Exam I - Echinococcus spp.

Question 1

What is the common name for Echinococcus granulosus?

Answer 1

Hyatid tapeworm

Question 2

What is/are the final host(s) for Echinococcus granulosus?

Answer 2

dogs (and other canids)

Question 3

What is/are the intermediate host(s) for Echinococcus granulosus?

Answer 3

herbivores (wild and domestic) and humans

Question 4

Describe the appearance of the Echinococcus granulosus adult

Answer 4

In final host, entire tapeworm is 6 mm long with 3-4 segments. Scolex with 4 suckers and 2 rows of hooks. Small and therefore difficult to see in a freshly opened small intestine

Question 5

Describe the appearance of the Echinococcus granulosus egg

Answer 5

Eggs are 25-40 um in diameter, and typically taeniid with brown color, radial striations in the shell and appearance of 6 embryonic hooks.

Morphologically, they are indistinguishable from Taenia spp.

Question 6

Is the life cycle of Echinococcus granulosus direct or indirect?

Answer 6

Indirect.

Question 7

Describe the life cycle of Echinococcus granulosus.

Answer 7

• Indirect. The tapeworm sheds 1 gravid segment with eggs, & these are shed in feces.
• These develop to oncospheres, which are capable of prolonged survival outside the host (viable on ground for up to 2 years)
• After ingestion by the intermediate host, egg hatches and the hexacanth larva penetrates the intestine and migrates to the liver and lungs, as well as other organs.
• A hyatid cyst develops, and is the infective stage to the final host.
• It becomes larger, is slow growing, and mature in 6-12 months.
• When final hosts such as canids ingest an infected intermediate host, the scolices envaginate and attach to the mucosa of the small intestine and mature.
• PPP is 45-60 days

Question 8

What is the infective stage of Echinococcus granulosus

Answer 8

hyatid cyst

Question 9

What is the PPP for Echinococcus granulosus?

Answer 9

PPP is 45 - 60 days

Question 10

What is/are the site(s) of infection for Echinococcus granulosus?

Answer 10

Adult cestodes in small intestine.

In intermediate hosts and humans, unilocular hyatid cysts in liver, lungs, and other organs.

Question 11

Describe the pathogenesis associated with Echinococcus granulosus

Answer 11

Adult tapeworms are nonpathogenic and thousands may be present in a dog without clinical signs.

When humans are the intermediate hose, the hyatid develops in a pulmonary or hepatic site. This is often pathogenic.

Question 12

Which diagnostic method(s) would be appropriate for diagnosing Echinococcus granulosus?

Answer 12

• fecal float may show eggs, but eggs are morphologically indistinguishable from *Taenia *eggs
• Scotch tape method - apply a piece of transparent, clear tape to the perianal area, sticking the tape to a microscopic slide, and examining it for eggs.

Question 13

What is the common name for Echinococcus multilocularis?

Answer 13

Alveolar hyatid tapeworm

Question 14

What is/are the final host(s) for Echinococcus multilocularis?

Answer 14

wild canids, domestic dogs, cats, or coyotes

Question 15

What is/are the intermediate host(s) for Echinococcus multilocularis?

Answer 15

cattle, horses, swine, rodents, and humans

Question 16

Describe the appearance of Echinococcus multilocularis adult

Answer 16

In final host, entire tapeworm is 6 mm long with 4-5 segments. This is small and therefore difficult to find in a freshly opened intestine. Scolex with 4 suckers and 2 rows of hooks. Similar to entire adult cestode for Echinococcus granulosus

Question 17

What is/are the site(s) of infection for Echinococcus multilocularis?

Answer 17

Adults in small intestine. Multilocular hyatid cysts primarily in liver, with metastases to other organs

Question 18

Describe pathogenesis associated with Echinococcus multilocularis in humans

Answer 18

Invasive growth of hyatid cyst in humans can be fatal