A horse in York County has tested positive for the West Nile virus, according to the Maine Department of Agriculture, Conservation and Forestry.The horse showed signs of the virus last week before testing positive.The horse, which is receiving care, was not vaccinated against West Nile, officials said.This is the first confirmed case of West Nile virus in horses in Maine on record, the MDACF said in a news release.The virus is transmitted through the bite of an infected mosquito.A pool of mosquitoes tested positive for the virus last month.