BACKGROUND: Babesiosis is an emerging, tick-borne zoonosis caused by intraerythrocytic protozoa of the genus Babesia. Babesia microti is the main pathogen causing human disease and is endemic in the northeastern and upper midwestern parts of the USA. Severity of infection ranges from mild, self-limited, febrile viral-like illness accompanied by nonspecific symptoms to life-threatening infection complicated by severe hemolytic anemia, disseminated intravascular coagulation (DIC), acute respiratory distress syndrome (ARDS), and renal or/and hepatic failure. Splenic rupture (SR) is a very rare but life-threatening complication of severe B. microti infection.

CASE REPORT: A 79-year-old female farmer from Wisconsin, USA was admitted during summer with hemorrhagic shock secondary to spontaneous splenic rupture. She was transfused with 3 units of packed red blood cells (PRBC) and underwent emergent splenectomy. Postoperatively, she recovered well and was discharged on postoperative day 4. However, she was re-admitted on postoperative day 10 for febrile hemolytic anemia. Further exposure history was obtained and was significant for multiple tick bites 8 weeks preceding the index hospitalization. She was promptly diagnosed with babesiosis and Lyme disease co-infection. She responded favorably to 10 days of azithromycin and atovaquone and 21 days of oral doxycycline.

CONCLUSIONS: Despite its rare occurrence, SR due to B. microti infection is a dreaded complication that can rapidly progress to hemorrhagic shock and death. In contrast to other complications of babesiosis, SR is not correlated with parasite burden or immune status of the affected host. Babesiosis should be considered as part of the differential diagnosis in patients from endemic areas presenting with atraumatic splenic rupture.

Keywords: Babesia microti, Lyme Disease, Splenic Infarction, splenic rupture