Parasitology Review Flashcards
Intestinal Protozoa, Extraintestinal protozoa, nematodes, trematodes and cestodes
A traveler returning from the Amazon rain forest was screened for parasites on their return. The images above images of organisms that were seen on a PVA smear, stained with trichrome stain and examined at 1000× magnification.
These two images are different stages of the same organism/species.
What is your identification of this organism ?
a. Giardia lambia
b. Chilomastix mesnili
c. Entamoeba coli
d. None of the above
b. Chilomastix mesnili
Chilomastix mesnili is correct. Shown in the images are a cyst stage and a trophozoite stage.
Both have a single nuclei. Cysts of Entamoeba coli and Giardia would have more than one nuclei.
Also:
The cysts are lemon shaped and in the size range of seven to ten micrometers with a large nucleus having a large karyosome, there are fibrils along the cytostome
The trophozoites are pyriform and in the size range of ten to twenty four micrometers. The troph contains a large nucleus at the anterior end with peripheral chromatin that is granular.
https://www.cdc.gov/dpdx/chilomastix/index.htmlLinks to an external site. And click the image gallery folder
A family visited several U.S. states during a two week vacation. Approximately eight days after their trip, two family members began experiencing diarrhea. They went to their family physician and reported that while they were traveling they swam in hotel pools and at a waterpark. The physician requested stool samples for an ova and parasite (O & P) examination, along with other testing. The samples collected for the O & P were preserved in 10% formalin. The image below shows objects seen on a modified acid-fast ZN stained slide made from a formalin-ethyl acetate (FEA) concentrate of one of the stool specimens. The same objects were seen in specimens from the other family member who was ill.
The objects measured 4.5-5.5 micrometers in diameter.
True or False: The objects below are positive for the modified acid fast ZN stain?
What is your identification for case #3 above:
a. Cyclospora cayatenensis oocysts
b. Cryptosporidium species oocysts
c. Isospora (Cystoisospora) species oocysts
d. Mycobacterium tuberculosis acid fast bacilli
TRUE
b. Cryptosporidium species oocysts
A baby with nausea, watery diarrhea, and anorexia, went to the ER. They ordered an O & P on the stool sample collected. The objects seen on the Formalin preserved sample (FEA SOP) wet mount slide stained with Lugol’s (Dobell O’Conner’s) iodine are seen in image A:
The PVA sample’s trichrome stained slide of the patients fecal specimen are seen in images B, C, & D.
The average size of the organisms 12 microns (µm) in length & 7 µm in width.
Which of the following statements are true:
a. The cyst form is only seen in image A
b. The cyst form is seen in images B and C but not in image A
c. All three images demonstrate the cyst form
d. None of the images show the cyst form. They are all trophozoites
In case 4 above: Besides nuclei what other structures do the cysts contain?
a. axonemes and median bodies
b. flagella and cytostomes
c. cilia and contractile vacuoles
d. flagella and food vacuoles
For Case 4 above based on the size, stage, shape, nuclei count, and other internal structures what is your ID of the organism?
a. Entamoeba coli
b. Chilomastix mesnili
c. giardia species
d. Dientamoeba fragilis
c. All three images demonstrate the cyst form
a. axonemes and median bodies
c. giardia species
This was a case of giardiasis caused by Giardia species (G. lamblia, G. duodenales, G. intestinalis). Only cysts of the parasite were observed in this specimen.
Morphologic diagnostic features include:
the presence of oval (sometimes round) smooth-walled cysts measuring 11 to 14 µm in length and 7 to 10 µm in width.
the presence of 2-4 nuclei in the cysts. All 4 nuclei are rarely visible in the same focal plane.
the presence of a longitudinal axostyle and perpendicular median (parabasal) bodies
An MLS is puzzled when she finds cysts resembling E. histolytica/dispar or E. hartmanii. A way of distinguishing Entamoeba histolytica/dispar cysts from cysts of Entamoeba hartmanii is:
a. E. histolytica/dispar cysts have four nuclei and E. hartmanii have eight
b. E. histolytica/dispar cysts are larger (12-15 um) than E. harmanii cysts (6-8 um)
c. E. histolytica/dispar cysts have red blood cells in the cytoplasm, but E. hartmanii do not
d. all of these are correct
b. E. histolytica/dispar cysts are larger (12-15 um) than E. harmanii cysts (6-8 um)
A 42-year-old man complained of diarrhea for 2 weeks following an international assignment that included travel to countries in Southeast Asia and the Indian subcontinent. He explained to his physician that his symptoms began shortly before he returned to the United States. An ova and parasites (O & P) examination was ordered, and Figures A-C show what was observed. Figures A is from a wet mount stained with Lugol’s iodine, and Figures B and C are from a trichrome stained fecal smear. The objects ranged in size from 20-25 micrometers.
What is the identification of this organism?
a. Entamoeba coli
b. Entamoeba histolytica
c. Entamoeba hartmanii
d. Dientamoeba fragilis
b. Entamoeba histolytica
It is acceptable to call this E. histolytica since ingested RBC’s are found (Figure B)
An adult patient went to a local ER due to fevers & chills. They reported that they had traveled to Burma & Thailand recently for several weeks. The physician ordered a malaria test. Thick and thin smears were made & stained using Wright’s stain from the Hematology Dept.
Three images of objects seen at 1000x oil immersion are above. Careful review of the whole slide showed more of the same/similar forms.
Would you describe the infected RBCs as enlarged?
a. Yes, the infected RBC’s are enlarged
b. No, the infected RBC’s are normal size
How would you describe the trophozoites seen in some of these images?
a. Ameboid trophs seen in image 2 and 3. (Image one is a gametocyte.)
b. Large compact troph seen in image 1 and ameboid trophs seen in image 2 and 3
c. Signet rings with double dots and applique forms
d. There are no trophozoites seen in any of the three images.
a. Yes, the infected RBC’s are enlarged
a. Ameboid trophs seen in image 2 and 3. (Image one is a gametocyte.)
TRUE or FALSE. Is there stippling (Schuffner’s dots) seen in any of the infected RBCs below?
Based on these images and criteria discussed: What is your identification / speciation for this sample ?
a. Plasmodium falciparum
b. Plasmodium vivax
c. Plasmodium ovale
d. Plasmodium malariae
e. Babesia species
FALSE
b. Plasmodium vivax
NOTE: The lack of stippling/Schuffners dots is due to the use of Wright’s stain instead of Giemsa. It usually takes Giemsa stain with tight PH control to see malarial stippling.
The band form seen in the fourth image is suggestive of Plasmodium malariae however the RBC is enlarged which does not fit that species.
A couple of the RBC’s do look oval however none of them show true fimbriation seen in P. ovale. The presence of distorted un-infected RBCs nearby indicate that this feature is not due to the parasite.
An MLS is reading trichrome smears and notes the following in the trichrome smear. What are these?
a. Entamoeba histolytica
b. Blastocystis hominis
c. Giardia lamblia
d. White blood cells
d. White blood cells
WBC’s can resemble parasites in trichrome smears.
A specimen arrives in the lab for Ova and Parasite testing (O&P). Only the Formalin vial is received. How should this specimen be processed?
Refer to CDC if needed: https://www.cdc.gov/dpdx/diagnosticprocedures/stool/specimencoll.html Links to an external site.
a. Use the formalin vial for both the concentrate and the trichrome
b. Only perform a concentrate. Formalin can’t be used for trichrome staining
c. Only perform a trichrome stain
d. Pour the specimen down the drain
b. Only perform a concentrate. Formalin can’t be used for trichrome staining
The following images contain a Giemsa-stained preparation of vaginal secretions from a woman experiencing vaginal pain and discomfort. The objects measure approximately 15-20 micrometers.
What is the most likely identification of this parasite?
a. Giardia lamblia
b. Chilomastix mensili
c. Trichomonas vaginallis
d. Leishmania braziliensis
c. Trichomonas vaginallis
A 19 year old male patient returned from South America and came to the ER with fever and chills.
Blood smears were made and stained with Giemsa stain.
Many of the trophozoite ring forms in images one and two were seen in the specimen. The majority were in RBCs of normal size. Also seen was the rare form in image three.
What is your identification of this organism ?
a. Babesia species
b. Plasmodium falciparum
c. Plasmodium vivax
d. Plasmodium malariae
e. Plasmodium ovale
f. Plasmodium Knowlesi
b. Plasmodium falciparum
Even though the second image showed an enlarged RBC the text of the question explained that most of the infected RBCs were of normal size. P. falciparum invades all ages of RBCs so can be seen in any RBC size with normal RBC predominating. This ability to infect all RBC ages is part of the reason that falciparum is the most deadly of the four (five) species.
Crescent gametocytes are diagnostic for falciparum.
The whole slide should still be read as mixed infections can be found.
Ray is a patient who arrives in the ER complaining of fever, chills, fatigue, and myalgia. Ray tells the physician that he had recently been on vacation in New England and had found a tick embedded in his neck.
Examination by the physician notes that Ray also has an enlarged liver and STAT hematology results indicate a mild anemia.
The ER physican orders thick and thin blood smears which exhibit the following:
Based on the patient history and images, what is the ‘most likely’ parasite in these images?
a. Babesia spp.
b. Plasmodium falciparum
c. Plasmodium ovale
d. Plasmodium malariae
a. Babesia spp.
A five-year-old child went to a local clinic with complaints of abdominal cramping, excessive gas, diarrhea, and weight loss. Stool specimens were collected in formalin and polyvinyl alcohol (PVA) and sent to the laboratory for routine ova-and-parasite (O&P) examination. The images below show what was observed on a trichrome-stained slide prepared from stool preserved in PVA. All images were taken at 1000x magnification.
What is your diagnosis?
a. No parasites seen
b. Chilomastix mensili
c. Entamoeba histolytica
d. Giardia duodenalis
In the images from the previous case, there is a second organism noted. (note the round bodies with green center)
What is this organism?
a. Cyclospora spp
b. Blastocystis hominis
c. Endolimax nana
d. Candida albicans
d. Giardia duodenalis
b. Blastocystis hominis
Blastocystis has a large central body surrounded by a narrow rim of cytoplasm with inclusion bodies
A 45-year-old patient originally from Mexico presented with a left groin lymphocele, erythema, swelling in his lower extremities, and fever and chills approximately one month after receiving a heart transplant. Blood specimens were collected in EDTA and sent to Hematology for work-up. Objects of interest were observed by the attending pathologist on a thin blood film stained with Wright stain.
What organism do you suspect?
a. Trypanosoma brucei
b.Leishmania spp.
c. Trypanosoma cruzi
d. Trichomonas vaginalis
c. Trypanosoma cruzi
Correct, this is a case of Chagas disease.
Organism characteristics include a small kinetoplast and the ‘C shaped’ form of the organism
Above are images from a CAP survey a few years ago. Travel history was not given but for the sake of this case study let’s say the person was well traveled recently in Asia and Africa.
Most of the images are from the thin smears and there is one thick smear image also.
Which of the following choices would be the best result to turn out, as a STAT preliminary result on this sample ?
a. Plasmodium falciparum
b. Plasmodium species NOT falciparum
c. Plasmodium falciparum: further ID to follow, possible mixed infection
d. No parasitic forms seen
Regarding the CAP specimen images in the first question what do you think the final results will be?
a. Plasmodium falciparum and Plasmodium vivax
b. Plasmodium falciparum and Plasmodium ovale
c. Plasmodium falciparum and Plasmodium malariae
d. Plasmodium falciparum and Plasmodium knowlesi
c. Plasmodium falciparum: further ID to follow, possible mixed infection
The crescent shaped gametocytes are diagnostic for Plasmodium falciparum but the trophozoites stages are too large for falciparum and they are in enlarged RBCs with stippling.
Also: the RBCs infected with the trophozoite stages tend to be elongated and fimbriated.
b. Plasmodium falciparum and Plasmodium ovale
Note that the trophozoites that are too large for P falciparum are in RBCs that are often oval and fimbriated. Also the stipping in some is very heavy
A 40 year old pig farmer saw his doctor for intermittent diarrhea and abdominal pain. The physician had him submit a stool sample for ova and parasite testing. Figure A was captured at 200x magnification and show what was found in high numbers. Figures B and C show a higher magnification (400x) of the same objects.
The object in image B measures 70 µ The object in image C measures 60 µ
What is the best answer for these observations ?
a. The organism is an egg of the roundworm Trichuris trichiura as seen in image B.
Image C is an artifact
b. The organism is an egg of the roundworm Ascaris lumbricoides as seen in image B.
Image C is an artifact
c. The organism is an egg of the roundworm Ascaris lumbricoides as seen in image B.
Image C the Ascaris hatched out in its motile miracidia stage.
d. Image B is an egg of the roundworm Ascaris lumbricoides
Image C is the trophozoite stage of Balantidium coli
e. Image B is the cyst stage of the ciliate Balantidium coli
Image C is the motile trophozoite stage of Balantidium coli
- TRUE or False. True or False:
At least one of the two organisms seen in the previous question has been associated with contact to pigs which can harbor the organism:
d. Image B is an egg of the roundworm Ascaris lumbricoides
Image C is the trophozoite stage of Balantidium coli
Comment: Mixed infections of parasites are not uncommon. In fact once you find one parasite in a sample the odds have just gone up that another species may be found.
It is good to note at this point that both Ascaris lumbricoides eggs and Balantidium coli trophs (and cysts) are easily mistaken for artifacts.
- True
Comment: This is true for both organisms. Balantidium coli while rarely seen in humans is often associated with contact to pigs which can carry this organism.
Ascaris lumbricoides is more common in humans and the route of exposure varies. But there have been articles associating some human cases with contact to pigs:
https://wwwnc.cdc.gov/eid/article/21/2/14-0048_article
In the image below what is the correct list of helminth eggs seen:
a. Trichuris trichiura egg
Toxocara egg
Ascaris lumbricoides egg
b. Toxocara egg
Capillaria philippinensis egg
Strongyloides stercoralis egg
c. Hookworm egg
Ascaris lumbricoides egg
Capillaria philippinensis egg
d. Ascaris lumbricoides egg
Capillaria philippinensis egg
Strongyloides stercoralis egg
e. Hookworm egg
Trichuris trichiura egg
Ascaris lumbricoides egg
f. Hookworm egg
Trichuris trichiura egg
Artifact resembling Baylisascaris procyonis egg
e. Hookworm egg
Trichuris trichiura egg
Ascaris lumbricoides egg
Comment:
Hookworm egg: Oval and Thin shell
Ascaris lumbricoides egg: Oval and Thicker shell: and this one is decorticated.
Trichuris trichiura egg: Football shape with polar plugs
Stool specimens were collected from Haitian patients at a refugee clinic for routine ova-and-parasite (O&P) examination. The stool specimens were collected in 10% formalin and polyvinyl alcohol (PVA) and sent to the laboratory for processing and examination. Figures A and B show what was observed in low numbers in a concentrated wet mount of the formalin-preserved stool from one of the patients. The objects measured on average 53 micrometers long by 22 micrometers wide.
What is your identification of this parasite?
a. Enterobius vermicularis
b. Hookworm
c. Trichuris thrichiura
d. Ascaris lumbricoides
c. Trichuris thrichiura
The following is observed in a concentrated specimen from and O&P sample:
It measures 60 micrometers in length.
What will you call this ova?
a. Ascaris lubricoides
b. Hookworm
c. Trichinella spiralis
d. Trichuris thrichiura
b. Hookworm
A white object measuring ~ 1cm long by 0.5 cm wide. was collected from a stool sample from a 21 year old female patient. It was sent in to the lab for identification. (1st image)
It appeared to have a genital pore on one side of the proglottid. Using applicator sticks eggs were expressed from the proglottid and can be seen in the next two images. 200x and 400x. They measured 34 to 41 µ
What is your identification at this time ?
a. Taenia solium
b. Taenia saginata
c. Taenia species
d. Diphylobothrium latum
c. Taenia species
Comment: It is not possible to speciate Taenia from eggs. Further examination of the proglottid is needed.
Partial credit was given for the correct species as some may have seen the subtle details in this unstained proglottid. Though confirmation by injecting india ink is preferred, as will be seen in the next question
The proglottid was injected with india ink as seen above:
What is your identification ?
a. Taenia solium
b. Taenia saginata
c. Ascaris lubricoides
d. Diphylobothrium latum
b. Taenia saginata
Comment: Taenia saginata proglottids have 15 to 20 uterine branches; T. solium proglottids will have 7 to 13 branches.
A patient from the Great Lakes area presents with vague abdominal symptoms and a macrocytic anemia. She had recently been on a fishing trip.
An O&P concentrate on the patient’s stool sample reveals the following ova measuring 75um long:
What parasite (genus and species do you suspect?
a. Diphyllobothrium latum
b. Hymenolepis nana
c. Taenia saginata
d. Taenia solium
a. Diphyllobothrium latum
Comment: Infection with Diphyllobothrium latum can be acquired by eating freshwater fish infected with the parasite.
A nine-year-old female refugee from Eritrea with neutropenia and eosinophil counts within normal range had a stool examination as part of a refugee screening. Microscopic examination of an iodine wet mount preparation of a formalin-ethyl acetate (FEA) concentration of the stool sample submitted found what is shown in Figures A, B (taken at 400x) and C (at 1000x). What is your diagnosis?
a. Hymenolepis diminuta
b. Hymenolepis nana
c. Taenia solium
d. Diphyllobothrium latum
b. Hymenolepis nana
Comment: This was a case of hymenolepiasis caused by Hymenolepis nana (the dwarf tapeworm).
Morphologic features shown included:
Eggs within the size range for H. nana (30-50 micrometers).
Presence of an oncosphere with hooklets, which are somewhat inconspicuous in image (red arrows; Figures B).
Polar filaments between the inner and outer membranes (blue arrows, Figure A and C).
Infection has worldwide distribution and is most commonly seen in children
Case study from CDC Case #457
During a routine urinalysis microscopic exam of a sample, the MLS observed the 100 x microscopic field seen below:
TRUE or FALSE: This can just be ignored because it is just white blood cells and debris.
FALSE
Comment: There are WBC’s in this image.
While the larger object may not be clear, it would be premature to ignore it. The MLS should make another wet mount of the urine sediment to confirm.
Due to the objects seen in the previous question above, the MLS made another wet mount of the urine sediment to confirm their suspicions of this object.
The following was seen and measured 130 micrometers long.
What is your identification of this object?
a. This is an artifact
b. Schistosoma mansoni
c. Schistosoma haematobium
d. Schistosoma japonicum
e. Trichomonas vaginalis (This is the only parasite possible to see in a urine sample)
c. Schistosoma haematobium
Comment: Remember that parasites can be seen in other departments in the lab besides Microbiology/Parasitology.
This parasite was detected by an observant evening shift generalist that was covering Coag., Blood Bank, Hematology, Chemistry, and UA that night.
A 19 year old male patient returned from South America and came to the ER with fever and chills.
Blood smears were made and stained with Giemsa stain.
Many of the trophozoite ring forms in images one and two were seen in the specimen. The majority were in RBCs of normal size. Also seen was the rare form in image three.
What is your identification of this organism ?
a. Babesia spp.
b. Plasmodium falciparum
c. Plasmodium vivax
d. Plasmodium ovale
e. Plasmodium malariae
b. Plasmodium falciparum
Comment: Plasmodium falciparum is correct.
Even though the second image showed an enlarged RBC the text of the question explained that most of the infected RBCs were of normal size. P. falciparum invades all ages of RBCs so can be seen in any RBC size with normal RBC predominating. This ability to infect all RBC ages is part of the reason that falciparum is the most deadly of the four (five) species.
Crescent gametocytes are diagnostic for falciparum
