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

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Emerging pathogens and you

Emerging Pathogens and You

Maria Gallo, Ph.D.

HHMI/ICORE, June 16, 2008


Common disease organisms

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


Contributing factors

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


Contributing factors cont

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


Vibrio cholerae

Vibrio cholerae

Dr. John Snow

1853, Soho, England

Dr. Robert Koch

1884, Berlin, Germany

Filippo Pacini, Ph.D.

1854, Florence, Italy


Vibrio cholerae1

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


Salmonella enterica

Salmonella enterica

Daniel Elmer Salmón, DVM,

1885, Washington,D.C.

Dr. Theobald Smith, 1885, Washington, D.C.


Salmonella

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


Salmonella1

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


Escherichia coli

Escherichia coli

Dr. Theodor Escherich,

1885, Munich, Germany


Escherichia coli1

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


Annual cost of pathogenic e coli

Annual Cost of Pathogenic E. coli

Source: Economic Research Service, USDA, Oct. 20, 2000.


Sars severe acute respiratory syndrome

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


Plant disease bacteria 10 15 crop loss

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


Plant disease bacteria

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


Plant disease bacteria1

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


Plant disease fungi

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


Plant disease fungi1

Plant Disease Fungi

  • Toxic Fungus: Aspergillusflavus

    • corn, peanut, and others

    • aflatoxin

      • potent carcinogen


Plant disease fungi2

Plant Disease Fungi

  • Rusts: most destructive

    • famines, economic depression

    • cereals: harms growth and seed

Puccina species

Courtesy Clemson University Cooperative Extension


Plant disease fungi3

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


Plant disease fungi4

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


Plant disease fungi5

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


Plant disease viruses

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


Disease viruses

Disease Viruses


Plant disease viruses1

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


Plant disease viruses2

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


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