Page 131 - Medical Parasitology_ A Textbook ( PDFDrive )

124 11 Cestodes: Tapeworms

Fig. 11.5 Egg of
Taenia

a b c

Fig. 11.6 Taenia solium. (a) Scolex, (b) Gravid proglottid, (c) Larvae (cysticercus cellulosae)

The strobila consists of less than 1000 proglottids. The gravid segments are about
12 mm long and 6 mm broad and each gravid segment has 7–13 lateral uterine
branches (Fig. 11.6b). They are hermaphrodites. The gravid segments are expelled
in chains through the host’s anus.
Cysticercus cellulosae is the larval form of T. solium (Fig. 11.6c) and also the
infective form of the parasite to humans. It can develop in various organs of pig as
well as in human. Its morphology is similar to cysticercus bovis. The morphology
of the invaginated scolex of cysticercus cellulosae is similar to the adult scolex of
Taenia solium.

Life Cycle (Fig. 11.7)
(1) Eggs or gravid proglottids in faeces of infected humans are passed out. (2) Cattle
(T. saginata) and pigs (T. solium) become infected by ingesting vegetation contami-
nated by eggs or gravid proglottids. (3) Oncospheres hatch, penetrate intestinal wall
and circulate to muscles to develop into cysticerci. (4) Humans acquire infection by
ingesting raw or undercooked infected meat containing the larvae. (5–6) Adults
develop in the small intestine of human and scolex attaches to the mucosa of the
small intestine.