Plasmodium (protozoa that causes malaria)
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Transmitted by female Anopheles mosquito.
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Lifecycle includes liver (exoerythrocytic) and blood (erythrocytic) stages.
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Vivax and P. ovale form dormant hypnozoites in liver—cause relapses.
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Falciparum infects all RBC stages—highest parasitemia and severity.
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Symptoms (fever, chills) correlate with RBC rupture during schizont release.
Diagnosis of malaria
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Thick smear: Screening and parasite burden.
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Thin smear: Species identification.
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Rapid antigen tests: Useful in low-resource settings.
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PCR: High specificity, used in research.
Treatment principles
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Choice depends on species, severity, geography, and prior prophylaxis.
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Falciparum and P. knowlesi require urgent treatment due to severity.
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Primaquine needed for P. vivax and P. ovale to eliminate liver hypnozoites.
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IV therapy for severe malaria (e.g., IV artesunate or quinine, the latter has more side effects and not regularly available in United States).
Babesia (protozoa that causes Babesiosis)
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Transmitted by Ixodes tick (same as Lyme disease).
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Babesia microti is most common species in United States (Northeast, Midwest).
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Risk factors for severe disease: Asplenia, immunocompromised, elderly.
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Symptoms: Fever, hemolytic anemia, splenomegaly, hepatomegaly.
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Diagnosis: Blood smear (Maltese cross), PCR, serology.
Babesia treatment
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Mild to moderate: Atovaquone + Azithromycin.
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Severe: Clindamycin + Quinine.
Learning goals
- Compare and contrast the Plasmodium species lifecycles and describe how the stages correlate with clinical manifestations, diagnosis, and potential complications
- Describe the approach to choosing an anti-malarial based on Plasmodium species, geographic origin of infection, and side-effect profile
- Describe the epidemiology, clinical manifestations, and diagnostic testing modalities for Babesia
Required pre-class preparation
Study materials
These materials are not required; they are supplementary to large-group session. They are intended as a curated guide to content focused on the learning objectives. There are both textbook and video resources for this session for students to use per their preference. For each reference, I have designated the learning goal addressed with a learning goal icon and and number.
Click the book icons below to go to the library resources listed.
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Parasites > Protozoa> Sporozoa > Blood and Tissue > Malaria/Plasmodium and Babesiosis
- Section on Plasmodium spp
- 1 Section on the life cycle of malarial parasites: Good written description of the life cycle to accompany graphics of the life cycles (such as the CDC life cycle diagram or Figure 51-2).
- 1 Section on Morphology of Erythrocytic parasites and Physiology: While the microscopic appearance is paramount in malaria diagnostics, for your purposes, focusing on features that differentiate P. falciparum from the others is highest yield.
- 1 Section on Pathogenesis: The pathogenesis of malaria explains a lot of the clinical manifestations and the complications.
- 1 Figure 51-2. Malaria life cycle
- 2 Section on Treatment: Provides detailed discussion about the approach to treatment based on stages of the parasite life cycle. For a more basic overview of treatment approach, see Levinson’s text.
- 1 Section on Babesia
Plasmodium species comparison chart
This is an optional study guide. Details for P. malariae have been completed for you as an example.
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P. falciparum |
P. vivax |
P. ovale |
P. knowlesi |
P. malariae |
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Predominant geography |
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Rare. Temperate and subtropical |
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Erythrocyte target |
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Senescent cells only |
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Interval between merozoite release from RBCs |
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72 hours |
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Characteristic findings on smear |
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Band forms and all asexual stages seen |
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Dormant hepatic form/Relapsing (Y/N) |
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N |
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Severe Malaria (Y/N) |
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No cerebral malaria or circulatory collapse. Progressive renal disease in chronic infection |
check yourself
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