Horse Health

Equine Herpes Myeloencephalopathy (EHM) Updates: 

Equine Herpes Myeloencephalopathy (EHM) Updates: 
New San Mateo County Quarantine 
November 7, 2018: A 24 year old Arabian mare, originating from a San Mateo 
County facility, displaying neurologic signs has been confirmed positive for 
Equine Herpesvirus Myeloencephalopathy. The mare was removed from the 
property and placed in isolation and quarantined. CDFA is investigating to 
identify exposed horses which will be monitored for clinical signs and 
temperatures taken twice daily. Any horse displaying a fever or compatible 
clinical signs will be tested. CDFA will continue to monitor the situation 
and post new information as it becomes available.

Rabies Confirmed In San Luis Obispo County

Since June 2017, three bats have been tested positive for rabies in San Luis Obispo county. This is an important reminder to check your horse's vaccination records and make sure they are up to date. There are typically around 60 confirmed rabies cases in horses in the United States every year.

What Can Rabies Look Like?

Rabies is not typically an easy diagnosis in horses as the signs vary case
by case, but some common symptoms are:

  • Neurological signs such as: behavioral changes, changes in gait, trouble swallowing, and hypersalivation.
  • Aggressiveness
  • Tremors
  • Fever
  • Depression

It is important to ensure that your horses receive their rabies vaccine once
a year. Rabies infection in unvaccinated horses is uniformly fatal. For
further information about the rabies cases in San Luis Obispo County go to:

Sonoma County Farm Bureau Wildfire Information for Rural Areas

Sonoma County Farm Bureau is working with the Sonoma County Emergency Operations Center at the Fairgrounds, Sonoma County Horse Council and Sonoma County Animal Services to ensure that farmers, ranchers, and livestock have the support needed to overcome the damage caused by the destructive wildfires in Northern California.

Sonoma County Farm Bureau is coordinating donations of feed and supplies for livestock and horses. The Farm Bureau office has secured a storage yard and is in the process of gathering feed, particularly hay, for distribution to affected farmers throughout the county.

To donate goods including hay and livestock supplies or to request assistance, Sonoma County Farm Bureau can be reached at or 707-544-5575.

Equine Health Program Updates - CDFA

By Katie Flynn, BVMS, MRCVS

Equines Entering California through Border Stations

Border station personnel are required to document all horses crossing into California. This includes California horses returning to California. Thus, all horse trailers are required to stop at the border station crossings to provide destination information and required entry documentation. To facilitate prompt, efficient transition through the station, an Equine Only – California Entry Document has been developed. This document can be completed in advance and provided to the border personnel for verification.

Equine owners and transporters are encouraged to download and complete the document for presentation to station personnel.

To download the document, visit

Equine West Nile Virus Cases in California

For 2017, a total of fourteen (14) horses have been confirmed positive for West Nile Virus (WNV). The positive horses were located in Glenn, Contra Costa, Fresno, Kern (2), Riverside (4), Plumas, Lassen, Tehama and San Joaquin (2) counties. Eleven (11) horses were unvaccinated and three (3) horses had unknown vaccination status. Seven (7) horses died or were euthanized and seven (7) horses are recovering.

The California Department of Food and Agriculture (CDFA) continually monitors and investigates equine neurologic cases for the presence of WNV in California. CDFA urges horse owners to consult their veterinarian concerning a WNV vaccination program to ensure maximum protection of their horses.

For more information visit:

The Effects of Artificial Fluoridation of Water (AFW) on Horses

Ted S Stashak DVM, MS, Diplomate ACVS

  • Some concern has recently been voiced by horse owners regarding the fact that the Sonoma County Board of Supervisors is considering adding fluoride (F) to our water supply, and the effect this may have on horses in the county. To become better informed about the possible negative effects of AFW on horses, a literature search over the past 30 years was done. Additionally an internal medicine specialist and toxicologist at UCD, and a pathologist specializing in bone pathology at Colorado State University were consulted. The following is a summary of the findings from these sources.
  • Summary: In 1974 the US National Academy of Sciences established a dry weight dietary fluoride tolerance of 60 ppm F for horses. Since then two reports (2006 and 2008) identifying chronic fluorosis in a separate groups of horses, in Pagosa Springs CO and Hitchcock TX, drinking AFW at a concentration <1.3 ppm F, have been published. Both articles describe a long period of exposure to AFW, without contamination from other F sources, and classical signs and laboratory evidence of F toxicity. No soil or water testing or assays for other F sources was reported in either study. Peer-reviewed literature in scientific journals, to date, showed no published reports documenting fluorosis in horses due to ingestion of fluoridated public water alone.
  • Discussion: The 2006 and 2008 reports were published in a non-peer reviewed journal and are missing important information necessary to confirm that AFW alone was the cause for the signs of chronic fluorosis in these horses. Fluoride being one of the most common elements in the environment is found in soil, rock, water, air and plants. No soil, water or feed testing was reported in these articles. While the horse’s symptoms improved following discontinuation of drinking the AFW; the authors did not rule out the exposure to other sources of F (e.g. use of fluoride-containing pesticides, fluoride-containing rodenticides, insecticides, and other chemicals etc.), which when added to the ppm in the AFW could have resulted in toxic levels 
  •  Conclusions: Evidence to date indicates that F concentrations allowable in US public water systems are well tolerated by horses and do not cause fluorosis. Supporting this, is a fact that many horses nationwide drink AFW as their major source of water and fluorosis is avery rarely reported condition. For more information fluorosis in horses the reader is referred to the following