Stallions and Mares in Quarantine

Personnel

Because the CEM program is federally controlled, the care and culture procedures are performed by trained technicians and are not part of the teaching program at UC Davis.  If a horse needs medical care outside of the CEM testing, a staff veterinarian from the William R. Pritchard Veterinary Medical Teaching Hospital is called to evaluate the patient.

Photo of quarantine friesian

How do we test stallions for CEM?

Stallions carry the T. equigenitalis bacteria within their genitalia and do not show the systemic antibody response necessary to produce a positive blood test.  Because bacterial culture alone can produce false negatives, test breeding is used to substantiate the culture.  A stallion is bred to two mares known to be CEM-free.  Those mares are then tested for CEM.  The Center for Equine Health uses carefully selected mares that have been vaccinated against EVA for test breeding.  Stallions reside in quarantine typically for 33 to 38 days unless there are extenuating circumstances.  Treatment of stallions with antibiotics due to illness during the quarantine period will extend the testing process as mandated by the USDA, because systemic antibiotic administration impedes the culture process.

Day 1 – USDA protocol requires cultures of external genitalia (prepuce/urethra sinus, fossa glandis and distal urethra).  Cultures are generally finalized within 7 days of submission.

Day 8 – Once negative culture results are returned, the stallion is bred to two CEM-negative test mares.  The stallions and the test mares are handled by experienced personnel during breeding.

Days 8 to 12 – The penis and sheath are washed with Nolvasan scrub, and the penis is packed with antibiotic ointment.   The stallions are washed and treated for 5 days.

Days 11, 14 and 17 – Each test mare is cultured.

Day 24 – Test mare culture results are finalized.

Day 29 – Blood from the test mares is evaluated for CEM antibodies.  Test mares will have a positive result if exposed to T. equigenitalis.

Days 33 to 38 – Health testing requirements are finalized and the stallion is released from quarantine.

Photo of quarantine horse

How do we test mares for CEM?

To test mares for T. equigenitalis, USDA protocol requires a swab of the external genitalia and cervix for culture and a blood test.  Culture of the clitoral sinuses and fossa is done on Days 1, 5 and 8.  In addition, on Day 8 a cervical culture is also taken.  These swabs are sent in special transport media to laboratories approved by the USDA.  On Days 8 through 12, the mares are washed with 2% Nolvasan scrub and their external genitalia are packed with antibiotic ointment.

Treatment of mares with antibiotics due to illness during the quarantine period will extend the testing process as mandated by the USDA because systemic antibiotic administration impedes the culture process.