Environmental Health for Microbial Agents

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 diameterAcid 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 Nostoc Anabaena and Aphanocapsa

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