intro to parasitology

definitive/final

host where adult or sexual reproductive phase occurs

intermediate

host where larval development or asexual reproductive phase occurs before parasite becomes infectious

incidental (accidental)

host that is not required for completion of a life cycle

-usually a dead end

reservoir

host that harbors a species of parasite that is also parasitic for humans

-can infect humans with the parasite

carrier

asymptomatic host colonized by a parasite

vector

parasite that can serve as means of spread

trophozoite

motile, feeding stage

cyst

non feeding, non motile, infective stage

excystation

transformation of cyst to trophozoite after swallowing of cystic form by host

protozoa

parasites can be intestinal, tissue, blood, extraintestinal, nematodes, cestodes, trematodes

vectors

arthropods are parasites and serve as … for parasites

-arachnids and insects

intestinal

protozoa type

-amebae

-flagellates

-ciliates

-coccidia

-microsporidia

tissue, blood

protozoa type

-sporozoa

-flagellates

extraintestinal

protozoa type

-amebae

-flagellates

-ciliates

-coccidia

nematodes (roundworms)

protozoa type

-intestinal

-tissue

-blood

cestodes (tapeworms)

protozoa type

-intestinal

-tissue

trematodes (flukes)

protozoa type

-intestinal

-liver

-lung

-blood and tissue

fecal

most common specimen for parasite recovery

2-3, 10 days

number of fecal specimens collected within x period of time for maximal parasite recovery

motile

fresh specimens examined immediately for motile/nonmotile parasite examination

wet prep

-specimen arrival within 20 min of collection

-looking for motile amoeba

-saline

sedimentation

-fecal concentration technique

-formalin-ethyl acetate sedimentation concentration: centrifuge tube

-para-pak spin: filters and centrifuge tube

flotation, zinc sulfate

-fecal concentration technique

-suspends orgs at top of high density fluid

formalin (10%)

-fecal preservation

-iodine wet prep

-DFA stains

-morphology of helminths, eggs, larvae, protozoan cysts

MIF (merthiolate-iodine-formaldehyde)

-fecal preservation

-not good for trichrome

SAF (sodium, acetate, acetic acid, formalin)

-fecal preservation

-acid fast stains

Schaudinn’s fluid

-fecal preservation

-mercuric chloride and 95% EtOH

PVA (polyvinyl alcohol)

-fecal preservation

-resin added to Schaudinn’s fluid

-slide adhesion

copper, zinc sulfate

-fecal preservative

-substitutes for mercuric chloride in modified PVA

ecofix

-most commonly used fecal preservative

-environ friendly (no mercuric chloride)

-no need for formalin and other fixative

-concentrates and preserves

-expensive

Lugol’s iodine

-stain for concen wet prep

-eggs and cysts

-70% ethanol-iodine removes mercury from fixative

eggs, cysts 

what Lugol’s iodine stains

trichrome

-main stain used for permanent stains

-blue green: troph cyto, cysts

-dark red-purple: nuclei, inclusions, karyosomes, chromatoidal bars, RBCs

-green: background, yeast

iron hematoxylin

stain works best if SAF used

oocysts (Cryptosporidium, Cyclospora, Isospora)

what modified acid fast stain stains

calcofluor white

fluorescent stain for Microsporidia

blood

specimen for Plasmodium spp. recoery

-EDTA best

thick

blood smear prep lyses RBCs with distilled water to leave parasites and WBC nuclei

thin

blood smear prep to see individual RBCs

Giemsa, Wright

stains used to visualize parasites in blood smears

Loa Loa

blood collection for best reco mid-day (10-2)

Brugia, Wucheria

blood collection for best reco at night after 8 pm

Mansonella, Ochocera

blood collection for best reco anytime

Malaria, Babesia

blood collection for best reco at start of fever spike

respiratory

-BAL best sample

-Filarform larvae of Srongyloides

-eggs of Pargonimus

tissue

sample goes to path

aspirates

sample requested to rule out tapeworm cysts or amoeba

urine

sample to rule out Schistosomiasis

pinworm

sample uses scotch tape or “swube” paddle

CSF

sample used to look for motile amoeba

vaginal

wet prep sample to look for Trichomonas

Ab

detection by EIA for E. histolytica, Cryptosporidium, Giardia, Trichomonas

Cryptosporidium, Giardia

have both EIA and PCR procedures to detect Ab

ocular micrometer

device on microscope

-calibrated every 2 yrs

-measures org length and width