Contagious Equine Metritis Average Cost

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What are Contagious Equine Metritis?

Unfortunately, CEM can be a silent infection, meaning some mares and stallions do not show symptoms of infection. This is what leads to accidental passage of the infection to the other horse of the mating pair. It is caused by a gram-negative bacterium known as Taylorella equigenitalis that has multiple strains; some are resistant to streptomycin which is an antibiotic. Samples will be collected from your horse’s genital region and examined to see what organisms are present. If your horse does have CEM, treatment will be started immediately which involves washing the affected area, and a medicine applied afterwards. Treatment in chronic cases may require surgical correction to completely remove the infection. Recovery typically goes smoothly once your horse is properly diagnosed.

Contagious equine metritis, also known as CEM, is an extremely contagious venereal disease that horses can pass along to any other horse they mate with. If you suspect your horse is having some urinary or genital issues, contact your veterinarian.

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Symptoms of Contagious Equine Metritis in Horses

Symptoms of mares may include:

  • Copious amount of mucopurulent vaginal discharge
  • Shortened estrus cycle
  • Lesions 
  • No symptoms at all

Stallions do not show any symptoms of infection even when they are carriers.


Contagious equine metritis is caused by the bacteria Taylorella equigenitalis. This bacteria is gram-negative, microaerophilic (meaning it needs oxygen to thrive), and is a coccobacillus. There are multiple strains with one being resistant to streptomycin and the other being susceptible to it. This is very important when it comes to treating your horse.

Causes of Contagious Equine Metritis in Horses

An infected horse with CEM but now showing symptoms is the most common source of new outbreak. This infection is primarily passed from one horse to another during the mating process. The transmission rate is extremely high so every mare that gets bred with an infected stallion will become infected. Medical instruments and mating instruments can also carry the bacteria from one horse to another.

Diagnosis of Contagious Equine Metritis in Horses

Testing of bodily fluid samples will need to be conducted in order for the veterinarian to confirm if your horse has CEM or not. In mares, the veterinarian will need to take swab samples from the sinuses, endometrium, and clitoral fossa. In stallions, swab samples should be taken from his urethral fossa, the preputial cavity, the urethra, shaft of the penis, and when possible, pre-ejaculate or ejaculate material. The veterinarian will examine the samples to see what type or organisms are present in the samples. She may need to culture a sample in order to see if it is the resistant or susceptible strain. This will play a major role in treatment if the veterinarian is choosing to administer antibiotics.

The veterinarian may want to do other routine lab work to ensure nothing else is going on. Blood work in the form of a chemistry and complete blood count (CBC) will be performed to allow the veterinarian a look at how the rest of the organs and body are handling the infection.

Treatment of Contagious Equine Metritis in Horses

When treating a mare, sometimes she is able to rid herself of the infection without medicinal assistance within a few weeks. If yours needs to be treated, you use chlorhexidine surgical scrub to thoroughly clean the clitoral area and then apply nitrofurazone ointment. In cases where the mare becomes chronically infected, the veterinarian may recommend surgical removal of the clitoral sinuses since this is where the infection is harbored.

For stallions, you have use chlorhexidine surgical scrub to clean the extended penis. You follow up by applying the nitrofurazone ointment. This should be done once a day for 5 days, and then your horse can be retested for CEM at least 10 days after the last treatment was applied.

Recovery of Contagious Equine Metritis in Horses

Before the veterinarian can declare your stallion free of the contagious equine metritis organism, he needs to be sampled and retested at least three times. The process for the mare is very similar. 

If your horse is diagnosed with CEM and you properly follow the veterinarian’s medical directions, your horse should recover. However, there are the cases in mares where the infection becomes chronic but if you go forward with the mentioned surgery, she should be rid of the infection.

If you are planning on breeding your horse with an unknown one, be sure to get the complete medical history before anything else. This will help ensure your horse will not become infected. If your mare was bred on accident due to the neighbor’s stallion jumping the fence, you may want to take her in for testing to ensure she does not have something she can pass along to the foal during or after birth.