Parastitic Infections

Question 1

What should you look for in stool that indicates the presence of a parasitic infection?

Answer 1

worm segments or entire worms.

Question 2

What microscopic technique should you use for identification of parasites?

Answer 2

Wheatley’s trichome stain on stool prior to concentration, used to detect protazoa.

Question 3

What is the concentrated specimen scanned for?

Answer 3

eggs, cysts, larvae.

Question 4

What is microscopic examination the most common detection method for?

Answer 4

Giardia lamblia and cryptosporidium sp.

Question 5

describe the use of NAT in stool detection

Answer 5

detects specific organism nucleic acid sequence in specimen. very few assays available. It is used when organisms detection/identification very difficult by other methods.

Question 6

describe the use of serologic testing in stool detection

Answer 6

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.

Question 7

Is culture used regularly for identification of parasitic infections? what about susceptibility testing?

Answer 7

No, it is used only for research and reference labs. susceptibility testing is not performed on parasitic organisms.

Question 8

Describe specimen collection for stool:

Answer 8

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

Question 9

What does proto-fix do?

Answer 9

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.

Question 10

What some examples of rejected specimens/

Answer 10

dry, unpreserved
swabs
leaking container
contaminated with oil, barium, toilet water or urine
multiple specimens in a 24 hour period
fresh specimen delayed transport

Question 11

Describe Giardia lamblia (protozoan)

Answer 11

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.

Question 12

What is Giardia lamblia two life cycles?

Answer 12

1. trophozite : active, feeding form of organisms

2. cyst: survival state of organism when in harsh environment, this is infective form for man.

Question 13

Describe Giardia lamblia disease state?

Answer 13

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)

Question 14

How are humans infected by Giardia lamblia?

Answer 14

1. drinking contaminated water
2. eating contaminated, uncooked food
3. person to person spread (fecal oral route)

Question 15

What are cysts resistant to?

Answer 15

cysts are resistant to normal chlorination levels. can resist human stomach pH. Water should be filtered, boiled or treated with iodine.

Question 16

How can you combat the cysts found in water by Giardia lamblia

Answer 16

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.

Question 17

How is Giardia lamblia diagnosed?

Answer 17

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.

Question 18

what is the treatment for Giardia lamblia?

Answer 18

tinidazole, metronidazole, and nitazoxanide.

Question 19

How do you get infected by Cyrptosporidium sp.?

Answer 19

Infection is by fecal/oral, ingest oocysts (lifecyle protected by outer shell that allow sod survival outside the body for long periods of time

Question 20

Where can you find Cryptosporidium sp.

Answer 20

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.

Question 21

What is one of the most frequent causes of waterborne disease among humans in the US?

Answer 21

Cryptosporidium sp.

Question 22

Describe the symptoms of Cryptosporidium sp.

Answer 22

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.

Question 23

Describe intestinal parasites screen testing:

Answer 23

many labs offer an immunodiagnosis for antigen screen for both Cryptosporidium sp. and giardia lamblia.

Question 24

Describe enterobius vermicularis - pinworm

Answer 24

• 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.

Question 25

When do pinworm eggs become infective in enterobius vermicularis?

Answer 25

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.

Question 26

What does enterobius vermicularis clinically look like?

Answer 26

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.

Question 27

What is the laboratory diagnosis made for enterobius vermicularis?

Answer 27

macroscopoic ID of the female worm. It is white, opaque, visible with the naked eye.

Question 28

How do you collect the worms for enterobius vermicularis?

Answer 28

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.

Question 29

What is the treatment for enterobius vermicularis?

Answer 29

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.

Question 30

Enterobius vermicularis treatment?

Answer 30

careful handling, frequent changing of underclothing, night clothes, towels, and bedding can help reduce infection. These items should be laundered in hot water.

Question 31

What two parasites are detected via stool antigen assay:

Answer 31

giardia and cryptosporidium. It is usually performed before a full ova and parasite examination is ordered.

Question 32

What is detected via microscopic identification of eggs or adult worms from perianal?

Answer 32

enterobius vermicularis