About Medical Parasitology

New Infections

Ova & Parasite (O&P) Exams

CPT Codes

Quizzes, General

Quizzes, Histology

Quizzes, Blood

Review Tests


Information Tables

Organism Index (A-Z)

Untitled Document

Presentation of Quiz #9

A 61-year-old male presented to his physician with a history of symptoms, beginning about three weeks after he returned from a trip. Symptoms included general malaise, followed by fever, chills, headaches and back pain. The man lived in southern Texas and had returned from a photographic safari to Africa, including Kenya, Tanzania, Uganda, and South Africa. He had seen a physician prior to returning to the United States and had received some antimalarial medication. He was an active wildlife photographer and was often exposed to a number of life zones and resident plants, animals, insects, etc., both at home and on trips outside of the United States.

Although both the patient and several others in the group remembered being bitten by insects, he was the only one who was symptomatic. On examination he was found to have several swollen areas, including a lymph node on his neck and a draining lesion on his upper arm.

Blood was drawn for routine hematology procedures and a specimen was also drawn to be sent to microbiology for examination as blood films stained with Giemsa stain. Based on his travel history, additional laboratory revealed a slightly elevated white blood cell count with a relative lymphocytosis. His gamma globulin level was elevated with a marked elevation of the IgM.

Please comment on the possible diagnosis related to the history of insect bites, the patient's clinical symptoms and the relative travel history. Routine examination of thin blood films revealed the following:

1. Thin blood film

2. Thin blood film

3. Thin blood film

Scroll Down for Answer and Discussion







Answer and Discussion of Quiz #9

The images presented in Diagnostic Quiz #9 are the following:

  1. Trypanosoma brucei rhodesiense
  2. Trypanosoma brucei rhodesiense (note dividing forms - not seen in Trypanosoma cruzi infection)
  3. Trypanosoma brucei rhodesiense

Comment: This was a case of African trypanosomiasis, probably caused by T. b. rhodesiense (East African Trypanosomiasis) based on travel history (Kenya, Uganda), the severity of symptoms, and overall description of the case. Although the man lived in southern Texas where Trypanosoma cruzi is found (cause of Chagas' disease, American Trypanosomiasis), the African trypomastigotes and the American trypomastigotes look quite different.

Trypanosoma cruzi

Trypanosoma b. rhodesiense


The African trypomastigotes (both East and West African trypomastigotes) (see right photograph above) have a very small kinetoplast (the dot at one end of the organism), while T. cruzi tends to have a very large kinetoplast that appears to go beyond the body of the organism (see left photograph above). Both organisms can actually be in a "C" shape; this configuration alone does not indicate infection with T. cruzi.

The course of infection in African trypanosomiasis occurs in three stages. Soon after inoculation of the metacyclic trypanosomes by an infected tsetse fly, an inflammatory lesion develops at the site of inoculation; this lesion is called the trypanosomal chancre. Trypomastigotes then invade the local lymphatics and later the bloodstream. After a time, the organisms invade the choroid plexus and enter the brain and cerebrospinal fluid (CSF). There is quite a bit of variation between the two diseases caused by East African and West African trypanosomiasis. In the East African disease (T. b. rhodesiense), chancres are common, the hemolymphatic stage is severe, and rapidly progresses to a fatal meningoencephalitis, often within months of infection. With the West African form of the disease (T. b. gambiense), chancres are uncommon, the hemolymphatic stage may not be seen, and meningoencephalitis progresses very slowly, often over several years, thus the "sleeping sickness" syndrome.

During the course of the infection, the number of trypomastigotes in the blood fluctuates. This relapsing parasitemia is due to the host's immune response to the parasites. Each decline in parasite number results from the antibody-mediated destruction of trypomastigotes bearing a particular variant surface glycoprotein (VSG). Each new wave of parasitemia represents the growth of a trypomastigote population expressing an antigenically different VSG. This process of ANTIGENIC VARIATION is a feature of all African trypomastigotes. Since each trypomastigote expresses only one VSG at a time and has as many as 1,000 different VSG genes, the number of different variable antigen types (VATs) that can be expressed during an infection is quite large. The continued response of the host to the new/different variable antigen types leads to elevated gamma globulins, particularly the IgM levels, including the CSF. Generally, if an individual does not have an elevated IgM, they almost certainly do not have African trypanosomiasis.

Key Points - Laboratory Diagnosis

  1. Trypomastigotes are highly infectious, and health care workers must use bloodborne pathogen precautions.
  2. Trypomastigotes may be detected in aspirates of the chancre and enlarged lymph nodes in addition to blood and CSF.
  3. Concentration techniques, such as centrifugation of CSF and blood, should be used in addition to thin and thick smears (Giemsa or Wright's stain).
  4. Trypomastigotes are in highest numbers in the blood during febrile periods.
  5. Multiple daily blood examinations may be necessary to detect the parasite.
  6. Blood and CSF specimens should be examined during therapy and 1 to 2 months posttherapy


  1. Garcia, L.S. 2016. Diagnostic Medical Parasitology, 6th Ed., ASM Press, Washington, D.C.
  2. Warren, K.S. and A.A.F. Mahmoud.1990. Tropical and Geographical Medicine, 2nd ed., McGraw-Hill Inc., New York, NY.


Each Quiz has a two section format: the first section will present the Quiz topic and the second section will provide a discussion of the answer and/or various options in response to the Quiz situation presented to the user. In some situations, there may be more than one correct response.

The content within this site is made possible through the extensive contribution of Lynne S. Garcia, M.S., MT(ASCP), CLS(NCA), BLM(AAB), F(AAM), Director, Consultantation and Training Services (Diagnostic Medical Parasitology and Health Care Administration). For additional information, she can be contacted at LynneGarcia2@verizon.net.

Reference: Garcia, L.S. 2015. Diagnostic Medical Parasitology, 6th Ed., ASM Press, Washington, D.C.

Quiz 1 Quiz 2 Quiz 3
Quiz 4 Quiz 5 Quiz 6
Quiz 7 Quiz 8 Quiz 9
Quiz 10 Quiz 11 Quiz 12
Quiz 13 Quiz 14 Quiz 15
Quiz 16 Quiz 17 Quiz 18
Quiz 19 Quiz 20 Quiz 21
Quiz 22 Quiz 23 Quiz 24
Quiz 25 Quiz 26 Quiz 27
Quiz 28 Quiz 29 Quiz 30
Quiz 31 Quiz 32 Quiz 33
Quiz 34 Quiz 35 Quiz 36
Quiz 37 Quiz 38 Quiz 39
Quiz 40 Quiz 41 Quiz 42
Quiz 43 Quiz 44 Quiz 45
Quiz 46 Quiz 47 Quiz 48
Quiz 49 Quiz 50 Quiz 51
Quiz 52 Quiz 53 Quiz 54
Quiz 55 Quiz 56 Quiz 57
Quiz 58 Quiz 59 Quiz 60
Quiz 61 Quiz 62 Quiz 63
Quiz 64 Quiz 65 Quiz 66
Quiz 67 Quiz 68 Quiz 69
Quiz 70 Quiz 71 Quiz 72
Quiz 73 Quiz 74 Quiz 75
Quiz 76 Quiz 77 Quiz 78
Quiz 79 Quiz 80 Quiz 81
Quiz 82 Quiz 83 Quiz 84
Quiz 85 Quiz 86 Quiz 87
Quiz 88 Quiz 89