cestodes (tapeworms) Taenia saginata (beef tapeworm) and T.
solium (pork tapeworm). Taenia solium can also cause
Life cycle of
Taenia saginata and Taenia solium
Humans are the only definitive hosts for Taenia saginata and
Taenia solium. Eggs or gravid proglottids are passed with feces
the eggs can survive for days to months in the environment. Cattle (T.
saginata) and pigs (T. solium) become infected by ingesting
vegetation contaminated with eggs or gravid proglottids
In the animal's intestine, the oncospheres hatch
invade the intestinal wall, and migrate to the striated muscles, where
they develop into cysticerci. A cysticercus can survive for several
years in the animal. Humans become infected by ingesting raw or
undercooked infected meat
In the human intestine, the cysticercus develops over 2 months into an
adult tapeworm, which can survive for years. The adult tapeworms attach
to the small intestine by their scolex
reside in the small intestine
Length of adult worms is usually 5 m or less for T. saginata
(however it may reach up to 25 m) and 2 to 7 m for T. solium.
The adults produce proglottids which mature, become gravid, detach from
the tapeworm, and migrate to the anus or are passed in the stool
(approximately 6 per day). T. saginata adults usually have 1,000
to 2,000 proglottids, while T. solium adults have an average of
1,000 proglottids. The eggs contained in the gravid proglottids are
released after the proglottids are passed with the feces. T.
saginata may produce up to 100,000 and T. solium may produce
50,000 eggs per proglottid respectively.
are worldwide in distribution. Taenia solium is more prevalent
in poorer communities where humans live in close contact with pigs and
eat undercooked pork, and is very rare in Muslim countries.
taeniasis produces only mild abdominal symptoms. The most striking
feature consists of the passage (active and passive) of proglottids.
Occasionally, appendicitis or cholangitis can result from migrating
proglottids. Taenia solium taeniasis is less frequently
symptomatic than Taenia saginata taeniasis. The main symptom is
often the passage (passive) of proglottids. The most important feature
of Taenia solium taeniasis is the risk of development of
identification of eggs and proglottids in feces is diagnostic for
taeniasis, but is not possible during the first 3 months following
infection, prior to development of adult tapeworms. Repeated
examination and concentration techniques will increase the likelihood of
detecting light infections. Nevertheless, speciation of Taenia
is impossible if solely based on microscopic examination of eggs,
because all Taenia species produce eggs that are morphologically
identical. Eggs of Taenia sp. are also indistinguishable from
those produced by cestodes of the genus Echinococcus (tapeworms
of dogs and other canid hosts). Microscopic identification of gravid
proglottids (or, more rarely, examination of the scolex) allows species
TAKE EXTREME CARE IN PROCESSING THE SAMPLES! INGESTION OF EGGS CAN
RESULT IN CYSTICERCOSIS!
may prove useful especially in the early invasive stages, when the
eggs and proglottids are not yet apparent in the stools.
comparison with other intestinal parasites
simple and very effective. Praziquantel* is the drug of choice.
* This drug is
approved by the FDA, but considered investigational for this purpose.