Parasitology Flashcards
A parasite that cannot live apart from its host
Obligatory parasite:
An organism capable of living an independent or a parasitic existence; not an obligatory parasite, but potentially parasitic.
Facultative parasite
Usually a free-living organism that can become parasitic if it is accidentally ingested or enters a wound or other body opening.
Facultative parasite
The presence of parasites in the blood (e.g., malaria schizonts in red blood cells).
Parasitemia
A parasite established on the body of its host.
Ectoparasite
The association of two different species of organisms in which the smaller species lives on or within the other and has a metabolic dependence on the larger host species.
Parasitism
The animal in which a parasite passes its larval stage or asexual reproduction phase.
Intermediate host
: Infection of a host other than the normal host species
Accidental (or incidental) host
A parasite may or may not continue full development in an accidental host
The animal in which a parasite passes its adult existence, sexual reproductive phase, or both.
Definitive host
: An animal that harbors a species of parasite that is also parasitic for humans and from which a human may become infected.
Reservoir host
that harbors a parasite that does not reproduce but merely goes on to infect a new host.
Transport host
A host harboring a parasite but exhibiting no clinical signs or symptoms.
Carrier
The association of two different species of organisms in which one partner is benefited and the other is neither benefited nor injured.
Commensalism
unicellular eukaryotic microorganisms.
Protozoal parasites
Three types of protozoal parasites based on locomotion
-Phylum Sarcomastigophora: Locomotion by pseudopodia or flagella
- Phylum Ciliophora: Locomotion by cilia
-Phylum Apicomplexa: Apical complex can be seen with an electron microscope, reproduction is both sexual and asexual
Locomotion by pseudopodia or flagella
Phylum Sarcomastigophora
Locomotion by cilia
Phylum Ciliophora
Apical complex can be seen with an electron microscope, reproduction is both sexual and asexual
. Phylum Apicomplexa
wormlike invertebrates
Metazoan (helminths) parasites
Two types of Metazoan (helminths) parasites
-Phylum Nemathelminthes: Nematoda: roundworms
- Phylum Platyhelminthes: flatworms
Nematoda: roundworms
Phylum Nemathelminthes
flatworms
Phylum Platyhelminthes
two types of Phylum Platyhelminthes: flatworms
-Cestodes
-Trematodes
body flattened and segmented
Cestodes (tapeworms
flukes -body flattened, leaf-shaped, and nonsegmented)
Trematodes
possess a hard exoskeleton and jointed appendages.
flies, mosquitoes, bugs, lice, fleas, ticks, mites
Arthropods
3 broad groups of parasites?
Arthropods
Metazoan (helminths) parasites
Protozoal parasites
(unicellular organisms) and
a. Amoebae; e.g. Entamoeba, Naegleria
b. Flagellates; e.g. Giardia, Trichomonas
c. Sporozoa; e.g. Plasmodium, Babesia, Toxoplasma
d. Cilliates; e.g. Balantidium
Protozoa
Nematodes; e.g. Ascaris, Ancylostoma
b. Cestodes; e.g. Taenia, Echinococcus
c. Trematodes; e.g. Fasciola, Schistosoma
Helminths (multicellular organisms)
Direct wet mounts: Protozoan motility in fresh unpreserved liquid or runny or bloody specimens within ____ minutes of specimen passage
30
Trophozoites begin to disintegrate after ____ minutes.
30
For a routine parasitic workup, it is recommended that patients submit stools from…
three normal bowel movements, one every other day, or within a 10-day period
what is the specimen transport?
-A two-vial system
-One vial should contain 8 to 10 mL of a fixative, for example, Schaudinn’s solution, or SAF (sodium acetate-acetic acid-formalin), that contains polyvinyl alcohol (PVA) and a second vial should contain 8 to 10 mL of 10% formalin.
-Added to this are 2 to 3 mL of feces
Single-vial systems…
Ecofix, Parasafe, Unifix, Proto-fix) are available which offer advantages such as immunoassay compatibility and lack of mercury compounds in the formulation.
Smears for trichrome staining: The ____ tube.
PVA
For the formalin-ethyl acetate concentration method : ____formalin or the PVA tube.
10%
The zinc sulfate flotation method can be performed using the …
10% formalin vial.
Liquid stool within _____minutes
Semisolid stool within _____ hour
Formed stool within ____ hours of collection
30
1
24
Hookworm eggs mature and hatch if allowed to remain at room temperature and they may be confused with ____________ larvae unless carefully observed.
Strongyloides
___________ cysts may be found more commonly than trophozoites in formed stools and are often easier to identify than trophozoites.
Protozoan
Trophozoites are found more commonly in…
liquid stools.
Because trophozoites do not survive long, all specimens must be examined ….
in a timely manner.
When amebiasis or giardiasis is suspected, several specimens (at least _______) should be examined one ___________.
three, every other day
If barium salts have been given, it is necessary to wait from ___- ___ days before submitting a specimen for parasitic examination.
5-10
If antibiotics have been given, new fecal collections should not begin until ____ weeks after therapy has ended.
2
Mushy or liquid stools suggest possible ___________ of intestinal protozoa.
trophozoites
Protozoan cysts are found more frequently in….
formed stools
Helminth eggs and larvae may be found in…
either liquid or formed stools.
Bloody mucus suggests ulceration and some of this material should be preferentially examined microscopically for ___________
trophozoites.
Direct saline wet mount is used for?
Rapid screening technique used to study trophozoite motility.
. Fecal concentration
Increases the chance for recovering ___________
parasitic forms
from the breakdown of eosinophils and may be seen in the stool or sputum of patients with parasitic diseases.
Charcot-Leyden crystals
The crystals are slender and pointed and stain purplish-red in the trichrome stain, as shown in this image. These crystals can appear in a variety of sizes and only indicate an immune response, but the cause may or may not be a parasitic infection.
Charcot-Leyden crystals
Flotation Methods:
uses liquids with a _______ specific gravity than that of eggs or cysts so that parasites float to the surface so the concentrate can be skimmed from the top of the tube.
final specific gravity of ______
higher specific
1.18
most commonly used reagent for floatation methods?
zinc sulfate
what method does not easily recover operculated eggs or infertile Ascaris eggs?
Flotation Methods
Flotation method:
the high specific gravity kills____________ and causes distortion of certain other fragile eggs, such as H. nana.
trophozoites
A major pathogen in this group and the cause of amebic dysentery in humans.
It can occur in other primates, dogs, cats, and rats.
Entamoeba histolytica
40 to 50 million people develop colitis or extraintestinal disease annually with 40,000 deaths.
Entamoeba histolytica
where is prevalence high for Entamoeba histolytica?
how is it transmitted?
-in the subtropics and tropics
-sexually by homosexual males ,“gay bowel syndrome.” Up to 30% of some populations of this at-risk group can harbor E. histolytica/ E. dispar.
-flask-shaped ulcerations of the intestinal wall and bloody dysentery.
-invades the intestinal wall and multiplies in the mucosal tissue.
E. histolytica
Liver abscesses: most common
E. histolytica
which mastigote form is in the human for Trypanosoma brucei?
trypomastigote
Name for pinworms
enterobius vermicularis
