In this episode of the Disease Du Jour podcast, Erin Newkirk, DVM, discussed contagious equine metritis (CEM), especially with regard to the current outbreak in Florida.
What Is CEM?
CEM is a highly infectious venereal disease caused by the bacteria Taylorella equigenitalis. The disease spreads through breeding, sheath cleaning, and contaminated equipment. “Even as simple as the bucket handle of the wash bucket from stallion to stallion is one of the ways it could be transmitted,” said Newkirk.
CEM typically causes temporary infertility in mares. Stallions tend to be silent carriers of the disease and don’t seem to experience clinical infection.
Where Is CEM Endemic?
Newkirk said CEM was first diagnosed in England in the 1970s. The disease was also present in the U.S. during the ‘70s, but it was eradicated through aggressive quarantine, treatment, and retesting protocols; only sporadic cases have occurred in the U.S. since then.
CEM is still endemic in Great Britain, Japan, Korea, Northern Ireland, and South Africa, as well as all countries in the EU. Any mares or stallions that enter the U.S. from those countries must undergo an additional CEM quarantine.
Vulnerabilities for CEM Spread in the U.S.
Newkirk said recently imported geldings pose one of the biggest threats for CEM spread in the U.S. Stallions are often gelded before import and therefore don’t undergo CEM quarantine when they arrive. “Those new geldings could still have the organism present, and so they could be bringing CEM into our country unknowingly,” said Newkirk.
Typically, these geldings don’t spread the disease because they aren’t involved in breeding activities. However, procedures such as sheath cleaning can result in disease transmission.
Current CEM Outbreak in Florida
Transmission among geldings is responsible for the current CEM outbreak in Florida. “[CEM] was actually spread amongst most of the geldings within the herd via sheath cleaning,” said Newkirk. Of the 49 confirmed cases in this outbreak, 46 are geldings, and three are breeding animals.
“The initial case was a mare that was bred by live cover, and she had uterine fluid after breeding, so they just cultured it,” said Newkirk. When the culture came back positive for CEM, the USDA investigated the stallion, who was also positive. They then investigated the other horses at the stallion’s facility, which is when the geldings started lighting up.
“It doesn’t seem from their tracebacks that this particular outbreak actually came from breeding stock,” said Newkirk. “Those stallions that they had were bred and raised here in the U.S., and they believe it came through a gelding, but they haven’t gotten to the bottom of the story.” Testing is still ongoing, and while Florida is at the center of the outbreak, some horses in North Carolina, South Carolina, and Virginia are also involved.
Newkirk said it’s too soon to speculate if the USDA will change its protocols following this outbreak. However, one hope is the USDA will consider a PCR test, which gives faster results than a culture. Another question is whether geldings from endemic countries will be tested on some level, “but it’s just way too soon to get to that point,” she said.
What Happens When a Horse Tests Positive for CEM?
Newkirk said horses that test positive for CEM are usually already undergoing import quarantine, which is supervised by states and the USDA. “Those ones you typically don’t hear about because it’s actually stopped, treated, and controlled prior to becoming part of the U.S. horse population,” she explained.
In this recent outbreak, as soon as the mare tested positive for CEM, the state and the USDA were immediately notified. Because CEM is a foreign animal disease, both state and USDA authorities oversee the quarantine, testing, treatment, and release process from beginning to end.
The USDA-established treatment protocol for mares includes intrauterine antimicrobials, an external wash with a 2% chlorhexidine scrub, and topical application of silver sulfadiazine or nitrofurazone for at least five consecutive days. The same topical treatment is used for stallions.
The USDA requires a 21-day hold before retesting. After the 21-day hold period, mares undergo an additional 14- to 21-day testing protocol before they can be released. The stallion testing protocol is much lengthier: The stallion must live cover two mares, and those mares must test negative before the stallion can be released. This process can take months to complete.
How Can Veterinarians Prevent CEM Spread?
Newkirk said routine screening is one way to prevent CEM spread in the U.S. She recommends annual bacterial cultures for domestic stallions to confirm they’re negative for the disease. She also recommends testing mares with infections.
It’s also important to practice proper biosecurity when collecting stallions. Veterinarians should clean equipment thoroughly between uses with disinfectants that are effective against CEM. Using gloves while cleaning sheaths and not reusing supplies between horses is another important protective measure.
Final Thoughts
“CEM helps remind us how interconnected our whole global equine community is,” said Newkirk. “The ability for the U.S. to be considered CEM-free is what helps protect our economy, our breeders, our ability to travel internationally without restrictions, and it’s very important to continue to support this because it has long and far-reaching impacts if that were to change.”
About Dr. Erin Newkirk
Erin Newkirk, DVM, is Co-Founder of WellGrove Equine, an equine wellness, reproduction, and CEM quarantine facility in South Florida.
Newkirk is a 2007 graduate of the University of Florida College of Veterinary Medicine and began practicing in South Florida that same year, becoming a well-rounded veterinarian proficient in all aspects of equine medicine. In 2019, she decided to chase her entrepreneurial dream by starting WellGrove Equine.
Among many things, Newkirk continuously strives to enhance and develop WellGrove Equine’s reproduction services. In addition, Newkirk is one of the most experienced professionals involved in the import testing procedures for CEM in the U.S., and she was chosen by the Department of Agriculture to lead the symposium on CEM protocol.
Related Reading
- Disease Du Jour: Importing Horses to the U.S.
- Contagious Equine Metritis and Equine Viral Arteritis
- AAEP Publishes Contagious Equine Metritis Guidelines
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