Intestinal nematodes (Part 2) Flashcards
List the general characteristics of a nematode.
Roundworms, Non-segmented, tapered at both ends, tough, protective coating or cuticle, separate sexes, fairly long living (years), related to worm burden.
What is the diagnostic form usually found in intestinal nematodes?
Eggs in feces
Rank the nematode eggs in ascending or descending order according to size
Handout?
Arrange the adult nematode worms in ascending or descending order according to size
Handout?
Differentiate between the adult worms of Ancylostoma & Necator.
Ancylostoma- has two pairs cutting teeth
Necator- Have cutting plates
Describe the method of choice for obtaining pinworm specimens.
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
What is the name of the infective form in Nematodes life cycle?
Filariform Larvae
What is the name of the free-living form in Nematodes life cycle?
Rhabditiform Larvae
Describe the appearance of Ascaris.
Thickness of pencil & cuticle has circular striations, creamy white.
Clinical Manifestation of Ascaris
- Asymptomatic
- Asthmatic (allergic Rx to parasite)
- Pneumonitis, Bowel obstruction, adults may migrate to other tissue
- Adults can emerge from nose or mouth
Which type of hookworm is still prevalent in rural areas of U.S. (Kentucky and South)
Necator americanus
Which nematode is associated with lung involvement?
Hookworm, Ascaris, Strongyloides stercoralis,
Which nematode is associated with ground itch at site of penetration?
Hookworm
Clinical manifestations of Hookworms.
- Bronchitis but no sensitization like Ascaris
- Anemia since adults secrete anticoagulant and ingest blood
- hemorrhages, mental/physical development impairment in children
Since eggs and larvae of two genera are indistinguishable in hookworm, how can we report that?
Report “Hookworm”
How do we get “cutaneous larvae migrans” or “creeping Eruption (CLM) in humans?
- Larvae migrate through subcutaneous tissues causing irritation
- Animals, beaches/sandboxes & bare feet :(
Which Nematode is found in some areas of Appalachia or rural Southeastern U.S. and doesn’t need host?
Strongyloides stercoralis
How do we get autoinfection in Strongyloides stercoralis?
Larvae penetrate intestine or perianal skin –> circulation (autoinfection)
clinical manifestation of Strongyloides stercoralis
- mild/no symptoms unless immunocompromised
- rarely skin irritation
- non-bacterial pneumonia with eos, respiratory failure
Which form of Strongyloides stercoralis is seen in sputum-immunocompromised patient?
Filariform larvae
This is the only organism that is agar plate cultured.
Strongyloides stercoralis
Describe the Agar plate culture in Strongyloides stercoralis.
- 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
Most common Nematode in the U.S.A
Enterobius vermicularis (pinworm)
This nematode mostly found in families or Crowded conditions by inhalation or ingestion of eggs or retroinfection and children most often infected.
Enterobius vermicularis (pinworm)
Describe life cycle of Enterobius vermicularis.
- Migration of female outside anus at night to lay eggs
- Eggs infective within hours (no external maturation required). Lab caution!!
Clinical manifestations of Enterobius vermicularis.
- Anal itching (pruritus)
- often asymptomatic
Clinical manifestations of Trichuris trichiura.
-Prolapsed rectum in repeated infections.
This Nematode is found worldwide and southern U.S.
Trichuris trichiura
Associate the appropirate nematode with the creaping eruption
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