Parasitology Intestinal Protozoa Flashcards
Defining characteristics of amoebae
Contain pseudopodia (cytoplasmic protrusions) free living, pathogenic/non-pathogenic. found in the intestinal tract and other areas. motile trophozoites may be observed in stool as well as non-parasitic structures
Defining characteristics of flagellates
Contain flagella (extensions used for movement). Genera may live in the gastro intestinal tract, genitourinary tract, blood stream, or tissues
Defining characteristics of sporozoa
Unicellular with apical complex. In the gastrointestinal tract of vertebrates throughout life (isospora, cyclospora, & cryptosporidium) and cyst forming coccidia (extra intestinal development)
Defining characteristics of microsporidia
Obligate intracellular, spore-forming parasite. Display characteristics of prokaryotes (fungi). Are acquired from the inhalation or ingestion of spores
What are the 3 key virulence factors of Entamoeba histolytica?
- amebic lectin: binds parasite to galactose-containing sugars on host cells
- amoebapores: adherence-dependent cytolysis
- cysteine protease
What are the two Entamoeba species that are microscopically indistinguishable? How can they be differentiated? Why is it important to differentiate these?
Entamoeba histolytica and Entamoeba dispar. Entamoeba histolytica may contain RBC and causes dysentery. Patients should not be treated unless they are confirmed to have Entamoeba histolytica
What is the number of nuclei and measurement of Entamoeba histolytica cysts?
Mature cysts have 4 nuclei. Cysts measure 12 to 15 µm
Describe the trophozoite of Entamoeba histolytica.
single nucleus with centrally placed karyosome. Uniformly distributed peripheral chromatin. cytoplasm has a granular or “ground glass” appearance. measure 15 - 20 µm. Ingested RBC
Describe the trophozoite of Entamoeba dispar.
single nucleus with centrally placed karyosome. Uniformly distributed peripheral chromatin. cytoplasm has a granular or “ground glass” appearance. measure 15 - 20 µm.
What is the number of nuclei and measurement of Entamoeba dispar cysts?
Mature cysts have 4 nuclei. Cysts measure 12 to 15 µm
What is the only Entamoeba species with more than four nuclei in the cyst stage?
Entamoeba coli
True or False: It is relatively easy to distinguish Iodamoeba buetschlii trophozoites from Endolimax nana trophozoites.
False
What is the only species of Entamoeba that ingests white blood cells?
Entamoeba gingivalis
What is the treatment regimen for Entamoeba coli?
none
What is the treatment regimen for Iodamoeba buetschlii
none
What are the three tests that can be used to diagnose Blastocystis hominis?
- Routine stool examination
- Antigen detection using enzyme-linked immunosorbent assays (ELISAs)
- Antibody detection using ELISA and fluorescent antibody tests
Describe the microscopic morphology of Blastocystis hominis.
Spherical to oval cyst-like structures. central body or “vacuole” surrounded by a thin rim of cytoplasm containing up to 6 nuclei
What is the number of nuclei and measurement of Entamoeba dispar cysts?
Mature cysts have 4 nuclei. Cysts measure 12 to 15
Describe Entamoeba coli trophozoites
Measure: 15-50 µm
Nucleus: single nucleus with large eccentric karyosome and course irregular peripheral chromatin
Cytoplasm: coarsely granular and vacuolated
Pseudopodia: short and blunt and movement is nondirectional
Describe Entamoeba coli cysts
Measure: 10-35 μm
Nucleus: 8 to 16 nuclei with compact or diffuse karyosome with coarse irregular peripheral chromatin
Cytoplasm: diffuse glycogen
Describe Endolimax nana trophozoites
Measure: 6-12 μm
Nucleus: single nucleus with large irregularly shaped karyosome and no peripheral chromatin
Cytoplasm: granular and highly vacuolated
Difficult to distinguish from Iodamoeba buetschlii
Describe Endolimax nana cysts
Measure: 5-10 μm
Nucleus: 4 nuclei with large karyosome with no peripheral chromatin. Visible in iodine-stained wet mounts
Cytoplasm: diffuse glycogen lacks chromatoid bodies
Describe Iodamoeba buetschlii trophozoite
Measure: 8-20 μm
Nucleus: single nucleus with large central karyosome and surrounded by refractile, achromatic granules
Cytoplasm: granular and highly vacuolated. movement is sluggish and non-progressive
Difficult to distinguish from Endolimax nana
Describe Iodamoeba buetschlii cysts
Measure: 5-20 μm
Nucleus: single nucleus with large eccentric karyosome. Visible in iodine-stained wet mounts
Cytoplasm: large compact mass (vacuole) of glycogen
Describe Entamoeba hartmanni trophozoite
Measure: 5-15 μm
Nucleus: single nucleus with small compact centrally or eccentrically-located karyosome
Cytoplasm: finely granular. Movement non-progressive
Describe Entamoeba hartmanni cyst
Measure: 5-10 μm
Nucleus: 4 nuclei with small discrete centrally located karyosome
Cytoplasm: may contain diffuse glycogen
round or elongated chromatoid bodies with rounded ends
Describe Entamoeba polecki trophozoite
Measure: 10-25 μm
Nucleus: single distorted/irregularly-shaped with small to minute centrally located karyosome
Cytoplasm: vacuolated, hyaline border. blunt pseudopodia may be seen
Describe Entamoeba polecki cysts
Measure: 9-25 μm
Nucleus: single nucleus, binucleate forms are rarely seen. large nucleus up to 1/3 of cyst. Karyosome is pleomorphic, minute to large and compact or diffuse
Cytoplasm: inclusion mass of variable size, numerous chromatoid bodies, small to large rods with round or splintered ends
Laboratory diagnosis of Giardia
antigen detection and wet mounts from multiple samples
Characteristics of Giardia
Trophozoites are teardrop shaped with two large nuclei. Sucking disk and flagella may be seen
Cysts are oval to ellipsoid. Mature cysts have 4 nucli and immature cysts have 2
May be seen with iodine and trichrome-stained smears
Vector of Dientamoeba fragilis
helminth eggs (e.g. Ascaris and Enterobius)
Travel history for Diantamoeba fragilis
mental institutions, missionaries, and NAtive Americans in Arizona
Vector of Chilomastix mesnil
fecal contamination of food or water
Travel history for Chilomastix mesnil
warm clilmates
Distinguishing characteristics of Chilomastix mesnil
pear shaped trophozoite. Anterior end is rounded and contains a single nucleus and a distinct oral groove.
Cysts have a typical curved cytostomal fibril called the shepherd’s crook
Specimen of choice for Trichmonas vaginalis
Female: vaginal and urethral secretions
Male: anterior urethral or prostatic secretions
Laboratory diagnosis for Trichomonas
wet mount and direct immunofluorescence antibody staining
Trichomonas characteristics
5 flagella; 4 anterior and 1 posterior
undulating membrane that goes down 1/2 of trophozoite body
large nucleus located at wider anterior end
Laboratory diagnosis Balantidium coli
routine stool examination, particularly wet mount
Balantidium coli characteristics
only ciliate to infect humans.
pigs are reservoir
two nuclei in both trophozoite and cyst
anterior end is somewhat pointed and has a cytostome (primitive mouth opening)
Naegleria fowleri infectivity
amoeba enter the nasal cavity and migrate to the brain
rapidly cause PAM (Primary amebic meningoencephalitis)
Acanthamoeba infectivity
granulomatous amebic encephalitis: associated with underlaying disease (no freshwater contact)
Amebic keratitis: associated with direct exposure to contaminated material or solutions. wearing contacts is the leading risk factor
Specimen of choice for Toxoplasma
serum samples obtained from peripheral blood are preferred
Toxoplasma infectivity
raw or undercooked meat.
cats favoring the survival and spread of oocysts
soil exposure
congenital toxoplasmosis
Specimen of choice for Babesia
blood
Babesia vector
ticks of the genus Ixodes
Babesia life cycle
- Tick: Sporozoites introduced into non human host
- non human Host: Sporozoite to trophozoite to merozoite to gamete
- Tick: ingests gametes
- Tick: fertilization in gut. sporogony to sporozoites
- Tick: Sporozoites introduced into human host
- human: Sporozoite to trophozoite to merozoite
Trypanosoma cruzi travel history
the Americas from the southern US to southern Argentina. Mostly in poor rural areas of Mexico, Central America.
Trypanosoma cruzi vector
triatomine bug
