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
??
Schistosoma mansoni
A traveler returning from Africa presents with irregular fevers. A blood film taken two weeks later looks like this image.
P falciparum
??
P Vivax: gametocyte stage
??
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.
??
babesia
(unlikely to see extracellular forms with any type of malaria)
??
P Falciparum (gametocyte stage)
??
Babesia
??
Giardia
??
Strongyloides larva
(don’t see Pinworm in stool. Pinworm would be much larger - tho you need a size scale to tell)
??
Strongyloides, in resp secretions
??
Toxoplasma. From a tissue biopsy.
??
Two toxoplasma at the end of a ciliated epithelial cell from lung. Unusual finding.
??
Cryptosporidium
Acid Fast stain
??
Cryptosporidium
??
Ascaris eggs
??
Pinworm eggs
??
Trichomonas around an epithelial cell in a wet prep
??
Pinworms (note that they are rather big)
??
Schisto egg in tissue
??
Schistosome surrounded by eosinophils
