Human Granulocytic Anaplasmosis
Human granulocytic anaplasmosis (HGA) was documented as a distinct disease in Minnesota and Wisconsin in 1994. The bacterium that causes HGA has a confusing history. Initially, it was known as Ehrlichia phagocytophila or E. equi, and at one time it was thought to be the cause of human granulocytic ehrlichiosis. However, HGA differs from the two types of ehrlichiosis in having the black-legged tick as the vector, and, accordingly, the same geographical distribution as Lyme disease.
- A bacterium with the scientific name Anaplasma phagocytophilum.
- It is an intracellular parasite that undergoes development within white blood cells, especially granulocytes.
- Fever, headache, joint pain, and muscle ache.
- 20-30% of patients develop a body rash, but it typically does not the involve the hands and feet.
- Infections usually are mild, but severe cases can result in death.
- A wide range of mammalian hosts, including domestic pets, livestock, deer, elk, and rodents.
- Ixodes scapularis, black-legged tick, in the eastern U.S.
- Ixodes pacificus, Western black-legged tick, in the Pacific Coast states.
- From infected Ixodes ticks to humans via their bite.
- From infected Ixodes larvae to nymphs to adults via transstadial transmission.
- NOTE: there is no human-to-human transmission.
- Symptoms, together with onset in late spring into summer.
- Antibiotic prescribed by a physician.