Title : Malaria mimicker: Babesia on the rise
Abstract:
Introduction: Babesiosis is a parasitic infection caused by the protozoan of the genus Babesia. In North America, the most common disease-causing species is Babesia microti, and the primary vector is Ixodes scapularis, also known as the black-legged or deer tick. Babesia microti is an intracellular parasite infecting erythrocytes and symptoms can range from asymptomatic to life threatening sepsis.
Case Description: A 64-year-old male presented to the emergency department in Saint John, New Brunswick after a two-week history of feeling progressively dyspneic with activity, febrile with rigors, fatigued, and lethargic. He also described right upper quadrant abdominal pain. A CT scan of his abdomen was performed to evaluate the abdominal pain and showed splenic infarcts and mild colitis. A chest X-Ray was performed to evaluate the patient’s dyspnea and showed atelectasis and possible basilar consolidation. Blood work was significant for hemolytic anemia, thrombocytopenia, elevated CRP, LFTs, creatinine, and lactate. Peripheral blood smear revealed delicate ring forms with single infection, no extracellular forms or mature stages to assist in differentiation between malarial species or babesiosis. Additional history revealed that the patient had lived in New Brunswick since December 2022 with no recent international travel, however he had lived in Northern India up until the 1970s. There was recent travel to Nova Scotia 5 days prior to presentation. The patient did not recall any tick bites. Given his remote history of having lived in a malaria endemic region with potential Plasmodium vivax exposure and the severity of his current illness, the patient was placed on atovaquone/proguanil and azithromycin empirically to cover for both malaria and babesiosis. Plasmodium PCR returned negative, atovaquone/proguanil was discontinued, and the patient remained on atovaquone and azithromycin with a planned duration of 10 days. At this point, Babesia was favoured based on pathology and eventually confirmatory test with serum PCR positive for Babesia microti. The patient continued to improve clinically, mobilizing well, and remained afebrile. Lab abnormalities and cytopenia were normalizing. Parasitemia levels started at 5% and dropped to <0.1% prior to discharge.
Discussion: This case illustrates the overlap in lab and smear findings of malaria and Babesia. In the context of patients with no travel history suggestive of malaria or with appropriate risk factors, babesiosis should be placed on the differential for otherwise unexplained hemolytic anemia especially given its rise in Canada and the Atlantic provinces.
