Anaplasmosis. Anaplasmosis is a disease caused by infection of the bacterium, Anaplasma phagocytophilum. In the eastern United States, the disease is spread by the bite of an infected black-legged tick, Ixodes scapularis, commonly known as the deer tick.This is the same tick that can transmit Lyme disease.Anaplasmosis is also known as human granulocytic anaplasmosis (HGA) and can be similar to another tick-borne disease, ehrlichiosis. However, these are distinct diseases that are transmitted by different ticks.naplasmosis is a disease caused by infection of the bacterium, Anaplasma phagocytophilum.