Contagious equine metritis

Contagious equine metritis (CEM)



Contagious equine metritis is a bacterial mating infection of horses that causes temporary infertility in mares. Humans are not infected.


There are reports of the occurrence of contagious equine metritis worldwide. The pathogen has also been regularly detected in many EU countries in recent years. In 2022, a total of 204 positive cases have been reported to the European Reference Laboratory.

Host animals

Horses and other equidae

Infection route

Transmission mainly occurs through mating or artificial insemination. Indirect transmission via contaminated equipment or persons is possible.

Incubation time

2-12 days


In mares, vaginitis, cervicitis and endometritis with mucopurulent discharge and temporary infertility occur. However, striking clinical manifestations are often absent, and umrusis is often the only symptom. Abortions are extremely rare. Infected stallions show no clinical symptoms.


A combination of systemic antibiotic therapy with local antiseptic washing is used in both the mare and the stallion. Especially in mares, freedom from pathogens is not always achieved.


Regular testing of all breeding animals before mating or semen collection and exclusion of positive animals from breeding. Hygiene management to prevent indirect transmission.

Situation in Austria

Contagious equine metritis is, according to European animal health legislation, a disease whose introduction and spread within the EU must be prevented and which must be monitored. Positive test results must therefore be reported to the official veterinarians. Currently, there is no special surveillance program in Austria.

Specialized information

Contagious equine metritis is a non-systemic disease of the reproductive organs unique to equids, caused by Taylorella equigenitalis, an immobile, Gram-negative, microaerophilic rod. Taylorella are very fastidious and reproduce very slowly. Therefore, cultures are incubated for at least 7 days, and some countries require a longer incubation period as part of import controls.


Infected stallions are asymptomatic carriers and show no symptoms. In mares, symptoms vary widely from clear clinical signs of vaginitis, cervicitis, and endometritis with mucopurulent vaginal discharge to subclinical infections. Temporary infertility lasting several weeks develops regardless of the degree of other symptoms. The general condition is usually not affected. After recovery, mares may remain carriers of the germ for months to years and act as a source of infection. The pathogen can also be transmitted to the foal at birth.


The detection methods recommended by WOAH are direct pathogen detection by cultivation and PCR. For confirmation of the disease in an asymptomatic carrier animal, direct pathogen detection by cultivation is necessary. The cultural detection method is also usually prescribed for international trade. Sampling, transport Swab samples for cultivation must be sent to the laboratory refrigerated in transport medium with activated charcoal. Swab samples for PCR are sent without transport medium. No more than 48 hours may elapse between sample collection and testing. Unrefrigerated samples must be examined within 24 hours. Sampling for both culture and PCR must not occur until at least 7 days after parenteral antibiotic therapy and 21 days after local antibiotic therapy. Sample collection mare

  • Clitoral fossa
  • Sinus clitoridis
  • Uterus or cervix

Sampling stallion

  • Glandular fossa
  • Urethra
  • Penile shaft (envelope site)
  • For insemination stallions a swab of pre-secretion or semen


Institut für veterinärmedizinische Untersuchungen Mödling

Last updated: 10.10.2023

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