Anaplasmosis

Human granulocytic anaplasmosis is a tick borne rickettsial infection caused by Anaplasma phagocytophilum, which infects neutrophils.

• Vectors: Ixodes scapularis and I. pacificus (North America), I. ricinus (Europe), and I. persulcatus (Asia).
• Peak incidence in late spring to summer; incubation 5 to 14 days after tick bite.
• Risk factors for severe disease: age over 60, immunosuppression, and delayed treatment.
• Case fatality under 1%, but 7% need ICU care.

• Abrupt fever, rigors, headache, myalgia, malaise, and nausea.
• Leukopenia, thrombocytopenia, and raised transaminases are characteristic.
• Rash is rare (under 10%), which distinguishes it from other rickettsioses.
• Severe complications: acute respiratory failure, septic shock like state, rhabdomyolysis, secondary infections, hemophagocytic lymphohistiocytosis, and meningoencephalitis.

• Clinical suspicion and empirical treatment, without waiting for confirmation.
• PCR of whole blood (best in the first week, before antibiotics), blood smear showing morulae in neutrophils (25 to 75% in acute disease), and paired serology (IFA IgG fourfold rise).
• Blood: leukopenia, thrombocytopenia, mild anaemia, elevated AST and ALT, and CRP.
• Exclude ehrlichiosis, Lyme disease, babesiosis, Rocky Mountain spotted fever, viral infections, and sepsis.

• Doxycycline 100 mg orally or IV twice daily for 10 days (children under 45 kg: 2.2 mg/kg twice daily; doxycycline is appropriate for all ages including young children, for short courses). Treat for at least 3 days after fever resolves and until clinical improvement.
• Rifampicin 300 mg twice daily for 7 to 10 days is an alternative in pregnancy or doxycycline allergy.
• Response to therapy occurs within 24 to 48 hours; failure suggests alternative diagnosis.
• Supportive: fluids, antipyretics, ICU care, and treatment of complications.
• Test and treat concurrent Lyme disease (doxycycline covers both).
• Tick prevention: repellents (DEET 20 to 30%), permethrin treated clothing, prompt tick removal.