Babesia

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Babesia

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BABESIA osms.it/babesia PATHOLOGY & CAUSES RISK FACTORS ▪ Malaria-like parasitic infection ▫ Ixodes tick transmission ▪ Phylum Apicomplexa (same as Plasmodium, Toxoplasmosis) ▪ Common species ▫ Babesia microti most predominant (northeast, upper midwest United States) ▫ B. duncani (Western United States) ▫ B. divergens (Europe) ▪ Endemic area resident ▪ Endemic area travel, especially May– September ▪ Blood transfusion (last six months) ▪ Age > 50 ▪ Biologically male ▪ Asplenia ▪ Decreased immunity (malignancy, HIV/ AIDS infection, immunosuppressive drugs) ▪ Coinfection with Borrelia and/or Anaplasma ▪ Premature birth CAUSES COMPLICATIONS ▪ Ixodes scapularis tick: only recognized vector ▫ Same tick transmits Borrelia burgdorferi (→ Lyme disease; concurrently infects ⅔ babesiosis-infected individuals) and Anaplasma phagocytophilum (→ human granulocytic anaplasmosis; concurrently infects ⅓ babesiosis-infected individuals) ▫ Contaminated blood transfusion → rare human-to-human transmission ▪ Life cycle ▫ Two hosts: white-footed mouse, Ixodes tick (deﬁnitive) ▫ Blood meal → Babesia-infected tick sporozoites into mouse host → sporozoites directly invade mature mouse erythrocytes → sporogony (asexual reproduction; budding) → in blood, some parasites differentiate into male, female gametes → gametes unite → sporogonic cycle → sporozoites → tick bites human → 1–4 week incubation → sporozoites enter erythrocytes → sporogony ▪ Sporogony ▫ Asynchronous with host → no massive hemolysis (versus malaria) ▪ Tick’s nymph stage is most infectious 412 OSMOSIS.ORG ▪ ↑ occurence in anemic/parasitemic individuals ▫ Congestive heart failure ▫ Noncardiac pulmonary edema ▫ Acute respiratory distress syndrome ▫ Splenic infarct ▫ Splenic rupture ▫ Septic shock ▫ Myocardial infarction ▫ Disseminated intravascular coagulation ▫ Death SIGNS & SYMPTOMS ▪ Mostly asymptomatic, may persist undiagnosed months/years ▪ Blood-stage parasite multiplication → clinical manifestation ▪ Non-speciﬁc ﬂu-like symptoms (misdiagnosis common) ▫ Fatigue (gradual onset) ▫ Fever, chills, sweats ▫ Headache, myalgia, arthralgia ▫ Anorexia, nausea ▫ Cough

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Babesia

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A 56-year-old man presents to the hospital with two weeks of fever, fatigue, headache, and myalgia. The patient spent the last three months hiking in Africa, North America, and South America. Bloodwork reveals elevated hepatic transaminases as well as severe anemia. A thick and thin smear of peripheral blood is prepared with Giemsa stain. Examination of the smears under light microscopy shows cross-shaped inclusions within several erythrocytes. Which of the following organisms is most likely responsible for this patient’s findings?

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