II. Epidemiology

  1. Region affected
    1. Sporadic cases worldwide
    2. Endemic areas predominately in United States (Northeastern and Midwest U.S.)
      1. Massachusetts Islands: Nantucket, Martha's Vineyard
      2. New York Islands (Long Island, Shelter Island)
      3. Connecticut
      4. Cases also noted in California and southern states
  2. Peak transmission: May to September
  3. Incidence: 1000 to 2000 cases per year in U.S.
  4. Transmission
    1. Reservoir
      1. Multiple hosts including the white-footed mouse
    2. Tick-borne infection (Ixodid ticks)
      1. Ixodes dammini or Ixodes Scapularis
      2. Ixodes ricinus
      3. Tick must attach for 24 hours before transmission
    3. Less common transmission
      1. Red Blood Cell Transfusion
        1. Risk 0.17% in endemic regions
      2. Transplacental and perinatal transmission
  5. Incubation
    1. After Tick Bite: 5 to 33 days (may be as long as 9 weeks in some cases)
    2. After Blood Transfusion: over 60 days
  6. Ages affected: 40 to 50 years old

III. Pathophysiology

  1. Protozoans
    1. United States (mostly in Northeastern U.S.)
      1. Babesia Microti (small mammal and primate hosts)
    2. Europe
      1. Babesia divergens (rat, gerbil, cow hosts)
      2. Babesia bovis
  2. Infection
    1. Invades and replicates within Red Blood Cells
    2. Similar to Malaria

IV. Risk factors: Severe infection

  1. Older age (>60 years old)
  2. Asplenic patient
  3. Immunodeficiency (e.g. AIDS)
  4. Rituximab

VI. Symptoms

  1. Onset 1-9 weeks after exposure (Tick Bite)
  2. Similar to Malaria symptoms
  3. Generalized symptoms (Influenza-like symptoms)
    1. Fever, chills and diaphoresis (drenching sweats)
    2. Weakness
    3. Weight loss
    4. Arthralgia
    5. Myalgia
    6. Fatigue
    7. Diaphoresis
  4. Gastrointestinal symptoms
    1. Anorexia
    2. Nausea
    3. Abdominal Pain
    4. Vomiting
    5. Diarrhea
  5. Respiratory symptoms
    1. Cough
    2. Shortness of Breath
  6. Genitourinary symptoms
    1. Dark Urine
  7. Neurologic symptoms
    1. Headache
    2. Photophobia
    3. Neck and back stiffness
    4. Altered Level of Consciousness

VII. Signs

VIII. Differential Diagnosis

  1. Falciparum Malaria
    1. Both cause Hemolytic Anemia and Renal Failure
    2. Both cause high fever, Jaundice and Hemoglobinuria
  2. Other tick-borne illness
    1. Deer Tick (Ixodes tick) is also the vector for Lyme Disease and Anaplasmosis

IX. Labs

  1. Complete Blood Count
    1. Hemolytic Anemia (unique to Babesia compared with Lymes and Anaplasmosis)
    2. Decreased Leukocyte count
    3. Thrombocytopenia may be present
  2. Renal Function
    1. Increased Serum Creatinine and Blood Urea Nitrogen
  3. Liver Function Tests
    1. Increased transaminases (AST, ALT)
    2. Increased Lactate Dehydrogenase (LDH)
    3. Increased Serum Bilirubin
  4. Urinalysis
    1. Proteinuria

X. Diagnosis

  1. Peripheral Smear (Wright stain or Giemsa stain)
    1. Intraerythrocytic Parasites
    2. Similar to plasmodium (Malaria) except
      1. Babesia form tetrads (Maltese cross) within the RBCs
      2. No hemozoin pigments in RBCs
      3. Extracellular merozoites
    3. Contrast with intracellular Monocyte inclusions in Ehrlichiosis (morulae)
    4. Low Test Sensitivity (repeat samples may be needed)
  2. Serologic Detection
    1. Immunofluorescent Antibody titer >1:64
    2. Polymerase chain reaction
  3. Babesia PCR
  4. Consider co-transmission of other tick-borne infection
    1. Borrelia Burgdorferi (Lyme Disease)
    2. Anaplasmosis

XI. Management: Antibiotics

  1. Babesia is among a couple of Tick Borne Illnesses that do not respond to Doxycycline (Tularemia is the other)
  2. Mild to Moderate Disease: Combination Atovaquone and Azithromycin (preferred regimen)
    1. Antibiotic Course: 7 to 10 days (extend to 6 weeks for relapsing or persistent infection)
    2. Atovaquone (Mepron) 750 mg orally twice daily AND
    3. Azithromycin (Zithromax)
      1. First day: 500 mg orally
      2. Subsequent days: 250 mg orally daily
  3. Severe Disease: Combination Quinine and Clindamycin
    1. Antibiotic Course: 10 days
    2. Quinine (dosing is for salt component)
      1. Adult: 650 mg orally three times daily
      2. Child: 8 mg/kg (up to 650 mg) orally every 8 hours
    3. Clindamycin
      1. Adult: 300-600 mg IV q6 hours or 600 mg orally tid daily (or 1.2 g orally twice daily)
      2. Child: 7-10 mg/kg (up to 600 mg) IV or oral every 6-8 hours
  4. Exchange Transfusion
    1. Indicated in Critical Illness
    2. Blood Parasitemia exceeding 10%
    3. Massive Hemolysis
    4. Asplenic patient

XII. Course

  1. Variable
  2. Carried asymptomatically for years in some patients
  3. Mortality: 6-10% in severe cases (esp. Immunocompromised, Asplenia)

XIV. References

  1. Della-Giustina, Fox and Siegel (2021) Crit Dec Emerg Med 35(4): 17-23
  2. (2016) Sanford Guide to Antibiotics App, accessed 4/12/2016
  3. Green and Millsap (2016) Crit Dec Emerg Med 30(1): 4
  4. Boustani (1996) Clin Infect Dis 22:611-5 [PubMed]
  5. Krause (2000) N Engl J Med 343:1454-8 [PubMed]
  6. Mylonakis (2001) Am Fam Physician 63(10):1969-74 [PubMed]
  7. Pace (2020) Am Fam Physician 101(9): 530-40 [PubMed]
  8. Pruthi (1995) Mayo Clin Proc 70:853-62 [PubMed]

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Related Studies

Ontology: Babesia (C0004572)

Definition (MSHCZE) Prvok vyvolávající babesiózu. Velikost cca 2 m, vyvíjí se v klíšťatech a u teplokrevných živočichů. B. bovis a B. divergens se vyskytují u skotu, B. microti u drobných hlodavců. Vývoj u nich probíhá v erytrocytech. (cit. Velký lékařský slovník online, 2013 http://lekarske.slovniky.cz/ )
Definition (MSH) A genus of tick-borne protozoan parasites that infests the red blood cells of mammals, including humans. There are many recognized species, and the distribution is world-wide.
Definition (CSP) genus of tick borne protozoan parasites that infests the red blood cells of mammals, including humans; there are many recognized species, and the distribution is world wide.
Concepts Eukaryote (T204)
MSH D001403
SnomedCT 35029001
LNC LP19999-9
English Piroplasma, Babesia, Babesias, Piroplasmas, babesia, Babesia Starcovici, 1893, Genus: Babesia, Nuttallia, Babesia (organism), Babesia, NOS, Nuttallia, NOS
French Piroplasma, Piroplasme, Babésia, Babesia
Swedish Babesia
Japanese バベシア, Babesia属, バベシア, バベシア属, ピロプラズマ属, フタゴバベシア, ピロプラスマ属, ピロプラズマ
Czech Babesia, Infekce způsobená rodem Babesia
Finnish Babesia
Italian Piroplasma, Babesia
Polish Babezja
Hungarian babesia
Norwegian Babesia, Piroplasma
Spanish Babesia (organismo), Babesia, Piroplasma
German Babesia, Piroplasma
Dutch Babesia, Piroplasma
Portuguese Babesia, Piroplasma

Ontology: Babesiosis (C0004576)

Definition (MSH) A group of tick-borne diseases of mammals including ZOONOSES in humans. They are caused by protozoa of the genus BABESIA, which parasitize erythrocytes, producing hemolysis. In the U.S., the organism's natural host is mice and transmission is by the deer tick IXODES SCAPULARIS.
Definition (MSHCZE) Onemocnění způsobené parazitujícím prvokem Babesia, který se vyskytuje zejm. u hlodavců a na člověka se přenáší kousnutím klíštěte. Příznaky jsou do jisté míry podobné malárii, prvok rovněž napadá červené krvinky a může způsobit jejich rozpad (hemolýzu). U lidí je onemocnění vzácné, těžký průběh může mít u splenektomovaných osob. Léčí se chemoterapeutiky. (cit. Velký lékařský slovník online, 2013 http://lekarske.slovniky.cz/ )
Definition (NCI) A parasitic infection caused by Babesia. It is transmitted by ticks and infects the red blood cells. Signs and symptoms include fever, fatigue and hemolytic anemia.
Definition (CSP) tickborne disease caused by infection with protozoa; occurs in wild and domestic animals; in humans causes malaria-like symptoms, myalgia, nausea and splenomegaly; classic zoonotic disease.
Concepts Disease or Syndrome (T047)
MSH D001404
ICD9 088.82
ICD10 B60.0
SnomedCT 187241002, 276204002, 21061004
LNC LA10434-1
English Babesiases, Babesiasis, Babesioses, Babesiosis, Piroplasmoses, Piroplasmosis, babesiasis, babesiosis, babesiosis (diagnosis), Babesia infections, Babesiosis [Disease/Finding], Babesia Parasite Infections, Infections, Babesia Parasite, Babesia Parasite Infection, Infection, Babesia Parasite, babesia infection, Infection by babesia (disorder), Infection by Babesia, Infection by babesia, Babesiosis (disorder), piroplasmosis, Piroplasma; infection, Babesia; infection, infection; Babesia, infection; Piroplasma, Infection by Babesia, NOS
Italian Infezioni da Babesia, Babesiasi, Piroplasmosi, Babesiosi
Japanese バベシア感染, バベシアショウ, バベシアカンセン, バベシア症, バベシア病, ピロプラズマ病, ピロプラスマ病, ピロプラスマ症, ピロプラズマ症
Swedish Babesios
Finnish Babesioosi
Czech Infekce způsobené babesiemi, Babesióza, babezióza, babesióza, piroplazmóza
Korean 바베스열원충증
French Infection parasitaire par Babésia, Infections à Babesia, Babésiellose, Babésiose, Piroplasmose
Polish Babezjoza
Hungarian Babesia fertőzések, babesiosis
Norwegian Babesiose
Dutch Babesia; infectie, Piroplasma; infectie, infectie; Babesia, infectie; Piroplasma, Babesia-infecties, babesiosis, Babesiose, Babesiosis, Piroplasmose
Spanish babesiasis, babesiosis (trastorno), babesiosis, infección por Babesia, piroplasmosis, Infecciones por babesia, Babesiosis, Babesiasis, Piroplasmosis
Portuguese Infecções por Babesia, Babesiose, Babesíase, Piroplasmose
German Babesia-Infektionen, Babesiasis, Babesiose, Piroplasmosis