A very Important message from the American Horse Council


To: AHC Organizations

Date: June 11, 2009 




CEM Outbreak Update


In December 2008, the Kentucky Department of Agriculture announced that a quarter horse stallion tested positive for Contagious Equine Metritis (CEM) during routine testing for international semen shipment. Since this discovery a full epidemiological investigation has been underway to locate, test and quarantine any potentially exposed horses. An exposed horse is one that was bred to a positive horse, either naturally or via artificial insemination, or one that is otherwise epidemiologically linked to a positive horse, as determined by State and Federal animal health officials. 

Currently, a total of 21 stallions, including one that is now a gelding, have been confirmed as positive for CEM. Additionally, a total of 5 mares have been found positive for CEM. In addition to the 21 positive stallions and 5 positive mares, locations have been confirmed for 944 additional horses exposed to CEM. The total 970 horses are located in 48 States. The source of the outbreak has yet to be determined, but the investigation continues to pursue all available information in order to determine the origin of the outbreak. 

There are 276 exposed or positive stallions in 29 States and 694 exposed or positive mares in 46 States. The only states without any positive or exposed horses are Hawaii and Rhode Island. The 21 positive stallions were found in seven States: one in Georgia, three in Illinois, three in Indiana, one in Iowa, four in Kentucky, one in Texas, and eight in Wisconsin. The five positive mares were found in three States: two in California, two in Illinois, and one in Wisconsin. All positive horses, and all exposed horses that have been located, are currently under quarantine, and testing and treatment protocols are under way.

Of the 276 stallions, 76 have now completed their entire testing and treatment protocol and are now negative for CEM. Of the 76 that are now negative, 67 were exposed stallions and 9 were stallions that had previously tested positive. Those nine stallions, four from Kentucky, three from Indiana, one from Texas, and one from Wisconsin, are now free of CEM after being treated and re-tested. Another 106 exposed stallions are negative on their initial sampling cultures but have additional testing requirements to complete before being declared CEM free. Of the 694 mares, a total of 478 have completed testing and treatment and are negative for CEM; that total includes one formerly positive California mare that has completed her treatment and testing protocol and is now negative.

All four of the positive Kentucky stallions were on the central Kentucky premises during the 2008 breeding season. The Texas and Indiana stallions also spent time on the Kentucky premises during 2008. The positive Wisconsin stallions were not in Kentucky, but four of them were co-located during at least one breeding season in Wisconsin with a positive stallion that was on the Kentucky premises in 2008. The fifth, sixth, seventh, and eighth Wisconsin stallions all spent time at the same breeding facility used by the fourth positive Wisconsin stallion, by the three positive Illinois stallions, and by the Iowa stallion. The Iowa stallion has since been gelded. The positive Georgia stallion was co-located with three positive Wisconsin stallions in 2008.

The positive Wisconsin mare was bred by the second positive stallion in Wisconsin. Each of the positive mares in Illinois and in California was bred by artificial insemination (AI) in 2008 using semen from a positive stallion. Both California mares were exposed by AI to the first positive stallion in Wisconsin and the first Illinois mare was exposed to a positive stallion now in Indiana. The second positive mare in Illinois was exposed by AI in 2008 to the second positive Illinois stallion.

CEM Outbreak Summary:


# Exposed Horses

# Positive Horses

Total Involved

# Completed Testing & Treatment

# States Involved





478 (incl. 1 positive)






76 (incl. 9 positives)










AHC Letter to Agriculture Secretary Vilsack


The American Horse Council expressed concern over the current CEM outbreak in a letter to the U.S. Secretary of Agriculture Tom Vilsack. The AHC states concerns over the current CEM occurrence and investigation, and the need to find the source of this outbreak, complete the investigation, eradicate the disease and return to U.S. to a CEM free country status. The letter to Secretary Vilsack can be found on the AHC website – www.horsecouncil.org. -Click here to download the letter from the AHC



Restrictions on U.S. Horses Exported to Mexico

Since the first detection of CEM in a stallion in Kentucky, Mexico implemented export restrictions by prohibiting any horses from the state of Kentucky. Since then, USDA and Mexico have been in negotiations over the KY prohibition and additional restrictions on exporting U.S. horses into Mexico. The U.S. and Mexico have reached an agreement on export restrictions related to the current CEM outbreak. 

The restrictions divide states into two categories: those that have had a diagnosed CEM positive horse and those that have not had a confirmed positive. For states that have a diagnosed positive, a series of three sets of cultures with negative results for CEM are required before the horse will be allowed entry into Mexico. For states that have not had a diagnosed positive horse, one set of cultures with negative results is required. This currently applies to both horses that are being exported temporarily as well as permanently.

USDA continues to negotiate with Mexico on these restrictions, particularly for horses being exported temporarily and to determine what point a state becomes CEM free. The protocols for exportation to Mexico can be found on the USDA website: 


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