Parasitology 2 - Parasitic Metazoans (Michael)

Question 1

What are the two major groups of parasites

Answer 1

Parasitic protozoans (unicellular)
Parasitic metazoans (multicellular)

Question 2

Describe the life cycle of Schistosoma spp.

Answer 2

• The eggs are eliminated from the host into freshwater via faeces or urine. This is the diagnostic stage.
• The eggs hatch and release miracidia.
• The miracidia penetrate snail tissue.
• Proliferation of sporocysts in the snail.
• The snail releases cercariae into the water. This is the infective stage.
• The cercariae infect humans by skin penetration.
• During penetration the cercariae lose their tails and become schistosomulae.
• The schistosomulae live in blood vessels, draining the bladder or intestine. The schistosome eggs cause pathology.
• Schistosome eggs are eliminated in the faeces or urine.

Question 3

Describe symptoms and treatment of schistosomiasis

Answer 3

Early symptoms

• Blood in urine (haematuria)
• Anaemia and malnutrition
• Growth retardation

Medium symptoms
- Inflammation and distension of the abdomen

Late symptoms

• Portal hypertension
• Bladder cancer

Treatment

• Treated using praziquantel which removes the coat of human cells that cover the parasite.
• Administered once per year.

Question 4

Describe the symptoms and treatment of filariasis (elephantiasis)

Answer 4

Symptoms
- Worms block the lymphatic ducts causing a build up of fluid in the lower limbs and genitals.

Treatment

• Treated using ivermectin which reduces the chances of larvae circulating around the body.
• Washing with soap and water clears secondary infections.

Question 5

Describe how trichinosis is caused

Answer 5

• Caused by the nematode Trichinella spiralis.
• Worm lives in muscle tissue of wild mammals.
• Humans consume undercooked meat of infected mammals.
• Larvae penetrate human intestinal mucosa.
• Larvae circulate around the body.
• Can lead to heart failure, respiratory complications, and kidney malfunction.

Question 6

Name a parasite and its disease which affects animals

Answer 6

Liver fluke (Fasciola hepatica) causes fascioliasis

Question 7

Name a parasite which affects plants

Answer 7

The potato cyst nematode Globodera pallida

Question 8

What is the vector for onchocerciasis

Answer 8

Black fly Simulium