Echinococcus spp

Question 1

Classification

Answer 1

Metazoa
(family of the cestodes)

Question 2

Indirect or direct:

Hosts:

Answer 2

Indirect life cycle

Dogs are final hosts
Sheep are intermediate
Humans are rarely intermediate hosts

Question 3

Transmission and life cycle

Answer 3

Adult echinococcus resides in intestine of dog. Dog releases proglottid eggs in feces.

After ingestion of eggs by an intermediate host, the egg hatches in intestine and releases six-hooked oncospheres that penetrate the intestinal wall and migrate through the circulatory system into various organs, especially liver and lungs

In these organs, the oncosphere develops into a thick walled hydatid cysts that enlarges gradually, producing protoscolices and daughter cells that fill the cysts interior.

The definitive host becomes infected by ingesting the cyst containing organs of the infected intermediate host (so for example the dog eats sheep meat). After ingestion the protoscolices evaginate, attach to the intestinal mucosa. Here they develop into adult stages.

Question 4

Diagnosis:

Answer 4

Imaging techniques supported by positive serologic tests.

Serology to detect antibodies, however, false positive reactions may occur in persons with other cestode infections.