Page 128 - Medical Parasitology_ A Textbook ( PDFDrive )

Pseudophyllidean Tapeworms 121

Spirometra

Distribution
Spirometra can accidentally infect human and cause sparganosis. Sparganosis has
been reported mostly from Japan and Southeast Asia. The disease is caused by spar-
ganum (plerocercoid larva) of the parasite.

Habitat
In human, plerocercoid larva is found in subcutaneous tissue and other organs. It
does not grow into adult in human. Adult worms live in the intestinal tract of defini-
tive host (cats and dogs).

Morphology
The sparganum larvae are white, wrinkled and ribbon shaped. They measure from a
few millimetres to several centimetres in length. The anterior end can invaginate and
appears like sucking grooves as seen in the scolex of the mature worm.
The eggs of Spirometra resemble the eggs of Diphyllobothrium latum but smaller.
Life Cycle (Fig. 11.3)
(1) Unembryonated eggs are passed in faeces of cats and dogs. (2) Eggs embryonate
in water. (3) Coracidia hatch from eggs and are ingested by crustaceans. (4)

Infected crustacean ingested
by second intermediate host
(fish, reptiles, amphibians).
Procercoid larva released
from crustacean, develops
into plerocercoid i
larva. 5 Predator eats
infected second
intermediate host
Procercoid 6 i = Infective Stage
larvae in body d = Diagnostic
cavity of Stage
crustaceans
4
8

7
Coracidia hatch Adults in small
from eggs and are intestine
ingested by 3
crustaceans.
d
2 Eggs embryonate 1 Unembryonated eggs
in water passed in faeces
Fig. 11.3 Life cycle of Spirometra. (Reproduced from https://www.cdc.gov/dpdx/sparganosis/
index.html)