Anaplasmosis (Trail Fever): Tick-Borne Infection Symptoms, Treatment, and Prevention

Anaplasmosis (formerly human granulocytic ehrlichiosis) is caused by Anaplasma phagocytophilum, an obligate intracellular bacterium transmitted by Ixodes ticks (same vector as Lyme). “Trail fever” is a colloquial veterinary term.

Clinical Presentation

• Fever, chills, severe headache, myalgia, malaise.
• Leukopenia, thrombocytopenia, elevated transaminases.
• Rare: respiratory failure, DIC, meningoencephalitis (more in immunocompromised).

Diagnosis

• PCR on whole blood (gold standard, early).
• Morulae in granulocytes on peripheral smear (specific, insensitive).
• Serology (IFA): 4-fold titer rise convalescent vs. acute.

Treatment

• Doxycycline 100 mg BID × 7–10 days (all ages, including children; preferred over rifampin).
• Defervescence typically within 24–48 hrs.
• If allergic/pregnant: rifampin alternative.

Prevention

• Tick avoidance: permethrin-treated clothing, DEET/Picaridin on skin.
• Prompt tick removal (<24 hrs attachment reduces transmission).
• Landscaping: reduce leaf litter, deer access.

Co-infection with Lyme (Borrelia) or Babesia is common—test if clinical picture warrants.