BIOS 5445: Human Ecology Dr. Stephen Malcolm, Department of Biological Sciences

Transcription

1 BIOS 5445: Human Ecology Dr. Stephen Malcolm, Department of Biological Sciences Lecture 8. Mortality - Disease: Infectious diseases. Non-infectious diseases. Pollution. Responses to stress. Fat. Lecture 8: Slide - 1

2 2. Infectious disease - Vector-borne diseases: Most common vectors are arthropods. Mechanical and biological transmission. Examples: Malaria: Largest source of human mortality. Caused by Plasmodium protozoa. Transmitted by Anopheles mosquitoes. Onchocerciasis (river blindness): Filarial worms migrate to eye. Transmitted by black flies, Simulium damnosum. Flies breed in fast-flowing water. Conflict between needing water and incidence of parasites: like schistosomiasis (caused by a fluke) with snail vector. Lecture 8: Slide - 2

3 3. Human response to malaria (Fig. 9-7): Lecture 8: Slide - 3

4 4. Infectious disease - Direct transmission: Coughs, sneezes & touch transmit droplets. Respond to aggregations of humans generated by intensive agriculture. Examples: Measles - viral. Influenza - viral: Changes in viral protein coat lead to antigenic drift & foils host immunity. Can result in global pandemics: killed million people. Animal reservoirs (pigs and birds) lead to great antigenic variation. Lecture 8: Slide - 4

5 5. Incidence of measles (Fig. 9-8): Type I waves (a) in large island populations with continuous incidence. Type II waves (b) in medium-sized island populations with regular incidence/absence cycles. Type III waves (c) in small island populations with irregular incidence. Lecture 8: Slide - 5

6 6. Virgin soil epidemics: Introduced diseases can be especially virulent Contact with highly aggregated people can be disastrous with <90% mortality because everyone is susceptible. May have resulted in collapsed cultures in the Americas. Examples: Native Americans and Pacific Islanders upon contact with smallpox and measles carried by explorers/immigrants from densely populated Europe. Lecture 8: Slide - 6

7 7. Disease and sanitation: Fecal-oral route through contamination of water and food. Exacerbated by mechanical vectors. Problems first generated when nomadic lifestyles were abandoned in favor of sedentary, agricultural lifestyles. Examples: Hookworm in human intestine. Cholera - caused by Vibrio cholerae bacterium in fecal/body fluid-contaminated water. Lecture 8: Slide - 7

8 8. Human response to cholera (Fig. 9-10): Lecture 8: Slide - 8

9 9. Disease and intimate contact: Mostly sexually-transmitted diseases. Examples: Gonorrhea is caused by the gonococcal bacterium, Neisseria gonorrhoeae. Treponemal diseases caused by bacterial spirochetes: Venereal syphilis: Yaws: Pinta: Mostly horizontal by genital contact (>90%), some vertical from mother to fetus. Both direct transmission & fly vectors, mostly in poor children. Mild skin disease. Nonvenereal (endemic) syphilis: Transmission by contact and water/food. Treponemal disease - cross resistance among diseases. Lecture 8: Slide - 9

10 10. AIDS: Acquired Immune Deficiency Syndrome caused by human immunodeficiency virus (HIV) - a retrovirus (RNA-based). Extremely fast mutation rate (faster than influenza) of both HIV-1 and HIV-2. Targets immune system. Transmitted horizontally in body fluids by sexual contact (homosexual and heterosexual), transfusions and injections (immunizations & drug use). Transmitted vertically from mother to fetus. Lecture 8: Slide - 10

11 11. Interactions among nutrition, disease and other stressors: Negative feedback: Poor nutrition leads to reduced immune system function and enhanced susceptibility to disease. This in turn leads to lethargy and reduced mental ability that results in less ability to gather nutritious food. Warfare can also generate the same negative feedback through the disruption of food production and distribution systems. These factors can also interact with abiotic conditions such as altitude and temperature to generate problems from hypoxia and cold stress. Lecture 8: Slide - 11

12 12. Non-infectious or chronic diseases and modern stress: Generating wealth in urban/suburban environments also creates new problems from stress, pollution and overconsumption of resources. Problems generate chronic diseases such as cancer, hypertension, heart disease and diabetes. Lecture 8: Slide - 12

13 13. Cancer: Gene mutations that alter regulation of cell proliferation. Causes: Mutagens: Physical or chemical agents that might affect rates of mutation and interact with genetic susceptibility. Examples include cigarette smoke, viruses and radiation. Specific cancers may have specific environmental causation. Incidence varies among populations: Geographical variation. Higher incidence in modernized than traditional societies. Strong environmental influence. Strong correlations with rates of urbanization, level of education, per capita Gross Domestic product (GDP) and amount of imports. Higher modern incidence not a product of greater longevity. Lecture 8: Slide - 13

14 14. Hypertension: A symptom of stress. Persistently high arterial blood pressure. Increased risk of stroke, heart disease, blindness & kidney failure. Higher incidence in modernized societies. Characteristic rise in blood pressure with age in modernized societies but not in traditional societies. Lecture 8: Slide - 14

15 15. Heart disease: Atherosclerosis: Hard, lipid-containing deposits or plaques on wall of coronary arteries: Blockage causes heart attack. Arteriosclerosis: Hardening of the arteries can lead to aneurysm (vessel ballooning) and rupture. Higher incidence in modernized societies: Immigrants also adopt host country incidence of heart disease within 1 or 2 generations. Lecture 8: Slide - 15

16 16. Diabetes mellitus: Inability to metabolize carbohydrates through lack of hormone insulin or inability to use insulin. 2 forms: Insulin-dependent diabetes mellitus (IDDM): Often in young people - juvenile diabetes caused by autoimmune response to stop insulin production. Noninsulin-dependent diabetes mellitus (NIDDM): More common, with late onset. Cells have few insulin receptors and respond poorly. Associated with obesity and modernization. Thrifty genotypes - feast-and-famine cycles select for physiologies that promote rapid buildup or loss of fat. Lecture 8: Slide - 16

17 17. Pollution: Chronic diseases both caused and influenced by natural and anthropogenic actions: Air pollution: Smoke - cooking fires, energy creation, industrialization, transport, tobacco use. Smog - combination of smoke and water vapor: Photochemical smog from action of sunlight on vehicular and industrial chemicals in air pollution (SO x and NO x chemicals). Water Pollution: Disease and toxic chemicals from industry and agriculture. Heavy metal poisoning. Toxic organics & solid waste. PCBs (polychlorinated biphenyls) and industrial solvent TCE. Lecture 8: Slide - 17

18 18. Physiological response to stress (Fig. 10-2): General stress is a mediating variable between a stimulus and a response. Two forms of biological response to general stress: (1) Via pituitary and adrenal glands (Fig. 10-2). (2) Via sympathetic nervous system (Fig. 10-3). Lecture 8: Slide - 18

19 19. Physiological response to stress (Fig. 10-3): Fight-or-flight prepares for major physical effort. Loads blood with glucose & oxygen. Increases blood circulation. But may impair immune system. adrenaline and noradrenaline Lecture 8: Slide - 19

20 20. Urbanization and stress: Situations characterized by novelty, unpredictability, or perceived lack of control lead to increased stress responses. Stress in an English village influenced epinephrine levels through psychosocial arousal (both pleasant and unpleasant): Daily activities at work and in home and travelling. Modernization also appears to increase stress as measured by excreted hormones (epinephrine and norepinephrine, Fig. 10-4): Especially for immigrants not fully integrated. Stress can also generate high cortisol bursts and lowered immunoglobulin associated with outbreaks of infectious diseases: Caused by social stress from divorce, work away from home and conflict such as riots or warfare. Children are especially susceptible. Lecture 8: Slide - 20

21 21. Hormonal response to stress in Filipino Americans in Honolulu (Fig. 10-4): Lecture 8: Slide - 21

22 22. Fat and chronic disease: Tendency towards increased adiposity with modernization. More food calories consumed than are being used & caloric excess is stored as fat. Overnutrition is a form of malnutrition. Fatness varies with genetic background, sex, age and variables such as eating, exercise, stress, smoking & socioeconomic status (including modernization (Fig. 10-5). Fat associated with chronic diseases: Cardiovascular disease, diabetes & some cancers. Lecture 8: Slide - 22

23 23. Changes in adiposity with modernization in Samoans (Fig. 10-5): weight skinfold Lecture 8: Slide - 23

24 13. References: Kormondy, E.J., & D.E. Brown Fundamentals of human ecology. Prentice Hall. 503 pp. (chapters 9 & 10). Lecture 6: Slide - 24