HLTC07 - Lec 10 - Disease Emergence (near-verbatim)

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Trinity College Courses
Caroline Barakat

C07 10: Factors influencing the emergence of diseases Date: Nov 21, 2012 Slide 2: Lecture Outline  Background Info – where is this info coming from – UN and WHO – in terms of patterns of disease  General factors (4 main factors linked to emerging diseases)  Role of human pressure on ecosystems: o Land use changes o Mass production o Xenotransplantation o Microbial change  The influence of each of these factors on emergent diseases Slide 3: Background  Lederber et al. 1992;– multi-disciplinary report from US Dept of Medicine  Several objectives of the report: o 1) Identify significant emerging diseases past few decades (50’s to 90’s) o 2) Determine strategies to deal with them o 3) Recommend actions to confront future threats and to lessen their impacts on public health (less morbidity/mortality) – so that it can be dealt with a lot easier  Key thing about report – it embraced the global perspective; didn’t just focus on US and their emerging diseases but rather: o Global frame of reference  This report also avoided disease specific questions and wanted to focus on raw factors that are linked to emergence of many diseases; not disease-specific factors  Approach based on factors of emergence  Smolinski et al. 2003 – was a follow-up report that extended the work of 1992 group to identify further factors in the emergence of diseases  In first report, 6 factors identified; 2 report made list of factors to 13 Slide 4: Examined factors 1) Human demographics and behavior 2) Technology and industry 3) Economic development and land use and land use changes 4) International travel and commerce a. Travelling, diseases can go from one end of global to another 5) Microbial adaptation and change 6) Breakdown of public health measures a. Maybe the emergent diseases weren’t identified as fast as they should’ve and weren’t under control as efficiently 7) Human susceptibility to infection 8) Climate and weather 9) Changing ecosystems 1 C07 10: Factors influencing the emergence of diseases Date: Nov 21, 2012 a. Ties in with economic development and land use 10) Poverty and social inequity 11) War and famine 12) Lack of political will 13) Intent to harm a. Bio-terrorism This is broad, ppl sat and discussed why is it that we have emerging diseases – came up with this list of 13 factors. Real diseases and how these factors tie into these emerging real diseases. Land use changes – can inter-play with economic development and land use In some cases, everything’s connected. One main thing that had to do with the emergence of diseases – human pressures on the ecosystem (due to mainly population growth) – everything else would pretty much fall into this broad category  More than ½ recognized human pathogens are zoonotic – originate from animals Slide 5: Human pressures on the ecosystem  Among the approximately 177 newly emerged human diseases in past 3-4 decades, about 58% are zoonotic (disease emerges when it moves from one vertebrate species to humans – typical way for transmission)  A balance was shifted @ one point in time where that pathogen moved from a vertebrate an animal and infected humans  Factors that facilitate the process: (due to human pressures on ecosystem from pop’n growth) o Poor sanitation o Encroachment of humans on animal habitats o Maintaining food animals in crowded conditions to meet demands for food production  Industry  More animals in crowded spaces  Spread of diseases and then to humans o Extensive use of antimicrobials  Recurring theme  One of the 13 factors linked to the emergence of diseases  Used too much and it causes microbial resistance  Ecological changes include: (due to ecological pressure rather than evolutionary changes; ecological changes that arise from this pressure include o New agricultural practices  Grow more crops; irrigation = new – agricultural revolution  New practices lead to certain enviro that would lead to emergence to certain diseases o Urbanization  Linked to deforestation & crowding 2 C07 10: Factors influencing the emergence of diseases Date: Nov 21, 2012 o Globalization  Travel from one place to another o Climate change Slide 6: Examples of proximity – pressure on the land – exposure to animals – pathogens that cross species barrier and start infecting humans  Rapid acceleration of Poultry agriculture in SE Asia thought to have converted avian flu into cases that are known to humans o Originated in poultry/pigs/horses etc; o Due to close contact btn diff domestic animals and humans  1918 flu pandemic – avian in origin (close proximity to domestic chickens)  HIV epidemic – transmission between monkeys or apes and humans? 4 MAIN FACTORS LINKED TO EMERGING DISEASES: Slide 7: Changes in Land Use – Deforestation – includes many things = cut down trees, streams may be re-directed for irrigation, building cities, dams, urban dwellings etc;  changing land use – disrupts original balance --> leads to ecological changes  Rate of deforestation worldwide estimated @ 40M acres/year o Exposes land to sunlight o Creates pools of water (no infiltration)– breeding grounds (malaria, snail fever)  Ex) New Guinea Highlights o Before and after – more dry, arid o Area that was relatively malaria free but after forest clearance – became home to anopheles mosquito – malaria infected  Similar trends seen in Kenya, Madagascar, Uganda & Rwanda – were malaria free but b/c of changes in land use – became home to malaria-transmitting mosquitoes  Yellow fever and dengue fever in sub-saharan countries – transmitted via mosquitoes – so when you have good breeding ground for mosquitoes to flourish – infect ppl  We now see increasing cases of west Nile virus – carried via mosquitoes as vectors o Remove still water – breeding ground Slide 8: Changes in Land Use – Reforestation  Lyme disease – recognized in US in 1975 in town of Old Lyme in SE Connecticut where residential development being built – growing trees again project – more greenery o Deer population took home in this region; deer were infested with ticks that carried lyme disease  result: lyme disease in humans b/c of close proximity o Hard to diagnose lyme disease  Inter-relationships between various micro-organisms and animals – biodiversity in certain ecosystems and changes in land use by humans o Came from reforestation and ppl being close to animal reservoirs 3 C07 10: Factors influencing the emergence of diseases Date: Nov 21, 2012 Slide 9: Changes in Land Use – Irrigation & Dams  Rift Valley fever o By mosquito transmission o Surged in Africa due to construction – stagnant bodies of water, mosquitoes breed o Viral zoonosis – caused by virus – originated from domestic livestock but it passed onto humans due to practices linked to dam construction  Aswam Dam – schistomiasis o Egypt o Shift in diff types of agents for snail fever (schistosomiasis) – diff balances in system  S
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