The 2020 vesicular stomatitis virus (VSV) outbreak is growing with the Texas Animal Health Commission (TAHC) confirming the virus on an El Paso County, Texas, premises, marking the third case of VSV in Texas this year.
In an April 29 situation update, the U.S. Department of Agriculture's Animal & Plant Health Inspection Service (APHIS) reported that, to date, 14 premises have been identified in six counties across three states — New Mexico, Arizona and Texas.
In Texas, TAHC said the horse involved in the new case has been isolated on the premises and is being monitored. The El Paso site will remain under state quarantine until 14 days from the onset of lesions in the last affected animal on the premises.
“VSV is spread by direct contact with infected animals or spread by insect vectors like black flies, sand flies, and biting midges,” said Dr. Andy Schwartz, TAHC executive director. "An epidemiological investigation is underway on the VSV-positive premises to identify the means for disease transmission."
It is important to note, the National Veterinary Services Laboratories (NVSL) confirmed the VSV virus as the Indiana serotype, TAHC said. This is a different strain from the previously announced Starr County, Texas, confirmation; however, it is the same strain of VSV that has been confirmed in horses in nearby Las Cruses, N.M.
TAHC said since the El Paso VSV infected horse has not recently traveled, this could indicate that VSV-infected insects are the likely source of infection on this premises.
APHIS confirmed that both the VSV-Indiana and VSV-New Jersey serotypes have been identified this year. VSV-Indiana occurred in the U.S. in 2019, while VSV-New Jersey was last isolated in the U.S. in the 2014-15 outbreak, APHIS said, noting that both serotypes are known to circulate in endemic cycles in southern Mexico. The last U.S. outbreak involving both serotypes occurred in 1997-98.
Vesicular stomatitis is a viral disease that primarily affects horses and cattle and occasionally swine, sheep, goats, llamas, and alpacas. VSV can cause blisters and sores in the mouth and on the tongue, muzzle, teats or hooves of susceptible animals. Additional signs of infection include fever, drooling or frothing at the mouth, reluctance to eat, lameness or laminitis if lesions develop around the coronary band. Lesions usually will heal in two or three weeks, and most animals recover with supportive care by a veterinarian.
The U.S. 2020 VSV outbreak began on April 13, when NVSL confirmed the first VSV-positive premises in New Mexico. Arizona's index case was confirmed April 22, and Texas's first case was confirmed April 23.