Waterborne Diseases: Linking Public Health and Watershed Data

1
Waterborne Diseases Linking Public Health and
Watershed Data

• Debalina Das1 Sarah M. Dorner2,3
• 1Department of Public Health, 2Massachusetts
  Water Resources Research Center, 3Department of
  Civil and Environmental Engineering
• University of Massachusetts Amherst

2
Outline

• Introduction
• Research Objectives
• Case Studies Blackstone River Watershed,
  Merrimack River Watershed, Deerfield River
  Watershed
• Results and Discussion
• Conclusions

3
Introduction

• Microbial contamination in water continues to be
  a public health concern
• Drinking water
• Irrigation water
• Recreational water
• Zoonotic pathogens are of increasing concern
• Three fourths of the emerging infectious diseases
  are zoonotic
• impacts on human health and agricultural
  production

4
Introduction Cont.

• Etiology of waterborne disease outbreaks in the
  United States (1991-2002)

From Craun et al. (2006) Journal of Water and
Health
5
Introduction Cont

• The level of water treatment necessary is based
  on raw water quality
• The standard for microbial contaminants in
  treated drinking water is zero (EPA, 2006)
• Raw water quality can be highly variable
• Knowledge of sources of contamination necessary
  for implementing effective mitigation strategies
• Reliable data on pathogen occurrence in
  watersheds are often limited

6
Introduction Cont..

• Weather is often a factor in waterborne disease
  outbreaks
• Waterborne disease outbreaks have been associated
  with intense precipitation events
• A statistically significant association between
  rainfall and disease in the United States 51
  of waterborne disease outbreaks (P0.02)
  (Curriero et al., 2001)
• Climate information recommended for early warning
  systems for epidemics
• In the Northeastern US, predictions of future
  climate include increased precipitation
• Possibility of an increased risk of waterborne
  illnesses associated with heavy precipitation

7
Exposure to Pathogens from Rivers

• Bacteria are a major source of river water
  quality impairment, but public health
  consequences typically unknown
• Rivers are used for recreation
• Examples of municipal water supplies from rivers
  
• Delaware and Schuylkill Rivers - Philadelphia
• Merrimack River Lawrence, Lowell, Methuen and
  Tewksbury, MA

8
Environmental Factors

• Land use and watershed protection measures
  important for microbial risk assessment.
• Urban land use may be associated with pathogen
  contamination events
• Aging municipal infrastructure potentially an
  important contributor to pathogenic contamination
• e.g. Lowell, MA - 9 combined sewer overflows
  located upstream of drinking water intake
• 772 cities in the U.S (4) have combined sewer
  overflow systems (CSOs)
• Intensive livestock farming has also been
  associated with increased densities of pathogens
  in water and higher human risk of disease

9
Other Pathways of Exposure to Pathogenic
Microorganisms

• Travel to other regions of the world
• Human to human transmission
• Pet to human transmission
• Food

10
Research Objectives

• To examine public health data from Massachusetts
  to determine if a link exists between waterborne
  diseases and watershed conditions
• To improve estimates of exposure to pathogens
  given watershed conditions.
• To develop a pathogen vulnerability index for
  Massachusetts watersheds

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Research Objectives Cont

• To determine and explain any seasonal trends in
  confirmed human cases of Giardia infections
• To determine the impact of land use (urban versus
  rural) or the presence of Combined Sewer
  Overflows (CSOs) on the frequency of reported
  confirmed Giardia cases on watershed basis.
• To examine the relationships between
  precipitation, streamflow, watershed
  characteristics and confirmed human cases of
  Giardia

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Hypotheses

• Human recreational behaviors and seasonal uses of
  water will play an important role in frequency of
  cases of reported human Giardia infections
• Periods of intense precipitation and higher
  stream flow will lead to an increase in the
  number of cases of human Giardia infections in
  the Merrimack River Watershed

13
Hypotheses Cont.

• Urban watersheds will have more cases (per
  100,000) of human Giardia infections than
  watersheds that are predominantly forested and
  rural.
• The Merrimack River Watershed with CSOs upstream
  of drinking water sources will have more human
  cases per 100,000 than other watersheds of
  Massachusetts which dont have CSOs in their
  drinking water sources.

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Pathogens Considered

• Confirmed human cases of giardiasis, shigellosis,
  cryptosporidiosis, campylobacteriosis, and shiga
  toxin-producing E. coli were obtained from the MA
  Department of Public Health
• Data is organized by city and zip code for the
  years 1988 to 2006.
• Few of the cases have known origins

Photo Credit H.D.A Lindquist, U.S. EPA
15
Giardia as a Model Pathogen

• Giardia has been chosen as model pathogen for
  understand relationship of gastrointestinal
  illnesses cases in Massachusetts and watershed
  characteristics

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Giardia

• Giardia is one of the most commonly identified
  etiologic agents in waterborne disease outbreaks
• Giardia is a zoonotic protozoan parasite
• It has a multitude of environmental sources that
  may be influenced by watershed hydrology
• More resistant to conventional drinking water
  treatment
• It is transmitted through the fecal-oral route
  and has an incubation period of 7 to 14 days
• Common sources sewage effluent, feces of
  domestic animals, livestock and wild animals

17
Study Areas

• Blackstone River Watershed
• Deerfield River Watershed
• Merrimack River Watershed

Selecting three watersheds using GIS
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Blackstone River Watershed

• Total drainage area 640 square miles, 382
  square miles are in MA
• Birthplace of America's Industrial Revolution.
• Calculated total MA watershed population
  340,297
• Chosen as representative of a highly impacted
  urban watershed
• Has CSOs, but not used directly for drinking water

Source Mangarillo (2006)
19
Blackstone River Watershed

• Sources of contamination
• storm water runoff, sewerage overflows, failed
  septic systems, hydraulically inadequate
  wastewater treatment facilities, resuspension and
  transport of contaminated river sediments

Source Mangarillo (2006)
20
The Impact of Dams

• Worcester County, largest number of dams (n425)
  of all U.S. counties
• 1 dam for every mile
• Dams allow for the deposition of bacteria
  resuspension during periods of higher flow

Photo source Narragansett Bay Commission
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Deerfield River Watershed

• Considered to be a cold clean river
• Renowned for whitewater and high water quality.
• Multiple recreational uses
• Drainage area is 665 square miles.
• Calculated MA population is 31,337.
• Chosen as representative of a rural, less
  polluted watershed

22
Merrimack River Watershed

• Total drainage area 5,010 square miles(1,200
  square miles are in Massachusetts).
• One of the major towns is Lowell, MA
• Drinking water sources are impacted by combined
  sewer overflows (CSOs).
• Calculated population in Massachusetts portion of
  the watershed is 390,887

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Precipitation, Land Use and Temperature Data

• ArcGIS 9.2 (ESRI, Boston, MA) used for
  processing land use, census population, and
  watershed delineation data files
• The base maps were obtained from MassGIS
• Hydrometric data were obtained from the U.S.
  Geological Survey
• Daily precipitation and temperature were obtained
  from the National Climate Data Center for gauges
  in each of the study watersheds

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Statistical Analyses

• Statistical analysis was performed using
• SPSS 15.0 (SPSS Inc., Chicago, Illinois) for
  cross and autocorrelation, ANOVA
• SAS 9.0. (SAS Institute, Inc., Cary, North
  Carolina) for regression

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Results and Discussion
26
Watershed Comparison

• T-tests were performed to evaluate the effects of
  watershed characteristics on the number of human
  cases of Giardiasis
• No significant difference (P 0.546) was found
  between the urban Blackstone River Watershed and
  the rural Deerfield River Watershed
• The Merrimack River Watershed had significantly
  higher numbers of confirmed cases of Giardia
  infection (P0.003) as compared to the urban
  Blackstone River Watershed

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Watershed Comparison (ANOVA)

• ANOVA among yearly number of Giardia cases per
  100,000 population in all three watersheds showed
  no significant difference (P 0.1092)
• However, an ANOVA between the Blackstone and
  Merrimack watersheds showed significant
  differences (P 0.0264) in the number of Giardia
  cases

28
Annual Cases of Giardia
Comparison of total annual reported Giardia cases
per 100,000 in the Blackstone (BS), Deerfield
(DF), and Merrimack (MMc) River Watersheds
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Influence of Precipitation, Temperature and
Stream flow

• Detailed analysis of the influence of
  precipitation, temperature and stream flow on
  human Giardia cases was performed for the
  Merrimack River Watershed
• The Merrimack River Watershed had the highest
  incidence of Giardiasis, therefore it was chosen
  as the final case study

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Average Precipitation and Stream flow data at
Lowell, MA
Average total monthly precipitation in Lowell
(1988-2006)
Monthly Discharge of the Merrimack River at
Lowell (1924-2006)
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Precipitation and Streamflow

• Stream flow is greatest in the spring when
  snowmelt occurs, declines during the summer, and
  then increases in the fall
• Average total monthly precipitation is greatest
  in October

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Monthly Distribution of Giardia Cases (1988-2006)
Total monthly confirmed cases show that the month
of August has the highest numbers of reported
cases of Giardia
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Stream flow and Giardia

• The peak number of Giardia cases occurs in the
  summer, which is consistent with the hypothesis
  that recreational waters are the primary pathway
  for parasite transmission
• No relationship exists between streamflow and
  illnesses because the highest number of cases
  occur in summer months when streamflow is lowest
• Illnesses are low in the spring when streamflow
  is highest
• Some of these infections may have been acquired
  by different mode of transmission such as food or
  person to person contact

34
Cross correlation between Monthly Precipitation
and Giardia cases
Very little positive correlation found
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Crosscorrelation Between Precipitation and
Giardia cases

• No significant cross correlation between
  precipitation and Giardia cases for daily or
  weekly values
• Many days and weeks have zero Giardia cases or
  precipitation amounts

36
Cross correlation between Temperature and Monthly
Total Giardia cases
37
Autocorrelation of Monthly Giardia cases
38
Regression Model between Monthly Precipitation
and Giardia cases
P 0.9590
Giardia cases
Precipitation inches100
39
Regression Model between Monthly Mean Temperature
and Giardia cases
P 0.0001
Giardia cases
Temperature F10
40
Conclusions

• Combined sewer overflows in a drinking water
  source may have an impact on the number of cases
  of gastrointestinal illnesses
• No cross correlations were observed between
  precipitation and Giardia cases however, extreme
  events were not examined
• Cross correlations were observed between reported
  Giardia cases and temperature
• More Giardia cases were observed when
  temperatures were higher
• Giardia dies off more rapidly at higher
  temperatures
• Most waterborne Giardia exposures are likely from
  recreational exposures
• Outside of the summer outdoor water recreation
  period, the month of October has the highest
  number of Giardia cases which may be related with
  peak precipitation (not stream flow)

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Other Considerations

• Little information is available with regards to
  the origin of these reported illnesses, such as
  whether these cases are foodborne or waterborne.
• Human cases of gastrointestinal illnesses are
  typically underreported
• Individuals may acquire illnesses outside of
  their watershed boundaries

42
Acknowledgments

• Massachusetts Department of Public Health
• Jianyong Wu, Environmental Health Science, Umass,
  Amherst
• University of Massachusetts Graduate School Grant
  and services (Travel Grant Award Department)