Colorado recovers from decade’s worst year for VS
Fence Post Editorial Director
VS quarantines during past decade
2014 (to date)
Colorado - 334
Nation - 396
Colorado - 2
Nation - 36
Colorado - 0
Nation - 2
Colorado - 0
Nation - 5
Colorado - 0
Nation - 13
Colorado - 100
Nation - 445
Colorado - 199
Nation - 294
Source: Animal and Plant Health Inspection Service, USDA
Warm weather is waning and so are cases of Vesicular Stomatitis, an insect-borne livestock disease that struck Colorado and Weld County in force this year.
Colder temperatures offer natural relief, killing off fly populations that place horses, cattle and other livestock at risk of infection.
However, Colorado will not see quarantines fully lifted until the winter’s first frost, said state veterinarian Keith Roehr.
“We have seen prolonged mild temperatures through October. There has been a reduction of cases but still an average of one to two new cases a day. That trend will likely continue until we get a good freeze,” Roehr said.
He anticipated full removal of the state’s 60 remaining quarantines, from 334 to date, by mid-November, before the winter livestock show season.
At the disease’s peak, Roehr said the state experienced 10 to 15 new cases a day. Although 2014 was not the first serious year for VS in Colorado, it stands out as the worst state outbreak in the past decade.
Early Colorado cases took the state by surprise, appearing first in northern counties rather than spreading upward from the south.
In the hardest hit areas — Boulder, Larimer and Weld — cases mostly continued to drop as affected livestock completed their four-to-six weeks of isolation. Of 90 quarantines established in Weld County this year, 7 remained as of Oct 22. In Boulder, the number had dropped from 76 to two, while Larimer had dropped from 84 to eight.
New instances have appeared mostly in Pueblo County, where the disease remains near its peak and continues to rise. As of Oct. 22, the county had 23 quarantines, up from 18 the week prior. Other new cases this week appeared in Adams, Larimer and Logan counties.
Combined, Boulder, Larimer and Weld counties bore the brunt of VS cases in Colorado and nationally, representing two-thirds of all quarantine cases nationwide in 2014.
In the past decade, the highest number of cases nationally came in 2005 with 445 quarantines established across nine states.
This year’s burden fell on just two states: Colorado with 334 quarantines to date and Texas with 62. The geographical distribution of the most recent outbreak set the year apart, causing questions as to how the disease skipped from central Texas to northeastern Colorado.
“Distribution and movement of the disease are, for the most part, random,” Roehr said, explaining the state does not know exactly how VS arrived in Colorado.
“Fly migration is the chief means of spread, and those flies do have a migration pattern from south to north. To see the disease move several hundred miles through migration of flies is typical.”
Although VS patterns are difficult to pinpoint, in past years the disease has spread through the southwest before appearing in Colorado, said Keith Maxey, livestock agent for CSU Extension-Weld.
“One of the really unusual things about it from past cases is that typically when there was an outbreak, it would start in southern states and then in summer months, as things warmed up, we would see it work itself up and you could almost track it up to Colorado and eventually Northern Colorado,” Maxey said. “This year it skipped from Texas to Northern Colorado and that was a really unusual thing.”
Roehr described the disease as modeling a wildfire. Although unlikely in any given area, the right spark and the right conditions can provoke rapid spread, particularly in a livestock-heavy state like Colorado.
Horses appear to have the greatest susceptibility to the disease, which also infects mules, cattle, bison, sheep, goats, pigs and camelids.
“A thought is that when flies bite, the skin on the nose and lips of the horse is thinner and there is more area that is not covered with hair and may have more susceptibility,” Roehr said.
The disease then manifests as vesicles, erosions and sloughing of the skin on the muzzle, tongue, ears, teats, groin area and above the hooves, CDA officials said.
While the disease does not have a high mortality rate, its symptoms are often painful for infected livestock and can greatly diminish their quality of life and productivity, Maxey said.
“Particularly for people in production and trying to grow livestock for food, they were quite concerned about the possibility because it could dramatically reduce production capabilities,” Maxey said. “A cow with sores does not want to produce much. It cannot drink sufficient water and feed, and that could have a tremendous economic impact on producers.”
In the horse community, disease concerns slowed down the summer show season and provoked cancellations, said JoAnn Conter, president of the northern chapter of the Colorado Draft Horse Association.
“It impacts whatever community that show is being held in because people come in and spend money in that community. It definitely had a financial impact in places where shows were canceled,” Conter said.
“We have a draft horse show in Sterling and we had ours but that happens on Father’s Day weekend, so that was earlier. But we had people who chose not to come.”
Roehr said cases had occurred this summer of horses contracting the disease while being transfered off of their home property. These cases likely arose from encounters with flies rather than other livestock. While the disease is infectious, he said it is not highly contagious between animals.
CDA officials do not expect problems for participants in winter livestock shows. By the time of Denver’s National Western Stock Show in January, Roehr said the potential for spread should be minimal.
He recommended livestock owners continue to take precaution with insect control measures and that they complete certificates of veterinary inspection.
For 2015, CDA officials hope to gain access to a VS vaccine, currently restricted by the World Organization for Animal Health.
“The vaccine wasn’t permitted for production because it was listed as a foreign animal disease,” Roehr said.
CDA officials are currently working to have VS delisted, which would permit use of vaccines being developed by the Colorado Serum Company.
In this scenario, livestock owners would be able to follow the disease’s spread and vaccinate their animals during high-risk years. ❖
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