Now that Old Man Winter has more than taken up residence across the West and Southwest, the U.S. Department of Agriculture's Animal and Plant Health Inspection Service is waving the all clear flag on what has been termed the worst outbreak of Vesicular stomatitis virus (VSV) in over a decade.

Dr. John Clifford, deputy administrator for Animal and Plant Health Inspection Service (APHIS), notified the World Organization for Animal Health (OIE) on Dec. 29 that the 2014 VS outbreak in the United States is officially over.

"All premises previously under quarantine in Nebraska and Texas have been released," he said. "All the remaining premises under quarantine in Colorado will be released 21 days after lesions of all affected animals on the premises have healed. This VSV event is considered closed," Clifford informed the OIE last week.

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While a more serious outbreak of VS outbreak in Texas was officially all but over in

October, according to the Texas Animal Health Commission (TAHC), lingering cases in Texas and stubborn resilience of the disease, especially in Colorado, kept animal health concerns elevated and kept some restrictions in the movement of horses and livestock in Colorado in place. A late season case of VS was also confirmed at one premise in Nebraska.

Tough year for VS

Vesicular stomatitis, an insect-borne livestock disease that struck Texas and Colorado particularly hard this year, occurs every few years, mostly in Western states. The virus primarily affects horses and cattle. VS also can affect sheep, goats, llamas, alpacas, swine, deer and some other species, including bobcats, raccoons and monkeys.

Humans can become infected with the disease when handling affected animals, but this is a rare event. Animals infected with the disease can usually be clear of the virus and its lesions within a period of 21 days or less. The virus is not fatal to infected animals, but because the disease carries the same type of symptoms as the more dreaded foot and mouth disease, animal health officials remain on high alert each time VS surfaces.

In the past decade, the Southwestern and Western United States have experienced a number of VS outbreaks, which usually occur during the warmer months, often along waterways. In some years, only a few premises in a single state have been affected. In other years multiple states and many premises have been involved.

Josie Traub-Dargatz, DVM, professor of equine medicine at Colorado State University and an equine commodity specialist for USDA-APHIS-VS Center for Epidemiology and Animal Health, reports no one protocol exists for managing diseases like VS from state to state, but says "the No. 1 goal is to protect the health of the equine and livestock population." This includes quarantining an entire facility that has confirmed cases of infectious disease.

To date, a total of 433 VSV-positive premises (New Jersey serotype) have been confirmed in three U.S. states: Colorado (370 premises), Nebraska (one premises), and Texas (62 premises). There have been 17 counties affected in Colorado (Adams, Arapahoe, Boulder, Broomfield, Douglas, Elbert, El Paso, Fremont, Huerfano, Jefferson, Larimer, Logan, Morgan, Otero, Pueblo, Sedgwick, and Weld Counties); one county affected in Nebraska (Wheeler County); and 13 counties affected in Texas (Bastrop, Falls, Guadalupe, Hidalgo, Jim Wells, Kinney, Lee, McLennan, Nueces, San Patricio, Travis, Val Verde, and Williamson Counties).

Of the 433 total VSV-positive premises, 403 have been positive equine premises, 27 have been positive bovine premises, and 3 premises have had both cattle and horses positive.

Overall, a total of over 4,400 horses were suspect of VSV infection and over 9,000 bovine were suspect in 2014. TAHC officials credit proper animal health awareness and response for keeping the outbreak at manageable levels.

Clifford told the OIE in the 28th and final report on the outbreak, dated December 29, that a comprehensive epidemiological investigation into the outbreak has been completed.