California Strangles Outbreak; At Least 60 Horses Affected

A strangles outbreak has placed a boarding stable in northern Los Angeles County, Calif., under quarantine, and more than 60 horses at the farm remain under close observation. The outbreak of the highly contagious upper respiratory disease caused by the Streptococcus equi bacterium flared up at the stable in November 2004, and the L.A. County Department of Health Services (LADHS) Disease Control division began the stable lockdown the week of March 13.

"We were informed of the outbreak about four months into the situation," said Patrick Ryan, DVM, chief veterinarian for LADHS. "We've alerted most of (the horse owners in) north Los Angeles County regarding the outbreak, telling them they should continue to guard their horses against the disease." Only the infected stable was quarantined.

"The horses that are most at risk are the younger horses, two years old and younger, because they haven't usually been exposed. Previous exposure helps develop immunity," Ryan said. "Many times they have not even been vaccinated for strangles." How long a strangles vaccine confers immunity depends on many factors, and horse owners should consult with their veterinarian on how often they should vaccinate.  

Strangles is spread by inhalation or ingestion of S. equi found in the nasal discharge or pus from draining abscesses of infected animals. The bacteria can be spread by close contact, flies, contact with contaminated equipment, or even on the clothing of owners caring for infected horses. Not all infected horses become ill. Protect your horses by isolating new horse arrivals at your farm for two to four weeks before allowing them to mingle with your herd and also keep your horses' vaccinations current. Strict disinfection measures can help eliminate sources of infection if strangles hits your barn. For more information on strangles, see

Ryan and the LADHS became involved when one of the horse owners at the stable contacted the department. "Apparently their control efforts were not effective, and not all the horse owners were aware of what was going on," he said.  Horses had been moved on and off the premises before the implemented quarantine. Sixteen horses became clinically ill and one horse was sick for over a month (and eventually was euthanatized).

"Several changes in stable management have been made and the situation appears to be under control," said Ryan. He hoped to lift the quarantine before the first week of April. The name of the stable is not being released at this time.

About the Author

John V. Wood

John V. Wood is an Emmy Award-winning journalist, and now teaches his craft to high school students in North Carolina. Wood has been published in numerous national magazines/newspapersover his career, and published his first book in June 2010. Wood currently lives in Willow Spring, NC.

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