Parasitic Helminths (Nematodes i.e roundworms) Flashcards
What is the common name for Enterobiasis?
Pinworm disease
What is the prevalence of enterobiasis?
greater than 500 million cases worldwide
What is the most common helminth in the U.S.
Enterobiasis (pinworm disease)
What is the geographic distribution of enterobiasis (pinworm disease)?
world-wide
What is the most common nematode infection in temperate zone?
enterobiasis (pinworm disease)
What is the life cycle of enterobiasis (pinworm disease)?
- humans ingest embryonated eggs that hatch in small intestine.
- Larvae migrate to colon, mature to adult male and female worms
- After copulation females migrate to perianal region and lay 10,000 fertilized eggs and then die.
- eggs embryonate on perianum
Are enterobiasis suceptible to drying out?
no they are very resistant to dessication
If you have enterobiasis in the colon what are the symptoms?
no symptoms
What will a heavy enterobiasis infection cause?
pruritis ani. scratching may lead to cellulitis; occasional aberrant infection of vagina; probability of reinfection is extremely high
(blank) can result from egg hatching and larval migration back into the colon in enterobiasis
autoinfection
How does your immune system respond to enterobiasis?
IgE and mast cells involved in worm expulsion
What is the treatment fr enterobiasis?
pyrantel pamoate (retreat after 2 weeks to kill new worms)
How do you prevent and control enterobiasis?
drug treatment; difficult to eliminate through hygiene; NO Vaccine
WHat is the common name for trichuriasis?
whipworm disease
What is the prevalence of trichuriasis?
greater than one billion human cases worldwide
What is the parasite that causes trichuriasis?
trichuris trichuria
What is the geographic distribution of trichuriasis?
worldwide
WHat is the life cycle of trichuriasis?
humans ingest embryonated eggs that hatch in small intestine
larvae migrate to colon where adult female and male worms mature and copulate. Adults embedded in columnar epithelium wher they lay fertilized eggs (3-5,000 eggs/day) that pass (unembryonates) in feces.
What do light trichuriasis infections look like?
asymptomatic
What do heavy trichuriasis infections look like?
may present as acute dysentery or a chronic colitis that resembles inflammatory bowel disease (e.g chrons disease); children develop chronic malnutrition, anemia, short stature
can cause tenesums which causes rectal prolapse
How does your immune system handle trichuriasis (whipworm disease)?
IgA, mast cells and IgE
How do you diagnose trichuriasis?
identification of characteristic bipolar eggs in stool sample; eosinophilia
How do you treat trichuriasis?
mebendazole or albendazole; surgical intervention for rectal prolapse
How do you prevent trichuriasis?
sanitary disposal of feces; NO vaccine
What is this:
Aberrant infections caused by the dog and cat ascarids Toxocara canis, T. felis and others (>10,000 cases/year in the U.S.; 40% prevalence in regions of Southern U.S.)
Visceral Larva Migrana
if a worm picture has teeth what is it?
ancylostoma duodenale
If a worm picture has a big toothless mouth?
necator americanus
What is the prevlance of hookworm disease?
greater than one billion human cases worldwie
What parasites cause hookworm disease?
ancylostoma dodenal (most virulent) necator americanus (less virulent)
What is the geographic distribution of hookworm disease?
A. duodenale is found in the mediterranean region, N. asia and part of s. America.
N. americanus previals in the W. hempsiphere but is also found in Africa, S. America and the pacific region
What is the life cycle of hookworm disease?
- Humans are infected by 3rd stage filariform larvae that penetrate skin
- Larvae migrate to lung, enter alveoli, then migrate up to trachea and are swallowed
- Adult male and female copulate in small intestine and unembryonated eggs are passed in feces (egg production: A. duodenal»N. americanus)
- Rhabditiform larvae in soil become infectious filiariform larvae.
What type of hookworm parasite produces more eggs, A. duodenal or N. americanus?
A duodenale
What is the clinical manifestation of hookworm disease?
pneumonitis
pruitic, papular, vesicular dermatitis
IN intestins-> severe infections cause blood loss, epigastric pain and nausea
What is the est. its of blood lost per day from humans infected with severe case of hookworm?
7 million liters
How does your immune system respond to hookworm disease?
IgA, mast cells, IgE
How do you diagnose hookworm disease?
eggs in stool; must find adults or larvae to sepciate hookworms
How do you treat hookworm disease?
albendazole; oral iron sulfate supplementation for anemia
What are the lab and clinical findings in hookworm disease?
- eosinophilia
- anemia
- iron deficiency anemia (CHF and death)
- edema and ascites (caused by protein malnutrition; common in children)
How do you prevent and control hookworm disease?
sanitary disposal of human feces?
What is this:
Aberant infections caused by the dog hookworm Ancylostoma caninum and others
cutaneous larva migrans
What is the prevalence of strongyloidiasis?
greater than 200 milion human cases worldwide
What is the parasite that causes strongyloidiasis?
strongyloides stercoralis
What is the geographic distribution of stronyloidiasis?
tropical, subtropical and temperate (southeastern U.S); animal reservoirs
What is the life cycle/biology of strongyloidiasis?
both parasitic and free-living phase
- 3rd stage filariform larvae go to human skin->blood-> lungs.
- get swallowed and go to small intestine
- adult parthenogentic lay eggs
- larvae molt twice
- 2nd stage rhabditiform larvae pass in feces
- S. stercoralis can have free-living cycle
What are the clinical manifestations of strongyloidiasis?
skin- seroiginous, creepingm urticarial eruptions
lungs- pneumonitis
GI- water, mucous-laden diarrhea
Autoinfection or hyperinfection in colon can lead to disseminated disease and death
How does your immune system respond to strogyloidiasis?
T cell function critical, but exact mechanism is unknown
How do you diagnose strongyloidiasis?
stool examination for 2nd stage rhabditifom larvae; eosinophilia
How do you treat strongyloidiasis?
ivermectin or albendazole
How do you prevent or control strongyoidiasis?
sanitary disposal of human/animal feces; no vaccine
What is the prevalence of trichinellosis?
1.5 million harbor parasites in US
What is the parasite that causes trichenellosis?
trichinella spiralis
What is the geographic distribution of trichinellosis?
worldwide (infects any mammal)
What is the life cycle/biology of trichinellosis?
- Humans acquire T spiralis by consuming poorly cooked meat bearing encysted larvae.
- -the larvae are liberated by digestive enzymes, penetrate columnar epithelial cells, molt four times, become female and male within columnar epithelium of s. intestine
- After cpulation, females deposite living larvae that spread via blood or lymph an must penetrate striated muscle cells to survive.
What do you call muscle cells that are infected with trichinellosis?
nurse cells
Humans often acquire trichinellosis by consuming improperly cooked (blank); humans are usually (blank) hosts (nurse cells calcify)
pork
dead end
What is the clinical manifestations of trichenellosis?
- severe gastroenteritis (diarrhea, vomiting, abdominal pain)
- larvae penetrate and kill cell types before death (myocarditis and encephalitis)
- larvae in striated muscle cells survive but cause a myositis (fever, myagia, periorbital edema)
- in extremly heavy infections-> muscles may become dysfunction (paralysis of diaphragm can be fatal)
What will the lab findings be like in trichinellosis?
eosinophils
elevated muscle enzymes (CPK, LDH)
How does your immune system respond to trichinellosis?
ADCC against free larvae; mast cell-mediated expulsion of adult worms)
How do you diagnose trichinellosis?
enzyme immunoassay to detect anti-Trichinella antibodies; definitive by muscle biopsy, squash prep and histopathology
How do you treat trichinellosis?
Prednisone for muscle inflammation; albendazoe to kill adults
How do you prevent and control trichinellosis?
cook or freeze pork; prevent pigs from eating meat scraps; no vaccine
What is this:
- female mosquito vector deposits 3rd stage filariform larvae on skin while biting
- larvae enter bite wound and go to lymphatics
- long, slender adult female and male worms mature and couplate in lymphatic vessels, then females produce microfiaria that circulate in bloodstream.
- Female mosquitos acquires microfilaria with blood meal. -Microfilariae penetrat gut, migrate to flight muscles then molt twice, migrate to probiscus.
Filariasis
What are the parasites that cause filariasis?
Wuchereria bancrofti and Brugia malavi
What is the geographic distributon of filariasis?
tropics and subtropics (pacific islands)
What is the prevalence of filariasis?
greater than 120 million human cases worldwide
In some strains of filariasis, microfilaria are found in the blood only during the (bank), while other strains only exhibit (blank)
day (diurnal periodicity)
nocturnal peridicity