According to the Federal Register, the daily journal of the United States government, effective March 13, 2013, a final rule regarding the importation of horses from countries affected with contagious equine metritis (CEM) by incorporating an additional certification requirement for imported horses 731 days of age or less and adding new testing protocols for test mares and imported stallions and mares more than 731 days of age will go into effect.
Preventing CEM in US horses
A final rule regarding the importation of horses from countries affected with contagious equine metritis goes into effect on March 13, 2013.
This document revises certain CEM-testing requirements for imported stallions and mares, and for test mares, that were amended in the interim rule. The interim rule was necessary to provide additional safeguards against the introduction of CEM through the importation of affected horses.
Imported mares that test positive for CEM are not returned to their country of origin. Rather, imported mares that test positive for CEM are treated and retested.
Mares over 731 days of age are accompanied at the time of importation by an import health certificate, but the health certificate does not include the breeding status of the mare. Our expectation, however, is that the owner, importer, or agent will tell the veterinarian in the United States or the exporting country the breeding status of the mare and that the veterinarian will test accordingly.
We recommend that accredited veterinarians performing CEM testing at the post-entry quarantine facility examine mares by rectal palpation or ultrasound to determine the breeding status as part of their standard operating procedures.
Previously, stallions were required to be cultured for CEM and test bred to two test mares after negative results from the cultures are obtained. The March 2011 interim rule amended that requirement to require that, prior to test breeding, three sets of cultures be collected from imported stallions rather than one set. The interim rule allowed test breeding to take place only after the first two sets of cultures had yielded negative results.
One set of cultures is to be collected from the stallion prior to breeding with negative results, consistent with our previous regulations. A stallion may be released from State quarantine only if all cultures and tests of specimens from the mares used for test breeding are negative for CEM and all cultures performed on specimens taken from the stallion are negative for CEM.
If any culture or test is positive for CEM, the stallion would be treated for CEM as described in § 93.301(e)(3)(i)(A) and retested by being test bred to two mares no less than 21 days after the last day of treatment. Given the interim rule's enhancements to the testing process for test mares, we believe that requiring one set of cultures to be taken from imported stallions will be sufficient to prevent the introduction of CEM.
The regulations exempts recently castrated stallions (geldings) from CEM-related importation requirements. Several commenters suggested that geldings be tested and treated for CEM, as recommended by the 2007 CEM Program Review. A concern was expressed that recently castrated stallions could maintain stallion-like behavior and attempt and achieve intromission with mares in estrus, thereby creating a risk for CEM transmission.
Geldings will not be used for breeding purposes, which is where the risk of CEM transmission is greatest. We do not believe that the possibility of incidental contact between a gelding and an in-season mare warrants the additional time and expense associated with CEM testing and treatment for geldings.
The regulations also exempt weanlings or yearlings whose age is certified on the import health certificate. One commenter suggested that newborn colts from CEM-infected mares should be tested and treated for CEM. In addition, the commenter suggested that all weanlings and yearlings be tested and treated for CEM as there is evidence that non-venereal transmission is possible.
We acknowledge that it is possible for a foal to be born with CEM if the dam was infected; however, the risk of non-venereal transmission of CEM is low and does not justify testing and treating imported weanlings and yearlings that have not been bred.