Echinococcus granulosus (1)

Question 1

What are the common names?

Answer 1

Hydatid tapeworm

Hydatid disease

Hydatids

Cystic echinococcosis

In dogs: echinococcosis

Question 2

What are the final hosts?

Answer 2

Dogs and wild canids

Question 3

What are the intermediate hosts?

Answer 3

Herbivores, especially sheep

Humans

Question 4

Describe adults

Answer 4

Up to 6 mm long

Question 5

Describe the 2nd stage larvae

Answer 5

Hydatid cyst

Location

 - Liver
 - Kidneys
 - Lungs

Question 6

Describe eggs

Answer 6

25-40 micro m

Thick shelled

Oval/Round

Question 7

Explain the life cycle

Answer 7

Shed 1 gravid proglottid at a time

Eggs capable of prolonged survival outside the host
- Viable on ground up to 2 years

Ingestion by intermediate hosts

Egg hatches

Hexacanth larva penetrates intestine

Migrates to liver, lungs, and other organs

Hydatid cyst develops - Infective to FH
- Hydatid cyst slow growing and matures in 6-12 months

FH ingests Hydatid cysts

Scolices evaginate, attach to mucosa of small intestine

Mature to adults

Dog-sheep cycle - Dogs scavenge wild game entrails

Many sylvatic cycles

 - Wolf-moose/reindeer cycles - Canada
 - Dingo-wallaby cycle - Australia

Canids then contaminate pastures

Domestic dog direct source of human infections

Hydatid cysts in sheep usually fertile
- In cattle tend to be sterile

Question 8

What is the site of infection for adults?

Answer 8

Small intestine

Question 9

What are the sites of infection for larvae?

Answer 9

Liver

Lungs

Other organs

Question 10

Describe the Pathogenesis

Answer 10

Nonpathogenic

Thousands may be present in dog without clinical signs

Humans ingest oncospheres and Hydatid cyst develops in pulmonary or hepatic site
- Result in respiratory symptoms or gross abdominal distension

Exogenous growth uncommon

Question 11

How do you diagnose?

Answer 11

Eggs seen in fecal samples of FH

 - Flotation method
 - Adhesive tape method
 - Cannot be distinguished from Taenia eggs
        - Taenia spp. Infections - proglottids in feces

Presence of proglottids cannot guarantee there are no Echinococcus spp.

Mixed infections can occur

Eggs distinguished with PCR

Question 12

How do you treat and prevent?

Answer 12

Praziquantel - Effective against adults in dogs

Dogs treated prior to implantation

Prevention difficult due to sylvatic cycles

Stray dog populations should be controlled

Uncooked meat/offal should not be accessible to dogs/wild canids

Question 13

What is important about Echinococcus granulosus?

Answer 13

It is ZOONOTIC