Parasitism Flashcards
Ectoparasites
live on the outside of organisms
Advantages of ectoparasites
easily move between hosts
not exposed to immune system of host
Disadvantages of ectoparasites
exposed to environment
exposed to predators and parasites
Endoparasites
live on inside of organism can be intracellular or extracellular
Advantages of endoparasites
safe from external environment
hosts rarely have internal, physical defenses to prevent feeding
Disadvantages of endoparasites
exposed to the host immune system
hard to move between hosts
Zoonotic diseases
jump from non-human animals to humans and main source of emerging infectious disease in humans resulting in epidemics
What are zoonotic disease epidemics related to?
habitat fragmentation, deforestation, climate change, etc.
S-I-R model
simplest way to model transmission of infectious disease that incorporates immunity of host
what does SIR stand for
S = susceptible to pathogen (100% begin here)
I = infected
R = resistance via immunity
Formula to predict changes in the population of infected hosts:
dI/dt = BSI - Ig
What do the units stand for:
dI/dt = BSI - Ig
BSI = gains to the infected class (B = transmission rate, S = susceptible hosts, I = infected hosts)
Ig = losses to the infected class ( g = recovery rate, I = number infected hosts)
What is Ro
the basic reproductive number of an infectious disease (aka number of new hosts who are infected by an infectious host in an entirely susceptible population)
If the number of individuals gained by the infected class is greater than the number of individuals lost from the infected class, ______.
If the number of individuals gained by the infected class is greater than the number of individuals lost from the infected class, DISEASE SPREADS.
aka in Ro = BN / g
if BN > g disease spreads
Ro > 1
the infection will continue to spread through the population (potential epidemic)
