Ehrlichiosis: This is a tick-borne illness similar to anaplasmosis, caused by bacteria of the Ehrlichia genus. It presents with similar symptoms such as fever, headache, and fatigue, making it a primary consideration in the differential diagnosis.

Lyme Disease: Caused by Borrelia burgdorferi, transmitted by the bite of an infected tick. Symptoms can include fever, headache, fatigue, and a characteristic "bull's-eye" rash, which overlaps with anaplasmosis symptoms.
Rocky Mountain Spotted Fever (RMSF): Another tick-borne disease, caused by Rickettsia rickettsii. It presents with fever, headache, and a rash, and is a common consideration in areas where ticks are prevalent.
Southern Tick-Associated Rash Illness (STARI): Characterized by a rash similar to that of Lyme disease, but caused by the bite of the lone star tick. While its symptoms can mimic anaplasmosis, it is typically less severe.

Rickettsialpox: Caused by Rickettsia akari, transmitted by the bite of an infected mite. It presents with fever, headache, and a rash, and while rare, can be severe if not treated promptly.
Tularemia: Caused by Francisella tularensis, which can be transmitted by the bite of an infected tick. It presents with fever, headache, and can progress to more severe forms like pneumonic tularemia if not treated, making it critical not to miss.

Babesiosis: A parasitic disease caused by Babesia, transmitted by the bite of an infected tick. It primarily affects red blood cells and can cause symptoms similar to anaplasmosis, including fever and fatigue, but is less common.
Tick-Borne Relapsing Fever (TBRF): Caused by various species of Borrelia, transmitted by the bite of an infected soft tick. It is characterized by recurring episodes of fever, headache, and muscle pain, and is rare in most areas.