Emerging Pathogens and You

1. Emerging Pathogens and You Maria Gallo, Ph.D. HHMI/ICORE, June 16, 2008

2. Common Disease Organisms • bacteria, fungi, viruses • can be host specific or have a broad host range (more difficult to control) • > 250 known water-, soil-, and foodborne human diseases

3. Changes in Human Demographics and Behavior Increasing numbers of people susceptible to infections with specific potential pathogens Rural urbanization allows infections to arise in isolated rural areas Decay of basic sanitation practices Contributing Factors

4. Contributing Factors, Cont. • Breakdown of Public Health Measures • Pathogens reemerge when classic measures breakdown • Microbial Adaptation • Microbes change in virulence and toxin production • Changes in Agricultural Practices • Increased river and stream pollution by agricultural waste and runoff

5. Vibrio cholerae Dr. John Snow 1853, Soho, England Dr. Robert Koch 1884, Berlin, Germany Filippo Pacini, Ph.D. 1854, Florence, Italy

6. Symptoms toxins lead to watery diarrhea symptoms within hours Transmission contaminated water, food (fish, shellfish), swimming feces of asymptomatic and sick human carriers no person-to-person transmission Infectious Dose (in healthy adults) 108-1011 cells antacids = more susceptible to infection Survival Outside Human Hosts biofilms; zooplankton, shellfish viable non-culturable state Vibrio cholerae

7. Salmonella enterica Daniel Elmer Salmón, DVM, 1885, Washington,D.C. Dr. Theobald Smith, 1885, Washington, D.C.

8. Salmonella • WHO: 1,400,000 instances of salmonellosis in the US • Salmonella cost per year US $3,000,000,000 • 2,300 serotypes • wide host range (humans, cattle, chickens (eggs),horses, rodents, cats, dogs, birds, reptiles, etc.) • Multi-drug resistant S.e.Typhimurium DT104 • Most common diseases caused by Salmonella: • gastroenteritis (self-limiting, 2-5 days) • enteric/typhoid fever (incubation 1-10/7-14 days, lasts 2-3 wks) • septicemia (incubation12-36 hrs, may lead to chronic infection) • symptoms and disease manifestation differ in hosts

9. Most “commonly-used” bioterrorism agent 1939 - Japanese Imperial Army contaminated rivers on the Manchurian border 1972 - “Order of the Rising Sun” obtains S. Typhi to contaminate water supplies in the Midwest 1984 - Rajneesh Cult. Successfully contaminates restaurants in Dalles, OR in an attempt to thwart local elections Salmonella

10. Escherichia coli Dr. Theodor Escherich, 1885, Munich, Germany

11. Escherichia coli • Normal flora of human GI • Uropathogenic E. coli. 90% of all UTI • Enterovirulent E. coli serotypes • Enteroinvasive E. coli (EIEC) • Enterohemorrhagic E. coli (EHEC=VTEC) O157:H7. Bloody diarrhea. Hemolytic Uremic Syndrome (HUS) • Enterotoxigenic E. coli (ETEC). Travelers diarrhea (cholera-like) • Enteropathogenic E. coli (EPEC). Diarrhea in newborn nurseries. • Enteroaggregative E. coli (EAggEC). Acute and chronic diarrhea in children

12. Annual Cost of Pathogenic E. coli Source: Economic Research Service, USDA, Oct. 20, 2000.

13. Agent: SARS coronavirus Global epidemic: Between November 2002 and July 2003, 8,096 known infected cases and 774 deaths Positive-strand, enveloped RNA viruses Pathogens of mammals and birds: cause enteric or respiratory tract infections http://www.cdc.gov/niosh/topics/SARS SARS: Severe Acute Respiratory Syndrome

14. Plant Disease Bacteria: 10-15% Crop Loss • Spots: fruits, leaves or stems • decrease photosynthesis • disfigure fruit Xanthomonas Spot on tomato fruit Courtesy Clemson University Cooperative Extension

15. Plant Disease Bacteria • Softrots • enzymes produced by the bacteria cause tissue to become soft and liquid • post-harvest loss Erwinia species on potato Courtesy UC Davis IPM Program

16. Plant Disease Bacteria • Wilts • clog conductive tissue so that water and minerals cannot get from roots to leaves Bacterial wilt on a tomato plant Courtesy Carlos A. Lopes, EMBRAPA, Brazil

17. Plant Disease Fungi • Can have devastating losses • produce toxin, secrete a slime, attack seedlings at germination, dead spots • Microscopic or larger (molds, mushrooms, yeast) • 100,000 known species • most live on dead organic matter which they help decompose • >8,000 cause plant disease

18. Plant Disease Fungi • Toxic Fungus: Aspergillusflavus • corn, peanut, and others • aflatoxin • potent carcinogen

19. Plant Disease Fungi • Rusts: most destructive • famines, economic depression • cereals: harms growth and seed Puccina species Courtesy Clemson University Cooperative Extension

20. Plant Disease Fungi • Blights: e.g. Southern corn leaf blight • 1970: destroyed 15% of US corn crop, billions $$$ lost Cochliobolus species Courtesy Clemson University Cooperative Extension

21. Plant Disease Fungi • Blights: e.g. Late blight of potato • 1846: great potato famine in Ireland • entire crop wiped out in 1 week • >1 million deaths • initiated emigration to the US • 4 to 8 million people in 10 years Phytophthorainfestans Courtesy Univ. of Minn. BlightCast Courtesy Univ. of Minn. BlightCast

22. Plant Disease Fungi Claviceps purpurea on Millet head • Blights: Ergot of grains • Salem witch trials (rye ergot) • forms hallucinogenic drugs in bread • crazy behavior, “bewitched” (stoned) • Black plague • can be poisonous Courtesy CGIAR-ICRISAT

23. Plant Disease Viruses • Smallest infectious agents • electron microscope to see them • not cells, but RNA or DNA wrapped in a coat of protein • few genes, few proteins produced • replication • coat protein • movement

24. Disease Viruses

25. Plant Disease Viruses • Parasitic • only reproduce in living cells • weakens the host • Many are vectored (delivered) by insects • aphids, thrips, leafhoppers, whiteflies • probing mouth parts

26. Plant Disease Viruses • Tomato Spotted Wilt Virus (TSWV) • thrips vectored, wide host range • huge threat to peanut production TSWV on Tomato fruit TSWV on a Peanut Leaf Courtesy SWEAT Courtesy Clemson University IPM Program