MODULE 7 IQ1: Causes of Infectious Disease

Question 1

disease definition

Answer 1

any process or condition that adversely affects the normal functioning of a living organism, or parts of a living organism which is characterised by signs and symptoms

Question 2

pathogen definition

Answer 2

any disease-causing agent that disrupts the normal functioning of an organism

Question 3

infectious disease definition

Answer 3

disease caused by another organism of infective agent, known as pathogen that can be transmitted from one host to another

Question 4

prions definition

Answer 4

abnormally folded prion proteins which are commonly found in the cell membrane of neurons

Question 5

prions effect

Answer 5

prions cause normal proteins to misfold as well, which causes the degradation and destabilisation of neuron synpases, causing apoptosis in brain tissue.
- naturally occuring protien –> immune system cannot recognise and attack it

Question 6

examples of prion diseases

Answer 6

CJD (Creutzfeldt-Jackob’s disease), Kuru Kuru disease

Question 7

virus definition

Answer 7

non-cellular pathogens, consisting of nucleic material (DNA/RNA) enclosed in a protein coat (capsid)
- reproduces by invading host cell

Question 8

examples of viruses

Answer 8

influenza A, AIDs, Human Immunodeficiency Virus (HIV), COVID-19

Question 9

bacteria definition

Answer 9

single-celled prokaryotic cells with no membrane bound organelles and nucleus
- cell wall is comprised of peptidoglycan

Question 10

examples of bacterial disease

Answer 10

salmonella

Question 11

fungi definition

Answer 11

eukaryotic organisms that can either be unicellular or multicellular
- cell wall comprised of chitin
- membrane bound organelles but no cytoplasm
- can be parasitic or sapophytic

Question 12

examples of fungal disease

Answer 12

tinea, athlete’s foot

Question 13

protozoan definition

Answer 13

single cell eukaryotic microscopic organisms ranging in size from 2-1000mm
- classified by their own phylum
- classified by their form of locomotion

Question 14

examples of protozoans

Answer 14

plasmodium falciparum –> causes malaria

Question 15

macroparasites definition

Answer 15

eukaryotic organisms that live in or on organism and survive by depriving host of its nutrients
- visible to naked eye and can be endoparasites or ectoparasites

Question 16

endoparasites vs ectoparasites

Answer 16

endo: live inside host’s body
- e.g. tapeworm
ecto: live outside host’s body

Question 17

epidemic definition

Answer 17

rapid spread of an infectious disease to many susceptible hosts in a given population within a short period of time, usually 2 weeks or less

Question 18

pandemic definition

Answer 18

epidemic of infectious disease that spreads across a large region within a short period of time, usually 2 weeks or less

Question 19

main factors that contribute to an epidemic

Answer 19

virulence, migration, host exposure and susceptibility

Question 20

virulence in epidemic meaning

Answer 20

severity or harmfulness of disease/pathogen and is mainly increased by mutations

Question 21

migration of pathogen in epidemic meaning

Answer 21

migration of individuals to new population that may bring disease to new population that has never been in contact with it before –> lacks immunity

Question 22

host exposure and susceptibility in epidemic meaning

Answer 22

host population may become more susceptible to disease if population’s genetics change/stay stagnant and if they lack appropriate infrastructure

Question 23

chain of infection

Answer 23

host –> reservoir –> portal of exit –> transmission –> portal of entry –> susceptible host

Question 24

transmission definition & types

Answer 24

definition: carrying of a pathogen from an infected host to a non-infected organism
types: direct, indirect contact, vector transmission

Question 25

direct contact definition & examples

Answer 25

transfer of pathogen via physical contact between host and non-infected organism
- e.g. sexual intercourse, skin-to-skin contact, biting in animals

Question 26

indirect contact definition & examples

Answer 26

transfer of pathogens via non-living intermediate between host and a non-infected organism
- e.g. sharing food and water, air and dust, surfaces and objects like bedding and medical equipment

Question 27

vector transmission definition & examples

Answer 27

type of indirect contact where transfer of pathogens occurs via living intermediate that is not infected
- e.g. arthropods, mosquitos

Question 28

koch’s contributions

Answer 28

ability to establish a specific microbial pathogen as the cause of a specific disease

Question 29

koch’s anthrax experiment

Answer 29

found infected sheep and cultured bacteria on agar plates –> injected healthy sheep with bacterium and they developed same symptoms and disease as well

Question 30

koch’s four postulates

Answer 30

1. the microorganism must be present in the tissues of the infected organisms and not in a healthy organism
2. the microorganism must be able to be cultivates from infected organism in pure culture
3. when uninfected organism is then inoculated with cultured microorganism, it should develop symptoms of the original disease
4. samples from second infected organism should be able to be isolated and found to be the same as the microorganism from first infected organism

Question 31

louis pasteur contributions

Answer 31

disproved the theory of spontaneous generation and created germ theory

Question 32

pasteur’s swan neck experiment

Answer 32

• heated long necks of flask and bent into S shape which allowed air to enter flask but dust/spores/microbes would settle in bend
• heated flasks to kill any microbes present
• removed S bend from one flask, exposing broth to air and left flasks to sit
• broth with open necked flask became cloudy, indicating contamination from germs while the other was unchanged and free of germs

Question 33

pasteur’s findings

Answer 33

microbial germs are airborne and life cannot be generated from a sterile medium
- microbes are agents of decay/contamination

Question 34

plant disease: Panama TR4

Answer 34

caused by fungus (fuasrium odoratissium)
- banana plantations in North Queensland
causes:
- yellowing of leaf margins and base of older leaves
- dead leaves collapsing along leaf stalk
- stem splitting at base of plant

Question 35

animal disease: Footrot

Answer 35

caused by bacteria (Dichelobacter nodosus bacteria)
- impacting sheep –> causes digestion of connective tissue between horn & flesh of hoof and under hoof
- survives under warm, moist conditions and spread via pasture or mud
causes:
- poor ewe fertility, poor growth rates, reduces wool production & quality, higher mortality rates

Question 36

adaptations of different pathogens

Answer 36

bacteria: Helicobacter Pylori (H.Pylori)
protozoan: Plasmodium Falciparum
virus: Human Immunodeficiency Virus (HIV)

Question 37

Helicobacter Pylori (H.Pylori) adaptations

Answer 37

• spiral shaped bacteria that causes stomach infections and ulcers in humans
• special flagella that helps it move in a screw-like motion through mucus lining of stomach
• produces urease –> conversion of urea to ammonia which protects bacteria by neutralising stomach acid
• releases cytotoxins that creates ulcers by destroying the stomach epithelial layer

Question 38

Plasmodium Falciparum adaptations

Answer 38

• main protozoan that causes malaria using mosquito vectors to bypass skin
• mosquito is infected through blood of infected host and when it feeds on another person, the pathogen is injected into persona’s blood

Question 39

Human Immunodeficiency Virus (HIV) adaptations

Answer 39

• causes AIDS by infected and destroying helper T lymphocytes