Description

Abscesses occur in horses both as a symptom and as a result of a particular disease. Pleurisy, strangles, and warbles are diseases that may be characterized by the accumulation of fluids in localized sites, creating inflammation resulting in swelling, fever, increased pulse, and discharge from the site of the abscess.

Pleurisy also known as pleuritis, is an inflammation of the pleura, or the fine membrane, that lines the chest and covers the lungs. This inflammation rarely appears in isolation and often accompanies various respiratory infections such as pneumonia or strangles. The appearance of rapid, shallow breathing with a cough suggests the development of pleurisy. A grunting sound characteristic of the condition often accompanies each breath. Abscesses related to pleurisy usually occur within the chest wall of the horse.

Strangles, also known as distemper, is an infectious and highly contagious disease which spreads rapidly and is evidenced by nasal discharge and swelling of the lymph nodes, a place where abscesses form.

Warbles are caused by the invasion of maggot-like worms that hatch from the eggs of the warble fly, a pest that frequents areas where cattle are kept. These abscesses appear as small lumps under the skin, producing painful sores.

Symptoms

• Common symptoms of pleurisy are rapid, shallow breathing. In the early stages, the pleurisy is usually "dry," since no fluid has built up between the layers of the pleura. An examination of the chest with a stethoscope reveals dry, rough sounds, as though two pieces of sandpaper are being rubbed together. As the condition develops, fluid is discharged into the pleural cavity, becoming "wet" pleurisy.
• Common symptoms of strangles or distemper are similar to those of the common cold: loss of appetite, lethargy, elevated temperature, increased pulse, and nasal discharge. Mucus runs from the nostrils, and the horse may have difficulty swallowing because of a sore throat. From there, the infection spreads to the lymph nodes between the angles of the lower jaw, the parotid nodes behind and under the ears, and may extend to the nodes at the base of the neck. The nodes are painful to the touch and, eventually, abscesses form.
• Symptoms of warbles include painful lumps under the skin that often turn into abscesses or fistulas.

Causes

Pleurisy is caused by bacteria invading the chest cavity, resulting in inflammation of the membrane that lines the chest cavity and covers the lungs, often in conjunction with various respiratory infections such as pneumonia or strangles.

Strangles is caused by a pus-forming organism called Streptococcus equi. It is highly contageous and is transmitted easily between horses. Lymph nodes are often affected and become abscessed. When the abscessed lymph nodes drain internally, the guttural pouches and sinuses can become infected. Known as a retropharyngeal abscess, this condition may damage the nerves at the back of pharynx, paralying the swallowing muscles or the muscles of the face and ears.

Warbles are caused by larvae that hatch from eggs the warble fly (also knows as the heel fly) lays at the base of the hairs and on the lower parts of the legs. When the eggs hatch, the larvae penetrate the skin and migrate throughout the body, ending up on the back of the horse, often under the saddle area. In horses, the larvae often die under the skin, producing either an abscess or fistula.

Prevention

Prevention of pleurisy involves prompt attention to any signs of respiratory infection.

Strangles vaccines are available, but many veterinarians advise against their use. The best prevention is to avoid exposure.

Unless horses are in stables or on a farm where cattle are strictly treated against the fly, prevention of warbles is almost impossible. Good fly control and proper use of insecticides will help protect horses from warbles.

Treatment

Treatment for pleurisy begins with an ultrasound examination of the horse's chest to determine the amount of fluid accumulation, as well as the exact location.

Treatment for pleurisy involves prescribing antibiotic therapy. If pleural fluid is excessive, the horse will have difficulty breathing and it becomes necessary to drain as much fluid as possible. A puncture is made behind the elbow and fluids are drained off. If too much fluid builds up, it may cause suffocation because of pressure on the outside surfaces of the lungs. This pressure prevents the intake of sufficient air.

Treatment for strangles requires complete isolation. Because this disease responds well to antibiotic treatment, a vet should be consulted and a course of antibiotic treatment started at the first appearance of symptoms. In addition, all feeding and grooming utensils should be disinfected daily in an iodine solution or comparable antiseptic and any bedding should be removed and burned.

Plenty of fresh air is important, but the horse should be kept comfortably warm and out of drafts. Treatment with hot compresses, applied directly over the involved lymph nodes to encourage the abscesses to drain to the outside, is important. In some cases, the abscesses may need to be opened surgically. A soft diet will help ease the difficulty in swallowing. Fortunately, the use of antibiotics has made this once fatal disease treatable.

Treatment for warbles consists of getting rid of the larvae and grubs that cause the condition. When grubs encyst in the horse's tissue, the resulting nodules are best treated by enlarging the breathing hole with a scalpel and removing the grub with tweezers.

Ivermectin is used to kill migrating larvae. Further protection is accompliished through use of insecticides and good fly control. Because warbles tend to congregate in areas where cattle are kept, it is best not to pasture horses near cattle.