WFSC 403 1st Edition Lecture 21 Outline of Last Lecture I Basic Concepts a Review II Math Models a Review III Effects of disease on individuals IV Effects of disease on populations a Threshold b Vaccination vs Cull c virulence d Cryptic Cycle V Evolution of host parasite systems a Virulence vs Transmissibility b Hot to maximize R0 c Does disease affect populations d Under what conditions does an epidemic occur Outline of Current Lecture I End chapter 13 II Effects of disease on population a Brucellosis b Rabies c Myxomatosis d Tuberculosis III Evolution of host parasite systems a Virulence vs transmissibility IV Chapter 14 V Basic concepts and a simple model Current Lecture Bison Brucellosis causes abortion no vaccine These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute o Figure A goes up with age been around longer are exposed more develop antibodies o Figure B indicator of exposure to pathogen o Why are small herds less Contact rate too low Run out of susceptible individuals o Why doesn t it run through the big herds Baby bison The period you are infected and infectious is relatively short Rabies o Culling is removing an infected individual from population o Vaccination is making an infectious individual no longer infectious o Vaccination is more effective than culling when thinking of not density dependent Myxomatosis in rabbits o Fewer died as time went on fewer died from the disease Not as virulent as when first introduced Tuberculosis in possums Possum key vector in transmitting disease to cattle Also passed into ferrets but ferrets don t pass it as easily to cattle Cryptic cycle o Pathogen circulating in nature reservoir population may not notice or care unless affecting population we are actually interested in o Change in virulence of the mouse typhoid bacterium after passage in laboratory mice o Pathogen is evolving but the mouse population is not evolving or co evolving with it If you kill host you are in very fast you don t have a lot of time to pass on to someone else If you kill it too quick you are going down with the ship o Take longer in host and wait for host to pass on the pathogen to another host Basic concepts and a simple model of population regulation o Important for conservation land management fisheries o Fluctuations in numbers Abundance varies from place to place metapopulations Limits to growth limiting and regulating factors o Balance of nature Density Independent does not depend on population density Populations in an unlimited environment Grows exponentially Density Dependent does depend on population density Populations limited grows sigmoid growth curve No way population can be limited unless some factor influences the birth or death rate First principle of population regulation no closed population stops increasing unless either the per capita birth rate or death rate is density dependent
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