(AP) — The Nebraska state veterinarian says the outbreak of a deadly horse disease hasn’t been found in other herds that had contact with the initial herd.

Dr. Dennis Hughes said Wednesday that the herd in northwestern Cherry County remains quarantined and will undergo more tests over the next few months.

Earlier this month the Nebraska Agriculture Department began an investigation after 12 cases of equine infectious anemia were diagnosed in the herd. Ten of the 12 were euthanized because there are no treatment options. The department says the remaining two horses were taken to the National Veterinary Services Laboratories in Ames, Iowa, for work related to the disease testing.

Experts say the disease affects only horses, mules and donkeys and is usually fatal. No other animals or humans can be infected.