Case Presentation:
An 89-year-old man was transferred to our facility for altered mental status, fever, acute renal failure, and thrombocytopenia. He was in his usual state of health until a week prior when his children noticed that he was talking to people who were not present. He lived alone and independently on 10 acres of property that included a wooded area where he hunted. He reported frequently finding ticks on his body.
Upon presentation, his vitals were blood pressure 90/40mmHg, heart rate 105bpm, and respiratory rate 20breaths/min. His physical exam was remarkable for disorientation to person, place, and time. His laboratory results revealed WBC 3.4×10^9/L, platelet count 33×109/L, ALT 72u/L, AST 127u/L, and creatinine of 7.2mg/dL. Blood cultures were obtained, and the patient was placed on piperacillin-tazobactam, vancomycin, and doxycycline.
Serology tests showed antibodies to Ehrlichia chaffeensisat a titer > 1:2048, and PCR was also positive. Piperacillin-tazobactam and vancomycin were discontinued, and the patient was continued on doxycycline. After three days of antimicrobial therapy, the patient’s mental status improved. He initially required hemodialysis; however, his renal function subsequently returned to normal, and dialysis was no longer required. We believed his acute renal failure was due to acute tubular necrosis caused by ehrlichiosis.
Discussion:
Ehrlichia spp. is a group of gram negative obligate intracellular bacteria that infects the cytoplasmic vacuoles of mononuclear phagocytic bone marrow cells, specifically monocytes[3].Ehrlichia chaffeensis is the species known to infect humans, and is spread by the lone star tick (Amblyomma americanum).
The illness does not have distinctive features; consequently, a clinician must have a high index of suspicion. The incubation period for ehrlichiosis is 7-14 days after tick exposure[1, 3, 4].The most common symptoms are malaise, high-grade fever, headache, and myalgia. Severe complications occur in about 17% of patients and include acute renal failure, adult respiratory distress syndrome and meningoencephalitis.Common laboratory abnormalities are marked increases in the hepatic aminotransferases and decreased WBCs and platelets.
Multiple modalities are used to diagnose ehrlichiosis.The IFA detects antibodies reactive with E. chaffeensis,and an antibody titer that is greater than 1:64 is positive; however, it may not be reactive in the acute illness so a repeat study is recommended in three weeks. PCR detects the DNA sequence of E. chaffeensis and can be used in the acute illness.
If a patient has a tick exposure and symptoms concerning for ehrlichiosis, one should treat empirically with antimicrobial therapy in the tetracycline family.Treatment should be administered for 14 days.[3].
Conclusions: If a patient presents with a fever and exposure to ticks, ehrlichiosis should always be considered.