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Flashcards in Module 1 Deck (57)
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1

Parasite

organism that lives upon or within another organism at whose expense it obtains something it needs for life

2

In the US, what are the parasites that are prevalent to children?

pinworms and round worms

3

What is the greatest source of infection?

Man

4

Harmful effects of parasites

-mechanical injury
-eating or digesting and absorbing host tissue
-poisoning
-robbing the host of nutrition

5

Ectoparasite

lives on surface of host

6

Endoparasite

lives inside a host

7

obligatory parasite

has to spend part of its life as a parasite

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facultative host

not normally parasitic but can become so

9

definitive host

host in which the parasite reaches maturity and reproduces; most important host

10

intermediate host

some development of parasite occurs but doesn't reach maturity

11

vector

insect that carries parasitic infection from one host to another; can be host

12

Main human host defensive mechanisms

-immunoglobulins in the mucous of intestines and respiratory tract, tears, saliva, and sweat
-phagocytosis
-reticuloendothelial system
-inflammation
-granuloma formation
-accommodation

13

Accommodation to parasites in humans

-parasite becomes immunologically inert
-parasite masks itself with host antigens
-parasite changes surface antigens

14

Stool types

-liquid: most likely to contain trophozoites
-soft: may contains pre-cysts
-formed: contains cysts, ova, and larvae

15

Times of collection for stool samples

10 day period, one every other day

16

Substances that interfere with the detection of intestinal parasites

-antibiotics
-bismuth
-kaolin
-antimalarials
-milk of magnesia
-mineral and castor oil
-barium enema

17

Other types of parasitic specimens

-sigmoid material
-duodenal contents
-urogenital material
-sputum
-aspirates
-biopsy material
-blood

18

Purge specimen

Fleet's enema

19

Why should there not be any urine or water in the stool specimen?

Water can contain free living organisms and urine destroys motility

20

Specimens required for routine exam

-2 normally passed
-1 after Fleet's enema

21

Ameobiasis protocol

-3 normal
-3 after enema

22

Preservation of specimens

-PVA: cysts, trophs, and/or ova; useful for liquid specimens

23

PVA

-3:1 ratio of PVA to stool
-allows specimens to slide for staining
-permanent stained slides for months or years in sealed containers

24

Advantages of PVA

-both preservative and fixative so suitable for permanent staining procedures
-excellent preservative for protozoan cysts and trophozoites

25

Disadvantages of PVA

-Giardia and Trichamonas don't concentrate well
-isospora is not usually seen

26

Advantages of formalin

-cysts are preserved for a long time
-specimens can be preserved to long periods of time without greatly compromising organism morphology

27

Disadvantages of formalin

-only for wet mounts: no permanent slides
-have to add formalin within an hour of passage

28

Schaudinn's Fluid

used for fixing fresh smears for permanent smears; found in PVA

29

MIF

good stain for most kinds and stages of parasites; not for permanent stains

30

Sodium Acetate Formalin

used only with iron hematoxylin stain; used for both concentrates and permanent smears