Contagious equine metritis (CEM) is a bacterial infection in horses caused by Taylorella equigenitalis. CEM is highly contagious and primarily spreads through venereal transmission and contact with contaminated breeding equipment.

CEM is characterized by severe inflammation of the reproductive tract in mares, leading to temporary infertility. While CEM only causes symptoms in mares, it can also infect stallions who act as asymptomatic carriers of the disease.

CEM is a significant reproductive disease in horses, known for its potential to disrupt breeding programs and cause economic losses. Treatment primarily involves antibiotics, including local treatment of the reproductive tract in mares and washing the external genitalia with antimicrobial solutions in stallions.

Prevention of contagious equine metritis involve rigorous screening of breeding horses, especially those travelling internationally. Strict hygiene, including proper disinfection of equipment and adherence to quarantine protocols, are key to controlling the spread of CEM.

Contagious Equine Metritis

Contagious Equine Metritis is venereal disease that can be transmitted through natural breeding, artificial insemination, or contaminated equipment.

The bacterium Taylorella equigenitalis is a gram-negative, rod-shaped bacterium belonging to the family Alcaligenaceae. It is known for its ability to colonize the genital tract of horses, leading to the development of clinical and subclinical infections.

CEM is characterized by mucopurulent vaginal discharge, endometritis (inflammation of the uterine lining), and, in some cases, infertility. CEM can result in prolonged estrous cycles and difficulties in becoming pregnant.

Infected mares can also transmit the bacterium to stallions during breeding, leading to the spread of the disease. Stallions can carry the bacterium in their reproductive tracts without showing clinical signs, making them notable carriers.

Although CEM is not life-threatening, it can cause significant economic losses from reduced breeding and costs associated with testing and treatment.

History of the Disease

The first recognized outbreak of CEM occurred in the United Kingdom in 1977. [1] Estimates suggest this outbreak cost the Thoroughbred industry between $20 – 30 million. [1] This led to a massive investigation into the disease, resulting in identification of the bacteria in 29 countries. [1]

In 1978, CEM was first identified in the United States, resulting in significant economic consequences with estimated costs of $13.5 million to resolve. [1] This outbreak arose from the import of two French stallions who were carriers of the disease. [2]

Small-scale outbreaks of CEM within the United States continued until 2008 when a widespread outbreak occurred. [2] This outbreak required extensive investigation to trace the infection source and horses that were potentially infected, with testing and treatment costs amounting to several million dollars. [1]

The first test-positive stallion lived on a large breeding farm that stood 22 stallions. [2] Through tracing, federal officials identified 28 carrier animals and 977 potentially exposed stallions and mares. [2] The horses resided in 48 different states and spanned 11 different breeds, highlighting the extensive reach of this outbreak. [2]

Many countries are currently CEM-free, including Canada, the United States, Australia, and the United Kingdom. However, testing protocols for stallions and mares imported into these countries are imperfect, which has led to outbreaks of CEM in the past.

Currently, researchers are investigating the role of imported embryos and semen as a source of potential CEM outbreaks. [3]