Environmental Health Microbiology ENVR 421

1. Environmental Health MicrobiologyENVR 421 Lecture 1 Mark D. Sobsey

2. Microbes and the Environment • Microbes are fundamental and essential to life on earth • Most microbes in the environment are harmless or beneficial • A small proportion of microbes are capable of causing disease in humans and/or other hosts • Some are “frank” pathogens and almost always have the potential to cause illness • Others are “opportunistic” pathogens and only cause illness in compromised hosts or unusual conditions of exposure • Yet others are capable of causing illness when they get into parts of the body by unusual circumstances that are normally unavailable to microbes (e.g., into deep tissues via wounds) • Microbes are almost everywhere on the planet and the more we look the more places we find them

3. Routes or Pathways of Exposure for Environmentally Transmitted Infectious Diseases • Water • Wastes • Food • Fomites • Vectors • many human pathogens have animal reservoirs; zoonoses • Air • Soil • Sediment

4. Pathogen-Human/Animal-Environmental Relationships • Many human pathogens are potentially transmitted by multiple environmental routes • Some pathogens exist in the environment independent from human hosts • their existence and perpetuation is not dependent on human or (for some) even animal hosts • Other pathogens depend exclusively on human for their existence and perpetuation • Viruses: smallpox (Variola) virus (eradicated); poliovirus • Bacteria: Shigella spp.; Salmonella typhi • Parasites: Ascaris lumbricoides (round worm)

5. History of Microbiology and Infectious Diseases: Role of Water in Cholera Transmission - London • Water, wastes and microbes are traditional/historical concerns • Sir John Snow: cholera in London and the Broad Street pump • A key historical event in environmental health, epidemiology, infectious disease, water hygiene, environmental engineering and GIS: he did it all! • Developed a population-based approach to track the spread of cholera in individual London boroughs; source was unknown • Plotted the distribution of reported cases on a map • In one London borough the source was water polluted by sewage, which entered the Thames above the water intake. • In another it was one water pump • Snow ordered the handle to be removed from the "Broad Street Pump“; locally the epidemic subsided. • Explained the etiology of cholera and the mechanism of its transmission via contaminated water.

6. Sir John Snow and his Maps of the Water Plants of London http://www.ph.ucla.edu/epi/snow.html#BROAD

7. Sir John Snow’s 1854 Map of the Broad Street Pump Outbreak Cholera cases, each marked by a hash, were clustered around the Broad Street Pump and were associated with drinking water from this pump

8. Microbiology and Infectious Diseases • Infectious disease risks from water, poor sanitation and hygiene, food and air are still with us in the developed and developing world • Global Water Supply and Sanitation Assessment 2000 • 2.4 billion people have inadequate sanitation • 1.1 billion people have inadequate/unsafe water • 4 billion cases of diarrhea every year • 2.2 million deaths from diarrheal disease every year • Most illness and death in children <5 years old • Less services in rural than in urban areas • Urban settlement/slums remain a problem • In the developing world wastewater treatment is rare • Water losses in large urban systems is typically 40% • Millennium Development Goals call for halving by 2015 the number of people lacking sustained access to safe water • a key goal for reducing World poverty

9. Global Burden of Infectious Diarrheal Disease and the Role of Water • Burden of infectious diarrhea is higher in developing than in developed countries • Developed: 1 illness per person per year • Undeveloped: about 5 illnesses per person per year • The attributable fraction of diarrheal illness for different exposure routes or sources may not be very different in developed versus developing countries: • 1/4th contact • ¼ water • ¼ food • 1/4 other • Most waterborne disease is caused by microbes – not chemicals

10. Classes or Categories of Pathogenic Microorganisms:The Microbial World Viruses: smallest (0.02-0.3 µm diameter); simplest: nucleic acid + protein coat (+ lipoprotein envelope) Bacteria: 0.5-2.0 µm diameter; prokaryotes; cellular; simple internal organization; binary fission. Protozoa: most >2 µm- 2 mm; eucaryotic; uni-cellular; non-photosynthetic; flexible cell membrane; no cell wall; wide range of sizes and shapes; hardy cysts Groups: flagellates, amoebae, ciliates, sporozoans (complex life cycle) and microsporidia. Helminths (Worms): multicellular animals; some are parasites; eggs are small enough (25-150 µm) to pose health risks from human and animal wastes in water.

11. THE MICROBIAL WORLD: • SIZES OF MICROBES

12. Viruses • smallest (0.02-0.3 micrometers diameter • simplest (nucleic acid + protein coat (+ lipoprotein envelope) • spherical (icosahedral) or rod-shaped (helical) • no biological activity outside of host cells/or host organisms • obligate intracellular parasites; recruit host cell to make new viruses, often destroying the cell • non-enveloped viruses are most persistent in the environment • protein coat confers stability • enteric viruses are most important for environmental health • transmitted by direct and indirect contact, fecally contaminated water, food, fomites and air. • respiratory viruses also important • transmitted by direct and indirect contact, air and fomites (some by water and food, too).

13. ENTERIC VIRUSES: ~25-100 nm diameter Nucleic acid + protein coat (+envelope) • Nucleic acid: • DNA or RNA • single or double-stranded • 1 or several segments • Capsid (protein coat): • multiple copies of 1 or more proteins in an array • Envelope: • lipid bilayer membrane + glycoproteins) • typically acquired from host cell membranes

14. Enteroviruses: ~27-30 nm diameter; single-stranded RNA; icosahedral protein coat (capsid)

15. Human Rotavirus: ~75 nm diameter; double-layered capsid; double-stranded, segmented RNA

16. ADENOVIRUSES: ~80 nm diameter; double-stranded DNA; protein coat with attachment fibers

17. Procaryotes: Bacteria and Others Cellular organisms Simple internal organization Multiply by binary fission Diameter ~0.5-1.0 micrometer Envelope: cytoplasmic membrane, cell wall & capsule (polysaccharide) Some have appendages: flagella: for locomotion pili: • attachment to other cells for genetic transfer; • virus receptor site

18. Pathogenic Bacteria Pathogenic bacteria possess virulence properties in the form of structures or chemical constituents that contribute to pathophysiology • Outer cell membrane of Gram negative bacteria: endotoxin (fever producer) • Exotoxins Pili: for attachment and effacement to cells and tissues Invasins: to invade cells Some bacteria make spores: • highly to physical and chemical agents and • very persistent in the environment Enteric and respiratory bacteria are important in environmental health

19. Escherichia coli cells: ~0.5 x 1.0 micrometers Typical rod-shaped bacteria: fecal indicator and pathogenic strains

20. Procaryotic Cell (left) and Eucaryotic Cell (right)

21. Unicellular Eucaryotes: The Protists • Complex internal organization: • organelles: nucleus, mitochondria, etc. • Wide range of sizes; 2 micrometers and larger

22. Protozoa • Important group of protists for environmental health • Uni-cellular; non-photosynthetic; flexible cell membrane; no cell wall • Wide range of sizes and shapes; 2 micrometers to 2 mm • flagellates • amoeba • ciliates • sporozoans (complex life cycle) • microsporidia

23. Cryptosporidium parvum oocysts: ~5 m diameterAcid fast stain of fecal preparation

24. Giardia lamblia: flagellate protozoan parasite Giardia lamblia cyst: ~10 x 8 micrometers

25. More Protists: Fungi • Fungi (yeasts and molds): • non-photosynthetic • immotile; • rigid cell wall • Molds: • grow as branched, interlacing chains or filaments (hyphae) called mycelia • Yeasts: • do not form mycelia • grow as single cells that bud • sexual reproduction possible Mitospores (conidia) of Penicillium, one of the asexual Ascomycota Yeasts

26. More Protists: Algae • Photosynthetic • Rigid cell wall • Wide range of sizes and shapes • 2 micrometers and larger Nostoc Anabaena and Aphanocapsa

27. Helminths (Worms) • Multicellular animals • Some are human and/or animal parasites • Eggs are small enough to pose environmental health problems from human and animal excreta in water, food, soil, etc. • Several major groups: • Nematodes (roundworms): ex. Ascaris • Trematodes (flukes; flatworms): ex. Schistosomes • Cestodes (tapeworms): pork and beef tapeworms • Most helminthic disease is not waterborne, but it is associated with water contact, food, and exposure to fecal wastes and fecally contaminated soil.

28. Roundworm: Ascaris lumbricoides

29. Roundworms: Hookworms

32. Recommended Readings • Relevant material in any microbiology text • Indicators for Waterborne Pathogens, National Research Council, National Academy of Sciences, National Academy Press, Washington, DC, 2004. • Chapters 1, 3 and 4 • Water Quality: Guidelines, Standards and Health. 2001. L. Fewtrell and J. Bartram, eds., IWA Publishing, London, for WHO, Geneva. • Chapter 4, 5 and 13 • Assessing microbial safety of drinking water: Improving approaches and methods, 2003. A. Dufour, M. Snozzi, W. Koster, J. Bartram, E. Ronchi and L. Fewtrell, eds., IWA Publishing, London for WHO, Geneva. • Chapters 1, 2 and 8