within host factors Flashcards
What is an example of density dependent effect on growth?
the more worms you have the smaller they are - density dependant effect on growth
What determines the threshold at which density dependent effects kick in?
Threshold at which density dependence effects kick in vary with parasite and host
What is parasite-induced host mortality?
parasite-induced host mortality - if you have more parasites then you can kill your host more easily; parasite infra-population dies when the host is killed
What is exploitation competition?
exploitation competition - host resources become limiting at certain densities; resource mediated (malaria parasites competing for the RBCs)
What is interference competition?
interference competition - parasites directly interfere with one another (bacteria kill closely related strains as they are more of a competition)
What are the two possible scenarios fro immune mediated apparent competition?
you have two pathogens that co-infect the host and both stimulate the immune system; when the immune system reacts it goes after booth of them but it takes one out more efficiently than another; instead of taking each other out they stimulate the immune system to do the work for them
they infect the organisms at different steps
How does over-dispersion interact with density dependance?
you have some hosts that have very large populations of the pathoge and a lot that have small populations of the pathogen
- explicitly modelled density dependence for a gibe individual worm burden
- estimated effective reansmission contribution eggs/gram of faeces or infectious larvae/fly
What happens when you calculate stuff based on the mean if you have over-dispersion?
if you take the mean approach you vastly overestimate the numbers and that happens because you don’t take into account the difficulty that comes with being at low density where the worms can’t find mates, it also fails to incorporate the burden that comes with overpopulation of the host
the overestimation is worse when the aggregation is strong in just few individuals and not spread throughout the host population
What is the relationship between aggregation and density dependent effects?
Aggregation is a very important determinant of density dependent effects;
- high aggregation → high densitty dependance
- even dispersal → decreased density-dependent effects
