What are Mastitis?
Mastitis is considered to be one of the most expensive diseases of large animals and can be fatal in certain cases. It is much more common in cattle than in horses, but lactating mares are still at risk for this painful condition. Not only is it painful for the mare, it can be dangerous for her foal as well. She will not be likely to let her foal nurse when she is in that much pain and the milk may not be as appetizing as well, leading to malnutrition. If your mare is acting as if her udder is painful or if you can see that it is visibly swollen, you need to take her to see an equine veterinarian. If you do not get sufficient treatment right away, abscesses or induration of the gland may occur.
Mastitis in horses is the inflammation of the mammary glands. Most often, this disorder affects mares within one or two months of giving birth but it can affect any mare of any age. If your mare’s udder is swollen sooner than six weeks before giving birth, you should call the veterinarian because it could be a sign that your mare is having an abortion. If your mare is lactating and her udder is swollen, the foal may not be nursing or there could be an infection or injury.
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Symptoms of Mastitis in Horses
The most common symptoms that are usually noticed first are a swollen and hot udder and standing or walking abnormally. She may also not let her foal feed and may just seem generally unwell. Other common signs of mastitis are:
- Painful and swollen udder
- High body temperature
- Walking stiff
- Standing with legs apart
- May kick foal away when trying to nurse
- Milk changes consistency (lumpy or watery)
- Death (rare)
While there may be many types of bacteria and fungi that cause the infection, the most common are:
- Aspergillus spp.
- Coccidioides immitis
- Gram negative bacteria
- Streptococcus agalactiae
- Streptococcus equi
- Streptococcus equisimilis
- Streptococcus viridans
- Streptococcus zooepidemicus
Causes of Mastitis in Horses
Bacteria or fungi may be the cause, but it is important to know the cause of transmission. Some of the most commonly reported ways to transmit mastitis are:
- Injury to udder that breaks the skin and causes infection
- Insect bites
- Dirty bedding material
Diagnosis of Mastitis in Horses
The veterinarian will not have any trouble diagnosing your horse if she has mastitis, although a thorough checkup is necessary to determine the cause of the mastitis. It is most often bacterial, but there are other causes such as fungi or parasites, so the veterinarian will start by getting your mare’s history. This includes medical and shot records, description of the symptoms, and when she last gave birth. Be sure to mention if there were any complications during birth and whether she is on any kind of medication.
A physical examination is done next, including height, weight, body condition code, palpation of abdomen, breath sounds, heart rate, respirations, body temperature, blood pressure, and reflexes. The veterinarian will also have you walk and trot your horse to see if she has any lameness and to watch how the muscles and joints function in motion. In addition, the veterinarian will be assessing your horse’s attitude, stature, conformation, and behavior.
Laboratory tests include a complete blood count (CBC), urine and fecal examination and culture, biochemistry panel, blood urea nitrogen (BUN), packed cell volume (PCV), and glucose level. The veterinarian will be looking for elevated neutrophils, leukopenia, and white cell count. The veterinarian will also get a sample of the fluid from your horse’s mammary gland to see if there are signs of inflammation, bacterial, and fungal culture. The samples must be taken from each teat, and care should be taken to maintain sterilization. The samples will be tested for cytological examination as well because the cultures often come back negative even when your horse has mastitis. Imaging with an ultrasound and x-rays of the mammary glands to help identify abscesses.
Treatment of Mastitis in Horses
Treatment for mastitis may be medication, therapy, or both. Therapy is most important to clear the infected tissue and milk that need to be removed. It usually includes hand milking your mare frequently to remove fluid and bacteria. Some of the other treatments are:
Some of the medications that may be used are trimethoprim-sulfonamide, combination of penicillin and gentamicin sulfate, non-steroidal anti-inflammatory (NSAID) medication for pain and inflammation, and there is a prepared mastitis treatment (marketed for cows) that can be injected into the infected mammary glands.
Therapy includes frequent hand milking and hot packs alternated with cold packs to reduce pain and swelling. Hydrotherapy is also a good form of treatment.
Recovery of Mastitis in Horses
Prognosis is excellent if you get treatment from an equine veterinarian. One complication is a relapse, which happens in about 15% of horses. With proper treatment, your horse should be back to normal within 2-3 weeks.