Septic Arthritis (Foals) in Horses

While more often septic arthritis is caused by a spread of bacteria through the blood, incidents of wounds, surgeries or injections can also be ways for bacteria to invade the joints and proliferate. Septic arthritis more often affects foals in their first month of life, and has been cited as the most common cause of mortality in foals younger than 7 days old. The joints most often affected include the tarsus, fetlock, stifle, and carpus.

Septic arthritis in foals most often occurs when bacteria in another part of the body invades the bloodstream, eventually causing an infection within the joints. Common sites of the bacterial origin are the umbilical tissues, lungs, and intestines. Often, this condition occurs along with, or results in, osteomyelitis, or an infection within the bone, making it harder to successfully treat. Symptoms of joint swelling and pain, lameness, and fever are an alert of an emergency situation in your young horse. Seek immediate veterinary help, as delayed treatment can lead to permanent joint and bone damage, or even death.

Symptoms of septic arthritis in foals include:

• Lameness that can become chronic
• Increased fluid in joint
• Joint swelling
• Distended joint
• Loss of joint function
• Thickened skin over bony prominences, such as carpi, hips, hocks and elbows
• Recumbency
• Pain
• Fever
• Diarrhea
• Pneumonia
• Failure to consume sufficient amounts of colostrum
• Reluctance to bear weight on affected limb
• Death

The main cause of septic arthritis affecting foals is bacteria that infects the bloodstream, and then infects the joint. There are many factors thought to contribute to this condition that include:

• An incident that caused the foal to be unable to ingest insufficient amounts of high quality colostrum from the mare, such as the mare leaking the colostrum before childbirth or the foal being delayed in nursing
• Bacteria infected umbilicus, intestines, or lungs
• Trauma
• Wounds over joints
• Infection that occurs during diagnosis or treatment of other joint issues, such as injections or surgeries
• Certain medications

Diagnosis of septic arthritis in a foal can be challenging, as the immune response of foals differs than those of adult horses, and can often cause symptoms to be delayed. However, a quick response to associated symptoms is recommended, as septicemia can occur as quickly as 36 hours from birth.

Your veterinarian will start with a physical examination. The joints will be palpated, using opposite joints for comparison. He will look for signs of effusion and pain. An arthrocentesis is performed to collect synovial fluid from the joint for bacterial cultures and other tests. Blood samples will also be taken for testing. If there is the presence of a wound over the joint, your veterinarian will examine the wound, looking for the leaking of synovial fluid. The presence of bacteria in the synovial fluid can help confirm the diagnosis.

Other diagnostic testing methods include X-rays and ultrasounds to locate the site of infection, as well as to identify bone involvement. An MRI or CT scan can identify the related condition of osteomyelitis in foals much earlier than X-rays. X-rays are then repeatedly used to monitor your foal for signs of a worsening infection or arthritis.

Treatment of septic arthritis should be started immediately once a diagnosis is made. The goals of treatment are to eliminate the bacteria, reduce joint inflammation and pain, remove any foreign material from wounds, remove tissues or proteins impeding healing in joints, and to prevent further joint damage by supporting a healthy joint environment. The therapies involved can be aggressive and costly, and in some cases, euthanasia may be recommended. Therapies include the use of drugs, and joint cleaning performed through lavage and surgical methods.

An initial intravenous antimicrobial injection given directly to the infection site is used to administer higher concentrations of the medication in order to be more effective. Oral antimicrobials can be given after that, and should be administered for 2 weeks past the cessation of symptoms. Pain relievers are given as needed, such as NSAIDs, lidocaine or epidural analgesics. Chondroprotective drugs, such as chondroitin sulfate, glucosamine, or hyaluronate sodium, can help to reduce the inflammation and foster a return to a healthy joint environment. Intravenous plasma can also be administered to support the immune system by increasing immunoglobulin levels.

Next, the site of infection must be cleaned of bacteria, foreign material, and excessive proteins, such as those present in pus. This can be done with a joint needle lavage, or through surgical methods, such as arthroscopy, also called keyhole surgery as it provides the most direct visualization, arthrotomy, and surgical arthrodesis. Some methods will require post-operative bandaging.

Following treatments, you may need to change bandages, monitor wounds or incisions, and administer medications. Your veterinarian may also monitor your foal by walking and trotting him in intervals, and retesting more synovial fluid samples. With treatment, recovery rates are still guarded for foals, with percentages of recovery ranging from 42% to 89%. Quick treatment is needed for your foal’s survival, and will help the success of your foal’s recovery.

Prevent septic arthritis in your foal through the use of practices aimed at reducing sepsis in newborns. Any wounds should be treated immediately to prevent the spread of bacteria.