2.03 & 2.04 Parasitic Infections GI Flashcards
How are GI protozoal infections acquired?
Fecal-oral transmission via contaminated food/water
what is the role of specific morphological forms of protozoal life cycles?
Cysts (Infective, environ resistant) & Trophozoites (Active, motile causing pathology)
Ingestion of infectious oocysts in water or food characteristic of?
Cryptosporidium spp.
Cysts survive in cold water; trophozoites emerge in the small intestine characteristic of?
Giardia intestinalis
Cysts ingested; trophozoites form in the gut characteristic of?
Entamoeba histolytica
Watery diarrhea; diagnosed using acid-fast stain, ELISA, or PCR for oocysts
Cryptosporidium spp
Greasy, foul-smelling stools without blood; identified via DFA or fecal antigen tests.
G. intestinalis
Bloody diarrhea, flask-shaped ulcers; diagnosed by stool microscopy (at least 3) for cysts/trophozoites
E. histolytica
Basic prevention of protozoal infections?
Water/food safety (e.g., boiling water), proper sanitation/hygiene, education on safe practices in endemic areas
Immunocompromised hosts with parasitic diseases at higher risk of systemic complications like what?
liver abscesses (amebiasis) and more chronic/severe disease (ex. chronic cryptosporidiosis in AIDS)
Giardiasis and cryptosporidiosis tend to be what in healthy hosts?
self limiting
What are the transmission pathways of intestinal nematode infections?
Fecal-Oral Transmission and Skin Penetration
Ascaris lumbricoides is spread via?
fecal-oral
Trichuris trichiura is spread via?
fecal-oral
What two nematodes have larvae that penetrate the skin?
Hookworms & Strongyloides stercoralis
How are nematode infections diagnosed?
Identification of characteristic eggs in stool + Scotch tape test
Stool sample lemon-shaped eggs indicative of what?
Trichuris trichiura
What diagnostic test for Enterobius?
Scotch tape test (pinworm)
basic prevention for nematode infections?
Proper sanitation to prevent soil contamination, Avoid walking barefoot, regular deworming and hygiene education
Which nematodes replicate in the environment?
Strongyloides stercoralis
public health implications of nematodes that replicate in environment?
Persistent infection (autoinfection) & Challenges in eradication
What are the clinical complications of chronic intestinal nematode infections?
Anemia, Malnutrition, even Rectal Prolapse
Severe Trichuris infections in children can lead to what complication?
Rectal Prolapse
Leaf-shaped; incomplete gut; require intermediate hosts
Trematodes
(Flukes)
Cylindrical, non-segmented; complete digestive system
Nematodes (Roundworms)
Flat, ribbon-like; segmented body (proglottids); absorb nutrients directly
Cestodes (Tapeworms)
Larvae encyst in tissues (e.g., brain), causing seizures and neurological deficits.
Cysticercosis via Taenia solium
Hydatid cysts in liver/lungs, causing mass effects or rupture complications.
Echinococcosis via Echinococcus granulosus
What are the transmission pathways of Cestodes?
Ingestion of encysted larvae in undercooked meat
What are the transmission pathways of Trematodes?
Consumption of contaminated aquatic plants, fish, or crustaceans with metacercariae
What diagnostic tools are used for cestode and trematode infections?
Stool examination for eggs/proglottids OR Imaging (e.g., CT/MRI) for cysticercosis or echinococcosis
Basic prevention for cestode and trematode infections?
Proper cooking of meat/fish & Sanitation and control of intermediate hosts (e.g., snails).
What is the diagnostic correlation of elevated eosinophil levels in helminthic infections?
Larval migration stages or systemic infections
Who do you typically see E. histolytica (bloody diarhea) infections with?
travelers to tropical regions, immigrants, poor sanitation for institutionalized residents
What will you find in non diarrhea stool samples of E. histolytica?
cysts with four nuclei
What is path pneumonic in a intestinal biopsy for E histolytica or amebic infection?
flask shaped ulcer
Amebiasis complications?
granulomatous lesions in cecum/rectosigmoid colon OR liver abcess
Common demographic of people with giardiasis?
hikers that drink stream water + people with untreated well water
Giardiasis transmission?
(most) contaminated water BUT ALSO uncooked veggies/fruits & person-person (fecal-oral-anal)
Common worldwide cause of travelers diarrhea?
giardia intestinalis
about how many infected carriers with giardiasis are asymptomatic and how long are they infectious for?
50% and they shed cysts for years
what condition predisposes people for giardiasis?
IgA deficiency
Why are fatty stools often seen in chronic giardiasis versus the watery in acute?
malabsorption of fat and protein at small intestine (weight loss + vit deficiency)
Best choice to diagnose giardiasis?
Direct Fluorescent Antibody (DFA) testing
How long to boil water?
1 minute (3 min at high altitudes)
Chronic diarrhea in AIDs patients?
Cryptosporidium spp
Associated with water activity (lake, pools, etc.) outbreaks in US peak early summer to fall and is the leading cause of self-limiting diarrhea in healthy people (persistent malnutrition in children) ?
cryptosporidiosis
Watery diarrhea = Giardia or Cryptosporidium?
Down to history vs. diagnostic tests
in what condition are oocysts immediately infectious/pathogenic from the get go?
cryptosporidosis
More sensitive and quicker than acid fast direct microscopy for cryptosporidium spp?
ELISA or DFA (fecal antigen)
NOTE
PCR for species types
Outbreaks associated with imported fresh produce in spring/summer from tropical/subtropical areas?
Cyclosporiasis
How is Cyclosporiasis is different from crypto?
longer duration (over 2 weeks) and can detect under UV light and requires treatment
What is very similar to cyclosporiasis?
cystoisosporiasis
What helminth has separate sexes?
nematodes/roundworms
what helminth has a complete digestive system?
nematode/roundworm
Who are most likely to develop symptomatic infection from nematodes?
children (5-14)
What form of nematodes make them most pathogenic to host?
adult forms
then most common helminth infection in the US?
enterobius vermicularis (human pinworm)
severe perianal itching at night, insomnia, teeth grinding? why?
enterobius vermicularis
(mature pregnant female lays eggs there)
Key strategy to catch and treat pinworms?
scotch tape test in morning and treat everyone in the household
where is trichuris trichiura infection located?
cecum and colon
round worm (ascaris lumbricoides) infection location?
jejunum (obstruction risk)
Eggs with polar plugs?
trichuris trichiuria (whip worm)
eggs with thick shell?
ascaris lumbricoides
eggs with thin shell?
hookworms (necator/ancylostoma)
rhabditiform larvae?
strongyloides stercoralis
intestinal blockage, mild to sever cough, eosinophilia, abdominal pain, vomiting,, diarrhea
ascariasis
most asymptomatic but if heavy worm burden, bloody painful diarrhea, rectal prolapse (children), chronic: growth impair/anemia/cognition impairment
trichuriasis
the major cause of iron deficiency anemia in children and women
hookworms
koilonychia, exertional dyspnea, heart murmurs, dermatitis, pneumonia, eosinophilia
hookworm
can distinctly replicate in the human host and free living environment + autoinfection post skin penetration
strongyloides stercoralis
high worm burden eosinophila, dry cough, diarrhea, vomiting, can migrate to lung, CNS, liver, and kidneys in immunosuppressed people
strongyloides stercoralis
When infected from pork meat cysts it causes minimal symptoms
T solium
When infected from eggs from infected humans it can have mass effect to CNS, seizures, hydrocephalus, and arachnoiditis
T solium
transmission from cysts in beef and can cause abdominal discomfort and proglottid migration
T saginata
from freshwater fish cysts that has minimal symptoms but can cause it b12 deficiency
diphyllobothrium latum
eggs from infected dogs or sheep, cattle, etc. that can have mass effect to pain, obstruction of organs, or secondary bacterial infections
Echinococcus granulosus aka hydatid cyst disease (CE)
raw or undercooked meat transmission, most asymptomatic but can have abdominal pain, loss of appetite, weight loss, nause/upset, complication cysticercosis with active proglottids in stool
taeniasis
the leading cause of adult-onset seizures in low-income countries (brain, muscles, eyes)
cysticercosis
taeniasis diagnosis?
stool samples on 3 different days and microscope view
the largest tapeworm that can infect humans?
Diphyllobothrium latum
dog tapeworm?
echinococcus
What always serves as the first intermediate host for trematodes (flukes) to complete the life cycle?
mollusks (snails + clams)
water plants, largest intestinal fluke, symptoms related to worm load, South and SE Asia,
fasciolopsis buski
aquatic plants, infects bile ducts and the liver causing migration-related and chronic biliary symptoms, especially in sheep regions
fasciola hepatica
undercooked fish, Chinese liver fluke, colonizes bile duct, cholangiocarcinoma (bile duct cancer), jaundice, hepatomegaly, gallstones, east asia
clonorchis sinensis
