This photograph depicted a dorsal view of an adult female western blacklegged tick, Ixodes pacificus, which has been shown to transmit Borrelia burgdorferi, the agent of Lyme disease, and Anaplasma phagocytophilum, the agent of “human granulocytic anaplasmosis” (HGA), which was previously known as “human granulocytic ehrlichiosis” (HGE), in the western United States. The small scutum, or tough, chitinous dorsal abdominal plate, does not cover its entire abdomen, thereby allowing the abdomen to expand many times when this tick ingests its blood meal, and which identified this specimen as a female. The four pairs of jointed legs, places these ticks in the Phylum Arthropoda, and the Class Arachnida.

Anaplasma phagocytophilum, initially thought to be a bacterium in the genus Ehrlichia, was the second recognized ehrlichial infection of humans in the United States and was first described in 1994. The agent is transmitted by the “blacklegged tick”, Ixodes scapularis, in the eastern states, and the “western blacklegged tick”, Ixodes pacificus, in the western United States.

Patients with ehrlichiosis generally visit a physician in their first week of illness, following an incubation period of about 5-10 days after the tick bite. Initial symptoms generally include fever, headache, malaise, and muscle aches. Other signs and symptoms may include nausea, vomiting, diarrhea, cough, joint pains, confusion, and occasionally rash.

Content Providers(s): CDC/ Dr. Amanda Loftis, Dr. William Nicholson, Dr. Will Reeves, Dr. Chris Paddock

Picture & text from CDC/PHIL. For more information on source & for information on color coding used above for different types of ticks, see Tick Pictures from CDC