Vesicular Stomatitis (VS) Education Module


CURRENT SITUATION (As of November 16, 2023)



California- Fresno, Inyo(11/27), Kings(11/27), Madera, Mariposa (11/24),  Merced, and Tuolumne(11/27). 

NOTE: Counties are removed from this list 30 days after the last premsises in the county has been released from quarantine. The date in parenthesis is the date of quarantine release for the last VS quarantined premises in that county. Counties with no dates listed have at least one premises remaining under quarantine . 


For the complete USDA Vesicular Stomatitis Situation Report: visit 


Vesicular stomatitis (VS) is a viral disease of horses and other animals. Infection results in vesicles (blisters), crusts, and ulceration of the lips, muzzle, nose, tongue, ears, sheath, teats, and/or coronary band. Transmission is predominantly by black flies, sand flies, and biting midges. The virus is in the active lesion, thus animals with active lesions can transmit the virus by direct contact, shared feed/water sources, and other carriers contaminated by infective lesions, vesicular fluid, and/or saliva. The lesions are self-limiting and typically resolve within 14 days. Humans can be infected from exposure to this virus and have mild flu-like symptoms.


USEF supports continuing competitions in VS Affected States and competitions which include horses from
VS Affected States provided the biosecurity measures listed below are implemented.


As we have learned over the last few years, we live in a world of equine infectious disease events which are outside of our control. Thus, we must make adjustments to best support competitions while protecting our equine athletes through the implementation of necessary biosecurity measures.

Critical Control Measures For ALL USEF licensed Competitions– Reporting of Vesicular Lesions

  • All competitions to institute immediate mandatory reporting of horses with vesicular lesions to competition management.
  • All competitions to require immediate isolation of horses with vesicular lesions or temperatures over 101.5°F.
  • All competitions to immediately report any horses with vesicular lesions to State Veterinarian’s office in the state in which the event is held AND to the USEF Equine Health and Biosecurity Veterinarian Dr. Katie Flynn ([email protected] or 859-225-6991)


Changes in USEF Vesicular Stomatitis Requirements
Effective September 1, 2023

U.S. Equestrian continues to work with state and federal animal health officials as well as subject matter experts on the Vesicular Stomatitis outbreak in California. Based on these discussions with experts, the current case data, the slowing of virus spread in California and the successful implementation of control measures at equine events, the USEF is making the changes to the protocols.

It is important competitors and competition staff continue to monitor the health of our equine athletes on the competition grounds. Failure to quickly identify lesioned horses and the resultant spread of the virus on the events grounds poses great risks to the future of our events. Ultimately, failure to take these biosecurity measures could lead to the cancellation of USEF competitions.

Below are the updated rules that will take affect on September 1, 2023:

  • USEF Requirements will now apply to VS Affected Counties.
    • USEF VS requirements will NO LONGER be applied to the entire state.
  • USEF Definitions for VS Affected Counties and VS Origin Horse:
    • For the purposes of USEF requirements for licensed events:
      • VS Affected County - a county which has had multiple USDA vesicular stomatitis confirmed or suspect premises within the last 30 days under quarantine for VS. (See list above for the most current list of counties which meet this definition.)
      • VS Origin Horse - a horse which has been in a VS affected county within the previous 14 days.
  • Competition Options for Hosting events during VS Outbreak
    • Restrict Entries (Applies to events in Non-Affected States) - Restrict entries from USDA confirmed VS Affected Counties under the condition that notification is made to USEF and all potential participants no less than seven (7) days prior to the start of competition and the notification is published in an obvious location on the competition's website homepage and social media sites.
    • Cancel the event - In cases where the prevalence of disease is high and/or there is an inability to implement appropriate biosecurity mitigation measures to control or mitigate risk, the most appropriate decision to best protect our equine athlete may be to cancel the competition.
    • Accept horses from USDA Confirmed VS Affected Counties and implement all biosecurity measures
      • Timed Official Certificate of Veterinary Inspection (Health Certificate) for horses from VS Affected Counties: Must be accompanied by an official Certificate of Veterinary Inspection (CVI) which includes a VS statement and issued within 14 days of entry to competition grounds by a licensed veterinarian who has examined the horse. Only state issued/ approved official CVI document shall be accepted.
        • NOTE CHANGE from within 5 Days to within 14 days of entry to the competition grounds
        • VS statement :“I have examined the animal(s) represented on this certificate of veterinary inspection and have found no clinical signs of vesicular stomatitis and they have not originated from a premises under quarantine for vesicular stomatitis.”
        • Optional VS Health Declaration: Competition management may elect to use the USEF VS Health Declaration Document as a method for owner/trainer to document residency outside a VS affected county. (See resources below for form)
      • Required Onsite Veterinary or designated individual examination of all horses from VS Affected Counties for vesicular lesions at time of entry to venue. No horse will be permitted entry to stabling, schooling, or competition area without veterinary examination. The horse with suspect lesions and the cohorts on the trailer will be rejected and prohibited entry.
        • Designated individual – An individual designated by the competition veterinarian OR an individual designated by the competition manager who has proof of completion of the USEF online VS educational module.
      • Recommend separate designated stabling area for horses from VS Affected Counties.
      • Monitor horses from VS Affected Counties for the duration of the event. Stall temperature logs required to be completed with twice daily temperature recordings.
      • Individual designated by competition management to directly observe horses originating from VS affected counties for vesicular lesions daily.
      • Immediate notification of State Veterinarian’s office and USEF Equine Health and Biosecurity Veterinarian of any suspect lesions.
      • Implement Vector Control Measures on the premises including but not limited to encouraging the use of individual vector control of fly sprays, wipes, or protective covering and premises control measures to eliminate fly breeding areas.

Additional Guidance on USEF Vesicular Stomatitis Requirements 

  • Permanent Resident Horses on USEF Licensed Competition Grounds in a VS Affected County- Permanent resident horses are defined as those which have permanently resided on the competition venue grounds for at least the previous 14 days.
    • Permanent Resident horses meeting the definition WILL NO LONGER require a CVI for entry to the competition in VS Affected County. However, they WILL be required to have an arrival examination for lesions prior to entry to the competition area.
  • Haul in Horses to USEF Licensed Competition Grounds- Haul in horses are defined as those who trailer into the event grounds and leave at the end of the competition day.
    • Haul in horses from a VS Affected County must enter with an official CVI issued within 14 days of INITIAL entry to the competition venue. These horses require inspection on the first day of entry to the venue grounds and maintain a twice daily temperature log which shall be submitted to management upon request. Ideally, but not required that these horses would have an arrival examination each day due to the potential exposure each evening away from the premises.
  • Multiple Consecutive Week Competitions at Same Venue: Horses Leaving and Returning
    • For Venues in a VS Affected County
      • Horses leaving and returning from a non-VS affected county: NO USEF requirements
      • Horses leaving and returning from a VS Affected County: If the horse has been gone more than 14 days a new CVI will be required. If the horse leaves for less than 14 days no CVI will be required.
  • Determining the VS Status of Competition Venue  – See above for the most current list of counties which meet the USEF VS affected counties definition. As the virus continues to spread and statuses of counties may change on a day to day basis, we recognize the challenges this poses to competition management.
    • For planning purposes, the county VS status of the competition venue will be determined (7) seven days prior to the event start date for that competition.
    • If the event venue county is in a non-affected county on day 7 prior to the event start date, no VS requirements are required, even if the county subsequently becomes classified as a VS affected county.
    • RECOMMENDATION: For events held in counties neighboring VS affected counties, competition management is strongly encouraged (but not required) to implement the VS protocols (onsite arrival examination, temperature/clinical sign monitoring, fly vector control measures).
  • Determining the VS Status of the Equine Origin Location– See the top of this webpage for the most current list of counties which meet the USEF VS affected counties definition. As the virus continues to spread and statuses of counties may change on a day-to-day basis, we recognize the challenges this poses to competitors.
    • For planning purposes, the county VS status of the equine origin location will be determined (7) seven days prior to the event start date for that competition.



Vesicular Stomatitis (VS)
Frequently Asked Questions

(.pdf version of FAQs)


Fly Prevention Important Notes

How To Get Rid of Flies - Article from US Equestrian Magazine on premise-based fly control, as well as some information from UltraShield on fly spray tips for use on horses.

Fighting Flies - Article from US Equestrian Magazine that looks at the future technology of fly prevention, but also includes good information about fly spray and proper use.

Limiting flies on premises is vital to slowing the spread of vesicular stomatitis.


Manure left around your barn area and pastures can create a breeding ground for flies. By removing manure regularly and consistently, you promote faster drying of the remaining ground which can reduce the number of flies on your property. A John Deere Compact Tractor, Materials Bucket and Manure Spreader, make a great package for keeping your barn clean and reducing pests.




Additional Resources

Vesicular Stomatitis Flyer

This flyer provides crucial information to prevent the spread of Vesicular Stomatitis (VS).

Vesicular Stomatitis - Fly Prevention Infographic

This infographic puts important details about Fly Prevention in an easy to share format

Vesicular Stomatitis - Protect Your Premises Infographic

This infographic focuses on the important steps that can be used to protect premises from the spread of VS.

Vesicular Stomatitis Fact Sheet

The Equine Disease Communication Center Vesicular Stomatitis Fact Sheet for Horse Owners. Basic disease information including modes of transmission, clinical signs and prevention.

Vesicular Stomatitis Health Declaration

Optional form to be utilized by competitors to declare residing outside a Vesicular Stomatitis State for the prior 14 days.

USDA Vesicular Stomatitis Presentation Slides

USEF hosted a Vesicular Stomatitis Webinar on May 31, 2023. These are the presentation slides of Dr. Angela Pelzel McCluskey, Equine Epidemiologist with USDA who gave an overview of the disease and previous outbreaks.

Temperature Log

Individual Stall Temperature Log