[Elizabeth_Zeibig]_Clinical_Parasitology__A_Practi(z-lib.org)

CHAPTER 6 Select Sporozoa: Plasmodium and Babesia
131
CASE STUDY 6-1
UNDER THE MICROSCOPE
Bruno, a 48-year-old businessman, presents at the emergency
room with a 12-day history of headache, myalgia,
nausea, and vomiting. Patient history reveals that Bruno is
a consulting engineer for the Panama Canal. On his latest
trip, he failed to take his prophylaxis for malaria. According
to his general physician’s records, all his immunizations
(e.g., hepatitis, flu) are up to date. His fever was 103° F
(39° C) at the time of initial examination, but alternated
with periods of extreme cold and cyanosis. A complete
blood count was ordered, along with parasite examination
and urinalysis. The thin Giemsa film yielded the morphologic
forms noted in the diagram as a, b, and c.
a
b
c
1. What parasite do you suspect? Note the genus and
species. (Objective 6-13A)
2. Which factors in these diagrams were important in
deciding the species of this organism? (Objective 6-13A)
3. Differentiate the three forms of the parasite shown in
the diagram. What are the differences in morphology
that allow you to differentiate forms b and c? (Objectives
6-11, 6-13A)
4. Given that the organism is the one you have identified,
what other morphologic forms are likely to be seen in
the peripheral blood of this patient? What additional
forms might be seen if a different species in this genus
were involved? (Objective 6-13H)
5. State the common name of the disease usually caused
by this organism. (Objective 6-13B)
6. How did Bruno contract this parasitic infection? (Objective
6-13C)
7. Dark red, cleft-shaped dots are seen in the red blood
cells of this patient. What are these dots called? Other
species in this genus show light pink, stippling-like dots
when infecting red blood cells. What are these dots
called? (Objectives 6-11)
FOCUSING IN
Malaria and babesiosis refer to disease processes
resulting from infections of parasites belonging to
the phylum Apicomplexa. Their respective genera
are Plasmodium and Babesia. Both genera of
parasites belong to the class of parasites that have
no obvious structures for the purpose of motility,
known as sporozoa. Of approximately 200 known
species of Plasmodium, only 10 have demonstrated
the ability to cause infection in humans.
There are over 100 known species of Babesia and,
of these species, four have been shown to cause
human disease. With one exception, this chapter
is limited to a discussion of the most common
clinical isolates in these genera. The most clinically
relevant organisms belonging to the genera of
Plasmodium and Babesia, and the ones included
in this discussion are Plasmodium vivax, Plasmodium
ovale, Plas modium malariae, Plasmodium
falciparum, Plasmodium knowlesi, Babesia
microti, and Babesia divergens.