Chapter 13 - Spread of pathogens Flashcards
what does a pathogen need to best survive and reproduce
- 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
Reservoir
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
Susceptible host
An organism that is vulnerable to developing infection when invaded by germs (eg very young children, elderly, those already ill)
6 portals of entry
- Skin (bite, blood feed, penetration)
- Mucous membranes
- Wounds
- Eyes and ears
- Respiratory system (nose/throat/lungs)
- Reproductive system
5 portals of exit
- Bite/blood feed/saliva
- Digestion
- Respiratory system (sneezing, coughing)
- Blood contact
- Reproductive system
sign
an objective and measurable experience of a pathogen host that is directly observable (body temp, pulse)
symptom
a subjective experience felt by a patient such as nausea or pain
definitive host
The host in which a pathogen replicates sexually (eg malaria in gut of mosquito)
intermediate host
The host in which a pathogen replicates asexually (eg malaria in liver and red blood cells)
what are the two modes of transmission
- Direct: Direct and close contact or through reservoir
- Indirect: Vector, airborne droplets/fomites, soil/water/vehicle
What is direct contact
Transmission due to physical touch between an infected host and a susceptible host via skin or body fluids (eg influenza)
what is close contact
Transmission of a pathogen in airborne droplets between an infected host and a susceptible host (sneezing coughing) eg influenza
what is direct transmission from a reservoir
Transmission from an inanimate reservoir/fomite to a susceptible host (eg soil for tetanus, influenza fomite)
What is indirect transmission through a vector
A living thing that transmits a pathogen from an infected host to a susceptible host (eg malaria and ross river via mosquito)
What is indirect transmission through airborne droplets/fomites
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
what is indirect transmission through soil, water and vehicles
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)
what is a zoonotic disease
A disease that animals pass to humans
fomites
a surface or non living object carrying an infectious agent
Thresholds
a certain level
globalisation
the process by which the world is becoming increaingly interconnected as a result of massively increased trade, economic, travel and cultural exchange
urbanisation
the increase in the proportion of people moving from rural areas to live in towns and cities
population density
the number of organisms of the same species living in a particular area at a specified time
what are the three main reasons why urban areas are more susceptible to infectious disease
High population density, Poor living conditions, lack of adequate healthcare provisions
what are the three interrelated factors influencing the spread of pathogens
Growth of pathogen population, mode of transmission, density of host population
why is the distribution of mosquito borne diseases likely to increase as a result of climate change
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
