Parasitology

Question 1

what parasite organisms are the modified acid fast stain best for identifying?

Answer 1

Cryptosporidium, Cystoisospora, and Cyclospora cayetanensis

Question 2

what is a cestode? give primary examples

Answer 2

a subclass of helminths, true tapeworm; includes Taenia spp (saginata/beef and solium/pig), Diphyllobothrium latum (fish), Hymenolepsis nana (dwarf), Echinococcus granulosus (dog, hydatid cysts!)

Question 3

What is a nematode? give primary examples

Answer 3

the roundworm class of helminths: Enterobius vermicularis (pinworm), Trichuris trichuria (whipworm), Ascaris lumbricoides (giant intestinal), Strongyloides stercoralis (threadworm), Necator americanus & Ancylostoma duodenale (hookworms), Trichinella spiralis, and Dracunculus medinensis (guinea)

Question 4

What are Filariae? Give 4 main pathogenic spp

Answer 4

type of nematode/roundworm that inhabit circulatory and lymphatic system, sometimes muscle and serous cavities or connective tissue
Loa loa, Wuchereria bancrofti, Brugia malayi, & Onchocerca volvulus

Question 5

What are trematodes/ 5 examples

Answer 5

flukes: Schistosoma spp (mansoni, japonicum, haematobium), Paragonimus westermani, Clonorchis sinensis, Fasciolopsis buski, Fasciola hepatic

Question 6

Three hemoflagellate extraintestinal protozoa:

Answer 6

Leishmania, Trypanosoma cruzi, and T. brucei

Question 7

In the protozoan phylum Apicomplexa there is a group of intestinal parasites that infect vertebrates; name the group and 4 main species and major stain used/diffs btw

Answer 7

Coccidia: Cryptosporidium parvum- 4-6um oocysts;
Cyclospora cayetanensis- 8-10 um oocysts; Cystoisospora belli- 25 -30 um ellipsoid oocysts; Toxoplasma gondii- don’t see the cysts, so diagnosed by serology for antibodies. The 3 previous are seen with modified acid fast stain

Question 8

Name 6 major intestinal protozoan amebae

Answer 8

Entamoeba histolytica/dispar; Entamoeba hartmanni; Entamoeba coli; Endolimax nana; Iodameoba butschlii; Blastocystis hominis

Question 9

Differentiate between E. histolytica/dispar, E. hartmanni, and Entamoeba coli based on size, nuclei and the peripheral chromatin and karyosome

Answer 9

E. histolytica/dispar (appear same unless ingested RBC meaning histolytica): “medium” cyst and troph, 12-15/ 15-20 um. Fine peripheral chromatin, small central karyosome and no >4 nuclei
E. hartmanni: SMALL, cyst 5-8 um, troph 5-10; fine peripheral chromatin, small central karyosome, never >4 nuclei
E. coli: LARGE at cysts 15-25, trophs 20-25. LARGE eccentric karyosomes, and clumpy uneven peripheral chromatin, up to 8 nuclei

Question 10

How is Endolimax nana diff from E. hartmanni since both small and similar

Answer 10

E. nana although has 4 nuclei, there is no peripheral chromatin

Question 11

Give an identifying characteristic of Iodameoba butschlii

Answer 11

Both cysts and troph have large karyosome, and cyst has a large iodine-staining vacuole

Question 12

what free-living ameoba can cause both granulomatous amebic encephalitis and amebic keratitis in contact wearers?

Answer 12

Acanthamoeba

Question 13

Name 3 flagellate intestinal protozoa

Answer 13

Giardia lamblia, Chilomastix, and Dientamoeba fragilis

Question 14

Diff btw Giardia, Chilomastix, and Dientamoeba fragilis

Answer 14

Dientamoeba has no cyst stage, the troph is ROUND AND BINUCLEATE, with fractured central karyosomes and no periph chromatin;
Giardia: cysts oval, 12 x 18 um avg, 4 nuclei, no peripheral chromatin and 2 -4 comma shaped median bodies. Trophs pear-shaped, 2 large nuclei opposite central axostyle, 2 parabasal bodies (old man)
Chilomastix: cysts round, 5-10 um, one nucleus, central karyosome, no periph chrmtn, clear cytostome. Troph- pear shaped, 5-25 x 5-10 um, ONE nucleus, eccentric karyosome, very large cystosome, spiral groove

Question 15

What is the only pathologic intestinal ciliate in humans and describe briefly

Answer 15

Balantidium coli. Rouond, 43-65 um, has a macronucleus and micronucleus in both cyst and troph stage. Cysts have a double cell wall with cilia in between

Question 16

Which Plasmodium spp: have enlarged infected RBCs, Shuffner’s dots? How do they differ?

Answer 16

P. vivax and P. ovale. The former has 12 to 24 merozoites/schizont, latter has 8-12 (less anyway). P ovale may also have OVAL infected cells, possible fimbriated, and a more compact mature trophozoite (P. vivax’s is amoeboid)

Question 17

What Plasmodium spp has more delicate ring-forms, a banana shaped gametocyte, and it is rare to see mature trophozoites or merozoites in PB?

Answer 17

P. falciparum

Question 18

How long is the replication cycle for P. malariae and thus interval of fever spikes? Describe the mature troph and # merozoites in a schizont

Answer 18

72 hours,a quartan fever; Mature troph can be described as a band & basketm and only 6 to 12 merozoites in a rosette form

Question 19

What Plasmodium spp have tertian fever spikes and how long is this?

Answer 19

P. vivax, P. ovale, and P. falciparum: q 48 hours

Question 20

what is the most lethal Plasmodium and which can have a true recurrence?

Answer 20

P. falciparum;

P. vivax and ovale

Question 21

Which Plasmodium infects older cells and which ALL?

Answer 21

older- malariae; falciparum all; other two infect young cells more often.

Question 22

Describe the differences in eggs of the 3 main Schistoma spp found in feces or urine

Answer 22

S. mansoni: large lateral spine (Think Manson stabbing sideways)
S. haematobium: large terminal spine (think “peeing down, bc it resides around and enters bladder, causing hematuria)
S. japonicum: a round egg, barely noticeable spine

Question 23

The egg of this trematode (fluke) is found in feces; Infective mertacercariae is acquired from undercooked crabs/crayfish; Adults form in lungs; Describe the egg

Answer 23

The Paragonimus westermani fluke; Yellow-brown (not as dark as egg of ascaris), thick shelled, oval, avg 90 um, obvious and shouldered operculum;

Question 24

This egg of the trematode/fluke variety looks similar to Paragonimus but is LARGER (2 spp look same)

Answer 24

Fasciola hepatica/ Fasciolopsis buski. average 120 um

Question 25

The smallest trematode egg; causes chronic biliary infection, spread by freshwater fish and intermediate by snails (as all the major flukes I’ve studied seem to be helped by snails)

Answer 25

Clonorchis sinensis, only 30 um with shouldered operculum and small abopercular knob

Question 26

How are Schistoma infections usually acquired? Hit: not like the other trematodes….

Answer 26

In CONTRAST to ingestion with water plants, freshwater fish or crabs as in Fasciola, Clonorchis or Paragonimus, Schistosomiasis is acquired by skin penetration (swimmer’s itch) by the fork-tailed cercariae in snail-infested water

Question 27

Diff btw the scolex of Taenia saginata and solium:

Answer 27

Saginata: 4 suckers and SMOOTH surface, “unarmed”
Solium: 4 suckers and many tiny hooklets on surface “armed rostellum”