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Intestinal Cestodes 169

thought to be a single organism. The life cycles of the
two species, T. solium and T. saginata, are practically
the same. However, humans are capable of acting as the
intermediate host for T. solium but not as an interme-
diate host for T. saginata. In the mid-nineteenth cen-
tury, a Hebrew scholar and theologian named Gottlob
Friedrich Heinrich Küchenmeister fed the pork tape- Source: Centers for Disease Control and Prevention (CDC)
worm to others who became infected. He has been cred-
ited with recognizing the differences between T. solium
and T. saginata based on the morphology of the scolex
of the two tapeworms, which are now named after their
primary hosts (pig and the cow) (Cox, 2002).
FIGURE 7-9 Taenia solium tapeworm scolex with its
Morphology 4 suckers, and 2 rows of hooks

The morphology of a Taenia solium tapeworm scolex
reveals four suckers and two rows of hooks, making it
almost impossible to dislodge the scolex from the tissue
where it is attached (Figure 7-9). In the human intestine
the cysticercus, or larval stage, for the organism develops
over approximately a 2-month period into an adult tape-
worm. These adults can survive for years by attaching to Source: Centers for Disease Control and Prevention (CDC)
and residing in the small intestine by using the suckers
and hooks located on its scolex.
Taenia saginata can grow to a length of up to 4 to
6 m long and 12 mm broad, but Taenia solium is slightly
smaller than T. saginata. T. saginata has a pear-shaped
scolex with 4 suckers but no hooks and no neck, whereas FIGURE 7-10 Egg of Taenia sp. with hooklets visible
T. solium has a neck. T. saginata has a long, flat body
with several hundred proglottids; T. solium is only about
0.1 m long, which translates to approximately 3 in long. retractable, conelike structure that is located on the an-
Each segment of the T. saginata is about 18 x 6 mm, terior end of the scolex and, in some species, is armed
with a branched uterus containing 15 to 30 branches; with hooks. Bothria are long, narrow, and weakly mus-
T. solium has proglottids that are 5 x 10 mm with 7 to 12 cular grooves characteristic of the pseudophyllidean
branches in the uterus. The eggs for both of the Taenia (order that includes D. latum) tapeworms, of which
species exhibit the same appearance as mentioned earlier Diphyllobothrium and Schistosoma spp. are members.
(Figure 7-10). They measure 35 x 45 micrometers and Acetabula (suckers like those of digenetic trematodes)
are roundish and yellow-brown. Peripheral radial stria- are characteristic of cyclophyllidean tapeworms, of
tions appear and a visible embryo with 3 hooklets. which Taenia spp. and Echinococcus are members
The scolex at the anterior end of the organism (Figure 7-11). Please note that the majority of human
contains a poorly organized and developed brain, tapeworms are cyclophyllideans.
called the “cephalic ganglion,” comprising the simple
nervous system typical of the tapeworm. When viewed Symptoms
externally, the scolex is characterized by organs that en-
able the parasites to hold fast to the tissues where they Most cases of taeniasis result in the individuals being
are feeding by attaching to certain organs of the host asymptomatic. If any symptoms occur, they usually
body. Depending on the species, these organs consist include mild diarrhea, abdominal discomfort, indiges-
of a rostellum, bothria, or acetabula. A rostellum is a tion, and mild fever may ensue. Slight increases in the