Introduction to Parasites

Question 1

Name the three main types of parasites.

Answer 1

Protozoa
Helminths (worms)
Ectoparasites

Question 2

Describe protozoa.

Answer 2

These are microscopic, single celled organisms.
They are free-living or parasitic in nature
Able to multiply in humans
Method of transmission:
Live in gut : faecal-oral route
Live in blood or tissue : insect vector

Question 3

List some common examples of protozoa.

Answer 3

Malaria
Amoebae
Flagellates

Question 4

Outline the process of infection by malaria.

Answer 4

Malaria is caused by plasmodium.
Infected mosquito bites human and plasmodium travels into blood (through mosquito saliva) and infects it.
Plasmodium (sporozoites) travel to the liver cells where they can asexually reproduce.
They mature within the liver and are released from liver into blood stream.
Once inside RBC, the mature plasmodium asexually reproduce, once again.
Also divide into gametocytes inside RBCs and can then be taken up again by female mosquito
Gametocytes reach the mosquitos gut where they mature and sexually reproduce.
They rupture releasing mature plasmodium that can make its way to mosquitos salivary gland to further infect.

Question 5

State the scientific name of a mosquito vector.

Answer 5

Anopheles mosquito.

Question 6

State the plasmodium species with the highest mortality rate.

Answer 6

P. falciparum.

Question 7

Describe the effects of amoebae.

Answer 7

Amoebae is spread through the faecal oral route.
Cause bloody diahorrea.
Cysts are found in stool (microscopy).
Cause (clinically) :
Intestinal and extra-intestinal infections
Liver abscess in late disease (reddish brown pus).

Question 8

List some examples of helminths.

Answer 8

Nematodes - round worms
Cestodes - tape worms
Trematodes - flat worms

Question 9

Describe the route of transmission in helminths.

Answer 9

Faecal - oral route.