EHV-1 Quarantine Lifted in Santa Barbara County, California
On Feb. 5 officials at the California Department of Food and Agriculture (CDFA) released a Santa Barbara County premises from equine herpesvirus-1 (EHV-1) quarantine. The release follows two negative EHV-1 tests seven days apart for the two surviving horses that previously tested positive on the premises. These two horses had their first negative test result on Jan. 22.

The first horse that tested positive, a 21-year-old Quarter Horse gelding, was reported to have neurologic signs of EHV-1 on Jan. 4. Veterinarians confirmed the horse as EHV-1-positive and euthanized him on Jan. 9 due to the severity of his clinical signs. At that time two remaining horses on the index premises were quarantined with enhanced biosecurity measures and twice-daily temperature monitoring enacted.

On Jan. 17 officials confirmed that an additional horse, a 6-year-old Quarter Horse mare, tested positive after displaying mild neurologic signs.

On Jan. 21 officials confirmed an aged Miniature Horse gelding on the same premises tested positive for EHV-1 after he developed  a fever. The 6-year-old mare and the Miniature Horse gelding are reported as recovering.

EHV 101

Herpesvirus is highly contagious among horses and can cause a variety of ailments in equids, including rhinopneumonitis (a respiratory disease usually found in young horses), abortion in broodmares, and equine herpesvirus myeloencephalopathy (EHM, the neurologic form).

In many horses the first or only sign of EHV-1 infection is fever, which can go undetected. In addition to fever, other common signs of EHV-1 infection in young horses include cough, decreased appetite, depression, and nasal discharge. Pregnant mares typically show no signs of infection before they abort, and abortions usually occur late in gestation (around eight months) but possibly earlier. Abortions can occur anywhere from two weeks to several months following EHV-1 infection.

Horses with EHM usually have a fever at the onset of the disease and might show signs of a respiratory infection. A few days later, neurologic signs such as ataxia (incoordination), weakness or paralysis of the fore- and hind limbs, urine retention and dribbling, loss of tail tone, and recumbency (inability to rise) develop.

Herpesvirus is easily spread by nose-to-nose or close contact with an infectious horse; sharing contaminated equipment including bits, buckets, and towels; or clothing, hands, or equipment of people who have recently had contact with an infectious horse. Routine biosecurity measures, including hygiene and basic cleaning and disinfection practices, should always be in place to help prevent disease spread.

Current EHV-1 vaccines might reduce viral shedding but are not protective against the neurologic form of the disease. Implementing routine biosecurity practices is the best way to minimize viral spread, and the best method of disease control is disease prevention.