Infectious disease 3/22/2012 8:03:00 AM
Infection versus other threats to survival
Major human pathogens and host pathogen coevolution
o Environmental co-factors +historical influences are key in
changing risks in infection and chances of survival through
morbidity by these diseases
Evolved defence against pathogens and pathogen strategies
o Immune response +pathogen counter adaptations
Biocultural interactions
o Technological efforts, extermination of vectors, poverty
o Tools are not applied everywhere, => social diseases, that’s
why some populations have more diseases than others
Malaria,cholera,TB,HIV/AIDS,bilharzia,river blindness
Hygiene+helminth hypotheses for allergies,asthma
Extrinsic Mortality
Intrinsic mortality: benefit from shutting things down(senescence)
o Biotic risks(source and level for humans):
Infection (parasites +other micro-organisms;high)
Major source of mortality for us
Predation(large carnivores:low)
Competition for food,mates,etc;moderate)
Injury(all the above;moderate,esp.conspecific violence)
Adaptations
o Repair systems
o Immune systems
Good for microorganisms defence
o Hormonal control of threat response
o Social grouping/exclusion;cooperation/warfare etc
o “theory of mind”
Infectious diseases
communicable diseases vs NCDs’s = caused by microorganisms that
use another individual’s resources to feed,grow,reproduce and
provoke immune response +/- disrupting function
o causes immune response,disrupts function at some point
2
there are symbiotic bacteria ex. Our guts do not
provoke immune system or affect our system
o attribution of disease to infection:germ theory
o Koch’s 4 postulates: focus on pathogenicity
Host+environment also key
o Types of pathogen
>1,200 known pathogen species;many classifactions
most illness and eath caused by a few
malaria,tb,hiv/aids
gastro-intestinal +lower respiratory pathogens
multicelled parasites eg.helminths
examples of major pathogens
Viruses
Pox,hiv ,hepatitis
Bacteria
Yersinia,salmonella
Other
prokaryo
tes
Chlamydia(psittaci),rickettsias(eg.typhus),mycoplasma(
ex.pneumonia)
Protozoa
Plasmodium(malaria),trypanosoma(sleeping
sickness),giardia(fever,gassy)
Helminth
es
Flatworms
(shistosoma),roundworms(eg.ascaris),tapeworms
arthopod
s
Mites,lice,botflies,common vectors
o malaria ,cholera,shistomiosis,river blindness
o does it need a vector, how transmitted
o helmets of warms
o know malaria is caused by blood born protozoan
evolutionary history
o climate zones+human migration
ancient,nomadic,low density ancestor
low virulence eg.onchocerciasis,schistosomiasis
tropical vectors: mosquito,tsete fly,water snail
recent,settledhigh density ancestors