Parasitic Infections - Protozoa and Helminths

Question 1

What are the general features of Helminths?

Answer 1

Multicellular
Differentiated organs
No circulatory tract
Have suckers, hooks or plates on the anterior end for attachment

Most do not have a full life cycle in humans
Touch cuticle (difficult for immune system to eradicate)
Some (e.g. blood flukes) can camouflage by coating with host molecules

Question 2

What are the 3 main classes of Helminths?

Answer 2

Nematodes (roundworms)
Cestodes (tapeworms)
Trematodes (flukes)

Question 3

Which class of Helminths have a cylindrical body and an alimentary canal?

Answer 3

Nematodes (roundworms)

Question 4

Which class of Helminths are flat, ribbon shaped and have no digestive tract?

Answer 4

Cestodes (tapeworms)

Question 5

Which class of Helminths are leaf-shaped and have blind-branched alimentary tract?

Answer 5

Trematodes (flukes)

Question 6

What are the main types of Nematodes?

Answer 6

Large roundworm (Ascaris lumbricoides)
Threadworm
Hookwork
Whipworm

Question 7

What are the symptoms of Ascariasis (infection with Large Roundworm)?

Answer 7

Heavy infection: Abdominal pain, malnutrition

Severe infection: Blockage of intestines

Question 8

What are the symptoms of infection with Threadworm?

Answer 8

Mild anal itching

Question 9

What are the symptoms of infection with Hookworm?

Answer 9

Slows growth and development

Anaemia

Question 10

What are the symptoms of infection with Whipworm?

Answer 10

Usually asymptomatic

Can cause bloody diarrhoea

Question 11

How do you normally become infected with Ascariasis/Nematodes?

Answer 11

Ingestion of eggs from the soil

or larvae in soil penetrate skin in the case of hookworm

Question 12

What can Filarial (Blood and tissue) Nematodes cause?

Answer 12

Lymphatic filariasis (Elephantiasis)
Onchocerciasis (River blindness)
Loiasis (infection with adult loa loa worm)

Question 13

How do you normally become infected with Cestodes?

Answer 13

Humans are usually the primary host:

- Ingestion of cyst (resting/dormant stage) from undercooked meat/fish

Question 14

How do you normally become infected with Trematodes (flukes)

Answer 14

Use snail as intermediate host (penetrates the skin of humans in water)

Question 15

What can Trematodes cause?

Answer 15

Schistosomiasis (Snail fever)

Question 16

What are the symptoms of Schistosomiasis (Snail fever)

Answer 16

Within days: rash or itchy skin (‘swimmers itch’)
After months: fever, chills, cough, muscle aches

Main damage is caused by the eggs stuck in tissues and so the reaction by the immune system

Question 17

How are Intestinal nematodes/cestodes usually diagnosed?

Answer 17

Eggs/larvae in a faecal sample

Question 18

How are Schistomas (Trematodes) usually diagnosed?

Answer 18

Eggs in faecal or urine sample

Question 19

How are Tissue nematodes usually diagnosed?

Answer 19

Microfilaria in blood

difficult to diagnose as in tissue

Question 20

What is normally used to treat filarial nematodes?

Answer 20

Ivermectin

Question 21

What is normally used to treat Intestinal nematodes?

Answer 21

Albendazole or Melbendazole

Question 22

What is normally used to treat tapeworms?

Answer 22

Niclosamide or Praziquantel

Question 23

What is normally used to treat Roundworms?

Answer 23

Piperazine

Question 24

What is normally used to treat Threadworm?

Answer 24

Piperazine

Question 25

What is normally used to treat Flukes?

Answer 25

Praziquantel