Flashcards in Parastitic Infections Deck (32):
What should you look for in stool that indicates the presence of a parasitic infection?
worm segments or entire worms.
What microscopic technique should you use for identification of parasites?
Wheatley's trichome stain on stool prior to concentration, used to detect protazoa.
What is the concentrated specimen scanned for?
eggs, cysts, larvae.
What is microscopic examination the most common detection method for?
Giardia lamblia and cryptosporidium sp.
describe the use of NAT in stool detection
detects specific organism nucleic acid sequence in specimen. very few assays available. It is used when organisms detection/identification very difficult by other methods.
describe the use of serologic testing in stool detection
detects patient antibody response to a specific parasitic organism. normally used when parasite is hard to recover from patient due to the type of tissue infected.
Is culture used regularly for identification of parasitic infections? what about susceptibility testing?
No, it is used only for research and reference labs. susceptibility testing is not performed on parasitic organisms.
Describe specimen collection for stool:
1. collect in a clean bed pan or use plastic wrap between seat and toilet bowl.
2. only stool is acceptable, no pee or TP
3. transfer to clean dry container
4. transport before 2 hours, if delayed then put something like proto-fix in stool
What does proto-fix do?
it kills living organism in stool, but preserves the morphology. A stool specimen submitted in proto-fix is not acceptable to be used for culture.
What some examples of rejected specimens/
contaminated with oil, barium, toilet water or urine
multiple specimens in a 24 hour period
fresh specimen delayed transport
Describe Giardia lamblia (protozoan)
It is the most common parasitic organism recovered in US population. several animals are reservoirs and serve as source of infection : beavers, muskrats.
It is a single celled organism with 2 life cycles.
What is Giardia lamblia two life cycles?
1. trophozite : active, feeding form of organisms
2. cyst: survival state of organism when in harsh environment, this is infective form for man.
Describe Giardia lamblia disease state?
1. asymptomatic -- can serve as carriers and a source of infection for others.
2. symptomatic: incubation period 1 to 4 weeks after ingestion.
- diarrhea which can lead to malabsoprtion syndrome
- abdominal cramps, nausea, flatulence, watery diarrhea, weight loss.
-steatorrhea (increased fats in stool)
How are humans infected by Giardia lamblia?
1. drinking contaminated water
2. eating contaminated, uncooked food
3. person to person spread (fecal oral route)
What are cysts resistant to?
cysts are resistant to normal chlorination levels. can resist human stomach pH. Water should be filtered, boiled or treated with iodine.
How can you combat the cysts found in water by Giardia lamblia
water should be filtered, boiled, or treated with iodine. boil water for at least 1 minute. use a filter that has an absolute pore zip of 1 micron or smaller. use iodine- chemicals may less effective than boiling or filtering bc the amount of chemical required to make the water safe is highly dependent on the temp, ph and cloudiness of the water.
How is Giardia lamblia diagnosed?
lab diagnosis may be difficult. microscopic identification (may require up to 6 stools specimens/alternate days). Immunodiagnosis is most sensitive form, and a single specimen is needed.
what is the treatment for Giardia lamblia?
tinidazole, metronidazole, and nitazoxanide.
How do you get infected by Cyrptosporidium sp.?
Infection is by fecal/oral, ingest oocysts (lifecyle protected by outer shell that allow sod survival outside the body for long periods of time
Where can you find Cryptosporidium sp.
it is located worldwide, in US in almost all surface water. Wide range of animal carriers. Very resistant to chemical water treatment. Need to filter/boil water.
What is one of the most frequent causes of waterborne disease among humans in the US?
Describe the symptoms of Cryptosporidium sp.
can be asymptomatic, symptoms begin 2-10 days (average of 7 days) after ingestion. there is watery diarrhea, stomach cramps and pain, dehydration, nausea/vomiting, fever, weight loss. If someone is immunocompetent, the symptoms can last up to 1-2 weeks. People w/AIDs could develop very serious illness.
Describe intestinal parasites screen testing:
many labs offer an immunodiagnosis for antigen screen for both Cryptosporidium sp. and giardia lamblia.
Describe enterobius vermicularis - pinworm
- it is a helminth (worm): nematode (roundworm)
- infected by : fecal/oral by ingestion of eggs
- location : worldwide
- most common helminth (worm) infection in US.
- adult worms live in intestine and rectum
- female migrates to anus, exits, deposits her eggs (approximately 10,000), then usually dies or returns to intestine/rectum.
When do pinworm eggs become infective in enterobius vermicularis?
within a few hours after being on the skin around the anus. They can survive for 2-3 weeks on clothing, bedding, or other objects. infection by ingesting infective pinworm eggs that are on fingers, under fingernails, or on clothing bedding, and other contaminated objects and surfaces. Because of their small size, pinworm eggs become airborne and ingested while breathing.
What does enterobius vermicularis clinically look like?
asymptomatic or perianal itching caused by the female pinworm laying her eggs. secondary bacterial infections due to itching. irritability (inability to sleep). females can experience vaginal itching.
What is the laboratory diagnosis made for enterobius vermicularis?
macroscopoic ID of the female worm. It is white, opaque, visible with the naked eye.
How do you collect the worms for enterobius vermicularis?
firmly apply the sticky paddle to perianal folds. paddle will pick up pinworm eggs. paddle is microscopically examined for characteristic eggs. Stool is NOT an appropriate specimen.
What is the treatment for enterobius vermicularis?
albendazole, mebendazole, or pyrantel pamoate. Treat again in 2 weeks after first dose. All household contacts and caretakers should be treated at once. Reinfection is very easy, strict observance of good hand hygiene is essential.
Enterobius vermicularis treatment?
careful handling, frequent changing of underclothing, night clothes, towels, and bedding can help reduce infection. These items should be laundered in hot water.
What two parasites are detected via stool antigen assay:
giardia and cryptosporidium. It is usually performed before a full ova and parasite examination is ordered.