Case Presentation: An 81-year old healthy male from Upstate New York without significant past medical history presented as a transfer from an outside hospital with a 5-6 day history of fevers, malaise, vague abdominal pain, and worsening confusion. There was no travel outside of the local area in the previous six months. The patient was an avid golfer but reported no recent tick bites. Blood smear testing on the day of admission returned positive for babesiosis with a parasite index of 13 percent. A DNA PCR sequencing confirmed the species to be Babesia microti. He was started on oral atovaquone, azithromycin, and doxycycline in the setting of a high rate of co-infection among Ixodes scapularis ticks for both Borrelia burgdorferi and Babesia microti. Within the next three hours, he developed massive hematemesis, respiratory failure, and oliguric renal failure. He was subsequently intubated and transferred to MICU. Clindamycin was added to the antiparasitic regimen. A repeat blood parasite index level returned at 25 percent and the patient was urgently started on an exchange transfusion. He was also started on piperacillin-tazobactam therapy for broad coverage in the setting of septic shock and multi-organ dysfunction. Following 48 hours of antiparasitic therapy and exchange transfusion, his parasitemia level dropped to 0.7%. He was slowly weaned off vasopressor therapy, DIC resolved with improved fibrinogen levels, was extubated in 72 hours and creatinine levels returned to baseline over course of seven days.

Discussion: Babesia infections range from asymptomatic to severe and sometimes are fatal. The severity of infection depends on the Babesia species and the immune status of the host. B. microti is the predominant species that infects humans in the United States. The incubation period of B. microti infection following a tick bite typically is one to four weeks. Severe babesiosis often occurs in older and/or immunocompromised patients and is associated with parasitemia greater than four percent. Severe babesiosis may also lead to complications, including persistent or relapsing disease. The most common complication is acute respiratory distress syndrome requiring intensive care. Shock, intravascular hemolytic anemia, multi-organ dysfunction are also observed.

Conclusions: Babesiosis is a tick-borne disease which shares the Lyme disease tick vector. Prompt microbiological smear examination along with a parasitemia index guides further therapy. In severe cases with parasitemia index greater than four percent; exchange transfusion should be carried out at the earliest for preventing fatality and improving patient outcomes along with co-administration of antibiotic therapy. A clinic follow up should be advocated to check for relapse.