Exam I - Strongyloides stercoralis

Question 1

What is the common name for Strongyloides stercoralis?

Answer 1

Threadworm

Question 2

Identify the final host(s) for Strongyloides stercoralis.

Answer 2

Dogs, cats, & foxes

Question 3

The long esophagus of Strongyloides stercoralis adult occupies about how much of its body length?

Answer 3

~1/3

Question 4

Describe the appearance of the Strongyloides stercoralis adult

Answer 4

Slender hair-like nematodes less than 1 cm length. Long esophagus occupies one third of body length.

Question 5

Strongyloides stercoralis belongs to which taxonomic order?

Answer 5

Rhabditida

Question 6

Is the life cycle of Strongyloides stercoralis direct or indirect?

Answer 6

Direct.

The life cycle has a parasitic (homogonic) and free-living (heterogonic) phase.

Question 7

What is the PPP for Strongyloides stercoralis?

Answer 7

PPP is 10-14 days

Question 8

Which phase of the Strongyloides stercoralis life cycle predominates when environmental conditions are favorable? Homogonic or heterogonic?

Answer 8

In favorable environmental conditions, the heterogonic phase predominates. The free-living

larvae hatch from eggs and develop in the soil directly to adult males and females. The females lay eggs, which develop into free-living L3.

These are infective percutaneously and per os.

Question 9

Describe the homogonic life cycle phase of Strongyloides stercoralis

Answer 9

• In the homogonic life cycle eggs containing a fully developed, sheathed L1 or liberated L1 are passed in feces.
• In the soil, L1 develop to L3
• Infective L3 penetrate the host’s skin or oral mucosa to undergo migration to the heart, through the lungs and up the trachea, are swallowed and then migrate to the intestine.
• There they develop to adult females (only) and parthenogenesis takes place. Some larvae arrest in somatic tissues.

Question 10

What is/are the site(s) of infection for Strongyloides stercoralis?

Answer 10

Adults in small intestine. Larvae in skin.

Question 11

Describe some clinical signs associated with Strongyloides stercoralis?

Answer 11

Young animals show diarrhea, anorexia, dullness and loss of weight, urticaria.

Question 12

Just to be sure… what is urticaria?

Answer 12

hives or welts

Question 13

Which diagnostic techniques would be most effective for diagnosing Strongyloides stercoralis?

Answer 13

L₁ and eggs with L₁ in **fecal flotation **

L₁ recovered with the Baermann technique for fresh feces

These stages diagnostic for the dog and cat, and human.