Intestinal nematodes (Part 2)

Question 1

List the general characteristics of a nematode.

Answer 1

Roundworms, Non-segmented, tapered at both ends, tough, protective coating or cuticle, separate sexes, fairly long living (years), related to worm burden.

Question 2

What is the diagnostic form usually found in intestinal nematodes?

Answer 2

Eggs in feces

Question 3

Rank the nematode eggs in ascending or descending order according to size

Answer 3

Handout?

Question 4

Arrange the adult nematode worms in ascending or descending order according to size

Answer 4

Handout?

Question 5

Differentiate between the adult worms of Ancylostoma & Necator.

Answer 5

Ancylostoma- has two pairs cutting teeth

Necator- Have cutting plates

Question 6

Describe the method of choice for obtaining pinworm specimens.

Answer 6

Cellophane tape preparation or paddle

• when first wakening (before showering)
• clear tape (not frosted) placed over end of tongue depressor (sticky side out)
• Perianal area touched with sticky tape, then tape stuck to slide

Question 7

What is the name of the infective form in Nematodes life cycle?

Answer 7

Filariform Larvae

Question 8

What is the name of the free-living form in Nematodes life cycle?

Answer 8

Rhabditiform Larvae

Question 9

Describe the appearance of Ascaris.

Answer 9

Thickness of pencil & cuticle has circular striations, creamy white.

Question 10

Clinical Manifestation of Ascaris

Answer 10

• Asymptomatic
• Asthmatic (allergic Rx to parasite)
• Pneumonitis, Bowel obstruction, adults may migrate to other tissue
• Adults can emerge from nose or mouth

Question 11

Which type of hookworm is still prevalent in rural areas of U.S. (Kentucky and South)

Answer 11

Necator americanus

Question 12

Which nematode is associated with lung involvement?

Answer 12

Hookworm, Ascaris, Strongyloides stercoralis,

Question 13

Which nematode is associated with ground itch at site of penetration?

Answer 13

Hookworm

Question 14

Clinical manifestations of Hookworms.

Answer 14

• Bronchitis but no sensitization like Ascaris
• Anemia since adults secrete anticoagulant and ingest blood
• hemorrhages, mental/physical development impairment in children

Question 15

Since eggs and larvae of two genera are indistinguishable in hookworm, how can we report that?

Answer 15

Report “Hookworm”

Question 16

How do we get “cutaneous larvae migrans” or “creeping Eruption (CLM) in humans?

Answer 16

• Larvae migrate through subcutaneous tissues causing irritation
• Animals, beaches/sandboxes & bare feet :(

Question 17

Which Nematode is found in some areas of Appalachia or rural Southeastern U.S. and doesn’t need host?

Answer 17

Strongyloides stercoralis

Question 18

How do we get autoinfection in Strongyloides stercoralis?

Answer 18

Larvae penetrate intestine or perianal skin –> circulation (autoinfection)

Question 19

clinical manifestation of Strongyloides stercoralis

Answer 19

• mild/no symptoms unless immunocompromised
• rarely skin irritation
• non-bacterial pneumonia with eos, respiratory failure

Question 20

Which form of Strongyloides stercoralis is seen in sputum-immunocompromised patient?

Answer 20

Filariform larvae

Question 21

This is the only organism that is agar plate cultured.

Answer 21

Strongyloides stercoralis

Question 22

Describe the Agar plate culture in Strongyloides stercoralis.

Answer 22

• Stool is placed on agar plate
• incubate @ RT for 2 days
• Larvae will migrate over agar, carrying bacteria, leaving visible tracks
• wash plate with formalin & examine larvae for ID

Question 23

Most common Nematode in the U.S.A

Answer 23

Enterobius vermicularis (pinworm)

Question 24

This nematode mostly found in families or Crowded conditions by inhalation or ingestion of eggs or retroinfection and children most often infected.

Answer 24

Enterobius vermicularis (pinworm)

Question 25

Describe life cycle of Enterobius vermicularis.

Answer 25

• Migration of female outside anus at night to lay eggs

- Eggs infective within hours (no external maturation required). Lab caution!!

Question 26

Clinical manifestations of Enterobius vermicularis.

Answer 26

• Anal itching (pruritus)

- often asymptomatic

Question 27

Clinical manifestations of Trichuris trichiura.

Answer 27

-Prolapsed rectum in repeated infections.

Question 28

This Nematode is found worldwide and southern U.S.

Answer 28

Trichuris trichiura

Question 29

Associate the appropirate nematode with the creaping eruption

Answer 29

?