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Intestinal Cestodes 177

indigestion accompanied with stomach pain, most in- egg balls and are eliminated in the host’s feces and are
fected persons are asymptomatic. then ingested by fleas. When the fleas are ingested acci-
dentally by another mammal after the tapeworm larvae
Life Cycle partially develop, the cysticercoid larvae that developed
in the flea are swallowed. Humans, particularly children,
The definitive host is generally a cat or dog. Gravid pro- become infected after accidentally ingesting the fleas
glottids are passed in the animal’s feces and the inter- containing larvae. The larvae from the fleas then mature
mediate host, the dog or cat flea, ingests the eggs, which to adulthood in the host.
continues the life cycle. Eggs may occur as clusters called
Disease Transmission

MICROSCOPIC DIAGNOSTIC Transmission of the D. caninum cestode occurs predom-
inantly as a result of hand-to-mouth ingestion of fleas
FEATURE from infected domestic animals in which the developing
cysticercoid larvae are found. Transmission of the infec-
General Classification—Cestode tion also results not only from fleas but from ingestion of
(cucumber or double-pore tapeworm) beetles and other arthropods that may be in contact with
domestic animals.
Organism Diphylidium caninum
Specimen Required Stool specimen
Laboratory Diagnosis
Stage Adult
Size Worm may reach a Characteristic gravid proglottids and egg packets found
length of up to following disintegration of proglottids in human feces
10–50 cm
Shape Segmented
Motility Not demonstrated
Other Features The larvae mature MICROSCOPIC DIAGNOSTIC
to adulthood in the FEATURE
intestine
Scolex has 4 suckers
as do most cestodes, General Classification—Cestode egg
and contains several
rows of small hook- Organism Diphylidium caninum
like spines on a cone- Specimen Required Feces
shaped rostellum of
Stage Egg packet
the scolex
Size The eggs range
D. caninum
from 30–60 μm
Shape Almost completely
concentric
Shell Thin and colorless
Other Features Colorless eggs have
6-hooked oncosphere
Delmar/Cengage Learning present in each egg
and are enclosed in
a membrane-bound
packet of usually 5–20
eggs per packet