Differentiating Babesia from Malaria

1
Differentiating Babesia from Malaria

• Devak Desai
• Junior Med Student
• July 12, 2005

2
Case Presentation

• Middle aged hypertensive and asplenic man
  presented with a pruritic rash on his right
  buttock accompanied by flu-like symptoms.
• 1010, arthralgias, myalgias, some nausea, and
  general malaise, and decreased appetite.
• Reports walking through a wooded area on Marthas
  Vineyard, an island off the coast of Mass.
• PE shows a well nourished man with no significant
  findings other than an erythmatous oropharynx
  without exudate.

3
Laboratory Data

• Normal WBC differential
• Blood smear numerous intraerythrocytes
  involving 2.7 of RBCs
• Direct Combs test was negative
• Positive serologic test for Lyme Disease

4
Peripheral Blood Smear

• Numerous erythrocytes are infected with the
  predominantly ring or pear-shaped form of Babesia
  microti.
• Pleomorphic rings with 1-3 chromotin dots per
  parasite.
• 3 dots is unique for Babesia.

5
Host Infection Cycle

• Infection begins when sporozoites are released
  from the deer ticks salivary gland during a
  blood meal.
• Sporozoites replicate directly in RBCs.
• Attachment and adsorption seems mediated through
  the C3b receptor.
• During invagination a clear vacuole appears.
• Babesia divided by asynchronous budding.
• The replicating structures are now called
  trophozoites.
• This is an asynchronous process with varying
  degrees of hemolysis.

6
Life cycle of Babesia spp. in the tick and
vertebrate hosts
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High Power

• White eccentric food vacuole in a ring form.
• Very transient stage in Malaria. Very rarely
  seen.

• Ring shaped trophozites
• The intraerythrocytic trophozoites multiply by
  binary fission or schizogony, forming two to four
  separate merozoites. .

8
the famous Maltese Cross

• Presence of 4 daughter merozoites in a tetrad
  is pathomnemonic.
• However, rarely seen.
• Never seen in malaria.

9
Multiply infected RBCs

• RBCs can be infected with multiple organisms at
  the same time. Up to 12 parasites may infect a
  single RBC.
• Plasmodium has up to 3 parasites/RBC.
• Unremarkable RBCs.

10
Other Sightings

• Parasite with a peripheral nuclear band
• Basket cell

• Syncytium of extracellular parasites
• Far more common in Babesia infections

11
Malaria Review
12
Epidemiology

• There are gt100 specicies of this intracellular
  parasite.
• Babesia microti is the predominant human
  pathogen, endemic to the NE and Midwest.
• 10-20 of adults are seropositive in endemic
  areas
• Natural parasite reservoir is rodents
• Carried by the hard-bodied Ixodes Deer tick.
• Also carries agents for Lyme Disease, and
  Ehrlichoisis.
• Can also be transferred transplacentally and
  through blood transfusion.

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Clinical presentation

• Ranges from asymptomatic infection to fatal
  illness (rare)
• No direct correlation between parasitemia and
  severity.
• More severe infection tends to occur in
  immunnocompromised, elderly, and the very young.
• The extreme end of the spectrum is often
  described as a malaria-like infection symptoms
  may include malaise, chills, mylagia, anemia,
  fatigue, and fever (as high as 1040).
• Some cases also described emesis, night sweats,
  weight loss, and hematuria.

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Special Case Splenectomy

• Most important risk factor for infection, esp.
  severe.
• Illness appears suddenly, with hemoglobinuria as
  the presenting symptom followed by jaundice due
  to severe hemolysis.
• Parasitemia can reach 80 of RBCs
• Can be a medical emergency.
• In the most severe cases, patients develop a
  shock-like picture, with renal failure and
  pulmonary edema.
• Chronic disease with many relapses over months to
  years may occur if not treated.

15
Co-Infection

• It is estimated from serologic surveys that as
  many as 13 of Lyme disease patients in
  babesia-endemic areas are coinfected with
  B. microti
• The initial symptoms of both babesiosis and Lyme
  disease overlap significantly.
• Like babesiosis, Lyme disease also presents with
  nonspecific symptoms of fever,fatigue, and other
  flu-like symptoms.
• Patients coinfected with B. microti and
  B. burgdorferi experience more severe symptoms,
  but does not increase the duration of Babesia
  parisitemia.
• Doxycycline will not kill Babesia.

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Diagnosis

• Diagnosis is based on clinical suspicion and
  history of exposure.
• Thick and thin smears remain most clinically used
  
• However, it is necessary to examine 200 to 300
  oil immersion fields before declaring a specimen
  negative.
• Various PCR detection assays are available for
  detection of B microtic and other species.
• More sensitive but also more time consuming and
  expensive.
• Indirect fluorescent antibody test can also be
  used as a confirmatory test.
• Can have false negatives (HIV) or false pos
  (autoimmune)

17
Treatment

• Current treatment is Quinine plus Clindamycin
• Better alternative treatment is Atovaquone plus
  Azithromycin
• This combo is almost as effective with fewer side
  effects.
• 72 receiving quinine and clindamycin had side
  effects attributed to the drugsdiarrhea,
  tinnitus, or vertigo
• 15 receiving atovaquone plus azithromycin
  experienced side effects (usually diarrhea or
  rash).
• For severe cases (asplenic) with high levels of
  parasitemia, RBC exchange transfusions may also
  be necessary.

18
Summary

• History check for recent travel
• Symptoms Babesia is milder and tends not to
  be cyclic.
• Smear Babesia has no schizonts, gametocyes, or
  ameboid trophozoites.
• Lab tests PCR or indirect antibody test.

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Conclusion

• Major deterrents to the diagnosis of babesiosis
  include the low index of suspicion by physicians
  (except in endemic areas), non-specific flu-like
  signs, and the use of automated cell readers that
  cannot detect merozoites in erythrocytes
• Disease is increasing in prevalence due to more
  people living in rural tick infested areas and as
  the number of immunocompromised in increasing.
• Also environmental such as the exponential rise
  in deer populations.
• Blood transfusion risk becoming an increasing
  problem.

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References

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  Jul
• Lantos PM. Krause PJ. Babesiosis similar to
  malaria but different Review. Pediatric Annals.
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