EHV-1: California Update

Source: CDFA

California EHV-1 Causing EHM Disease Update as of 1 PM 6/6/11

California has no new confirmed case of EHV-1. There is a total of 21 confirmed EHV-1/ EHM cases in the state. The last California confirmed case was on June 3, 2011 in Glenn County.

The positive confirmed cases are located in the following 12 counties: Amador(1), Colusa(1), Glenn(5), Kern(2), Los Angeles(1), Marin(1), Napa(1), Placer (3), Plumas(1), Shasta(1), Stanislaus(3) and Ventura(1).
Sixteen(16) of the confirmed positive EHV-1/EHM CA cases participated in the National Cutting Horse Association’s Western National Championships in Ogden, Utah.
One (1) of the confirmed positive EHV-1/ EHM CA cases participated only in the Kern County Cutting Horse Event on May 13th in Bakersfield, CA.
Four (4) of the confirmed positive EHV-1/EHM CA cases were exposed horses to an Ogden, UT participant.
Two (2) confirmed positive EHM horses were euthanized after showing severe neurological signs associated with EHM.
Eight (8) confirmed positive horses displayed neurologic signs
Thirteen (13) confirmed positive horses displayed a fever.
The total confirmed cases in California have been reduced by one (1). Initially, this horse had a low viral load on nasal swab and using an abundance of caution, was placed under quarantine. The Sacramento County horse in question did not have any clinical signs nor did any of the horses in the same barn. The lack of clinical signs dictates that this horse is not considered a confirmed case.

2011 Outbreak Situation Report – June 6, 2011

Equine Herpes Myeloencephalopathy

Equine Herpes Virus (EHV-1) infection in horses can cause respiratory disease, neurological disease, abortion in mares and neonatal foal death. The neurological form of the disease, is known as Equine Herpes Myeloencephalopathy (EHM). The neurological form of the virus has the potential to cause high morbidity and mortality. EHV-1 is easily spread and typically has an incubation period between 2-10 days. Respiratory shedding of the virus generally occurs for 7-10 days, but may persist longer in infected horses. For this reason, the isolation period recommendation for confirmed positive EHM cases is twenty-one (21) days. Clinical signs of EHM in horses may include nasal discharge, incoordination, hindquarter weakness, recumbency, lethargy, urine dribbling and diminished tail tone. The prognosis for EHM positive horses depends on the severity of signs and the period of recumbency. Employing supportive treatment with intravenous fluids, anti-inflammatory drugs, anti-viral drugs and other supportive measures may be beneficial since there is no specific treatment for EHM. Currently, no EHV-1 equine vaccine has a label claim for protection against the neurological strain of the virus.

May 2011 Outbreak

The National Cutting Horse Association (NCHA) Western National Championship held in Ogden, Utah April 30-May 8, 2011 had 400 competitors. On May 13, 2011, California Animal Health Officials were notified by the NCHA that fifty-four (54) California horses that competed in the event may have been exposed to the neurological strain of the EHV-1 virus. Some of these same horses were entered in the Kern County Cutting Horse event in Bakersfield, CA on May 13, 2011. One horse, that competed in Ogden, UT, was euthanized at the Kern County Cutting Horse event after showing severe neurological signs; EHM was the final diagnosis for this horse. All horses at the Ogden, UT and Bakersfield, CA events were potentially exposed to the disease.

California Confirmed EHV-1 Cases 06/06/11

Diseases Transmission & Prevention

Horse-to-horse contact, aerosol transmission and contaminated hands, equipment, tack and feed all have a role in disease transmission. Horses with severe clinical signs consistent with the neurological form of EHV-1 most often have a large viral load in nasal secretions presenting the greatest risk for disease spread. Immediate separation and isolation of identified suspect cases and the implementation of appropriate biosecurity are key disease control measures.

People can easily transmit this virus on their hands and clothing, so the consistent practice of appropriate biosecurity measures reduces the risk of disease spread to horses by people. To reduce this risk, individuals should thoroughly wash their hands between contacts with horses. Wearing disposable gloves that are changed between horse contacts and thoroughly cleaning and disinfecting footwear between entry into barns and stalls can also help minimize the risk of people spreading the virus between animals. Ideally, a person caring for a sick horse should not also work with healthy horses. When this is not practical, always handle healthy horses first and sick horses last. If horses are commingled with horses of unknown disease status, a degree of inherent risk exists for exposure to all contagious diseases. Many factors enhance or reduce the disease risk.

For additional information: CDFA:

http://cdfa.ca.gov/ahfss/animal_health/equine_herpes_virus.html

UCD Center for Equine Health

http://www.vetmed.ucdavis.edu/ceh/ehv1_general.cfm

USDA

http://www.aphis.usda.gov/vs/nahss/equine/ehv/

CDFA Animal Health Branch Offices

Sacramento (HQ)

916-654-1447

Modesto

209-491-9350

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