1. Environmental Health for Microbial Agents Environmentally transmitted infectious diseases -Water, food, fomites, vectors and air: –routes or pathways for for microbial exposure and transmission routes for infectious diseases. -A traditional and historical concern in environmental hlth. Sci. 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! Infectious disease risks from water, poor sanitation and hygiene, food and air are still with us. –A large number of households in RURAL Orange County, NC lack indoor plumbing –they have an outdoor well and a latrine (outhouse); year: 1999.

2. 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.

3. THE MICROBIAL WORLD: SIZES OF MICROBES

4. 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).

5. 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

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

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

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

9. 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

10. 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

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

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

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

14. 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

15. Cryptosporidium parvum oocysts: ~5  m diameter Acid fast stain of fecal preparation

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

17. 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

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

19. 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): ex. Schistosomes –Cestodes (tapeworms): pork and beef tapeworms

20. Transmission Infective stage: larvae –Necator americanus (hookworm) –Trichinella spiralis (trichinosis)

21. Trematodes Schistosomes (blood flukes)

23. Microbial Ecology: Colonization and the Normal Flora of the Body Microbes colonize and inhabit the environment as well as humans and other living things. -So-called "normal flora" colonize the skin, the oral cavity, the gastrointestinal tract, the upper respiratory tract (throat, nasal passages and nasopharynx), and parts of the genitourinary tract (urethra and vagina) Colonization by normal flora is often beneficial or neutral – harmful outcomes possible; can lead to disease and invasion of other parts of the body.

24. Transmission/Exposure Routes of Infectious Agents: Entry to and/or Exit From the Body Sites or Portals of Exit or Entry: Respiratory Enteric or Gastrointestinal Skin: especially if skin barrier is penetrated Genitourinary Eye

25. Routes or Methods of Entry Direct Personal Contact: Person (animal)-to-Person Indirect Personal Contact: Droplet, Fomites, Other Vehicles Water and Food (Gastrointestinal Tract) Vector-borne: often insects Intrauterine or Transplacental Organ Transplants, Blood and Blood Products