Parasitology Introduction

Question 1

What is a parasite?

Answer 1

organism that lives in/on a host, getting its food at the expense of the host - can be obligate or facultative

Question 2

What are three classes of parasites?

Answer 2

Helminths
Protozoa
Arthropods

Question 3

What are the three classes of helminths?

Answer 3

Nematodes (round worms)
Trematodes (flat worms)
Cestodes (tape worms)

Question 4

What are the three classes of protozoa?

Answer 4

Malaria
Flagellates
Amoebae

Question 5

What are the three main classes of arthropods?

Answer 5

Lice
Ticks
Mites

Question 6

Describe protozoa

Answer 6

Unicellular

Found on blood and tissue (arthropod vector) or intestines (faecal-oral route)

Question 7

What parasite causes malaria?

Answer 7

Plasmodium falciparum

Question 8

What is the vector for malaria transmission?

Answer 8

Anopheles mosquito

Question 9

How can plasmodium falciparum be detected in the lab?

Answer 9

Using a Giemsa-stained blood film - think/thin

Question 10

Describe how malaria is transmitted?

Answer 10

• sporozoites injected under the skin
• moves from blood to liver to mature
• merozoites re-enter circulation and invade RBCs
• sexual forms taken up by mosquitoes for further transmission

Question 11

What parasite causes amoebic dysentery?

Answer 11

Entamoeba histolytica

Question 12

Describe how amoebic dysentery presents clinically

Answer 12

• trophozoite ingests RBCs using pseudopodia

- causes cysts/intestinal infections/liver abscesses

Question 13

What parasite causes leishmaniasis?

Answer 13

Leishmania species - cutaneous/muco-cutaneous/visceral

Question 14

Describe the symptoms of leishmaniasis

Answer 14

• ulceration
• fever
• weight loss
• hepato-splenomegaly (liver and spleen swelling)

Question 15

How is a leishmania species transmitted?

Answer 15

Using a sand fly vector

Question 16

Give examples of infections caused by nematodes

Answer 16

Enterobiasis

Ascaris lumbricoides

Question 17

How is ascaris lumbricoides transmitted?

Answer 17

• eggs hatch in intestines
• larvae move to the lungs where they are re-swallowed
• worms develop in the small intestine

Question 18

Give examples of infections caused by cestodes

Answer 18

taenia saginata/solium

echinococcus

Question 19

How is taenia saginata transmitted?

Answer 19

Beef; cysts (worm formed) or eggs (cysts formed) in humans

Question 20

How is taenia solium transmitted?

Answer 20

Pork; cysts or eggs ingested

Question 21

How is echinococcus transmitted?

Answer 21

• ingestion of dog faeces
• eggs hatch and enter circulation
• cysts firm in the liver

Question 22

Give an example of an infection caused by a trematode

Answer 22

Schistosomiasis

Question 23

Describe how a schistosomiasis species is transmitted

Answer 23

• ova excreted by humans into water
• miracidia released
• snail penetrated
• cercaria emerge
• human penetrated
• lung to liver to mature (on to bladder)
• eggs causing bladder/intestinal imflammation
• Katayama fever (acute febrile episode presents)

Question 24

How are parasite infections diagnosed?

Answer 24

• helminths cause eosinophilia and elevated IgE levels
• microscopy of faeces/tissue
• serology to detect antibodies