Sarcoids in horses

What are Sarcoids?

Sarcoids are the commonest tumour of the horse. They can occur at any age although most appear between two and ten years. The cause is believed to be a cattle wart virus but the way the virus induces the tumours is unknown. Files may play a key role in transmission, so fly control is vital to prevent spread.

Sarcoids are found:

  • In areas where the skin is thin, has little or no hair, and has a tendency to sweat. This includes the groin, the head and around the eyes. These are also areas where flies feed.
  • Rarely on the upper trunk, back and neck, unless the skin has been traumatised. The trauma may be slight, for example, bridle rubs on the face or rein rubs on the neck.
  • On the limbs, often at the sites of wounds where they may be mistaken for proud flesh.

Should I Buy A Horse With Sarcoids?

Because in principle they are treatable, it may be unreasonable to fail a horse with sarcoids at a pre-purchase veterinary examination. The vet’s advice will depend on the number, size, type and location of the sarcoids, and whether previous attempts at treatment have been made.

However, if they are detected at a pre-purchase examination, insurance companies will normally exclude sarcoids from cover.

Key Facts About Sarcoids

  • Some horses and breeds (Lipizzaner) are naturally resistant and will never develop sarcoids.
  • Sarcoids should never be underestimated. They have the potential to grow and spread, and be resistant to treatment. Every year many horses are humanely destroyed because of uncontrollable sarcoids.
  • A horse may have only a few to over a thousand sarcoids.
  • Some sarcoids remain quiescent for years, whereas others may grow, multiply and ulcerate.
  • A few horses self-cure but these are very uncommon.
  • Treatment must be intensive. Treatment failure often prompts the sarcoid to re-grow in a more aggressive (and more difficult to treat) fashion.
  • Even when successfully treated, new sarcoids may appear on a treated horse at any time.
  • The earlier treatment is started the more effective it is. It has been stated that ‘The fewer sarcoids a horse has, the fewer it will get‘.

Recognising Sarcoids – What To Look For

There are five main types of sarcoid, and a rare sixth very aggressive (malevolent) type.

Type 1: Occult

These are often very subtle in their early stages and may be just a hairless area with a slightly roughened surface. They are often circular and can look like ringworm.

Type 2: Verrucose

These have a roughened, warty appearance and occur especially inside the elbow and on the groin. In this horse the sarcoid has probably developed due to trauma to the site, perhaps as little as a fly bite.

Type 3: Nodular

Usually covered by normal skin, these hard nodules occur especially in the groin. These may be multiple sarcoids or just one. Sometimes the skin overlying the sarcoid ulcerates.

Type 4: Fibroblastic

The pink fleshy appearance of this sarcoid is typical. These are especially aggressive and fast-growing sarcoids. Treatment failure of sarcoid types 1-3 often results in the development of this type at the treatment site.

Type 5: Mixed

Often several types will occur on one horses.

Sarcoid Treatment In Horses

Consult your vet as soon as you suspect your horse may have a sarcoid. The vet will determine the most appropriate treatment. The options usually are:

Do nothing

Very flat, occult legions may be left untreated but must be watched carefully to ensure they are not transforming into another type.

Surgical excision

This is a good option for some nodular sarcoids but there is high rate of re-growth with other types.

Application of rubber ligature

This is best reserved for nodular sarcoids with little or no skin involvement. It is sometimes combined with injecting a cytotoxic drug into the sarcoid.

Freezing with liquid nitrogen

This is only moderately effective and there is a high rate of re-growth. It is only appropriate for very shallow tumours.

Injection of the human BCG vaccine

The vaccine is injected into the sarcoid and is very effective in sarcoids around the eyes but there is a risk of side effects.

Injection of anti-cancer drugs

This is effective in some cases but the drugs are difficult to obtain, require multiple treatments and there are safety risks to personnel.

Use of cytotoxic creams

Currently this is the best method, provided the appropriate strength of cream is used and treatment protocol is observed.

Radiation therapy

This is very effective but also very expensive. It is usually reserved for small sarcoids present around the eyes or over the joints where collateral damage to the adjacent structures (almost inevitable to a degree with the other treatment methods) is undesirable.

mud fever prevention

How To Prevent Mud Fever

Although the condition is traditionally associated with mud coating the legs, many horses go through the whole winter in muddy fields without developing any signs. The conclusion is that it is not mud but constant wetting of the skin that is the main cause. Mud fever is also often rife in yards where the legs are washed frequently, and virtually absent from yards where the legs are almost never washed. It is always better to leave the mud to dry naturally on the legs (leg wraps or bandages applied over the mud will ‘wick’ away the moisture) and then brush off the next day.

Waterproofing the lower limbs, the heels especially, before exercise or turn out is good practice. Thick creams such as zinc and castor oil cream, ‘Sudocrem’ or proprietary barrier creams are effective. Udder cream although popular is a bit too thin and hence not very long lasting.

Leaving the lower legs unclipped does little to prevent the problem. Indeed mud fever may be more common in horses with hairier legs, due in part to the longer time these take to dry out and to the difficulty in spotting early lesions. If the legs must be washed then they must be dried also. Sulphur powder sprinkled generously on the heels is very effective (even when sprinkled on wet legs) this is probably due to the fact that they have a marked drying effect.

Get into the habit of running your fingers upwards against the direction of the hair at the back of the pastern every few days to detect the very small scabs indicating an early problem. if treated immediately these small lesions will respond very quickly.

What Is Summer Mud Fever (Leukocytoclastic vasculitis)

Very similar in appearance to mud fever, this condition occurs in hot dry conditions. It is believed to be an interaction between sunlight and blood vessels in the skin, although it is not true photosensitisation. The same horses are affected year after year.

Preventing Summer Mud Fever

Protect the white lower limbs by one of the following:

  • Keeping the horse indoors during the day in a sunlight free stable
  • Applying high-protection factor (at least factor 30) waterproof sun block daily to the white parts of the limbs applying stable bandages from the coronet to below the knee or hock
  • Using gaiter-type boots designed to be worn for mud fever prevention. These must extend from the coronet to below the knee hock.
What is grass sickness

What Is Grass Sickness?

Grass sickness is a disease of the intestinal system of grazing horses, seen usually from late spring to midsummer in horses aged from 2-7 years. Current research suggests that the disease is a form of botulism, caused by horses ingesting Clostridium botulinum or its toxin. Some, as yet unknown, conditions cause the organism to multiply on pasture. Cases are more likely to occur if:

  • There has been some soil disturbance in the pasture
  • The horses have recently changed fields
  • The horses have recently been moved to new premises
  • The horses have recently been wormed with an ivermectin-type wormer
  • The weather is cool and dry
  • There have been other cases on the premises before.

The toxin produced by this bacterium damages the nerves controlling the normal propulsive movements of the intestines, resulting in failure of the stomach to empty (it fills with fluid), no audible contractions of the intestines, and hence constipation. The disease occurs in several forms.

Acute Grass Sickness

The horse shows signs of acute colic. The stomach is tightly distended with a green fluid that can be retrieved with a stomach tube. Swallowing is difficult, and patchy sweating and muscle trembling occur. Many acute cases are assumed to be surgical colics and may be operated on, only to find that there is no correctible problem in the abdomen. There is no treatment, other than pain control. The disease has a rapid course, usually ending in the horse being humanely destroyed, although sometimes it is found dead in the field with a ruptured stomach.

Chronic Grass Sickness

In chronic grass sickness there is marked weight loss and the horse has an extremely gaunt, tucked up appearance. There is patchy sweating and tremors of the upper muscles of the fore and hind legs. There is dried sticky mucoid material at the nostrils. Very few droppings are passed, and those that are, are hard, dry and dark. The horse has a very poor appetite.

What To Do Next

If a suspect case occurs, the other horses in the group should be brought indoors and fed hay until grass sickness is confirmed.

Most chronic cases will eventually be humanely destroyed. A small proportion (probably less than 25%) may eventually recover but this may take up to a year and it requires a major commitment in time and effort by the owner. Careful nursing is required, including keeping the horse hydrated and especially maintenance of the appetite by offering palatable foods and frequent stimulation of the horse by changing its surroundings and company.