General- parasites Flashcards
What are Sarcodina?
Ameba (protozoa)
What are Mastigophora?
Flagellates (protozoa)
What are Ciliophora?
Ciliates (protozoa)
What are Sporozoa?
Protozoa that are nonmotile in adult stage
What are the categories of helminths?
- Flat worms/platylhelminths (trematodes and cestodes)
- Thorny-headed worms/acanthocephalins
- Roundworms (nematodes)
- Segmented worms (annelids)
What are ectoparasites?
Blood-sucking ectoparasites, fleas, ticks, lice, mites, etc. that burrow into skin and remain for a long time. May serve as vectors of other pathogens.
Which parasites can be cultured? What do they usually cause?
Acanthamoeba species and Naegleria fowleri; CNS and ocular infections
Common causes of acanthamoeba
Eye contact contamination causing ocular infection (e.g. dirty hands)
Which parasite may be seen in routine bacterial culture?
Strongyloides (note: not cultured this way)
Which parasite can cause CNS infection by Gram-negative rods? How?
Strongyloides; tissue invasion may bring GI flora into bloodstream (note: Gram-negative rods may cause meningitis in neonates and children without Strongyloides infection)
How is a Giemsa stain performed?
Drop of blood is hemolyzed for visualization of intracellular organisms. in thick smear. Thin smear is not hemolyzed, but morphology is preserved.
How many specimens are needed to check for parasites in a stool O&P?
3 specimens on 3 separate days.
Which parasites cannot be identified on stool O&P?
- Cryptosporidium
- Cyclospora
- Cystoisospora
- Microsporidia
Which stain is used if cryptosporidium is suspected?
Acid-fast stain (EIA or DFA can also be used)
When is stool antigen testing the optimal choice?
Giardia, Cryptosporidium, and Entamoeba (antigen testing also available for Plasmodium species)
Which parasites can be detected by serology?
Strongyloides, Entamoeba histolytica (disseminated only)
Loa loa (microfilariae)- Presentation
Swelling in skin; worm in conjunctiva
Loa loa (microfilariae)- Labs
Blood smear/Giemsa
Entamoeba histolytica- Presentation
Inflammatory diarrhea, liver abscess with ‘anchovy paste’ smell
Entamoeba histolytica- Labs
Stool O&P, antigen test, serology
Acanthamoeba- Presentation
Ocular and CNS infections
Acanthamoeba- Labs
Culture, stain, PCR
Pediculus humanus- Presentation
Head and body lice
Pediculus humanus- Diagnosis
Ectoparasite exam
Enterobius vermicularis- Presentation
Pinworm (itchy butt)
Enterobius vermicularis- Diagnosis
Scotch tape prep
Trypanasoma brucei- Presentation
African Sleeping Sickness
Trypanasoma cruzi- Presentation
Chagas disease
Trypanasoma- Labs
Blood smear/Giemsa stain
Strongyloides stercoralis- Presentation
Intestinal or disseminated infection
Strongyloides stercoralis- Labs
Stool O&P, serology
Babesia- Presentation
Hemolytic anemia and fever
Babesia- Labs
Blood smear/Giemsa stain or PCR; “Maltese Cross” distinguishes it from Plasmodium
Taenia/tapeworm- Presentation
Taenia solium/saginatum, cysticercosis
Taenia/tapeworm- Diagnosis
Stool O&P, imaging
Giardia- Presentation
Camper’s/Hiker’s diarrhea (steatorrhea)
Giardia- Diagnosis
Stool O&P (at least 3), antigen test; “Face” distinguishes it from other trophozoites
Echinococcus- Presentation
Hydatid cysts
Echinococcus- Labs
Stool O&P, imaging, serology
Trichomonas- Presentation
STI/vaginitis (yellow-green discharge)
Trichomonas- Diagnosis
Wet mount, molecular test
Scabies- Diagnosis
Skin scraping of leading edge
Schistosoma- Diagnosis
O&P of stool or urine
Plasmodium falciparum- Presentation
Malaria
Plasmodium falciparum- Diagnosis
Blood smear/Giemsa stain, antigen test
