Raleigh, N.C. — Equine piroplasmosis, a disease thought to have been eradicated from the United States, has resurfaced in North Carolina and 19 other states over the past two years, Steve Troxler, state commissioner of agriculture, said in a statement Thursday.

Blood tests identified EP in 11 horses in four locations across the state recently, Troxler said.

The N.C. Department of Agriculture and Consumer Services is conducting an investigation to determine the source of the disease and whether it has spread beyond the locations where the infected animals were housed.

Equine piroplasmosis is a blood-borne parasitic disease primarily transmitted to horses by ticks or contaminated needles. Mild cases of EP cause weakness and lack of appetite. Symptoms can include rough coats, constipation, colic, fever, anemia and low platelet counts.

"By law, suspected cases must be reported to the state veterinarian’s office," Troxler said.