Egg granuloma
in liver
Gut
Eggs pass out
in faeces
Miracidium hatches
out from egg
Miracidium penetrates snail
Sporocyst develop
in snail
Free-swimming
cercaria exit
snail
Cercaria penetrate
skin
Schistosomule
migrates
Worms mature into
adults
Liver
Gut
Lungs
Adult male and female
worms in mesenteric
blood vessels
Sheep eats metacercaria
Cercaria encysts
on vegetation
Cercaria migrates to
vegetation
Redia
Free-swimming cercaria
exit from snail Miracidium
penetrates foot
Free-swimming
miracidium
hatches out
Sporocyst
Eggs pass
out via
faeces
Liver
- Figure 4.11Fasciola Adult worm in bile duct
hepaticais commonly
known as the liver fluke.
The adult lives in the bile
duct. The eggs pass out
via the faeces into fresh
water and hatch into a
miracidium. The miracidia
invade an aquatic snail.
Within the snail the
miracidium forms first
into a sporocyst, then
into a redia and finally
into a cercaria. The free-
swimming cercaria encysts
on vegetation and remains
until eaten.
- Figure 4.10The adult
males and females of the
trematode Schistosoma
mansonilive within the
mesenteric blood vessels.
The eggs pass out with
the faeces and hatch in
fresh water into a free-
living miracidium. The
miracidium invades a fresh
water snail and develops
into a sporocyst. Within
the sporocyst, cercariae
with forked tails develop.
They escape into fresh
water from the snail and
swim until they come in
contact with the skin of
the host. The cercariae
penetrate the skin, shed
their tails, and the
juveniles (schistosomulae)
enter the dermal layers
and slowly migrate via the
lungs to liver and the
mesenteric blood vessels.
It takes about 28 days to
complete the migration
and mature.
