Contagious Equine Metritis Outbreak – Overview and Update

Introduction

Contagious Equine Metritis (CEM) is a transmissible, exotic venereal disease in horses caused by a bacteria Taylorella equigenitalis. A CEM infection usually results in infertility in mares and, on rare occasions, can cause mares to spontaneously abort.  Infected stallions exhibit no clinical signs.   Stallions and mares can become chronic carriers of CEM and be sources of infection for future outbreaks. The transmission rate is high and naturally occurs by mating, but contaminated instruments and equipment may be an indirect source of infecting horses. The bacteria can also be spread via semen collected for artificial insemination.  CEM can be treated with disinfectants and antibiotics.

CEM is a serious disease because it is highly contagious. When coupled with the fact that mares can be bred only during certain seasons, CEM can have a devastating effect on equine reproductive efficiency. Should CEM become established in the United States, the horse industry would suffer great economic losses.

The first cases of CEM in the United States were diagnosed on March 9, 1978, on thoroughbred farms in central Kentucky. In April of the following year, an outbreak occurred in Missouri. The disease was rapidly eradicated from both States and had not subsequently been found in the U.S. until 2008.

Investigation

The CEM investigation, which has been underway since December 2008, appears to be in its final stages.  The investigation began when a Quarter Horse stallion on a Kentucky farm tested positive for CEM during routine testing for an international semen shipment.  CEM is a foreign animal disease that is not endemic to the United States.

The most recent OIE (World Organization for Animal Health) report was published on December 18, 2009 and included the following information:

As of November 2009, four of the eight States that have had positive horses (Georgia, Indiana, Iowa, and Kentucky) completed testing and treatment protocols for all known positive and exposed horses and are currently considered free of CEM.

A comprehensive epidemiological investigation continues to be conducted by individual State Departments of Agriculture and United States Department of Agriculture (USDA) officials.  The source of the CEM outbreak has not yet been identified; the epidemiologic investigation continues to pursue all available information relative to determining the origin of this outbreak, but no conclusions have been determined.

The USDA provided funding for diagnostic tests and sample shipping costs for the testing of exposed horses directly linked to the investigation.  The estimated cost of veterinary services for testing and treating ranged from $1,500 to $5,000 per animal, depending on the state.  An exposed horse was considered to be one that was bred to a CEM-positive horse, either naturally or via artificial insemination, or one that is otherwise epidemiologically linked to a CEM-positive horse, as determined by State and Federal animal health officials.

CEM continues to be an area of great concern, and it was a highly discussed topic during the December 2009 American Association of Equine Practitioners (AAEP) annual convention in Las Vegas.  CEM has far reaching health, trade, and economic implications for the entire U.S. equine industry.

USDA Voluntary Testing Program

In February 2010, the USDA implemented a voluntary program to test up to 3,000 breeding stallions for Taylorella equigenitalis, the bacteria that causes CEM.  APHIS implemented this program in an effort to document that the presence of CEM is very low, if it is present at all, and to reduce or remove current testing requirements for horses and semen exported from the United States.

This voluntary program is in response to the on-going CEM incident involving approximately 991 horses found in 48 states.  Hawaii and Rhode Island are the only States in which an exposed or positive horse has not been found.

Owners will be able to provide their stallions for testing on a voluntary basis.  APHIS will pay for the diagnostic testing, but not for sample collection costs or test mares.  If a stallion is found positive, the horse will be quarantined, and APHIS will pay all costs and procedures related to tracing, testing, and treatment (including practitioner fees) for horses exposed to a positive stallion.

Stallion owners or accredited equine practitioners interested in participating in this program should contact a VS area office or their State animal health official’s office.

AHC Position

The AHC supports the continued discussion and evaluation of how to maintain a CEM free status in the U.S.  The AHC will continue to work with the USDA and the states to address the problem of imported CEM positive equines and semen and in helping the horse industry learn how to manage these animals in a way that minimizes their risk of exposure.