In May, Colorado state veterinarian Dr. Keith Roehr presented a webinar about the 2014 Vesicular Stomatitis (VS) outbreak in Colorado. He reported that between July 4, 2014 and Jan. 29, 2015, his office made 556 investigations and ultimately quarantined 370 premises that tested positive for VS. The late onset of Colorado’s winter in 2014-15 was blamed for such an extended outbreak duration.

What is VS?

VS is a contagious viral disease of all hoofed animals–particularly equines, swine and cattle; sheep, goats and camelids are affected less often. The virus occasionally spreads to humans and causes a flu-like disease and blisters in rare instances. It is believed to enter a herd via insect vectors (black flies, midges, sand flies, etc.) and then spread primarily through additional insect activity within the herd. Little transmission is believed due to direct livestock contact, animal movement, and mechanical means, such as contaminated equipment and facilities.

Signs of illness

Affected animals have erosions and sloughing of tissue on the lips, tongue (see photo), teats, prepuce, between the toes, and on hoof coronary bands. Blisters and vesicles occur on these areas early in the course of disease but are often missed by human caretakers. Other signs include fever, poor appetite, lethargy, weight loss, drooling, scabbed lesions, and lameness if feet are involved.

Photo by Dr. Jeanne Rankin, from


Why is VS important?

VS is present in the U.S. and occasional disease outbreaks occur. Also, although VS is very contagious and can cause many cases of illness on premises, animals rarely die from it. Nevertheless, the disease is particularly important for several reasons:

• The signs of VS are similar to three foreign animal diseases not present in the U.S.: foot and mouth disease, swine vesicular disease, and vesicular exanthema of swine. It is essential to differentiate VS from these other diseases quickly so the entry of one of these exotic diseases can be identified and dealt with promptly

• VS is infectious—outbreaks in the U.S. restrict some international trade until the outbreak is contained

• Its similarity to important foreign animal diseases make VS a reportable disease in the U.S.

• Animals afflicted with VS are in pain, stop eating, lose weight and produce less milk. A widespread outbreak could cause significant animal suffering and economic losses. Dr. Roehr shared that economic losses of dairy farms involved in the Colorado outbreak were over $1M on some farms when decreased production, increased labor, reduced livestock marketing options, diagnosis and treatment costs were considered.

Control measures

A vaccine for VS is not available in the U.S., so control of biting insects is the major component of VS control and prevention:

1. Reduce exposure to flies by reducing pasture time.

2. Eliminate stagnant water or keep livestock away from wet areas where insects of concern are more common.

3. Use effective approved insect repellants.

To reduce mechanical transmission of the virus, equipment and tools should not be shared between farms. During outbreaks, healthy animals should be monitored closely for early signs of illness (fevers and vesicles) so they can be isolated from other animals quickly.

State and/or federal veterinarians are responsible for making the diagnostic determination in cases of VS. They issue quarantine orders, stopping animal movement to and from affected premises. They also advise owners about disinfection measures and isolation of affected animals to protect unaffected animals on the premise.


VS outbreaks are a reminder for livestock owners to develop, fine tune, or brush the dust off farm biosecurity plans. Livestock owners will be the first line of defense in the event of the entry of a foreign animal disease into the U.S. Early detection is our best hope for containing economically-important diseases such and foot and mouth disease. Monitor your animals regularly for signs of illness and call your veterinarian immediately if you see vesicles, blisters, erosions, or the other signs previously mentioned. Let’s hope it is “only” VS or something more innocuous.

If you ever notice a vesicle, blister, ulcer or erosion on an animal’s mouth, teats, prepuce or feet, contact a veterinarian at once. Odds are this is not a foreign animal disease, but if it is, every hour of diagnostic and containment delay means an exponential increase in the cost of the outbreak, in both economic impact and animal suffering.

A recording of Dr. Roehr’s webinar is available at He discusses dairy cattle involvement in depth.

For additional information

Source: June 2015 WSU Dairy Newsletter

Dr. Susan Kerr, WSU NW Regional Livestock and Dairy Extension Specialist,