerated and cause pain.

Metastatic spread to internal organs may be associated to other problems, such as weight loss, colic, cardiac, respiratory or neurological signs.

How will my vet confirm my horse has melanoma?

Nodular lesions in older grey horses are very likely to be melanoma, particularly in typical locations mentioned above. In any case, your vet will need to know the history of the problem and perform a thorough clinical examination of the horse.
 
Fine needle aspirates may be taken, which identify characteristic black pigmented material. If necessary, cytological examination may be performed. Complete removal of nodules with histopathology is also possible.
 
Your vet will choose the best option for your horse depending on the appearance, location and extent of the lesions.
 
Ultrasound examination may help to define the margin of some nodules, particularly in the parotid/throat lash region.

Can my horse be treated for melanoma?

Early intervention is advised and surgical removal of any nodule while they are small is considered the best option. Even if progression may be very slow, it is best to treat a small lesion before it gets too big or becomes untreatable. Laser surgery also has good success rates.

In advanced cases, surgery may not be possible, especially if the tumour is locally invasive into surrounding tissue. Other treatment options include injection of the chemotherapeutic agent (cisplatin) into the melanoma. Cisplatin-impregnated beads can also be placed into the tumour mass. Due to the toxic nature of this drug, careful handling in specialist facilities is necessary.
 
In some cases your vet may choose to try systemic therapy with the oral drug cimetidine, but results are variable, and the clinical effectiveness of this drug is questionable.

More recently, a dog melanoma vaccine (Oncept) has been used in horses to limit the size/encourage regression of tumours. This vaccine is not licensed for use in horses in the UK but has shown some promising results. It is expensive and can only be administered by suitably qualified specialist vets.

How can I prevent my horse from developing melanoma?

Unfortunately, there is no way to prevent the development of melanoma.

It is important to regularly examine your horse, especially if grey, to identify any new skin nodules and monitor growth, with early action to remove masses when small. Advanced cases with metastatic disease are very difficult to treat and often euthanasia is the only option for these horses.