Parasitology intro

parasite

another organism living on or in another

Host

An organisms in which a parasite lives, they provide metabolic resources to the parasite

Commensalism

one individual recieves benefits and the other is neither helped nor harmed

Symbiosis

An association of two different species of organisms exhibiting metabolic dependence by their relationship

Accidental host

other host that is harboring a parasite not the traditional one

Definitive host

Host in which the adult and/or sexual phase of a parasite occurs

Intermediate host

A host in which larval or asexual phase of a parasite occur

Stool collection frequency that is preferred is

3 each at least one day apart and within no more than 10 days

What are interfereing substances on a O and P exam

barium, mineral oil, bismuth, antibiotics

What are some reasons for rejecting a stool sample for O&P

• urine contamination

• water contamination

• barium

• castor or mineral oil

• swab

• QNS

• Diaper

If there is a delay in transport what should you do with the stool

• use preservative

• refrigerate for up to 24 hrs

Formed stool has more

cysts

Watery stool has more

trophs

liquid stool time limitations

examine or preserve with in 30 min

Soft stool time limitations

examine or preserve with in 1 hrs

Formed stool time limitations

examine or preserve with in 24 hrs

What are the three preservatives for o&P exam

• dual system (PVA and Formalin)

• unifix

• total fix

Can a trichrome smear be made from a formalin preserved specimen?

NO

purpose of formalin

kill and preserve larvae, eggs, and extracts

Ether and ethyl acetate purpose

reduce bulk

rimming with an applicator stick purpose

getting rid of debris plug

gauze purpose

removes more debris

What should the concentration be for the zinc sulfate flotation method

1.18-1.2 specific gravity

What are three types of eggs that are not easily recovered by ZnSO4 flotation

• Schitsosomes

• operculated eggs

• ascaris sp.

What are the steps for making a trichrome smear up to holding 70% EtOH

Fresh- DSO to fix it then stain

PVA- make the slide, air dry for 24 hrs

Ethyl acetate has the parasites where

bottom

ZnsO4 has the parasites where

top

What is the purpose of the Iodine- EtOH step in preparing PVA smears for the trichrome stain

precipitating the mercury

What is the most important procedure for the accurate diagnosis of intestinal protozoal infections?

A smear

T/F, It is not necessay to examine the entire slide if eggs or cysts are noted within the first few fields

F

T/F, When examining a concentrate prep, you should first examine the entire slide on the 10X objective and then examine at least 1/3 of the slide on 40X

T

T/F, A specimen submitted to the lab in a diaper is not acceptable for an O&P testing

T

T/F, Smears made from PVA should be heat fixed before staining

F

Upon macroscopic examination of a stool the color is tan or white (this was not due to a medical condition) is this an acceptable specimen?

No, tan means barium

Macroscopic exam of black stool means

ingestion of iron or bleeding high in the GI tract

MAcroscopic color of stool is red meaning

blood in the lower intestines

T/F, all suspicious objects should be measured in a microscopic exam

T

What is the downside of iodine mounts?

they kill trophs so no motility is seen

What is the upside of iodine mounts?

helps visualize morphology

Examining a trichrome smear on 100X, how many immersion fields must be seen before calling negative

200-300

What is modified Kinyouns acid fast stain used for in parasitology

coccidia