Anaplasma phagocytophilum infection triggers encephalitis

Anaplasmosis is a tick-borne disease caused by the bacterium Anaplasma phagocytophilum. Symptoms typically start 1 to 2 weeks after a tick bite. And while some patients may be asymptomatic, others can experience life-threatening complications, including encephalitis.

In fact, the mortality rate is higher in patients who do not immediately receive doxycycline treatment, who are immunocompromised or have become infected through a blood transfusion.

In their article, “Anaplasma phagocytophilum Encephalitis: A Case Report and Literature Review of Neurologic Manifestations of Anaplasmosis,” Cosiquien and colleagues describe a 62-year-old patient who was admitted to the emergency department due to an acute onset of confusion.¹

The man was “confused and unable to maintain meaningful conversation,” the author’s state. He had a mild headache and a slight fever but no other symptoms.

The patient had acute onset of confusion, a mild headache and a slight fever but no other symptoms.

He was an avid gardener and reportedly had a tick bite four weeks before his symptoms began.

“Given the symptoms of headache, confusion, and fever, encephalitis was suspected, and a lumbar puncture (LP) was performed,” the author’s state.

The man was treated empirically with acyclovir, ceftriaxone, and vancomycin. But despite treatment, his fever and confusion worsened over the next 24 hours.

Subsequent PCR testing was positive for anaplasmosis and the patient began treatment with IV doxycycline. He made a fully recovery.

 “Within 24 hours of doxycycline initiation, his symptoms improved.”

Neurologic manifestations of anaplasmosis are less common than in other tick-borne diseases, such as ehrlichiosis, Lyme disease, and Powassan virus infection, according to the authors.

“… our patient responded promptly to intravenous doxycycline which further confirms that this indeed was encephalitis due to Anaplasma phagocytophilum,” the author’s state.

“As cases of anaplasmosis are becoming more frequent, it has become apparent that some patients, such as the one we report, present with predominantly neurological manifestations.”

The authors point out that although there was clinical and laboratory evidence of encephalitis, the patient’s MRI was normal.

They suggest, “In tick-endemic areas, clinicians should keep [an infection with anaplasma phagocytophilum] in mind in patients who present with encephalitis.”