Chapter 20.2, biological hazards

Organisms that carry disease

New diseases of 20^th century -- AIDS, ebola, west nile virus, hanta virus, mad cow disease

Old diseases – malaria, tuberculosis, yellow fever, hookworm

Environment’s role in disease

Pathogens – organisms that cause infectious diseases

Spread through air or water or by a secondary host such as mosquitos, ticks, fleas

Host – an organism in which a pathogen lives for at least part of its life.

See table II of diseases causes and # of deaths per year

Waterborne disease – nearly ¾ of infectious diseases are transmitted through water

water used for drinking, waste disposal, washing

A good breading ground for pathogens

Vectors – organisms that transmit diseases to people (like mosquitoes)

Building irrigation canals and dams – more standing water – habitat for vectors

Cholera – water polluted by human feces  cholera and dysentery  lose water by diarrhea and vomiting – dehydration – cause most infant mortality around the world

Malaria – caused by a parasitic protest carried by some species of mosquito – lay eggs in stagnant fresh water.

Environmental Change and disease –

Pollutants in soil spread through soil erosion and bare feet

Antibiotic resistance – pathogens evolve to be resistant to antibiotics

Antibiotics used in livestock  resistant Salmonella, Escherichia coli and other bacteria

Grow in improperly refrigerated meat, dairy and not killed when not cooked properly

Malaria on the march – global warming  more breeding grounds for mosquitoes

Mosquitoes have also evolved resistance to pesticides – spread through N. America and Europe

Emerging viruses ­– previously unknown viruses – AIDS, hanta virus, ebola, west nile

Vaccines very specific and viruses evolve to evade vaccines effectivness

Cross Species transfer – disease transfer from one species to another

HIV and West Nile, hemorrhagic fever  hemmorage – bleeding

Influenza, flu passes to bird and back to people

May be greatest threat to human health

May be caused by destroying natural habitats