Journal of animal science2010; 89(5); 1552-1560; doi: 10.2527/jas.2010-3368

Horse species symposium: contagious equine metritis: an insidious threat to the horse breeding industry in the United States.

Timoney, PJ

Abstract: Contagious equine metritis (CEM) has given rise to international concern since it was first recognized as a novel venereal disease of equids in 1977 and the etiologic agent was identified as a previously undescribed bacterium, Taylorella equigenitalis. Horse industry concerns over CEM centered on the ease with which this bacterium could be disseminated, the significance of T. equigenitalis as a cause of short-term infertility in the mare, and the existence of the carrier state in the stallion and the mare. The first known outbreak of CEM in the United States was in Kentucky in 1978. The economic impact on the Thoroughbred industry in the state was substantial. Before 2008, additional small-scale outbreaks occurred in Missouri in 1979, Kentucky in 1982, and Wisconsin in 2006, nearly all attributed to the importation of carrier animals. On each occasion, appropriate measures were taken to eliminate the infection, resulting in the United States regaining its CEM-free status. With the exception of the 1978 occurrence in Kentucky, none of the subsequent outbreaks significantly affected the horse industry. That changed dramatically in 2008, however, after the discovery of a Quarter horse stallion in Kentucky that cultured positive. Subsequent investigations turned up 23 carrier stallions and 5 carrier mares belonging to 11 breeds and located in 8 states. Shipment of infective semen and indirect venereal contact in stallion collection centers through the use of contaminated fomites were major factors in the spread of T. equigenitalis. Trace-back investigations of some 1,005 exposed and carrier stallions and mares in 48 states have failed to identify the origin of this latest CEM event. Neither clinical evidence of CEM nor decreased pregnancy rates were reportedly a feature in infected or exposed mares. In light of these findings, there was some question of whether or not the considerable expense incurred in investigating the latest CEM occurrence was warranted. Regaining CEM-free status for the United States will present considerable challenges.

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Publication Date: 2010-10-01 PubMed ID: 20889687DOI: 10.2527/jas.2010-3368Google Scholar: Lookup

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The research article explores the impact of Contagious Equine Metritis (CEM), a sexually transmitted disease in horses, in the United States. It specifically highlights how the disease affects the horse-breeding industry.

Understanding Contagious Equine Metritis (CEM)

The paper talks about CEM, a venereal disease in equids first recognized in 1977.
The disease is caused by a previously unknown bacterium, Taylorella equigenitalis.
The disease is primarily spread through sexual contact, and can cause short-term infertility in infected mares.
Serious concerns within the equine industry arise from the fact that this bacterium can spread easily and the existence of a carrier state in both stallions and mares.

The History of CEM in the United States

CEM’s first known outbreak in the U.S. was recorded in 1978 in Kentucky. The disease had a significant economic impact on the Thoroughbred industry of the state.
Since then, small-scale outbreaks have been reported in 1979 in Missouri, 1982 in Kentucky again, and 2006 in Wisconsin. Most of these outbreaks were linked to the introduction of carrier animals into the U.S. horse population.
Through diligent efforts to eradicate the infection, the U.S. was able to regain its CEM-free status each time, until the 2008 outbreak.

The 2008 CEM Outbreak

In 2008, a Quarter horse stallion in Kentucky was found to be CEM-positive, marking the beginning of a significant outbreak.
A comprehensive investigation revealed 23 carrier stallions and 5 carrier mares belonging to 11 breeds across 8 states.
According to the paper’s findings, the spread of the bacterium was mainly attributed to transport of infected semen and indirect sexual contact in stallion collection centers due to contaminated equipment.
Locking down the origin of this outbreak proved unsuccessful, despite investigations of over 1,000 possibly exposed or carrier animals across 48 states.

Implications and Future Concerns

This research brings up questions regarding the cost-efficiency of investigating CEM occurrences, given that in most cases, infected or exposed mares did not show clinical evidence of the disease or decreased pregnancy rates.
The article concludes implying that regaining a CEM-free status for the U.S. is increasingly challenging, especially as the scale of the outbreak and the number of potentially exposed animals rise.

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Timoney PJ. (2010). Horse species symposium: contagious equine metritis: an insidious threat to the horse breeding industry in the United States. J Anim Sci, 89(5), 1552-1560. https://doi.org/10.2527/jas.2010-3368