Parasitology

Question 1

Compare 2 forms of protozoa

Answer 1

Trophozoite: motile
Cyst: non-motile, infectious

Question 2

Diagnosis for intestinal protozoa

Answer 2

stool microscopy for cysts / trophozoites

Question 3

Diagnosis of Entamoeba histolytica

Answer 3

Stool microscopy:
- trophozoite with ingestion of red cells (active)
- cysts / trophozoite without internalized red cells (carrier)
Blood: Serology
Liver abscess aspirate: PCR
Imaging

Question 4

Treatment for Entamoeba histolytica

Answer 4

Paromomycin + Metronidazole / Tinidazole

Question 5

Microscopy showing trophozoite with internalised red cells. Which pathogen?

Answer 5

Entamoeba histolytica

Question 6

Intestinal protozoa with flagella, in falling leaf movement under microscope

Answer 6

Giardia lamblia

Question 7

Which pathogen gives diarrhoea with greasy stool with horrific odour?

Answer 7

Giardia lamblia

Question 8

Treatment for Giardia lamblia

Answer 8

Metronidazole / Tinidazole

Question 8

Pathogen that gives chronic diarrhoea in uncontrolled AIDS patients

Answer 8

Cryptosporidium spp.

Question 9

Diagnosis for Cryptosporidium spp.

Answer 9

Stool microscopy (with acid-fast stain)

Question 10

Treatment for Cryptosporidium

Answer 10

Nitazoxanide

Question 11

Pear-shaped trophozoite, no cyst stage

Answer 11

Trichomonas vaginalis

Question 12

Protozoa with flagella, with jerking or twitching movement

Answer 12

Trichomonas vaginalis

Question 13

Treatment for Trichomonas vaginalis

Answer 13

Metronidazole / Tinidazole

Question 14

Plasmodium spp. with
(a) irregular fever
(b) tertian fever (how many hour interval?)
(c) quartan fever (how many hour interval?)
(d) non-human infection
(e) severe manifestations
(f) continual reproduction in liver

Answer 14

(a) P. falciparum
(b) P. vivax, P. ovale (48h)
(c) P. malariae (72h)
(d) P. knowlesi
(e) P. falciparum
(f) P. vivax, P. ovale

Question 15

Life cycle of Plasmodium spp.

Answer 15

Sporozoites –> Schizont –> Merozoites –> Trophozoites

Question 16

Ring form within red cells under microscope

Answer 16

Plasmodium spp.

Question 17

Non-human host of Toxoplasma gondii

Answer 17

Cat

Question 18

Triad for congenital infection of Toxoplasma gondii

Answer 18

chorioretinitis + hydrocephalus + intracranial calcification

Question 19

Which pathogen is transmitted by kissing bug?

Answer 19

Trypanosoma cruzi

Question 20

Pathogen for Chagas disease

Answer 20

Trypanosoma cruzi

Question 21

Pathogen for African sleeping disease

Answer 21

Trypanosoma brucei

Question 22

Pathogen for Kala-azar

Answer 22

Leishmania spp.

Question 23

List of protozoa (4+1+3)

Answer 23

Intestinal
- Entamoeba histolytica
- Giardia lamblia
- Cryptosporidium
- Microsporidia
Vaginal
- Trichomonas vaginalis
Blood & tissue
- Plasmodium
- Toxoplasma gondii
- Trypanosoma cruzi

Question 24

Classification of Helminths

Answer 24

(A) Flukes (Trematodes) (B) Tapeworms (Cestodes) (C) Roundworms (Nematodes) A&B are flatforms (Platyhelminths)

Question 25

Body parts of tapeworms (2)

Answer 25

scolex proglottids

Question 26

Schistosoma spp. (3) (Which is MC in HK?)

Answer 26

S. mansoni 曼森 S. japonicum (MC) S. haematobium

Question 27

Pathogenesis of Schitosoma

Answer 27

habitat: fresh water penetrate through skin --> invade venous system --> larvae & eggs stimulate immune system eggs deposited in liver / bladder --> granulomatous reaction

Question 28

Pathogen for swimmer's itch, Katayama fever

Answer 28

Schistosoma

Question 29

Diagnosis of Schistosoma infection (2)

Answer 29

Eggs in stool / urine Rectal / renal biopsy

Question 30

Treatment for Schistosoma

Answer 30

Praziquantel

Question 31

MC parasite in HK

Answer 31

Clonorchis sinensis

Question 32

Transmission of Clonorchis sinensis

Answer 32

raw, undercooked freshwater fish

Question 33

Treatment for Clonorchis sinensis

Answer 33

Praziquantel, Albendazole

Question 34

Diagnosis of Clonorchis sinensis

Answer 34

Eggs in stool, duodenal aspirate Imaging showing flukes in bile ducts / gallbladder

Question 35

Which pathogen is transmitted by ingestion of infected crustaceans?

Answer 35

Paragonimus westimani

Question 36

Which parasite mimics TB?

Answer 36

Paragonimus westimani (bloody sputum)

Question 37

Diagnosis of Paragonimus westimani

Answer 37

eggs in stool / sputum

Question 38

Treatment for Paragonimus westimani

Answer 38

Praziquantel

Question 39

Which parasite is transmitted by ingestion of raw or undercooked pork? (How about beef?)

Answer 39

Taenia solium (Taenia saginata)

Question 40

Pathogen for cysticercosis

Answer 40

Taenia solium

Question 41

Pathogenesis of cysticercosis

Answer 41

ingest eggs --> develop into larvae --> penetrate through intestine --> form cysticercus in organs (in brain ==> neurocysticercosis)

Question 42

Diagnosis of taeniasis and cysticercosis

Answer 42

[taeniasis] eggs & proglottids in stool [cysticercosis] - brain scan - radiological survey of skeletal muscles - serology

Question 43

Treatment for taeniasis and cysticercosis

Answer 43

[taeniasis] Praziquantel [cysticercosis] Albendazole, Praziquantel

Question 44

Compare 2 Echinococcus spp.

Answer 44

Echinococcus granulosus: solitary cyst Echinococcus multilocularis: multiple cysts

Question 45

Pathogen for Hydatid disease

Answer 45

Echinococcus

Question 46

Treatment for hydatid disease

Answer 46

PAIR: percutaneous aspiration, injection of chemicals, re-aspiration

Question 47

Which parasites will migrate to alveoli and cause respiratory symptoms (e.g. cough)? (1+3)

Answer 47

Paragonimus westimani Ascaris lumbricoides, Hookworms, Strongyloides stercoralis

Question 48

Treatment for Ascaris lumbricoides (3)

Answer 48

Mebendazole, Albendazole, Pyrantel

Question 49

Hookworms (2)

Answer 49

Ancylostoma duodenale Necator americanus

Question 50

Which parasite gives IDA (sucking blood) and intense itching and rash between the toes?

Answer 50

Hookworms

Question 51

Pathogen for hyperinfection syndrome (what is it?)

Answer 51

Strongyloides stercoralis (repeated autoinfection under immunosuppression)

Question 52

Treatment for Strongyloides stercoralis

Answer 52

Ivermectin

Question 53

Pathogen for perianal itching (Diagnosis (3))

Answer 53

Enterobius vermicularis Dx: 1. Scrotch tape test [morning] 2. Observe for adult worms by naked eyes in perianal area [night] 3. eggs in nails

Question 54

Treatment for Enterobius vermicularis

Answer 54

Mebendazole, Albendazole, Pyrantel

Question 55

Which intestinal parasite tends to migrate to cecum & ascending colon and cause abdominal pain? (Diagnosis and Treatment)

Answer 55

Trichuris trichiura Dx: eggs in stool Tx: Mebendazole, Albendazole

Question 56

Which intestinal parasite migrates to skeletal muscles and causes muscular aches? (Diagnosis (2) and Treatment)

Answer 56

Trichinella spiralis Dx: encysted larvae in muscle biopsy, ↑ CPK Tx: Mebendazole, Albendazole

Question 57

Which intestinal parasite is transmitted by ingestion of undercooked marine fish?

Answer 57

Anisakis

Question 58

Pathogens for elephantiasis (2) (what is it?)

Answer 58

Filariae Chlamydia trachomatis serotype L1~L3 (lymphedema at lower legs & genitals, covered with thick, scaly skin)

Question 59

Filariae (3)

Answer 59

Wuchereria bancrofti , Brugia malayi, Brugia timori

Question 60

Diagnosis and treatment of filariae

Answer 60

Dx: microfilariae in blood smear Tx: diethylcarbamazine

Question 61

Pathogen for lizard skin and river blindness

Answer 61

Onchocerca volvulus

Question 62

Diagnosis and treatment of Onchocerca volvulus

Answer 62

Dx: microfilariae in skin biopsies Tx: Ivermectin

Question 63

Pathogen for cutaneous larval migrans / creeping eruption (2)

Answer 63

Ancylostoma braziliensis, Ancylostoma caninum

Question 64

Flukes (3)

Answer 64

Schistosoma Clonorchis sinensis Paragonimus westimani

Question 65

Tapeworms (4)

Answer 65

Taenia solium Taenia saginata Echinococcus Spirometra

Question 66

Roundworms (7+4)

Answer 66

Intestinal - Ascaris lumbricoides - Hookworms - Strongyloides stercoralis - Enterobius vermicularis - Trichuris trichiura - Trichinella spiralis - Anisakis Blood & tissue - Filariae - Onchocerca volvulus - Dirofilaria - Ancylostoma

Question 67

Ectoparasites (4)

Answer 67

Sarcoptes scabiei Pediculus humanus Phthirus pubis Myiasis

Question 68

Pathogen for burrows on skin (diagnosis)

Answer 68

Sarcoptes scabiei Dx: skin scrape for mite, eggs

Question 69

Management for scabies

Answer 69

Contact precautions Scabicide: Permethrin, Benzylbenzoate, Lindane Disinfection: machine wash of clothing & bedding with hot water cycle 60°C disinfest in a closed plastic bag for a week Contact tracing: treat household contact

Question 70

Treatment for body louse

Answer 70

Permethrin

Question 71

Treatment for Phthirus pubis

Answer 71

Permethrin