Transcript 09/14/07

Environmental Transmission of
Pathogenic Microbes – why they
are where they are when they are
Dr. Julie Ann Kase
Public Health Scientist – Bioterrorism and
Emerging Pathogens Unit
NC State Laboratory of Public Health
[email protected]
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1976 Legionnaires' disease
Outbreak of pneumonia occurred among persons attending a convention of the
American Legion in Philadelphia
– ~ 8,000 to 18,000 cases in the US each year; 5% to 30% die
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1981 AIDS
– report in MMWR of 5 CA men with severe immunodeficency (1983 HIV recovered
from lymph node)
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1993 Cryptosporidiosis
– 400,000 people sick and killed more than 100
– worst waterborne disease outbreak in the United States
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1995 Ebola Hemorrhagic Fever
– Ebola Virus initial recognition in 1976
– Occurred in Kikwit and surrounding area
– 315 cases 81% death of cases
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2002 (November) Severe acute respiratory syndrome (SARS)
– Viral respiratory illness that was recognized as a global threat in March 2003
– first appearing in Southern China in November
– November 2002 - July 2003, a total of 8,098 people worldwide became sick; 774
died
– By late July 2003, no new cases, and WHO declared the global outbreak to be over
•
Late 2003 and Early 2004 Avian influenza
– Outbreaks of influenza H5N1 occurred among poultry in eight countries in Asia
(Cambodia, China, Indonesia, Japan, Laos, South Korea, Thailand, and Vietnam)
– By March 2004, the outbreak was reported to be under control until late June 2004
– Human infections (H5N1) have been reported in Thailand, Vietnam and Cambodia
E. coli O157:H7 Outbreak Case
Counts by State
(As of October 6, 2006)
www.cdc.gov
Seek and Ye Shall Find
• Environmental Transmission
– Presence
• Cover our planet
– Several 100m deep in glacial ice sheets
– Deep-ocean thermal vents
– Survival and transport
• Media
– Water
– Soil
– Air
• Natural fate + influence of man’s actions
Microbial Survival in the Environment
Pathogen survival
• Differs widely among microbes:
– Bacteria:
• Spores survive better than vegetative cell
– Viruses:
• non-enveloped viruses survive better than enveloped viruses under
most environmental conditions
– Envelopes are relatively fragile compared to outer capsids (protein
coats)
– Parasites:
• protozoan (oo)cysts and spores and helminth ova survive better than
active life stages of these parasites or than those with no resting or
special environmental forms
– Fungi:
• spores survive better than other forms
Environmental Factors Influencing Survival
or Proliferation of Infectious Agents
• Temperature
– Greater inactivation/death rates at higher temps
– Environmental temperatures influence pathogen spread by insect
vectors
• pH
– Extreme pH inactivates microbes
– Important exceptions: enteric pathogens survive pH 3.0
• Moisture content
– Drying or low moisture inactivates /kills some microbes
– Ex. Preserving food by desiccation
• Sunlight (UV)
– Nucleic acids absorb the UV energy and is damaged
Environmental Factors Influencing Survival
or Proliferation of Infectious Agents
• Pressure (atmospheric & hydrostatic)
– Typical atmospheric pressure
– Use of high hydrostatic pressure in shellfish
• Weather
– Microbes levels may increase or decrease
– Warmer weather increases some microbes (ex. Vibrio bacteria in NC
coastal waters during warmer months) and vectors, like mosquitoes
– Wet weather carries microbes also resuspension in water resources
• Chemicals & nutrients
– Levels influence microbe survival
– Ex. Lack of nutrients (e.g. carbon, nitrogen) will limit proliferation
• Biological factors
– Predation, vectors, reservoirs (animals), microbe species/type
Environmental Transmission of Pathogenic
Microbes : Water, Soil, Air
• Microbes can be found anywhere in which water
is maintained in a liquid state
• Most human illness associated with water –
infectious, usually acute in nature but some have chronic
sequelae (e.g. stomach cancer (Helicobacter pylori),
myocarditis & diabetes (coxsackieviruses))
• Highly effective means of introducing an
infectious microbe to a large population
– Person-to-person not efficient in reaching a large
population
Environmental Transmission of Pathogenic
Microbes : Water, Soil, Air
Reservoirs for pathogenic microbes found in water:
humans, animals, environment
– Source tracking
– Human sources – important contributor of pathogens in
water
• Recreational activities (e.g. water theme parks)
• Domestic wastewater
– Discharge of wastewater into surface waters
– Aquifer contamination
Infectious Disease Water Transmission
Model
Environmental Transmission of Pathogenic
Microbes : Water, Soil, Air
Microbial agents associated with waterborne
diseases
– Enteric, non-enteric,and aquatic bacteria
– Enteric viruses
– Enteric protozoa
Environmental Transmission of Pathogenic
Microbes : Water, Soil, Air
Enteric bacteria
– Shigellosis: Shigella spp. (classical bacillary dysentery)
• occur around the world, with most victims being children in
developing countries
• 18,000 cases of shigellosis are reported in the United States
• Shigella dysenteriae type 1 – deadly epidemics in dev. world
• Spread can be via vector, food, water, and fomites
– Cholera: Vibrio cholerae serogroup O1 or O139 (1992) that
produces toxin
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Endemic poverty, summer rains, poor health & living conditions
56 countries, 101,383 cases (2345 deaths) in 2004
Africa - 94% cases in 2004
Easily treatable
– Infectious dose variable: usually high - 102 to 108 orgs
Environmental Transmission of Pathogenic
Microbes : Water, Soil, Air
Aeromonas hydrophila
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Commonly found in water but recently implicated as a cause of
GI illness, also wound infection
Potential to grow in water distribution systems, especially in
biofilms, where it may be resistant to chlorination
EPA list (candidate contaminant list) for drinking water
Legionella pneumophila
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Ubiquitous in water, aerosol transmission
Proliferate at high temperatures (hot water systems, cooling
towers and evaporative condensers)
Etiologic agent of Legionnaires’disease, Pontiac fever
Leptospira spp.
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Species not enteric or aquatic - Urine from dom. & wild animals
Outbreak during Eco-Challenge - grueling 2-week contest in late
Aug and early Sept [2000]
Leptospirosis
• Reports of outbreaks occurring following
flooding, tropical storms, hurricanes – all can
increase the exposure to contaminated water
• Asymptomatic, high fever, severe headache,
muscle aches
• LA- found in cattle, skunks, rodents
• Most common in tropic climates
• 1965-1993 incidence rate in LA = 1-14/100,000
people per year
Environmental Transmission of Pathogenic
Microbes : Water, Soil, Air
Enteric viruses
– Generally more persistent than enteric bacteria but can
not multiply in environment
– Survival influenced by physical, chemical, and
microbial factors as well as virus type
• Non-enveloped viruses most persistent – protein coat offers
stability and resistant barrier to stressors
• Majority of enteric viruses are non-enveloped
– Require more sophisticated detection methods
• Tissue cultivation, electron microscopy, molecular techniques
(e.g. PCR, nucleic acid hybridization)
• Limit microbe ID from clinical & environmental samples
• Distinguish between infectious/non-infectious - MAYBE
Environmental Transmission of Pathogenic
Microbes : Water, Soil, Air
– Implicated in majority of AGI outbreaks in US based
upon clinical & epidemiological evidence
• Rotavirus - the virus is stable in the environment, transmission can
occur through ingestion of contaminated water, global problem
• Norovirus - Among the 232 outbreaks of illness reported to CDC
from July 1997 to June 2000, 3% were waterborne; in 23% of
outbreaks, the cause of transmission was not determined
– Infectious dose: typically low, maybe 1 to 10 infectious
units
– Developing countries: Rotaviruses, Hepatitis A virus,
Hepatitis E virus
Environmental Transmission of Pathogenic
Microbes : Water, Soil, Air
Proposed EPA drinking water contaminant list
• The Safe Drinking Water Act directs that periodically publish a
CCL
• 2003 - regulatory determinations for nine contaminants from
the first CCL (60 contaminants in March 1998)
• Summer of 2005 - second cycle of preliminary regulatory
determinations - continue research on the list of contaminants
on the first CCL
• Make final regulatory determinations
– Adenoviruses
– Noroviruses
– Coxsackieviruses
– Echoviruses
“Payment Intervention Studies”: References
• Payment P., et al, (1991). A Randomized Trial to Evaluate the
Risk of Gastrointestinal Disease due to Consumption of
Drinking Water Meeting Current Microbiological Standards.
American Journal of Public Health 81 (6) 703-708.
• Payment P., et al (1997). A prospective epidemiological study
of gastrointestinal health effects due to the consumption of
drinking water. International Journal of Environmental Health
Research. 7(1). 1997. 5-31
Environmental Transmission of Pathogenic
Microbes : Water, Soil, Air
Payment et al. intervention studies
Wanted to know risk of GI illness associated
w/consumption of municipal drinking H2O
– Municipal H2O source = river polluted with human
sewage
– 1st study: 606 households; ~half had RO filters, others
no intervention; 15mo
• 35% higher rate of GI symptoms households w/o intervention;
symptoms & serologic evidence pointed to enteric viruses
– 2nd study: 1400 households; 3 groups w/tap H2O, 1
group purified bottle H2O; 16 mo
• ~20% more GI illness in tap H2O consumers
Environmental Transmission of Pathogenic
Microbes : Water, Soil, Air
Enteric protozoa
– Recently recognized as water borne pathogens
– Thick-walled protozoan cysts and oocysts are
environmentally resistant
– Recovery and detection technically challenging
• Filtering liters of water
• Immunofluorescence microscopy
• May not distinguish between nonviable/viable orgs
– Infectious dose is low
• C. parvum ~ 100 oocysts
Environmental Transmission of Pathogenic
Microbes : Water, Soil, Air
Enteric protozoa (cont.)
– Ex. Cryptosporidium, Giardia
• Size: Cryptosporidium oocysts (4-6 µm) Giardia cysts (7-14 µm)
• Animal reservoirs
• Size limits movement thru soil, thus surface waters contamination
mostly (esp. unfiltered)
• Greater than half of 300 surface water supplies in US contained
Cryptosporidium oocysts
– Ex. Toxoplasma gondii
• Matures only inside cats and spreads through their feces
• Lethal parasite that has infected or killed hundreds of California sea
otters
• Parasite can concentrate inside clams and other bivalves, favorite of
otters
• Flushable cat litter, affecting the ecosystem, including the clams that
otters eat
Environmental Transmission of Pathogenic
Microbes : Water, Soil, Air
Other aquatic microbes
• Cyanobacteria – algal blooms, dermatitis
• Naegleria fowleri – meningoencephalitis, usually fatal
– small, free-living ameba that occasionally infects humans and other
mammals
– 2003 case in North Carolina
• Acanthamoeba species – subcutaneous abscesses, conjunctivitis
– Contact lens wearers, EPA published warning: Acanthamoeba Guidance
Document EPA-822-B-04-001
– EPA determined not to regulate because “regulation would not present a
meaningful opportunity for health risk reduction”
• Schistosoma species – dermatitis, swimmer’s itch
– Debilitating (liver and intestinal damage) illness that results from infection of the
blood with a parasitic flatworm (schistosome)
– Found in Asia, Africa, and South America, especially in areas with water that is
contaminated with fresh water snails, which contain the parasite
Environmental Transmission of Pathogenic
Microbes : Water, Soil, Air
Categories of water-related infectious hazards
– Waterborne
– Water contact
– Water related
– Water washed
Environmental Transmission of Pathogenic
Microbes : Water, Soil, Air
Waterborne
– Physical contact w/microbially contaminated
H2O
– Bathing, recreational activities, ingesting water
(also ice)
– Example: cholera
Environmental Transmission of Pathogenic
Microbes : Water, Soil, Air
Water Contact
– Infections caused by aquatic
organisms
• Pathogenic
microorganisms or
macroorganisms (worms)
• Naturally spend part of life
cycle in aquatic envr or
within a host that resides
in water
– Ingestion or immersion in
water
– Example: Schistosomiasis
Environmental Transmission of Pathogenic
Microbes : Water, Soil, Air
Water Related
– Disease as a consequence of
being bitten by an
invertebrate vector whose
life cycle requires access to
H2O
– Influences of season, rain
events (monsoon, flooding)
– Example: Malaria (parasite)
and yellow fever, west nile
infection (viruses)
Environmental Transmission of Pathogenic
Microbes : Water, Soil, Air
Water Washed
– Infections associated
with inadequate
hygiene
– Eliminate hazard by
using microbe-free
water for cleaning of
eating and cooking
utensils, plates, self,
etc.
– Example: Shigellosis
Environmental Monitoring of Pathogenic
Microbes : Water, Soil, Air
• Improve microbiological water quality,
reduce diarrhea morbidity and mortality
associated with waterborne disease
• Standards for water quality
– EPA
– World Health Organization (WHO)
• Total and fecal coliforms
Environmental Monitoring of Pathogenic
Microbes : Water, Soil, Air
Methods to measure water quality
– Accurate and reproducible
– Rapid
– Relatively simple techniques, applicable to
most laboratories
– Common reagents, inexpensive
Environmental Monitoring of Pathogenic
Microbes : Water, Soil, Air
Detection of infectious agents in water
– Many are difficult to detect/quantify
• May require expensive equipment
• Complex techniques – specialized reference
laboratories
– Newly recognized agents, methods are still
being developed
– Pathogen occurrence surveys and special
studies
Environmental Monitoring of Pathogenic
Microbes : Water, Soil, Air
Detection of infectious agents in water
– Laboratory investigations of disease outbreaks
often never detect the etiologic agent
• Contamination was temporary (e.g. problem was
discovered and fixed before investigation)
• Microbe died off or flushed away
• Sensitivity/specificity of methods
• Size of event
Environmental Monitoring of Pathogenic
Microbes : Water, Soil, Air
Detection of infectious agents in water
– Microbial Indicator Organism
• Traditional approach to protect/assess the "sanitary"
quality of water (food) with respect to fecal
contamination
• Quantify bacteria commonly present in intestines of
warm blooded animals; surrogates for pathogens,
especially bacterial
• May not be reliable indicators of viruses and
parasites
Environmental Monitoring of Pathogenic
Microbes : Water, Soil, Air
Criteria for an Ideal Indicator of Fecal Contamination
• Applicable to all types of water (and other relevant samples)
• Present in feces, sewage and fecally contaminated samples when
pathogens are present; numbers correlate with amount of fecal
contamination; outnumber pathogens
• No "after growth" or "regrowth" in the environment
• Survive/persist > than or = to pathogens
• Easily detected/quantified by simple lab tests in a short time
• Constant characteristics
• Harmless to humans and other animals
• Numbers in water are associated with risks of enteric illness in
consumers (dose-response relationship)
Environmental Monitoring of Pathogenic
Microbes : Water, Soil, Air
The Quest for The Ideal Indicator(s)
• No single indicator (so far discovered) meets all of
the criteria of an ideal indicator
• It is unlikely that a single organism or (taxonomic)
group will meet all of the indicator criteria when
applied to viruses, bacteria and parasites
• Current microbial indicator criteria do not address
those pathogens that are not associated with fecal
contamination
Environmental Monitoring of Pathogenic
Microbes : Water, Soil, Air
Current and Candidate Bacterial Indicators of Fecal
Contamination
• Total coliforms: standards for drinking, bathing and shellfish
harvesting waters; not feces-specific (environmental sources)
• Fecal ("thermotolerant") coliforms: ditto for total coliforms
• E. coli: the "fecal" coliform; may occur naturally in tropics
• Fecal streptococci: another group of enteric, fecally excreted bacteria;
not feces-specific (environmental sources)
• Enterococci: Streptococcus faecalis and S. faecium; a sub-set of the
fecal streptococci considered more feces-specific; EPA guide-line for
bathing water quality used as standards in some states
• Clostridium perfringens: anaerobe; ?feces-specific?; very (too?)
resistant spores; candidate indicator for protozoan cysts
Environmental Monitoring of Pathogenic
Microbes : Water, Soil, Air
Microbial Indicators of Fecal Contamination and Treatment
Efficacy for Enteric Protozoan Pathogens
• Clostridium perfringens spores may be useful indicators of enteric
protozoan parasites
– Plentiful in feces, raw sewage, treated effluents and receiving
waters and soils
– Spores of aerobic bacilli (Bacillus spp.) may be useful indicators of
water treatment efficacy
– Plentiful in water and other environmental media
– But, not feces-specific
– Spores are reduced less than are conventional vegetative indicator
bacteria by water and sewage treatment processes
– Spores of C. perfringens and Bacillus spp. superficially resemble
enteric protozoan parasite cysts and oocysts
Environmental Monitoring of Pathogenic
Microbes : Water, Soil, Air
CANDIDATE VIRAL INDICATORS OF FECAL CONTAMINATION
OF WATER
Coliphages: viruses (bacteriophages) infecting E. coli and perhaps other
coliforms; attach directly to cell wall (somatic) heterogeneous group;
may not be feces-specific; host-dependent detection.
Male-specific (F+) coliphages: coliphages infecting "male" strains of E.
coli (posses pili); may be feces-specific.
May distinguish human from animal fecal contamination by group
classification (II & III human; I & IV animal);
but, pigs may harbor groups II & III, too.
Bacteroides fragilis phages: may be human feces specific; USA studies
do not show human-specificity; concentrations too low.
Salmonella phages: in human and animal feces; may indicate presence of
Salmonella bacteria; concentrations too low.
Cary residents told to boil water (Aug 18, 2006)
http://rdu.news14.com/content/story_links/?ArID=89457&SecID=231
Town of Cary Press Release
CARY, N.C. -- Officials told the approximately 100,000 residents of the
Wake County town of Cary to boil their water and they closed restaurants
because fecal coliform was found Friday in a sample from one home.
Results of the Town of Cary’s routine sampling and testing of its water
supply has revealed the presence of E. coli on Coronado Way in the
Coronado Village subdivision in central Cary.
Water Contamination In Cary Costs Restaurants Millions
August 22, 2006
http://www.wral.com/apncnews/9718848/detail.html
CARY, N.C. -- The restaurant shutdown ordered here over the weekend after
E. coli was found in the water supply may have cost owners and
employees some $6 million. Health officials ordered the town's 115,000 residents
To boil tap water and forced restaurants to close Friday night
after the bacteria was detected.
Cary has 'weird' water mix-up
News and Observer July 25 2007
"In a place like Cary, it never even occurred to me that this might even be a possibility,"
Vinay Jain said Tuesday as Cary workers walked through his house testing taps.
"This gives the impression of a Third World country.
At least in India, we knew the water was bad, and we boiled it."
Cary Families' Faucets Delivered Treated Wastewater
www.wral.com July 25 2007
N.C. family drinks lawn water for 5 months
www.sciencedaily.com July 26 2007
Environmental Monitoring of Pathogenic
Microbes : Water, Soil, Air
Sources of drinking water
• Surface water
– Widely used as a supply for municipal DW
– Need to protect from sources of contamination (land
run-off, wildlife, recreational activities)
• Ground water
– Comprises 95% of water serving rural populations in
US (>100 million people)
– Assumed that soil will filter out most microbes
– Rarely are private wells treated, also public H2O supply
Environmental Monitoring of Pathogenic
Microbes : Water, Soil, Air
• Traditionally, more than half waterborne
disease outbreaks – groundwater responsible
– From 1997-98 15/17 (88%) reported outbreaks
- groundwater responsible
– Most common pathogens identified = Shigella
spp. and Hepatitis A virus
– 2/3 of the time no etiologic agent identified
Environmental Transmission of Pathogenic
Microbes : Water, Soil, Air
Ground water recharge• Lack of water in arid SW US has prompted actions such as
the land application or injection of treated wastewater to
recharge subsurface aquifers
• Movement of viruses (small size=greatest potential to be
transported) thru soil mostly studied
– In one study, indigenous enteroviruses were found in 9m deep
well, 14m from recharge basin
– Movement of larger microbes (bacteria and protozoans)
theoretically less