L1: General Concepts of Medical Parasitology and Parasitism

Question 1

What is a parasite?

Answer 1

An organism that lives in or on another organism (its host) and benefits by deriving nutrients and protection at the other’s expense.

Question 2

What are the types of parasites?

Answer 2

1- obligatory parasites
2- facultative parasites
3- accidental parasites
4- endoparasites
5- ectoparasites
6- specific parasites
7- temporary parasites
8- saprozoic (spurious) parasites

Question 3

What are obligatory parasites?

Answer 3

They are parasites that can’t complete their life-cycle without exploiting a suitable host, If obligatory parasites can’t obtain a host it fails to reproduce.

Question 4

What are facultative parasites?

Answer 4

can either live freely (in soil or water) or as parasites in hosts when unfavorable environmental conditions occur.

Question 5

What are accidental parasites?

Answer 5

free-living organisms which enter the human body by mistake e.g. larvae of flies which are accidentally ingested and live in the intestine of man.

Question 6

What are temporary parasites?

Answer 6

visit its host from one time to another for feeding then leave.

Question 7

What are specific parasites?

Answer 7

affects only one host species.

Question 8

What are caprozoic (spurious) parasites?

Answer 8

a parasite species foreign to the host which has just passed through the alimentary canal without infecting the host. (For example, parasite eggs in the animal liver).

Question 9

What are ectoparasites?

Answer 9

a parasite that lives on the outside of the host.

Question 10

What are endoparasites?

Answer 10

a parasite that lives within the body of the host.

Question 11

What are the types of hosts?

Answer 11

1- Definitive host
2- Intermediate host
3- Reservoir host
4- Paratenic (transport) host
5- Vector host
6- Dead-End host

Question 12

What is a definitive host?

Answer 12

Host in which the parasite reaches its sexual maturity (adult stage).

Question 13

What is an intermediate host?

Answer 13

a host in which the immature (larval, not adult) stage of the parasite is found, or in which the parasite multiplies asexually.

Also termed amplifier host.

Question 14

What is a reservoir host?

Answer 14

An animal that harbors the parasite and acts as a continuous source of human infection.

Question 15

What is a paratenic host?

Answer 15

a host that harbors a parasite in an arrested state of development but the parasite remains alive and viable, ready to infect a subsequent suitable host.

Question 16

What is a dead-end host?

Answer 16

• a host from which infectious agents are not transmitted to other susceptible hosts.
• It means that the infection chain ends at that particular host, and further.

Question 17

What is a vector?

Answer 17

arthropod host that transmits the parasite from one host to another.

Question 18

What is the definition of host-parasite interactions (symbiosis)?

Answer 18

A relationship between two or more organisms that live closely together.

Question 19

What are the types of host-parasite interactions?

Answer 19

• Parasatism
• Commensalism
• Mutualism
• Phoreisis

Question 20

What is parasitism?

Answer 20

one of the two organisms (parasite) benefits, as it gains protection and nutrition at the expense of the other (host) that suffers from such association.

Question 21

What is commensalism?

Answer 21

both organisms live together and the commensal organism benefits without causing harm to the other.

Question 22

What is mutualism?

Answer 22

both organisms benefit from the association to an extent that both can’t live separately (a flagellate in the intestine of termite that feeds on wood).

Question 23

What is phoresis?

Answer 23

• In phoresis, there is no dependency but just carriage (Dientamoeba fragilis on Enterobius egg).
• phoront is usually the smaller organism and is mechanically carried by the other which is usually large.

Question 24

What is zoonoses?

Answer 24

infectious diseases that can be naturally transmitted between animals (usually vertebrates) and humans.

Question 25

What are the types of zoonoses?

Answer 25

ANTHROPOZOONOSIS

ZOOANTHROPONOSIS

Question 26

What is anthrozooponosis?

Answer 26

a zoonosis maintained in nature by animals and transmissible to humans.

Question 27

What is zooanthroponosis?

Answer 27

parasitic infections naturally maintained by humans but can be transmitted to other vertebrates.

Question 28

What is anthroporosis?

Answer 28

Anthroponosis is another term where parasitic infections are found in man alone.

Question 29

What is the classification of zoonotic disease?

Answer 29

According to the source of infection: feral (sylvatic) or domestic

According to the method of transmission: direct zoonosis - meatzoonoses - saprozoonosis

Question 30

What is feral (sylvatic) zoonoses?

Answer 30

• the source of infection is a wild animal with no close relationship to man.
• Humans become exposed to infection in the course of hunting.

Question 31

What is direct zoonoses?

Answer 31

Infection is directly transmitted from the reservoir host to man.

Question 32

What is metazoonosis?

Answer 32

infection is transmitted from the reservoir host to man via an arthropod.

Question 33

What is saprozoonosis?

Answer 33

infection is transmitted via a non-animal developmental site as the soil and water.

Question 34

What is studied in medical Parasitology?

Answer 34

Medical parasitology includes the study of 3 major groups of animals:

1. Parasitic helminths (worms).
2. Parasitic protozoa.
3. Arthropods directly cause disease or act as vectors of various pathogens

Question 35

What is domestic zoonoses?

Answer 35

The source of infection is man’s own domesticated animals.