What's That Bump?

By: Dr Sarah Behan, BSc, BVMS Hons

Courtesy of Horses and People Magazine - SUBSCRIBE to Horses and People Magazine here to read the most up to date articles

It is common to suddenly discover your horse has one or more lumps or bumps somewhere on its body.

In this article Dr Sarah Behan from from Equine Veterinary Dentistry explains some of the common skin conditions that may show up as lumps and bumps. As with most conditions, a correct veterinary diagnosis will determine the exact cause, so if you are unsure, the lump persists, it is painful or in a particularly sensitive area, a proper veterinary diagnosis is recommended.

Horses can have many troublesome lumps and bumps throughout their lives, some serious and others just annoying for the horse or owner. So, how do you know what the lump is? Or why it has occurred?

In this article I provide a list of some of the common lumps and bumps that may be found on your horse or pony’s body. It is not exhaustive and if you are unsure or concerned about a lump on your horse you should always get an examination by your veterinarian.

As with all veterinary problems, the first thing to do is to obtain a thorough history:

• Where is the lump?
• When did it first appear?
• What shape and colour is it?
• Is it soft or hard to touch?
• If it is under the skin, does it move freely?
• Did it come up quickly or has it been there a while now?
• Is it itchy?
• Does it cause pain, lameness or movement restriction?
• Is the horse currently afflicted by another condition or illness?

Tumours (neoplasia)

Tumours are uncontrolled or incorrect growths of cells which can invade normal tissue and disrupt function. There are several forms and although they are common in horses, they often cause little disruption.

Melanoma

These common tumours can be benign (slow-growing and not tending to spread) or malignant (fast-growing, aggressive or spreading to other tissues) and are predominantly seen in older horses that have turned from dapple grey to grey as they have aged.

Arabians, Andalusians and Percherons are predisposed to this type of tumour. They are usually found as firm nodular black or grey lumps which may become ulcerated. Common sites for melanoma include the dock of the tail, perineum and sheath, around the eye, the lips, the throatlatch area and lower limbs.

Surgery is a common treatment of choice, however, it may not always be appropriate, for example in cases with multiple tumours which make surgery difficult. Cryotherapy can also be attempted in areas difficult to perform surgery. Vaccination is a newer treatment that is being trialled. It acts as an immune stimulant that encourages the body’s own immune system to attack the melanoma cells.

Squamous cell carcinoma

Squamous cell carcinoma is a very common skin tumour, especially in older horses. Locally aggressive, these single small red lumps or non-healing ulcers appear most commonly at mucocutaneous junctions such as on the genitals, lips or eyelid margins. They are more common on lightly pigmented skin areas.

Squamous cell carcinomas can progress rapidly so should be checked by your vet and removed surgically while they are still small, to reduce the metastasis (spread) to other areas in the body.

Sarcoids

The most common tumours in horses, sarcoids come in several forms which can look quite different to each other. Fibroblastic sarcoids have an ulcerated surface and may appear much like excessive granulation tissue; while verrucous sarcoids have a wart like nodular appearance. Some can also have a combination of these forms. Occult sarcoids however are vastly different, having a flat hairless appearance. All sarcoids can be locally invasive and be very persistent. Most common on the head, on the legs and ventral (lower) trunk, they can be single or multiple in form.

A wide and clean surgical margin is the treatment of choice, however given the areas in which they usually occur this is hard to achieve, and reoccurrence is very common. Other treatment options which have been tried include cryotherapy, local radiation therapy and immunotherapy. However, occult and small verrucous forms are best left alone and monitored.

Papilloma

Also known as warts, papillomas occur most frequently in horses less than 3 years old in multiples around the nose and lips as the characteristic ‘wart like’ nodules. They can also be found as a more flattened lump or plaque (flat area) on the ears.

Although papilloma is a self-limiting disease which will resolve with time, horses should be isolated to reduce the risk of transmission to others.

Enlarged lymph nodes

Lymphoma and other causes of lymph node enlargement appear as swellings in the area of the lymph nodes (e.g. around the throatlatch area). Lymphoma is a form of malignant cancer that affects the immune system. The horse will usually have other symptoms of disease and should be seen by a veterinarian for assessment.

Other skin conditions

Exuberant Granulation Tissue

‘Proud flesh’ is mostly commonly seen on the lower limbs associated with wounds which have constant movement. Not itchy and non-painful, the granulation tissue which covers wounds during the healing process becomes excessive because the skin has a limited degree of contraction in these areas. It will appear as red, fleshy tissue protruding from the wound which may bleed easily when knocked.

Treatment may involve surgical debridement of the excessive granulation tissue and bandaging to improve wound healing.

Nodular Necrobiosis

One of the most common skin diseases in the horse, this non painful condition occurs most frequently in summer and may be related to hypersensitivity to insects.

It is characterised by firm, round nodules (bumps) in single or multiples without hair loss, pain or itchiness. The lumps are seen most commonly on the withers and back where the saddle sits, but can also be found over the girth, mane, rump or face.

Although primarily a cosmetic issue, treatment can involve corticosteroid injection into or around the lumps or surgical removal if causing problems under the saddle or have become large and calcified.

Habronemiasis

Commonly known as ‘Summer sores’, habronemiasis occurs commonly in warm and wet climates, and is caused by a hypersensitivity reaction to the larvae of a nematode (worm) which lives in the stomach of horses (Habronema species).

The larvae and eggs are passed in the faeces and are then deposited by maggots into wounds or chronically wet skin where a hypersensitivity reaction then occurs. Habronemiasis appears as single or multiple ulcerated nodules which may ooze a red discharge and excessive granulation tissue may also be present. The lumps have varying degrees of itchiness. Common areas on the horse include legs, abdomen, prepuce, urethral process of the penis and the inside corner of the eye. In the eye it may be seen as a yellow gritty plaque (flat lump).

Treatment revolves around not only reducing the worm burden through anthelminthic use, but also corticosteroids to reduce the severity of the hypersensitivity reaction. Fly control will also reduce reinfestation.

Onchocerciasis

Caused by a nematode (worm) parasite that lives in the neck of horses worldwide, their microfilaria migrate through the connective tissue to localize in the skin. This occurs most commonly in the ventral (lower) abdomen and lesions appear as crusting, redness, and depigmentation and hair loss in this area. There may also be varying degrees of pruritus (itching). It is thought to also be related to a hypersensitivity reaction to the intermediate midge host Culicoides sp. and these two diseases can occur concurrently.

Treatment for the disease is ivermectin, which will kill the microfilaria causing more intense itching in some horses. However, to kill the adult worm repeated treatments must occur at three month intervals.

Insect Bite Hypersensitivity

Known commonly as ‘Queensland Itch’, ‘Sweet Itch’ or ‘Summer Itch’, this seasonal disease occurs due to a hypersensitivity (allergic) reaction to the biting midge ‘Culicoides’ and is characterised by intense pruritus (itching). Lesions are usually the result of self-trauma and occur commonly on the midline of the back, ears, mane and tail, appearing as crusting, lichenification (increased skin folding), alopecia (hair loss) and increased pigmentation.

There may only be one horse in the herd affected by the disease. Control of symptoms must involve effective insect control and environmental considerations and if done correctly will result in complete remission of signs. Other treatments include corticosteroids to reduce itching and self-trauma.

Allergic reactions to many things can cause similar lesions to that of insect bite hypersensitivity. Pruritus (itching) and wheals (raised pitting areas) can come up very quickly following the insult.

Photosensitivity

Some plants and drugs cause a photosensitizing agent to become present in the bloodstream which will lead to skin damage in the areas where UV light can penetrate. There are primary causes including some plants and drugs and a secondary form caused by liver disease. White areas with sparse or no hair may show painful, localised fluid filled lumps which progress to be ulcerated and crusty. It can involve all white areas or the lower limbs only and can be very severe. Pigmented areas remain unaffected.

Treatment involves removing the photosensitising plant (if it is the cause) and stabling to reduce sun exposure. Severe cases will also need antibiotics and wound care.

Dermatophilosis

‘Rain scald’ is a common condition affecting horses who a kept outside during wet weather. It appears as moist crusty lesions affecting the dorsal (upper) area of the body where the rain would fall. The causal bacteria (Dermatophilosis congolensis) come from affected animals crusts, carrier animals or the soil. The lesions first appear as crusts as the base of matted hair and then progress to larger crusts and that area of skin will fall out to reveal erosions underneath. The lesions may be painful, but are not itchy.

Most important to treatment is keeping the horse dry, and sometimes this is all that is needed. Topical antibacterial treatment with povidine iodine or chlorhexidine will hasten the resolution of the problem, and oral antibiotics are sometimes required.

Pemphigus Foliaceus

This rare autoimmune disease appears as widespread crusts, pustules (small pus filled lumps) and vesicles (small fluid filled bumps) due to the production of antibodies to keratinocytes and therefore the adhesion (connection) between the cells. Appaloosas may be predisposed to the disease which quite often occurs with systemic illness. The lesions can start on the head, neck or forelimbs, but usually progress quickly to involve whole body. Sometimes only the coronary bands are affected. It can occur in adult horses and also foals usually less than 1 year of age.

Treatment in adult horses can be difficult, but includes immunosuppressive therapy. Foals that develop the disease usually have a better prognosis.

Bacterial Folliculitis and Furunculosis

Commonly seen in the saddle and girth areas but may present in other places, it appears as small lumps from the hair follicle which can progress to have crusts and hair loss. There is usually a predisposing factor such as being in a warm and wet environment or anything that affects the skin barrier.

Treatment involves topical antibacterial washes or systemic antibiotics in unresponsive cases. Underlying causes should also be removed.

The wrap up

If your horse has a lump or bump that you are unsure about or that persists, causes pain or is in a particularly sensitive area such as the eyes, genitals or lymph nodes, you should always get an experienced veterinarian to perform an examination, diagnose the problem and treat it appropriately.

About the Author: Dr Sarah Behan is the owner/vet at Equine Veterinary Dentistry, Donnybrook WA (www.facebook.com/evdentistry). Having grown up in regional Western Australia, owning and riding horses, Dr Behan graduated from Murdoch University in 2005 with merit honours. She spent the first year after graduating in mixed practice in Northam WA, before moving to an equine only practice on the south coast of NSW. After having a few years away from full time practice to raise her two children, she has started an equine dental practice in the south west of Western Australia, where she focuses on providing quality, caring dental and routine preventative care to the horses and ponies of the area. 

Thank you to Horses & People Magazine for sharing this article with us!

READ IT ON THE HORSES & PEOPLE WEBSITE

 For more informative articles, visit the Horses & People website www.horsesandpeople.com.au

To see the most up to date articles subscribe to Horses & People Magazine HERE