Babesia microti

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Babesia microti

• Jessica Grams
• Jennifer Wimpfheimer

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Outline

• Taxonomy
• Babesiosis
• Morphology
• Geographic Distribution
• Hosts
• Life Cycle
• Pathogenesis/Clinical Signs Symptoms
• Host Immune Response
• Diagnosis
• Treatment
• Public Health Concerns
• Crossword puzzle

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Taxonomy

• Kingdom Protista
• Phylum Apicomplexa
• Class Aconidasida
• Order Piroplasmida
• Family Babesiidae
• Babesia microti

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Babesiosis

• Prior to 1969 Babesia infections were rare and
  limited to B. divergens (a cattle parasite) and
  some others species that were parasitic in
  rodents.
• It was only seen in splenectomized patients who
  had disabled immune systems as a result of the
  splenectomy.
• 1969, Nantucket Island, Mass 1st human Babesia
  infection in a non-splenectomized patient.
• Hundreds of cases have been reported since.

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Morphology

• Easily misdiagnosed as Plasmodium in areas high
  in Malaria prevalence due to its ring shape
• Variation in shape and size
• Do not produce pigment

Intraerythrocytic Babesia microti
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Geographic Distribution

• Worldwide
• Europe B. divergens, most common
• United States B. microti, most common in NE and
  MW portions
• WA-1 strain recently found on west coast
• May not be as prevalent in malaria-endemic
  countries

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Hosts

• Definitive host Humans or Deer tick
• Vector Ixodes scapularis (Deer tick)
• Intermediate host White-footed mouse and other
  rodents and Deer
• When the deer or mouse pop. increases, the tick
  pop. does too.

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Life Cycle

• Babesia infected tick introduces sporozoites into
  the mouse host.
• Sporozoites enter erythrocytes and undergo
  asexual reproduction (budding).
• In the blood, parasites undergo male and female
  differentiation (micro- and macrogametes are
  formed).
• The deer tick (definitive host) takes a blood
  meal ingesting gametes, which can now undergo
  fertilization within the gut, 5. resulting in
  sporozoite formation. Spread to salivary glands.

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Life Cycle Contd

• 6. During a blood meal, the tick infects the
  human host. Inoculation occurs by a tick larva,
  nymph or adult.
• Sporozoites invade erythrocytes and a trophozoite
  differentiates, replicating asexually by budding
  responsible for the
• clinical manifestations. This
• forms 2-4 merozoites which
• eventually reinvade other RBCs.
• Humans are for all practical purposes dead-end
  hosts, because subsequent transmission after the
  tick feeds on a human is unlikely. Human to
  human transmission is well recognized to occur
  through blood transfusions. Babesia can be
  transmitted in utero.

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Pathogenesis (Signs Symptoms)

• 1-4 weeks (can last several weeks) fever,
  chills, headache, nausea, vomiting, and/or muscle
  aches (myalgia), hemolytic anemia, jaundice and
  splenomegaly.
• May be mild in otherwise healthy people
• May be asymptomatic
• Severe form of Babesiosis may be life-threatening
  if untreated (usually people who have been
  splenectomized, the elderly, or who have impaired
  immune systems).

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Host Immune Response

• Mice develop immunity
• CD4 T cells are partially responsible for
  resolution of primary infection and protection
  against re-infection.
• Influx in IgG due to the infection being in the
  blood

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Diagnosis

• Microscopic examination thick and thin blood
  smears stained with Giesma
• Antibody detection detects even low levels of
  parasitic invasion
• Indirect fluorescent antibody test (IFA) detects
  antibodies (IgM IgG) of patients with B.
  microti infection
• Recommended only if low levels of parasitemia or
  blood smear is inconclusive
• Diagnosis can be derived from molecular
  techniques, such as PCR
• Valuable in investigations of new Babesia species

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Treatment

• Clindamycin antibiotic with little or no side
  effects
• Quinine or Atovaquone antiparasitic
• Azithromycin antibiotic, some side effects
• Clindamycin combined with Quinine is treatment of
  choice
• FDA approved, but considered investigational

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Public Health Concerns

• Avoidance of endemic areas May-September
• Clothing that covers lower body and light colored
• Tuck pants into boots/shoes
• Repellent that contains Diethyltoluamide (DEET)
  should be applied regularly
• Inspect pets
• Avoid tall grass and brush
• Examine skin thoroughly and carefully remove
  ticks if found
• Avoid accepting blood donations from those with a
  history of tick bites

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• In conclusion, be aware of your surroundings,
  especially in areas with high deer tick
  populations.