International Equine Disease Report, First Quarter 2009

The International Collating Centre, Newmarket, England, and other sources reported the following disease outbreaks:

Contagious equine metritis (CEM) was confirmed on four premises in France. In December 2008, four stallions (three Quarter Horses, one American Paint) were identified as CEM positive in Kentucky. The stallions had stood the 2008 breeding season along with 18 other stallions at a facility in Kentucky specializing in semen collection for artificial insemination (AI). Stallions on this premise had relocated on numerous occasions throughout several states since 2004.

As of May 26, 2009, 20 stallions and one gelding have been confirmed by USDA's National Veterinary Services Laboratories (NVSL) as positive for Taylorella equigenitalis, the causative organism of CEM. Five mares were also confirmed positive for CEM. The positive stallions were distributed in Georgia (1), Illinois (3), Indiana (3), Kentucky (4), Texas (1), Wisconsin (8), and the one gelding in Iowa. Mares were distributed in California (2), Illinois (2), and Wisconsin (1).

All positive stallions have been or are in the process of being treated with antibiotics, test bred to two mares, and retested for CEM. Positive mares also are being treated and retested. Nine of the positive stallions (four in Kentucky, three in Indiana, one in Texas, and one in Wisconsin) have completed treatment and retesting and are now CEM negative.

Tracing of stallions and mares has so far identified 939 animals (272 stallions, 667 mares) in 48 states as infected or exposed to CEM by AI, natural cover, or location on the same premises. An exposed horse is one that was bred, either naturally or via AI, to a horse positive for CEM or one epidemiologically linked to a positive horse as determined by state and federal animal health officials.

Due to extensive and frequent interstate movement of stallions between breeding seasons prior to the detection of the outbreak, it has not been possible to identify the outbreak's source. In addition to transmission by AI and natural mating, lateral (on-farm) transmission between stallions as a result of communal use of contaminated equipment played a significant role in dissemination of CEM.

NVSL has completed antibiotic sensitivity testing of CEM isolates from 17 stallions, two test-positive mares, and the five infected mares. They all possess the same antibiotic profile and are resistant to streptomycin.

The last outbreak of CEM in the United States occurred in 2006 among three Lipizzaner stallions imported to Wisconsin from Eastern Europe.

Respiratory disease attributable to equine herpesvirus (EHV) was reported from Turkey on a single premise and to EHV-4 on two premises in the United Kingdom. Abortion attributable to EHV-1 was reported among three non-Thoroughbred mares on three premises in France; six Thoroughbred mares on one premise in Germany; two mares on two premises in Ireland plus a foal that died; and 23 mares on 11 premises in Japan. The United Kingdom reported EHV-1 abortions involving multiple cases on two premises and single cases on five premises. Twelve cases on 11 premises involving Thoroughbred mares were reported from central Kentucky. One case attributable to EH V-4 was reported from the United Kingdom.

One case of paralysis attributable to EHV-1 was reported from France. Coital exanthema (EHV-3) was diagnosed in a stallion from Ireland and a stallion and a donkey in the United Kingdom.

France reported a single case of Equine infectious anemia (EIA). Equine influenza was reported among Standardbred horses on eight premises in France and a single premise in the United Kingdom.

Turkey reported a mild clinical outbreak of leptospirosis on one premise and a mild single case of equine piroplasmosis (EP). In the United States, the last premises to house an infected EP horse involved in the 2008 outbreak in Florida was released from state quarantine on March 12. All positive animals had been removed; in-contact horses tested serologically negative 60 days later. The premises involved underwent tick surveillance; no EP-positive ticks were found.

Turkey reported a single case of rabies. Strangles was reported from Chile, France, Ireland, Switzerland, Turkey, and the United Kingdom.

This is an excerpt from Equine Disease Quarterly, funded by underwriters at Lloyd's, London, brokers, and their Kentucky agents.

Disclaimer: Seek the advice of a qualified veterinarian before proceeding with any diagnosis, treatment, or therapy.