4/15 Parasitology Lab + Lab Quiz Flashcards
During a well-child visit a mother tells you her 4 year old has perianal itching. You give the mother a collection device, which she returns to the office the next day. Examination reveals the diagnostic forms.
Pinworm
Enterobius vermicularis
Diagnostic stage = perianal egg (not worm)
In fresh scotch-tape preparation you find eggs that contain a larval worm. Concentrate on the characteristics of the eggshell, thick and flattened on one side.
An immigrant from West Africa presents with hepatomegaly and splenomegaly. A fecal parasite examination reveals the diagnostic form.
Strongyloides stercoralis:
Remember that the diagnostic stage is a larval worm (not an egg). Beware of the worm-like fecal artefacts. Look for a pointy tail and a gut.
A resident of Vermont, who has not travelled out side New England complains of abdominal cramping, foul-smelling floating stools. A fecal parasite examination shows the diagnostic stage.
Giardia
Diagnostic stage = trophozoites and cysts in feces
Pic: top = trophozoite, bottom = cyst
A traveler returning from Africa presents with irregular fevers. A blood film taken when first seen is demonstrated in the image below.
P falciparum (ring form)
A traveler who has visited friends and family in rural India returns with a febrile illness. A blood film reveals parasite forms.
P Vivax Gametocytes
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Schistosoma mansoni
A traveler returning from Africa presents with irregular fevers. A blood film taken two weeks later looks like this image.
P falciparum
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P Vivax: gametocyte stage
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Late-stage P Vivax with “Schuffner’s Dots” on the periphery of the RBC.
What is the most serious type of malaria?
What is most common in temperate regions?
Most serious = falciparum
Most common malaria of temperate zones (also common in tropics) = Vivax - because it can be dormant in a host’s liver and therefore survive cold winters.
Deciding between P vivax and P falciparum based on forms on blood smear: what are some characteristic features of each?
P falciparum: Some RBCs will have multiple rings inside them. Gametocytes are banana-shaped. May be brown pigment inside RBCs
P vivax: May have Schuffner’s Dots, infected RBCs are larger than surrounding RBCs.
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babesia
(unlikely to see extracellular forms with any type of malaria)
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P Falciparum (gametocyte stage)
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Babesia
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Giardia
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Strongyloides larva
(don’t see Pinworm in stool. Pinworm would be much larger - tho you need a size scale to tell)
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Strongyloides, in resp secretions
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Toxoplasma. From a tissue biopsy.
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Two toxoplasma at the end of a ciliated epithelial cell from lung. Unusual finding.
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Cryptosporidium
Acid Fast stain
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Cryptosporidium
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Ascaris eggs
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Pinworm eggs
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Trichomonas around an epithelial cell in a wet prep
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Pinworms (note that they are rather big)
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Schisto egg in tissue
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Schistosome surrounded by eosinophils
If you see a worm-like creature in a sputum sample, what could it be?
Hyperinfective stage of strongyloides (larva)
larvae enter into bloodstream via skin. partly mature in alveoli, then ascend resp tract to mouth, where you swallow them!!!!
from the GI tract, they burrow into mucosa of small bowel and lay eggs there.
ascaris: what is the only way to increase the number of ascaris in your system?
you’d have to eat more ascaris eggs. they don’t reproduce or proliferate inside us.
what if you see banana shaped forms in an aspirate sample? are they P falciparum?
nope, they are toxoplasma, trophozyte form.
roughly 33% size of RBCs (smaller than P falciparum)
