[Elizabeth_Zeibig]_Clinical_Parasitology__A_Practi(z-lib.org)

CHAPTER 11 The Trematodes
277
Quick Quiz! 11-13
In addition to its typical location, Paragonimus eggs
are also known to cause serious complications when
recovered in which of the following? (Objective 11-8)
A. Bile
B. Cerebrospinal fluid
C. Brain tissue
D. Feces
Quick Quiz! 11-14
A key feature that distinguishes Paragonimus from
the other trematode eggs is which of the following?
(Objective 11-9)
A. Prominent operculum
B. Obvious terminal shell thickening
C. Discrete shoulders
D. Three pairs of hooklets
Quick Quiz! 11-15
The typical transmission route of Paragonimus to
humans consists of which of the following? (Objective
11-5)
A. Consumption of contaminated crayfish or crabs
B. Swimming in contaminated water
C. Hand-to-mouth contamination
D. Walking barefoot on contaminated sandy soil
SCHISTOSOMA SPECIES
Schistosoma mansoni
(shis’to-so’muh/man-so’nigh)
Common name: Manson’s blood fluke.
Schistosoma japonicum
(shis’to-so’muh/ja-pon’i-kum)
Common name: Blood fluke.
Schistosoma haematobium
(shis’to-so’muh/hee-muh’-toe’bee-um)
Common name: Bladder fluke.
Common Schistosoma spp. disease and condition
names: Schistosomiasis, bilharziasis, swamp
fever, Katayama fever.
There are many species of schistosomes but
only five infect humans. Schistosoma intercalatum
is found in small pockets of Africa and
Schistosoma mekongi is found in Southeast Asia.
Neither will be discussed further because they are
of lesser importance. Although the differences
among the Schistosoma are numerous, the three
species of human significance have many similarities.
To avoid repeating much of the same
information, these organisms are discussed as a
unit in this section.
Schistosomiasis has recently been recognized
as a major parasite cause of morbidity and occasional
mortality, especially in sub-Saharan Africa.
Along with HIV and malaria, disability from
schistosomiasis caused by anemia, chronic pain,
diarrhea, exercise intolerance, and undernutrition
makes it a major problem in many parts of
Africa and other areas of the world.
Morphology
Eggs. The average Schistosoma egg is comprised
of a developed miracidium (Table 11-5).
The presence of lateral or terminal spines, as well
as the organism’s shape and size, aid in species
identification.
Schistosoma mansoni (Fig. 11-9) is relatively
large, measuring 112 to 182 µm by 40 to 75 µm.
The organism is somewhat oblong and possesses
a prominent large lateral spine.
The somewhat roundish Schistosoma japonicum
(Fig. 11-10) is the smallest of the Schistosoma
spp., measuring 50 to 85 µm by 38 to
60 µm. The egg is characterized by the presence
of a small lateral spine, which is often difficult
to detect on microscopic examination.
Schistosoma haematobium (Fig. 11-11) resembles
S. mansoni in size and shape. The somewhat
oblong egg measures 110 to 170 µm by 38 to