L5 - Parasitology

Question 1

What is a parasite?

Answer 1

it is an organism that lives on or in a host organism and gets its food from/at the expense of its host.

Question 2

What are the 3 main classes of parasites that cause disease in humans?

Answer 2

1. Protozoa
2. Helminths
3. Ectoparasites.

Question 3

What are Protozoa?

Answer 3

• Protozoa are microscopic, single
-celled organisms that can be free
-
living or parasitic in nature.
• They are able to multiply in humans allowing serious infections to
develop from a single organism.

Question 4

How is Protozoa transmitted?

Answer 4

• Protozoa living in the human intestine can be transmitted by the fecal
-oral
route
• Protozoa living in blood or tissues are transmitted by an arthropod vector

Question 5

What are the types of protozoa?

Answer 5

• Amoeba, e.g. Entamoeba
• Flagellates, e.g. Giardia, Leishmania
• Ciliates e.g. Balantidium
• Sporozoa
– organisms whose adult stage is not motile
e.g. Plasmodium, Cryptosporidium

Question 6

What are Helminths?

Answer 6

• Helminths are large, multicellular organisms (worms) generally visible
to the naked eye in their adult stages. In their adult form, helminths
cannot multiply in humans.

Question 7

What are 3 main groups of Helminths that are human parasites?

Answer 7

1. Nematodes (roundworms)
2. Trematodes (flukes)
3. Cestodes (tapeworms

Question 8

What are Ectoparasites?

Answer 8

• Blood
-sucking arthropods such as ticks, fleas, lice, and mites that
attach or burrow into the skin and remain there for relatively long
periods of time (e.g., weeks to months).

Question 9

State some medically important ectoparasites?

Answer 9

Mites
• Scabies
• Trombiculid

Ticks
• Hard
• Soft

Lice
• Pediculus humanus capitis
• Pediculus humanus humanus
• Pthirus pubis

Flies
• Botflies

Question 10

What are intermediate and definitive hosts?

Answer 10

• Intermediate
– host in which larval or asexual stages develop
• Definitive
– host in which adult or sexual stage occurs

Question 11

What are the 2 types of vectors and what is the difference?

Answer 11

• Mechanical when no development of parasite in vector

* Biological when some stages of life cycle occur

Question 12

What are the determinants of parasite infections where mode of transmission is Faeco-oral?

Answer 12

Household sanitation

Access to clean water

Personal hygiene behaviours

Question 13

What are the determinants of parasite infections where mode of transmission is Food?

Answer 13

Animal husbandry

Surveillance

Regulations and government controls

Question 14

What are the general determinants of parasite infections?

Answer 14

• Government resources and level of human development/per capita income
• Education
• Country-level and regional control programmes
• Availability of cheap and efficacious treatments
• Construction and building regulations (eg Chagas)
• Urban vs. rural residence
• Environmental sanitation