Chapter 13 - Spread of pathogens

Question 1

what does a pathogen need to best survive and reproduce

Answer 1

• Invade the host (portal of entry)
• Exploit a nutrient rich area of the host
• Avoid host defence mechanisms
• Replicate
• Portal of exit and transmit to new hosts

Question 2

Reservoir

Answer 2

An organism (eg wallaby) or habitat (eg soil) in which a pathogen can reside, and sometimes replicate, prior to entering a susceptible host. somewhere the pathogen does not go extinct

Question 3

Susceptible host

Answer 3

An organism that is vulnerable to developing infection when invaded by germs (eg very young children, elderly, those already ill)

Question 4

6 portals of entry

Answer 4

• Skin (bite, blood feed, penetration)
• Mucous membranes
• Wounds
• Eyes and ears
• Respiratory system (nose/throat/lungs)
• Reproductive system

Question 5

5 portals of exit

Answer 5

• Bite/blood feed/saliva
• Digestion
• Respiratory system (sneezing, coughing)
• Blood contact
• Reproductive system

Question 6

sign

Answer 6

an objective and measurable experience of a pathogen host that is directly observable (body temp, pulse)

Question 7

symptom

Answer 7

a subjective experience felt by a patient such as nausea or pain

Question 8

definitive host

Answer 8

The host in which a pathogen replicates sexually (eg malaria in gut of mosquito)

Question 9

intermediate host

Answer 9

The host in which a pathogen replicates asexually (eg malaria in liver and red blood cells)

Question 10

what are the two modes of transmission

Answer 10

• Direct: Direct and close contact or through reservoir

- Indirect: Vector, airborne droplets/fomites, soil/water/vehicle

Question 11

What is direct contact

Answer 11

Transmission due to physical touch between an infected host and a susceptible host via skin or body fluids (eg influenza)

Question 12

what is close contact

Answer 12

Transmission of a pathogen in airborne droplets between an infected host and a susceptible host (sneezing coughing) eg influenza

Question 13

what is direct transmission from a reservoir

Answer 13

Transmission from an inanimate reservoir/fomite to a susceptible host (eg soil for tetanus, influenza fomite)

Question 14

What is indirect transmission through a vector

Answer 14

A living thing that transmits a pathogen from an infected host to a susceptible host (eg malaria and ross river via mosquito)

Question 15

What is indirect transmission through airborne droplets/fomites

Answer 15

Pathogens can be transmitted inside airborne droplets (aerosols) that are sneezed or coughed into air and suspended for a period of time before being inhaled. They may land on surfaces and be transferred via a fomite

Question 16

what is indirect transmission through soil, water and vehicles

Answer 16

An inanimate object acts as an intermediary between the portal of exit from the reservoir and the portal of entry to the host (eg car tyres, shoes). Pathogens can also swim or be carried through water or wet soil (eg crown gall, chytridiomycosis, phytophthora)

Question 17

what is a zoonotic disease

Answer 17

A disease that animals pass to humans

Question 18

fomites

Answer 18

a surface or non living object carrying an infectious agent

Question 19

Thresholds

Answer 19

a certain level

Question 20

globalisation

Answer 20

the process by which the world is becoming increaingly interconnected as a result of massively increased trade, economic, travel and cultural exchange

Question 21

urbanisation

Answer 21

the increase in the proportion of people moving from rural areas to live in towns and cities

Question 22

population density

Answer 22

the number of organisms of the same species living in a particular area at a specified time

Question 23

what are the three main reasons why urban areas are more susceptible to infectious disease

Answer 23

High population density, Poor living conditions, lack of adequate healthcare provisions

Question 24

what are the three interrelated factors influencing the spread of pathogens

Answer 24

Growth of pathogen population, mode of transmission, density of host population

Question 25

why is the distribution of mosquito borne diseases likely to increase as a result of climate change

Answer 25

warmer temperatures and extra water bodies will increase the activity of mosquitoes and the number of breeding grounds where they can reproduce. An increase in the incidence of the mosquito vector leads to an increase in transmission