The Wyoming Livestock Board has attributed a recent horse death in Fremont County to vesicular stomatitis virus.
Details on the horse death cannot be disclosed due to privacy regulations.
The board this year has conducted 148 investigations of vesicular stomatitis virus in the state, resulting in 128 quarantines.
State veterinarian Jim Logan said the livestock board is requiring all livestock imported from any state where the virus has been found to carry a health certificate written within 14 days before entering Wyoming.
The order comes after new reports that vesicular stomatitis virus have surfaced in other states, Logan said.
"New cases continue to be reported daily," he told The Ranger.
The stricter rules are set while active infection and quarantines are in place for all livestock entering Wyoming.
Health certificates can be obtained from a veterinarian who has examined the animal in question.
Cases have been confirmed in Arizona, Colorado, Nebraska, New Mexico, South Dakota, Texas and Utah. States that still have premises under quarantine are Wyoming, Colorado, Nebraska, New Mexico, South Dakota and Utah.
In Wyoming, the virus has been found in Goshen, Platte, Sublette, Albany, Fremont, Converse, Weston, Natrona and Laramie counties.
A possible new case in Crook County is being investigated.
The viral disease is contagious and can spread to cattle, swine, goats, sheep, horses and even llamas.
Clinical signs of the virus include blister-like lesions in the animal's mouth, lips, feet, udder, ears and genitals. Other signs include anorexia, slobbering, frothing at the mouth, lameness, and scabby, crusted lesions on the muzzle.
Possible cases must be reported so samples can be tested for Foot and Mouth Disease.