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Anaplasmosis — RACP Adult Medicine MCQ

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HardInfectious DiseasesAnaplasmosisRACP Adult Medicine

A 50-year-old man from rural Victoria presents with high fever, headache, and a widespread maculopapular rash. He is a recreational bushwalker. Blood film shows intracellular organisms in neutrophils (morulae). PCR confirms Anaplasma phagocytophilum. What is the first-line treatment?

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Correct answer: C — Azithromycin

Human granulocytic anaplasmosis (HGA) is a tick-borne rickettsial-like infection caused by Anaplasma phagocytophilum. Characteristic morulae (mulberry-like inclusions) are seen within neutrophils on blood film. It is emerging in Australia. First-line treatment is doxycycline 100 mg BD, which should be commenced empirically whenever a tick-borne rickettsial-like illness is suspected. Duration is 7–14 days or for at least 3 days after defervescence. PCR confirms the diagnosis.

Reference: eTG – 2025 – Antibiotic Guidelines; CDNA – 2024 – Tick-Borne Diseases