Etiology

Contagious equine metritis (CEM) was first described in the United Kingdom in 1977 and the causative agent of it was initially named Haemophilus equigenitalis and subsequently included in a new genus: Taylorella. It is a contagious venereal disease that affects the equids characterized by endometritis, cervicitis, vaginitis, mucopurulent vaginal discharge and temporary infertility in females, being males asymptomatic carriers. T. equigenitalis is a Gram-negative coccobacillus, catalase, phosphatase and positive oxidase often pleomorphic. It is a Proteobacteria of the order Burkholderiales and family Alcaligenaceae.

Epidemiology

It is a disease of worldwide distribution. Infection occurs through direct contact during mating or indirectly through fomites (e.g. obstetric material). Males are asymptomatic carriers. In the case of females, clinical signs of variable duration accompanied by temporary infertility occurs, once this phase is over, they may remain as asymptomatic carriers. Foals born to carrier mothers may become carriers.

Pathogeny

In mares, it produces an intense neutrophilic endometritis that resolves with a mononuclear neutrophilic endometrial response. Once the clinical phase is over, the bacteria may persist confined to the sinus and clitoral fossa. In the males, no clinical signs occur, being the main sites of colonization the fossa and urethral sinus, urethra and prepuce.

Clinical signs

The characteristic clinical signs that affect females are endometritis, cervicitis, vaginitis, mucopurulent vaginal discharge and temporary infertility. In case of pregnancy, early abortions may occur.

Diagnosis

The official method of diagnosis is isolation by culture from swabs. Samples should be taken from urethral fossa and urethral sinus, urethra and prepuce in males and from clitoral sinus and clitoral fossa in females, transported in Amies medium with charcoal and under refrigeration conditions. The culture is carried out in specific media that allows the growth of this bacterium, inhibiting the growth of commensal bacteria containing trimethoprim, clindamycin and amphotericin B. The chocolate agar plates are cultured at 37ºC with a concentration of 5-10% of CO2, during a minimum period of 7 days. The colonies are up to 2-3mm, soft, full edge and yellow / greyish colour.
>In addition to the official method by culture, other techniques have been developed such as real-time PCR that allow detecting the DNA of the bacteria from swabs taken from the places mentioned above. This technique offers a sensitivity equal or superior to that obtained with culture with the advantage that it requires less time.
Complement fixation can be used as a serological method for the detection of recently infected females, although it does not allow detecting chronically infected females or carrier stallions.

Treatment

Infected animals can be treated by washing with chlorhexidine and applying ointments with 0.2% nitrofurazone. Diagnostic tests must be repeated 21 days after the end of treatment. In case of not responding to the treatment described above, a combination of systemic treatment with trimethoprim-sulfamethoxazole and a topical treatment by washing the external genitalia and the application of cream with 1% silver sulfadiazine can be used.

Prevention and control

Contagious equine metritis is included in List B of the OIE, its notification being mandatory in case of obtaining positive results in the control tests performed on equids
The control method consists of taking samples prior to the start of the reproductive season to know the status of the animal and improving hygienic measures to prevent the spread of infection among animals such as the use of disposable gloves for each animal and disinfection and sterilization of obstetric material.

Public Health Considerations

There is no evidence that T. equigenitalis can affect humans.