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The state’s first vesicular stomatitis cases of 2015 have been detected in horses, and Colorado State University’s Veterinary Diagnostic Laboratories have gained special certification to test for the highly contagious virus, which causes painful sores in animals’ mouths and forces mandatory quarantines.
Flies and midges are the main way the virus is spread; it is also spread through horse-to-horse contact and through indirect contact, as when tie-outs, trailers and grooming or feeding equipment used with an infected horse are later used with a healthy horse. CSU veterinarians join the State Veterinarian’s Office in urging horse owners to practice strict fly control and infection control while on the road at horse shows, fairs and rodeos to limit the spread of VS.
Horses on five properties in Montrose County, three in Delta County and one in Montezuma County have tested positive for vesicular stomatitis this year and have been placed under quarantine, state officials announced July 9.
Timely test results
On July 2, the U.S. Department of Agriculture, through the National Animal Health Laboratory Network, activated CSU’s Veterinary Diagnostic Laboratories as a testing site for the disease. The CSU labs are expected to provide a more timely response on local test results; historically samples have been sent to a lab in Iowa.
“We won’t have to ship samples out of state, we’ll be able to do the testing here,” said VDL Director Barbara Powers, adding that the turnaround time for test results could be cut from a few days to a single day. “We’re really excited about this opportunity.”
To gain authorization as a testing site, the CSU labs had to demonstrate that they could properly perform a new polymerase chain reaction test for VS that the USDA issued earlier this year.
In previous years, field vets from the Colorado Department of Agriculture or USDA were required to perform the disease investigations, because VS in horses was categorized as a “foreign animal disease.” But a new categorization allows local veterinarians to conduct initial investigations, collect samples, and collaborate with animal health officials regarding movement restrictions and quarantines.
As a result, quarantines may be lifted as soon as 14 days after the onset of clinical signs of the last affected horse on a property.
“Science has shown that the transmission of the virus is for a brief period of time after the initial clinical signs of VS,” said State Veterinarian Keith Roehr. “Our goal is to appropriately adjust our response to this disease to reduce the negative economic impact to the equine community.”
Colorado is the fourth state in the country to have confirmed cases of vesicular stomatitis this year, joining Arizona, New Mexico and Texas. Last year, a VS outbreak prompted 556 livestock investigations in Colorado and 370 quarantines.
“The primary spread of VS is thought to occur through insect vectors; the horses involved in these cases have no history of travel,” Roehr said of the state’s first VS cases of 2015. “Vesicular stomatitis can be painful for animals and costly to their owners."
The main symptoms of vesicular stomatitis virus are blisters, sores, and sloughing of skin in the mouth, on the tongue, on the muzzle and ears, and above the hooves. Lameness and weight loss may also occur.
There are no USDA-approved vaccines for VS. While rare, VS can occur in humans, usually among those who handle infected animals. VS in humans can cause flu-like symptoms and only rarely includes lesions or blisters.
In addition to horses, species susceptible to VS include mules, cattle, bison, sheep, goats, pigs and camelids. Livestock with clinical signs of VS are isolated until they are determined to be of no further threat for disease spread.
Tips for horse owners
• Strict fly control is important to avoid spreading the disease, so horse owners are advised to apply insect repellent daily (especially to the animal’s face and ears).
• Use barriers, such as fly sheets and face masks, and shelter horses during peak times for biting attacks, typically mid-morning and in the evening, ending at dusk. Biting intensifies at the onset of storms and may persist all day when overcast conditions occur.
• Feeding equipment, cleaning tools and health care equipment should not be transferred between animals.
• At shows, rodeos and fairs, horses should be kept separate from others and not tied where others have been tied. Keep your hands off other horses, and avoid letting other people handle your horse. Disinfect all show and travel equipment, including trailer, before and after use. Frequently wash hands and use hand sanitizer. Segregate your traveling horse from others for a week after returning home; monitor your horse for any signs of infection or illness during this time.
• Any non-equine livestock showing signs of VS still need to be investigated by a state or federal foreign animal disease diagnostician. Livestock owners who suspect an animal may have VS should immediately contact their local veterinarian. Any vesicular disease of non-equine livestock should be reported to the State Veterinarian’s Office in Colorado at 303-869-9130.
• Colorado veterinarians and livestock owners should contact the state of destination when moving livestock between states to ensure that all import requirements are met. A list of contact information for all state veterinarians’ offices is available at http://www.colorado.gov/aganimals.