State Livestock Department officials say the mare was exposed via a shipment of semen from a stallion in Kentucky diagnosed with contagious equine metritis. The disease causes temporary infertility and spontaneous abortion.

State veterinarian Marty Zaluski says the mare has been quarantined and is being tested, but the results are not back yet. The mare had been confirmed pregnant, but is now open. Infected horses can be treated with antibiotics and disinfectants.

Four stallions in Kentucky and three in Indiana have been diagnosed with the disease and approximately 300 horses in 38 states are being tested for exposure.