MLSC 3333 Quiz 1

Primary disease and risk factor

Sanitation—parasites are ubiquitous

Other risk factors for parasites

1. Unsanitary food handling

2. contaminated water

3. immunocompromised state

4. parasitic transmission via insect vector

5. blood transfusion/organ transplant

6. foreign travel to endemic regions of world

Frequent symptom

Diarrhea—accompanied by abdominal cramping

Other symptoms (depending on parasite)

• intestinal obstruction, weight loss and bloating

• organ involvement with ulcers, lesions, absess

• Bleeding, anemia, chills, fever, meningitis and encephalitis

Diagnosis based on observing

stages

• ova

• larva

• adult forms

Specimen types

stool is most common

• blood

• tissue

• body fluid (CSF, urine)

• sputum

Blood

leishmania, trypanosoma, plasmodium, onchocera

skin

onchocerca

vaginal/urethral

trichomonas

Oral (mouth or nasal)

Naelgeria, Entamoeba, trichomonas

Eye scrapings

Acanthamoeba

Tissue

Naegleria, Acanthamoeba, Leishmania

Urine

Schistosoma, Trichomonas

Sputum

Ascaris, Strongyloides, entamoeba

carrier

Asymptomatic host that harbors a parasite and is capable of transmission to others

commensalism

Host-parasite relationship that is beneficial to one and harmless to another

definitive host

Required for adult or sexual phase of the parasite's life cycle

mutualism

beneficial to both host and parasite

parasite

any organism that obtains its nutrients from another organism (maybe be harmful, beneficial or neutral)

symbiosis

association between 2 organisms

zoonosis

-Animal parasitic infection that humans acquire as accidental hosts

-Typically humans do not get this parasite but due to accidental interaction with animal

cestodes

tapeworms

ciliates

motile protozoans

cyst

thick-walled stage of amoeba that is resistant to adverse conditions. Typically found in the environment

ectoparasite

external parasite (e.g. ticks and lice)

egg

oocyst, ovum, zygote

endoparasite

internal parasite

filariae

blood or tissue roundworms requiring an insect vector for transmission

flagellates

protozoans with flagella

gravid

pregnant

helminths

includes nematodes (roundworms), cestodes (tapeworms) and trematodes (flukes).

hermaphroditic

tapeworms capable of self-fertilization. Both female and male sex organs

host

any living organism that harbors a parasite

hydatid cyst

Larval stage of Echinococcus granulosus

intermediate host

host containing the asexual phase of a parasite

larvae

juvenile stage of parasite

nematode

roundworm

oocyst

Encysted form of an egg

parasitic life cycle

stages in the development of a parasite; may require multiple hosts or specific nutrients

Parasitism

host-parasite relationship where one member benefits at the expense of the other

schizont—malaria

-Immature: early stage of asexual sporozoa trophozoite

-Mature: developed stage of asexual sporozoa trophozoite

trematodes

flukes

Specimen collection for stool

• clean, dry, leakproof

  • free of urine, water, soil, or other mats

Max samples

One sample per day

• 3 samples processed max

Fresh stool is

Examined, processed or preserved immediately

• note consistency of stool

Ova and parasite exam of fecal specimen

macroscopic examination

microscopic examination

Microscopic exam

• concentrate

• direct

• permanent stain

Macroscopic exam

• consistency and moisture

• color

  • black to green to clay and colors in b/w

  • normal = brown

  • antibiotics = red, purple, blue

  • barium = clay

• abnormalities

  • urine, pus, mucus, adult worms, proglottids

Distribution of consistency for protozoa

Formed = cyst

trophs = watery

parasite is thriving and changing constantly

examination of fresh specimen

purpose = to observe motile trophozoites

• liquid specimens —trophs

  • 30 minutes of passage

• soft specimens —cysts and trophs

  • 60 minutes of passage

• formed specimens

  • refrigerated overnight b4 exam

exam not performed STAT → preserve it

Types of preservatives

– 10% Formalin

– PVA (polyvinyl alcohol)

– MIF (merthiolate-iodine-formaldehyde)

– SAF (sodium acetate-acetic acid-formalin)

– Schaudinn’s fixative

– One vial fixatives

Stool preservation system

divide specimen and store in 2 preservatives

• 10% Formalin

• PVA (polyvinyl alcohol)

• 1 stool: 3VL of preservatives

  • mix and formed stool needs to be broken up

preserved for months

ADV of 10% Formalin

• all purpose fixative

• long shelf life

• preserves: hemlith eggs, larva, protozoan cysts, coccidia

Used for

• [ ] procedures

• acid fast and safranin stains

• immunoassays

DIS of 10% Formalin

• not for trichrome stain—permanent stain

• does not preserve protozoan trophs

• interfere with PCR tests

ADV of PVA

• preserves protozoan cysts and trophs

• EZ prep of permanent stains

• preserved samples remain stable for months

DIS of PVA

• no preserve helminths eggs, larvae, coccidia, microsporidia

• has mercuric chloride

• not used for

  • [ ] procedures

  • immunoassays

  • acid fast and safranin stains

microns

how big parasite it

wet mount

see motile trophozoites

[ ] procedure

separate parasite from fecal debris to inc chance of detecting org in small #

• 2 techniques

  • flotation

  • sedimentation

Flotation tech

use solution with higher specific gravity than organism

• org floats

• debris sinks

common solutions

• zinc sulfate

• sheather’s sugar

Flotation tech pros vs cons

pro —cleaner mat than sedimentation tech

cons—walls of eggs and cysts collapse = diff ID

• Operculated eggs don’t float

Sedimentation tech

Use solution with lower specific gravity than org

• org are [ ] in sediment

common: formalin-ethyl acetate

ADV = easier to performa & common

• INCLUDES OPERCULATED EGGS

PVA preserved specimens

used for permanent staining w/ trichrome to ID protozoan cysts and trophs

Trichrome stain

Confirmation step to ID protozoa—contrast is good

BG = green

Protozoan cytoplasm = light blue-green to light pink

karyosomes of nuclei = ruby red

MOST COMMON PERMANENT STAIN

Iron hematoxylin stain

alt for trichrome stain

Staining rxn

• trophs and cysts = blue gray

  • nuclei and cell inclusions stain darker than cytoplasm

• Yeast, RBC, crystals = blue gray to black

• BG: ligher shad of blue gray

cellophane tape

egg collection of enterobius vermicularis

enterotest (string test)

collect duodenal content for parasite exam

Sigmoidoscopy

collect colon mat

Blood

Knott [ ]

• slow speed cetrifugation to [ ] samples suspected of having low # of org

Buffy coat slides

leishmania or trypanosoma detection

direct fluorescent antibody (DFA)

used to identify Trichomonas vaginalis

Direct agglutination test (DAT)

-Used to diagnose leishmaniasis and Chaga's disease

ELISA

Used to identify Toxoplasma gondii

complement fixation (CF)

-Used to diagnose leishmaniasis, Chaga's disease and pneumocyctosis

Gel diffusion precipitation (GFP)

detects amoebic infections

indirect immunofluorescent antibody

-Used to diagnose amoebic, malarial and schistosome infections and toxoplasmosis

Miscellaneous procedures

DNA probes, flow cytometry and PCR

MOD acid fast stain

ID of Cryptosporidium parvum, Cyclospora cayetanensis, cystoisospora belli

• mod used to stain TB

For fresh or formalin fixed specimens

• PVA can’t be done