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37 Cards in this Set

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Host which contains the larval form of the parasite?
Intermediate host
Host which contains the adult sexual form of the parasite?
Definitive host
Contain both sexes in one helminth; cestodes and trematodes (except Schistosomes)?
Segments filled with eggs?
Gravid proglottids
Intestinal Nematodes (Roundworms):
-Ascaris lumbricoides
-Enterobius vermicularis
-Trichuris trichiura
-Strongyloides stercoralis
-Necator americanus
-Ancylostoma duodenale
Ascaris lumbricoides
large intestinal roundworm
Enterobius vermicularis
trichuris trichiura
strongyloides stercoralis
necator americanus
new world hookworm
ancylostoma duodenale
old world hookworm
Intestinal Nematodes (roundworms)general characteristics:
-males smaller than females and have a curved tail
-complete digestive tract
-worldwide distribution
Ascaris lumbricoides causes...
-visceral larval migrans-migration through viscera resulting in eosinophilia

-worm ball: blockage of intestine

-ascaris pheumonities: due to larvae migration in lungs
Ascaris lumbricoides can be diagnosed by:
-demonstration of egg in feces (round egg containing albuminous coating)
-recovery of worm from anus, nasal passage or sputum
Largest nematode?
Ascaris lumbricoides
Second most common nematode infection in U.S.?

5-9 y/o most prevalent in U.S.
Ascaris lumbricoides
Eggs become embryonated within hours=high rate of autoinfection

*treat entire family of an infected individual*
Enterobius vermicularis (pinworm)
Diagnose Enterobius vermicularis by:
-Scotch tape prepatation

perform after patient has been sleeping or early in the morning
Most common helminth parasite of human?
Enterobius vermicularis

*frequent in children due to poor sanitation habits*
Diagnose Trichuris trichuria by
characteristic egg in feces

football shaped with mucoid polar plugs
Clinical disease of Trichuris trichuria?
prolapsed rectum in heavy infections
Smallest nematode?
Strongyloides stercoralis (threadworm)
Type of infective larvae of Strongyloides stercoralis?
Filariform larvae
-short buccal cavity
-notch at end of tail
Where do Strongyloides stercoralis eggs hatch?
Mucosa of intestine
Rarely seen in feces
Stages of Strongyloides stercoralis infection:
1. cutaneous: initial skin penetration
2. pulmonary: larval migration through lungs
3. Intestinal: symptoms depend of worm load
Intestinal nematode with by free living and parasitic cycle?
Strongyloides stercoralis

Autoinfection: some of the rhabditiform larvae develop into filariform larvae in he bowel and reinfect the host
Hyperinfection syndrome of Strongyloides stercoralis occurs with?
-Immunocompromised (AIDS, drugs)...will exhibit eosinophilia and leukocytosis

-Organ transplantation
Hookworm life span?
2-14 years
Rarely seen in stools due to attachment to mucosa?
Hookworm (Necator americanus & Ancylostoma duodenale)
Differentiate Hookworm Adults?
Necator: cutting plates

Ancylostoma: 2 pair of teeth
Infective stage of hookworm?
Filariform larvae with long buccal cavity & pointed tail.
Hookworm larvae has what type of tail?
Pointed tail
Strongyloides larvae has what type of tail?
Notched tail
Ground itch (allergic rxn) is caused by
Hookworm (N. americanus & A. duodenale)
Diagnose hookworm by
-eggs in feces
-do NOT see larvae in fecus (unless specimen is left at room temp)
Anemia is a clinical disease of what type of intestinal nematode?
Hookworm (N. americanus & A. duodenale)

*Each adult worm consumes 0.2mL of blood/day*
Clincal diseases of hookworm?
-Allergic rxn
-Cutaneous larvae migrans