General Parasitology

Question 1

Define protozoa

Answer 1

unicellular eukaryotic cells that perform all physiological functions

Question 2

Define helminths

Answer 2

Elongated flat or round-worm like parasites measuring few mm - few metres.
Eukaryotic, unicellular, bilaterally symmetrical

Question 3

Protozoa examples

Answer 3

1. Amoeba - E. histolytica, Naegleria, Acanthamoeba
2. Flagellates - Giardia, Trichomonas, Leishmania
3. Apicomplexa - Malarial, Babesia, Toxoplasma, Sarcocystis, Cyclospora, Cryptosporidium

Question 4

Helminths examples

Answer 4

1. Cestodes - Taenia. Echinococcus, Hymenolepsis
2. Trematodes - Schisostoma, Fasciola, Clonorchis
3. Intestinal nematodes - Enterobius, Hookworm, Ascaris
4. Somatic - Trichinella, Dracunculus

Question 5

Autoinfection

Answer 5

Reinfection with larvae produced by parasites already in the body.
Ex: Taenia Solium, Enterobius vermicularis, Cryptosporidium parvum, Hymenolepis nana

Question 6

When should stool specimen be collected?

Answer 6

Before starting anti-parasitic drugs and closer to onset of symptoms

Question 7

How many times should stool specimen be collected?

Answer 7

3 specimens on alternate days

For intestinal amoebiasis, 6 specimens

Question 8

When should stool specimen be examined?

Answer 8

Liquid stool - within 30 mins
Semisolid - within 1 hr
Formed stools - within 24 hrs

Question 9

How can fecal specimens be preserved?

Answer 9

Room temp.

10 percent formalin can be used to maintain morphology of parasitic cysts and eggs

Question 10

What specimens other than stool can be collected?

Answer 10

Perianal swabs - Taenia, Enterobius vermicularis, Schisostoma mansoni
Duodenal contents - Giardia intestinalis, Strongloides stercoralis

Question 11

Mucoid bloody stool found in

Answer 11

Amoebic dysentery, intestinal schistosomiasis, invasive balantadiasis

Question 12

Colour of stool indicates

Answer 12

Dark red - Upper GIT bleeding

Bright red - Lower GIT bleeding

Question 13

Frothy pale offensive stool seen in

Answer 13

Giardiasis

Question 14

Chemicals used in direct wet mount

Answer 14

Drops of saline

Lugol’s iodine

Question 15

Magnification for direct wet mount

Answer 15

10x for helminthic eggs and larvae

40x for protozoan cysts and trophozoites

Question 16

Charcot Leyden crystals

Answer 16

diamond shaped
Breakdown products of eosinophils
Seen in stool or sputum in amoebic dysentery, ascariasis, bronchial asthma

Question 17

Saline mount

Answer 17

To detect trophozoites, cysts of protozoan parasites, eggs and larvae of helminths
Motility and bile staining property can be appreciated

Question 18

Iodine mount

Answer 18

Nuclear details of protozoan cysts, helminthic eggs and larvae can be seen
Motility and bile staining property cannot be appreciated

Question 19

Non bile staining eggs

Answer 19

Enterobius, Hookworm, Hymenolepis nana

Question 20

Permanent staining methods

Answer 20

1. Iron-hematoxylin stain
2. Trichrome stain
3. Modified acid fast stain - for coccidian parasites

Question 21

Concentration techniques

Answer 21

1. Sedimentation
   2, Floatation - Zinc sulphate flotation
   Sheather’s sugar floatation

Question 22

Floatation technique cannot be used in

Answer 22

unfertilized eggs of Ascaris
larva of Strongyloides
Taenia eggs
operculated eggs of trematodes

Question 23

Sheather’s sugar floatation technique for

Answer 23

Cryptosporidium
Cystoisospora
Cyclospora

Question 24

Egg counting methods

Answer 24

esp. for Trichuris, Ascaris, Hookworm
1. Direct smear counting method of Beaver
2. Kato-Katz thick film method
3. Stoll’s method or dilution egg counting method

Question 25

Blood examination used for

Answer 25

``` Plasmodium Trypanosoma Leishmania Babesia Wuchereria bancrofti Mansonella ```

Question 26

Blood concentration methods

Answer 26

1. Sedimentation 2. Cytocentrifugation 3. Knott concentration 4. Gradient centrifugation 5. Membrane filtration

Question 27

Immunodiagnostic methods used when

Answer 27

1. Early stages of disease 2. Parasites are in very small numbers 3. Reside in internal organs 4. Time constraint

Question 28

Ab detection tests useful in

Answer 28

``` Amoebic liver abscess: ELISA against 170kDa lectin Ag Visceral leishmaniasis Cysticercosis Toxoplasmosis Hydatid disease ```

Question 29

Ag detection tests

Answer 29

Amoebiasis ICT panel detects Giardia, E. histolytica, Cryptosporidium in stool Malaria Lymphatic filariasis

Question 30

Molecular methods

Answer 30

PCR, rt-PCR LAMP: for visceral leishmaniasis and malaria Biofire Film Array: detects E. histolytica, G. lamblia, Cryptosporidium, Cyclospora