Taylorella equigenitalis

Also known as: Contagious Equine Metritis — CEM

Introduction

Taylorella equigenitalis is the causal agent of contagious equine metritis (CEM). It is found exclusively in the genital tracts of stallions, mares and foals, specifically, in the urethral fossa of stallions and the clitoral fossa of mares.

The disease disrupts breeding programs on thouroughbred stud farms. Currently, the UK is free from contagious equine metritis.

Characteristics

The organism is a short, non-motile Gram-negative rod which is catalase, oxidase and phosphatase positive.

The bacterium is microaerophilic, grows slowly, and is fastidious as it requires chocolate agar and 5-10% carbon dioxide for growth.

It does not grow on MacConkey.

Pathogenesis and Pathogenicity

Transmission occurs during coitus or via contaminated instruments. The seminal fluid of stallions is contaminated with T. equigenitalis from the urethral fossa, and deposition in the uterus is required for infection to establish. The bacteria replicate in the uterus and cause acute endometritis. There is initial influx of mononuclear cells and plasma cells, followed by neutrophils, which cause a mucopurulent discharge. The acute endometrial changes only last a few days.

Clinical Infections

Contagious equine metritis is a highly contagious venereal disease of Thorougbred horses.

Infected stallions and mares are a reservoir of infection, and stallions and some mares are asymptomatic.

Most mares experience mucopurulent vulval discharge and temporary infertility after service with a carrier stallion. Inflammation of the uterus hinders implantation, the discharge may continue for 2 weeks, and mares may remain infertile for several weeks.

Mares may recover without treatment but 25% become carriers and re-infection can occur.

Foals become infected in utero or during parturition and may be source of infection for other horses.

Diagnosis

Specimens required for bacteriology include:

Mares: swabs from the clitoral fossa and sinuses and endometrium during oestrus

Fillies: swabs from the clitoral fossa

Colts: swabs from the penile sheath and tip of penis

Stallions: swabs from the urethra, urethral fossa, penile sheath and pre-ejaculatory fluid

Swabs should be placed in a charcoal-containing transport medium.

The organism can be isolated on chocolate agar with amphotericin B, crystal violet and streptomycin.

The colonies appear as small, smooth and yellow-grey.

Other diagnostic tests include:

Slide agglutination test

Fluorescent antibody test

Latex agglutination

PCR

Serology, but it only detects active infection

Treatment and Control

The external genitalia, including the clitoral fossa of mares and stallions should be washed with 2% chlorhexidine combined with antimicrobials such as crystalline penicillin. A 2% nitrofurazone ointment can be packed into the clitoral fossa.

The uterus of mares should be lavaged with a penicillin-containing solution daily for 5-7 days.

Persistently-infected mares may benefit from ablation of the clitoral sinuses.

CEM is a notifiable disease in the UK. Carrier animals and clinical infections should be detected by laboratory testing, and breeding should be stopped if the disease is diagnosed on a stud farm. Hygiene rules should be strictly adhered to.

Recovered animals should be sampled to ensure they are free from disease.

Stallions may be test-mated to 2 maiden mares to detect the spread of infection.

Taylorella equigenitalis Learning Resources
Flashcards Test your knowledge using flashcard type questions	Equine Reproduction and Stud Medicine Q&A 14

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