11 Microbial Diversity - Parasites

Question 1

Parasite

Answer 1

Organism that lives on or within a host and benefits at the host’s expense

Question 2

Commensalism

Answer 2

one partner benefits, other is not hurt

Question 3

Mutualism

Answer 3

Both partners benefit

Question 4

Symbiosis

Answer 4

any 2 organisms living in close association, commonly one living in or on the body of the other, as symbiotic, as contrasted with free living

Question 5

Facultative parasitism

Answer 5

When an organism can live free or establishes a parasitic existence depending on a host e.g. Ringworm

Question 6

Obligatory parasitism

Answer 6

When an organism establishes a permanent parasitic existence and is completely dependent on the host e.g. Plasmodium, head lice.

Question 7

Accidental or incidental parasitism

Answer 7

occasionally an organism parasitizes a species other than its usual host e.g. Hymenolepis diminuta (rat tape worm in man)

Question 8

Three major groups of parasites

Answer 8

1. Helminths (worms)
2. Protozoa
3. Arthropods

Question 9

Helminths

Answer 9

Multicellular and visible to the naked eye

Types: Roundworms (e.g., Ascaris), flatworms (e.g., Schistosoma), tapeworms (e.g., Taenia)

Question 10

Helminths life cycle

Answer 10

Typically involve both a definitive host (where the adult parasite reproduces) and an intermediate host (where larval or juvenile stages may develop)

Question 11

Protozoa

Answer 11

Unicellular and usually microscopic.

Can cause diseases like malaria (Plasmodium), amoebic dysentery (Entamoeba histolytica).

Question 12

Protozoa life cycle

Answer 12

Many protozoa have complex life cycles with asexual (e.g., binary fission) and sexual stages (e.g., gametogenesis)

Transmission may involve intermediate hosts, and infection often occurs through ingestion of cysts or vectors

Question 13

Arthropods

Answer 13

Invertebrates with jointed limbs (e.g., ticks, fleas, mosquitoes)

Ectoparasites (live on the outside of the host)

Question 14

Arthropods life cycle

Answer 14

Arthropod life cycles typically include egg, larval, nymph, and adult stages. Many arthropods are vectors, transmitting pathogens (e.g., protozoa, bacteria) from one host to another during feeding

Question 15

Types of parasites (5)

Answer 15

1. Endoparasites
2. Ectoparasites
3. Temporary parasite
4. Permanent parasite
5. Opportunistic parasite

Question 16

Endoparasite

Answer 16

live within the host causing infection

Question 17

Ectoparasite

Answer 17

live on the external surface of the host causing infestation

Question 18

Temporary parasite

Answer 18

only visits the host to get its meal

Question 19

Permanent parasite

Answer 19

always fixed to the host

Question 20

Opportunistic parasite

Answer 20

produces disease only in immunodeficient hosts

Question 21

Sources of parasitic infections

Answer 21

Water / soil / raw vegetables and fruit / animals / fish / vectors (arthropods) / blood

Question 22

Modes of infection

Answer 22

Injection / inhalation / penetration of skin and mucous membrane / bites / direct contact / blood transfusions / sexual

Question 23

How do parasites cause harm in its host?

Answer 23

Large number of parasites

Site of parasitism

Feeding habits

Competition for nutrients

Question 24

Types of host (3)

Answer 24

Definitive Host - parasite reaches sexual maturity and reproduces

Intermediate Host - parasite develops but does not reach sexual maturity

Reservoir Host - harbors the parasite but may not show symptoms; acts as a source of infection for other hosts.

Question 25

Direct transmission

Answer 25

parasite is passed from one host to another without the need for a vector

(e.g. direct contact, ingestion of infected material)

Question 26

Vector borne transmission

Answer 26

parasite is transmitted by a vector organism, such as a mosquito or tick, that acts as an intermediary

(e.g. malaria, Lyme disease).

Question 27

Zoonotic transmission

Answer 27

Transmitted between animals and humans

Question 28

Pathogenicity

Answer 28

Ability of a parasite to cause disease in its host

This depends on the parasite’s ability to invade tissues, evade the immune system, and reproduce within the host.

Question 29

Virulence

Answer 29

A measure of the severity or harmfulness of the parasite to the host, often related to how much damage the parasite causes

Question 30

Life cycles of parasites (2)

Answer 30

1. Simple - 1 host
2. Complex - multiple hosts (sexual in 1 host and asexual in another)

Question 31

Simple life cycles - direct

Answer 31

Parasite completes its entire life cycle in 1 host

Question 32

Simple life cycles - asexual

Answer 32

In some cases parasites can reproduce asexually in the host

Question 33

Complex life cycles - intermediate hosts

Answer 33

Asexual stages occur in the intermediate host before the parasite reaches sexual maturity in the definitive host

Question 34

Complex life cycles - vector transmission

Answer 34

Arthropods or other organisms act as vectors, transmitting the parasite between hosts

Question 35

Complex life cycles - larval stages

Answer 35

In helminths, larvae may infect an intermediate host, developing into cysts or larvae that are then consumed by the definitive host