Adults reside in the mucosa of human small intestine >>
Females lay unembryonated eggs >>
Eggs may embryonate inside the host, causing autoinfections
More commonly, eggs pass out of the host in feces >>
When fecal matter reaches water, the eggs embryonate >>
Small fish ingest the embryonated eggs >>
The eggs hatch, and larvae penetrate the intestines to invade the mesenteric tissue of the fish >>
Juveniles become infective after a few weeks of development >>
Humans become infected by eating raw or undercooked fish
Figure 5: adult female with eggs
hosts & reservoirs
Humans (C. philippinensis)
-Recent findings suggest that fishing-eating birds may be the natural definitive hosts.
Humans are the reservoir for C. philippinensis.
Rodents are the reservoirs for C. hepatica.
Cats and dogs are the reservoir for C. aerophila. Peromyscus maniculatus (deer mouse) and Clethrionomys gapperi (red-backed vole) are the major hosts in North America.
Intermediate host: Fish (C. philippinensis)
In the USA, documented hosts of C. philippinensis include
the mouse, rat, vole, chipmunk, groundhog, squirrel, mole, shrew, opossum,
weasel, fox, skunk, and raccoon.
Figure 6: Red-backed vole
introduction biological agent history & epidemiology clinical presentation diagnosis treatment & prevention