contagious equine metritis

Question 1

what is CEM?

Answer 1

An emergent bacterial disease that is
restricted to the equine reproductive tract.
►Caused by a previously undescribed
organism, Taylorella equigenitalis.

Question 2

international concerns of CEM

Answer 2

Potential to cause widespread short-term
infertility in mares.
►Frequency of occurrence of the carrier
state in stallions and mares.

Question 3

exposure to CEM in the stallion

Answer 3

T. equigenitalis exists as a commensal
colonising the external genitalia of the stallion.
►It causes neither clinical signs nor any
evidence of a local or systemic inflammatory response in the carrier stallion.

Question 4

clinical features in barren mares

Answer 4

Symptomatic infection
Mare “breaks dirty,” usually 2 - 13 days after being
bred.
►Variable inflammation of endometrium, cervix and
vagina.
►Thin, greyish - white vaginal discharge. ►Dried discharge in the perineal area, inside of the
thighs and on the tail.
►No evidence of systemic illness.
asymptomatic infection
mares return to estrus after a shortened diestrus period

Question 5

clinical features of pregnant mares

Answer 5

symptomatic infection
Variable vaginal discharge throughout
pregnancy.
►Low-grade placentitis. ►Abortion – very rare.
asymptomatic infection
Mare is inapparently infected with
T. equigenitalis.

Question 6

characteristics of t. equigenitalis

Answer 6

Gram-negative, non-acid fast coccobacillus /
bacillus.
►Microaerophilic – fastidious growth requirements. ►Resistant or sensitive to streptomycin. ►Sensitive to a wide range of antimicrobials. ►Cytochrome oxidase, catalase, alkaline
phosphatase positive.
►Non-fermentative and non-proteolytic.

Question 7

modes of transmission

Answer 7

Direct venereal contact (natural service).
►A.I. with extended semen and potentially with
cryopreserved (frozen) semen.
►Indirect venereal contact:
– contaminated fomites, e.g. speculum, forceps, tail bandages, etc.,
– poor hygiene practices in the breeding shed, stallion semen collection centers,
– contaminated teaser stallion
Trans-placental infection of the fetus.
►Contact of foal with infected placenta and / or
clitoral area of mare at time of foaling.
►Exposure of neonatal foal to contaminated
fomites, e.g. bedding / pasture soiled with infective vaginal discharge.
►Practice of washing external genitalia of colts in
training / breeding stallions.

Question 8

CEM carrier state (general)

Answer 8

Readily established in the stallion. ►Can occur in both barren and pregnant
mares.
►Congenitally acquired carrier state can
occur in colt and filly foals.
►Likelihood of persistence also in the
gelded male.

Question 9

carrier state in the mare

Answer 9

ariable frequency – can be as high as 20 - 25%. ►Variable duration – weeks, months or years. ►Two types of carriers – clitoral and uterine. ►Majority of carriers – clitoral carriers. ►The clitoral sinuses and fossa are the sites of
persistence of T. equigenitalis.
►The placenta can be infected in pregnant carrier
mares.
►Carrier mares are constant / intermittent shedders of
T. equigenitalis.
►Carrier mares are usually negative for serum
antibodies to T. equigenitalis.

Question 10

carrier state in the stallion

Answer 10

Frequency of occurrence variable. ►Carrier state can persist for years. ►T. equigenitalis harbored as a surface
contaminant in the urethral fossa, sinus, terminal urethra and sheath.
►Carrier stallions transmit T. equigenitalis to most
of the mares to which they are bred.
►Carrier stallions are negative for serum
antibodies to T. equigenitalis.

Question 11

diagnosis of CEM in mares

Answer 11

Cannot be based on clinical grounds alone -
similarity to infections caused by other venereal pathogens, e.g., S. zooepidemicus, K. pneumoniae, Ps. aeruginosa.
►Culture of T. equigenitalis from endometrial /
cervical / clitoral swabs or vaginal exudate.
►Detection of T. equigenitalis nucleic acid by PCR. ►Cytological examination of endometrial smears. ►Serological examination (CFT) of serum taken
21 - 45 days after breeding.

Question 12

diagnosis of CEM in stallions

Answer 12

Culture of T. equigenitalis from urethral fossa,
urethral sinus (diverticulum), distal urethra, external surface penis / sheath.
►Detection of T. equigenitalis nucleic acid by
PCR.
►Test breeding to 2 mares – subsequently
checked bacteriologically and serologically for evidence of T. equigenitalis infection.

Question 13

sampling sites/precautions for stallions

Answer 13

Penis should be erect at time of sampling to
optimise swabbing sites of persistence.
►No antiseptics / disinfectants should be used in
washing the external genitalia prior to swabbing.
►Swabs should not be taken for at least 1 week
(systemic) or 3 wks (local) after completion of treatment for CEM.

Question 14

handling swabs for CEM

Answer 14

Swabs must be placed immediately in an
antibiotic-free transport medium (Amie’s medium with charcoal).
►Samples should preferably be kept refrigerated
in transit to the laboratory.
►Optimally, swabs should be plated out within 24
hours and no more than 48 hours of collection

Question 15

CEM prevention

Answer 15

CEM should be made notifiable or, if non-notifiable, a
reportable disease.
►Prompt diagnosis of CEM by approved laboratories.
►Improved standards of hygiene and management on
breeding farms and stallion semen collection centers.
►Greater use of disposable / sterile equipment and
materials.
►Comprehensive screening of stallion and mare
populations to detect carrier animals.
►Stallions / mares positive for T. equigenitalis not bred
until successfully treated to eliminate the bacterium.

Question 16

prevention of CEM in countries free of the disease

Answer 16

Pre-export screening of stallions / mares or
semen for presence of T. equigenitalis.
►Post-import quarantine and testing of stallions
and mares, especially non-TB’s, from known CEM affected countries.
►Screening of stallion should include both
bacteriological / PCR examination and test breeding to 2 susceptible mares.
►Screening of semen to confirm its freedom from T. equigenitalis.