Other Protozoan Infections
Carla S. Wilson, MD, PhD
Key Facts
Terminology
American trypanosomiasis
T. cruzi is endemic in South and Central America
African trypanosomiasis
T. brucei complex (gambiense, rhodesiense)
Rural West and Central Africa
Game reserves of East Africa
Babesiosis
B. microti, B. divergens, B. duncani
Endemic areas in USA include Northeast, Upper Midwest, California, and Washington state
Clinical Issues
T. cruzi infection
Acute Chagas disease
Chronic Chagas disease with cardiac and gastrointestinal disorders
T. b. gambiense infection
Chronic sleeping sickness
T. b. rhodesiense infection
Acute sleeping sickness
Babesia
Malaria-like symptoms
Microscopic Pathology
Extracellular trypomastigotes in blood
T. cruzi, T. brucei complex
Trophozoites (ring forms)
Babesia
Top Differential Diagnoses
Babesia vs. P. falciparum
T. b. gambiense vs. T. b. rhodesiense
Morphology indistinguishable in smears
 T. cruzi hemoflagellates in peripheral blood are about 20 µm in length and commonly have a C, S, or U shape  . Only single monomorphic forms are seen. |
 The kinetoplast  of T. cruzi is larger than that of T. brucei and may appear as a bulge on the posterior end. The nucleus is centrally located  , while the flagellum is medium in length. |
TERMINOLOGY
Abbreviations
Trypanosoma (T)
Babesia (B)
Synonyms
Chagas disease (American trypanosomiasis)
African sleeping sickness (African trypanosomiasis)
Red water fever, tick fever (Babesiosis)
Definitions
Species that infect humans
American trypanosomiasis
T. cruzi
African trypanosomiasis
T. brucei complex (gambiense, rhodesiense)
Babesiosis
B. microti, B. divergens, B. duncani
ETIOLOGY/PATHOGENESIS
Trypanosomiasis
American trypanosomiasis
T. cruzi transmitted by reduvid bug (kissing bug)
Trypomastigotes passed in feces of bug during blood meal
Trypomastigotes enter breaks in skin, nasal, and oral membranes of humans
Transform to amastigotes in tissues and multiply
Develop into trypomastigotes that enter bloodstream when cells rupture
Infect tissues, especially skeletal and smooth muscles, nerves
Infection also occurs through
Blood transfusions from infected but asymptomatic individuals
Congenital Chagas disease seen in ˜ 5% of infants born to infected mothers
African trypanosomiasis
T. brucei complex transmitted by tsetse flies
Trypomastigotes inoculated during biting
Multiply in blood stream by binary fissio
Carried in bloodstream to lymph nodes, heart, other organs, CNS
Causes higher parasitemias than T. cruzi
Trypomastigotes change antigenic structure of glycoprotein coat to evade immune destruction
Babesiosis
Ticks (genus Ixodes) inject Babesia sporozoites into humans
Sporozoites invade RBCs
Undergo asexual division through budding
Trophozoites lyse RBCs and release merozoites
Merozoites invade RBCs
CLINICAL ISSUES
American Trypanosomiasis
Epidemiology
T. cruzi is endemic in South and Central America
Affects ˜ 8 million people
Prevalent in Brazil, Argentina, Mexico
Presentation
Chagoma
Inflamed swelling at site of parasite entry
Develop unilateral eyelid edema, conjunctivitis, facial lymphadenopathy
Acute infection
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