The black-legged tick has been identified by UC Davis researchers as the culprit transmitting an ailment called EGE to horses in California. The discovery is of interest to human health professionals because EGE (equine granulocytic ehrlichiosis) was recently shown to be almost genetically identical to a human disease called HGE or human granulocytic ehrlichiosis. "This is of particular concern because the black-legged tick belongs to a group of ticks also known to infect humans and animals with both Lyme disease bacteria and the protozoa that causes a disease known as babesiosis," says entomologist Robert Kimsey, co-author of a study appearing in the October issue of the Journal of Medical Entomology. "We now have to ask what the potential is for a mixed infection of these agents being simultaneously transmitted by this group of ticks," Kimsey says. He and his colleagues found that the black-legged tick was the only tick on all pastured EGE-positive horses in the study. They subsequently demonstrated that the black-legged tick could transmit EGE from an infected horse to a healthy horse.