Melanomas are tumours of the skin, which are derived from the pigment producing cells. They therefore have a heavily pigmented or darkened appearance. They are reasonably common and have a reported incidence of between 4 and 15%. They occur anywhere on the body but are more common in older horses with lighter coats. In fact in old grey horses the incidence has been recorded as high as 80%!
These tumours are initially benign (unlikely to spread) but eventually the majority of them develop into malignant tumours and spread.
Squamous cell carcinomas
Squamous cell carcinomas are a type of skin tumour and are reportedly the second most common skin tumour of horses. They most frequently occur in horses between the age of 8 and 14 years but have been found in horses from 1 year old to 29! They are more common in lighter coloured horses as sunlight has been implicated as a cause of them.
They can occur anywhere on the skin of a horse but are more commonly found on the hairless areas such as eyelids, lips, nose, vulva and prepuce. Early diagnosis is essential and your veterinary surgeon may even recommend removal of them to prevent further spread.
The most commonly diagnosed skin tumour found on horses are sarcoids and have been reported to account for nearly 90% of all skin tumours in horses. Luckily though they are non-malignant (unlikely to spread) but can invade local tissue and cause irritation to the horse. Also if they are knocked and bleed they will attract flies and increase the irritation.
Sarcoids can appear in a number of different forms and can look similar to other skin tumours. It is essential that any lumps are discussed with your veterinary surgeon as soon as they are noticed.
Rain scald is a bacterial infection of the skin of horses, which causes scabs to form on the back, rump and lower limbs. These scabs can be easily removed to reveal patches of moist raw skin. This condition is caused by prolonged wetting of the skin which allows the bacteria to invade.
It is important that you contact your veterinary surgeon for advice on rain scald as there are a few other conditions which can appear similar. Rain scald can be avoided by ensuring the skin remains dry so stabling the horse or applying a weather proof rug can reduce the risk of this condition developing.
This is a skin condition caused by an allergy to the saliva of certain biting flies or midges. The severity depends on the degree of allergy or reaction to the insect bites. The allergy causes the horse to be itchy and thus rub the skin, in fact they can actually rub the hair off the affected areas (upper neck, back, tail base and ventral abdomen). This problem is usually encountered in the warmer months when these insects are more active.
Reducing the exposure of horses to the flies is the best form of control of this condition. Therefore stabling the animals at high risk times, rugging the horse, reducing the number of insects present, and fly and insect repellents can all help to reduce a horses exposure. Your veterinary surgeon will be able to offer advice on forms of reducing the exposure as well as appropriate treatments that are available to control the itching.
Mud fever is caused by the same organism as rain scald and is associated with damp muddy conditions. However any damage to the skin surface can allow the bacteria to invade the skin and cause problems. Signs of the disease are matted, crusty scabs on the legs and these tend to be around the coronet, heels and pastern.
For mud fever by far and away prevention is better than cure and hence muddy areas of the paddock should be avoided. If legs do get muddy this should be allowed to dry and then brushed off and any scabs should be observed for signs for problems. Your veterinary surgeon will be able to provide further advice on the treatment of this condition.
Although Scabies or Sarcoptic mange has been eradicated from the UK mange due to the mite Chorioptes equi is still relatively common. The mite lives on the surface of the skin and its burrowing activities are what causes irritation to infected horses. This irritation causes the horse to nibble at the affected areas (hind limbs, belly forelimbs and groin).
Chorioptic mange as with other types of mange are associated with close contact of horses where the mite is able to easily pass between them. Treatment for mites is by adopting good hygiene practices as well as certain parasiticides of which your veterinary surgeon will provide advice on the most suitable for your horse.
Ringworm is not as its name suggests caused by a worm but it is actually due to infection of the skin by one or two types of fungi – Trichophyton or Microsporum. These fungi live in the environment (e.g. dirt, wooden fences etc) and horses pick them up when in contact (e.g. rubbing themselves on a fence). Horses may also be infected by other horses or animals (e.g. cattle) or infected tack or grooming utensils. Young horses are at greater risk than older horses as immunity to the fungi develops with age.
Signs of ringworm are small 1-2cm circular tufted areas from which the hair will eventually fall out revealing scaly skin. Ringworm generally occurs on areas of the body in contact with tack, clothing and riding boots. Treatment is aimed at both the horses and removing any possible sources of contamination. Your veterinary surgeon will be able to provide you with further advice on appropriate treatments and prevention measures.
Warts are caused by a virus similar to that which causes warts in humans. It is generally passed from the mare to the foal during suckling and so warts are sometimes termed “milk warts”. The warts tend therefore to develop on the head i.e. muzzle, and eyelids, but can also be found down the forelimbs. Once a horse is older than 18 months warts are very rarely seen and transmission between young horses is common.
Warts usually regress by themselves but can cause trouble if they become infected. Your veterinary surgeon will be able to offer advice if you are at all concerned.