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Lecture 3

HLTB21 lecture 3 sep 19 .docx

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Department
Health Studies
Course
HLTB21H3
Professor
R Song
Semester
N/A

Description
HLTB21- September 19, 2013- Lecture 3 Infectious Disease and Human History • Disease-causing pathogens have co-evolved with us • With Homo sapiens’ expansion ~ 120,000 years ago: human- microorganism contacts limited to infectious agents whose life cycles could accommodate frequent residential shifts of migratory human gatherers and hunters • Infectious diseases likely limited by small group size of early humans and their relative genetic and behavioural homogeneity > very densely unpopulated • Spread of infectious disease restricted by transitory lifestyles and broad geographical ranges of such groups • With migration & population expansion: contact with disease • Most dramatic shift in human-microorganism interactions occurred within past 10-15,000 years, due to agriculture and sedentism (non-migratory lifestyle).....then urbanization and industrialization  Micro pathogens and worms are very effective pathogens that can wipe out a population The “Paleolithic Baseline” Two classes of pathogens afflicted Paleolithic hunter-gatherers: • Heirloom species: affected our anthropoid and hominine ancestors (prior to 6 million years ago) and continued to parasitize them as they evolved into hominids; head and body lice, pinworms, internal protozoa, bacteria such as Salmonella typhi and staphylococci, and possibly yaws • Souvenir species: those that are “picked up” along the way (of daily activities); are usually zoonotic pathogens whose primary hosts are non-human animals, infecting humans only incidentally; zoonoses are passed on via insect and animal bites, by preparing and consuming contaminated flesh, and via contact with urine and feces of infected animals Epidemiological Transition • With expanding historical populations, mortality declined and structure of causes of death shifted from predominantly infectious diseases to mostly chronic degenerative diseases... (due to faster decline of infectious diseases due to technological and behavioural changes) Expanding, Stable and Declining populations  Population increased post-agriculture  Today we’re in a declining phase (in most Western nations)- more of us dying than being born  Stable phase: adoption of birth control, which led families to decrease in size; post WW2 when they’re not dying because of infectious disease but rather with chronic diseases - Clearly associated with changes in population > Resulted in also good things, such as life span has increased as families have decreased, medical technologies have become advanced th Preindustrial: 19 century Europe, LE increased to 40 Developing countries: 6- years LE Life span reflects infectious disease spread Measels: crowd disease-> larger populations living together in one place Epidemiological Transition • The Age of Pestilence and Famines • The First Epidemiological Transition • Agriculture and ↑ population ... • Increase in infectious disease mortality • Our ability to control animals; make them live in our community so we can slaughter them Agriculture and ... • Food composition and nutritional quality • Food processing technology and mastication • Population growth • Population distribution 
and health • Work load and activity patterns • You’re no longer isolated from people ; living closer with them • After we became farmers, we worked harder than hunter-gatherers The First Epidemiological Transition Agriculture and ↑ population results in: 1. Occupational stratification : creation of different jobs; egalitarian society (everyone’s responsible for their little parts that’s accepted by the community) -> differentiation of social equality . Hunter gatherers considered egalitarian, but farmers were more stratified (different levels, usually social status and economic status, political power, etc) 2. Sedentism (being stationary; people living closely together and staying in one place) & altered land use patterns (to farm tracts of lands) 3. Contamination of water sources : more people living together so more infections 4. Within-group exposure to pathogenic microorganisms 5. Increase between- and within-group heterogeneity in susceptibility or resistance to infectious agents 6. Increased group interactions (more frequently, longer pds) 7. Encroachment of human habitation (and agricultural fields) to wilderness perimeters, thus increasing contact with vectors of zoonotic viruses and bacteria (i.e., from domesticated animals) ; especially those living close to us (for ex. sometimes people keep animals in their sheds) Cultural evolution but also brought along great consequences  6 millions years, the majority were hunter gatherers, only in the 10,000 years people have been farmers and not roaming around like hunter-gatherers  They could control how much food surplus they had  Hunter gatherers live in small band, spread out in the landscape and essentially follow the food (animals) in order to hunt them, so you’re very mobile, which has an effect in community size  very small bands (i.e. 50)  Manipulating water sources, controlling water (irrigation, canals, etc.)  Dental Health We lose teeth with cavity; we can also die from cavities because it destroys bone • Caries • 
Abscess • Calculus deposits: build up of food that’s calcified on our teeth • Tooth loss
 • Tooth wear Malnutrition Protein malnutrition (and caloric) -> Meat becomes a status food -> consequences for poor nutrition • Mild-to-moderate micronutrient 
malnutrition • Deficiencies in Vitamins A, B, C, D, • Iodine • Iron • Ca • Zn • Anemia: deficiency in iron (today, cereals and breads have iron) • porotic hyperostosis: manifestation on the surface of the skull • cribra orbitalia: chronic anemia that affects the orbits of the eye; reactive bone as a response to chronic anemia > we see this more in farming than hunter-gatherers > Body adapts to an infectious circumstance by withholding iron Growth and Development  Growth and height due to different SES  Genetic
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