A previously independent and active 89-year-old male without past medical history was brought to the hospital by his son with a 6-day history of progressively worsening confusion. Per the son, the patient lived alone on a 10-acre property that included fruit orchards, a fishing pond, and 100 acres of surrounding woodlands on which the patient hunted for deer, turkey and boar. He also drank water from a recently decontaminated well, consumed unpasteurized milk, ate fruits from his orchard and ate meat he hunted himself. The patient did not have a primary care physician, did not consume alcohol, tobacco products, prescription or over-the-counter medications. On further inquiry, the son related that their peach orchard was infested with swarms of mosquitos, and his father would often pick ticks off his skin after coming indoors.
On exam, the patient was initially febrile, completely altered from his baseline and unresponsive to verbal commands. His cardiopulmonary exam was normal, he was able to protect his airway, had a non-tender abdomen without splenomegaly and cold, clammy extremities. Initial labs were pertinent for 94% segmented neutrophils without leukocytosis, thrombocytopenia, elevated BUN 142mg/dL, creatinine 7.1mg/dL and a blood smear without schistocytes. CT scan of the head/chest/abdomen/pelvis did not yield acute or infectious findings. Given his uremia and kidney failure, hemodialysis was promptly initiated. Infectious Disease Consultants recommended a detailed work-up for bacterial, viral and fungal cultures and serology, and the patient was initiated on intravenous doxycycline, ceftaroline and piperacillin/tazobactam. With daily hemodialysis and empiric treatment, the patient’s uremia began to resolve. 4 days after admission, serology and PCR confirmed infection with Ehrlichia chaffeensis, and empiric therapy was de-escalated. Eventually, the patient’s altered mentation, kidney injury and thrombocytopenia improved. He was discharged with a 14 day course of oral doxycycline.
Human monocytotropic ehrlichiosis is a rare and potentially life-threatening infection by an obligate intracellular gram negative bacteria transmitted by the lone-star tick. Ehrlichia can infect pets and livestock, and less frequently, immunocompromised humans. Mild cases present with flu-like symptoms including fevers, headaches, myalgias and arthralgias, but can progress to severe multi-system disease without prompt treatment. Given the non-specific presentation, diagnosis and treatmentis often delayed leading to an estimated case fatality of 1.8%.
Diagnosis of ehrlichiosis strongly relies on clinical signs and symptoms; however, these may be non-specific. Thus, it is critical to collect a thorough history of possible tick exposure and use exam findings and blood testing to aid clinical suspicion. Serological testing can produce a false negative result in the first 7 to 10 days of illness, so nucleic acid-based testing is also advised. Importantly, treatment should be initiated based on clinical suspicion and should not be delayed for specialized testing.