Water quality, availability, and acute gastroenteritis on the Navajo Nation – a pilot case-control study

The Navajo Nation includes approximately 250,000 American Indians living in a remote high desert environment with limited access to public water systems. We conducted a pilot case-control study to assess associations between acute gastroenteritis (AGE) and water availability, use patterns, and quality. Case patients with AGE and non-AGE controls who presented for care to two Indian Health Service hospitals were recruited. Data on demographics and water use practices were collected using a standard questionnaire. Household drinking water was tested for presence of pathogens, coliforms, and residual chlorine. Sixty-one subjects (32 cases and 29 controls) participated in the study. Cases and controls were not signi ﬁ cantly different with respect to water sources, quality, or patterns of use. Twenty-one percent ( n ¼ 12) of study participants resided in dwellings not connected to a community water system. Eleven percent ( n ¼ 7) of subjects reported drinking hauled water from unregulated sources. Coliform bacteria were present in 44% ( n ¼ 27) of household water samples, and 68% ( n ¼ 40) of samples contained residual chlorine concentrations of < 0.2 mg/L. This study highlights issues with water availability, quality, and use patterns within the Navajo Nation, including sub-optimal access to community water systems, and use of water hauled from unregulated sources.

Poverty, geographic isolation, lifestyle constraints, and healthcare utilization challenges are likely contributors to health disparities and the increased disease rates borne by the Navajo people. In particular, access to safe drinking water for persons residing within the Navajo Nation can be limited. It is estimated that 21-32% of reservation households are not connected to public water systems compared to 0.5% of households nationally and 9% for American Indian tribes overall (First Things First Navajo Nation Regional Partnership Council ; Indian Health Service Sanitation Facilities Construction Program ; Centers for Medicare and Medicaid Services ). The Navajo Tribal Utility Authority (NTUA) and Navajo Nation Department of Water Resources (NDWR) provide watering points that include public water taps at trading posts, Chapter houses, schools, and border towns, in order that regulated water may be hauled for human consumption. However, while staff from over 50 of the 110 Navajo Chapters indicated in a NDWR telephone survey that watering points are the primary or secondary sources, respondents in over 20 Chapters noted that unregulated, untreated livestock wells were the primary or secondary source of drinking water for the people in their Chapter (Navajo Nation Department of Water Resources ). These water sources have been found to be contaminated by fecal coliforms and can contain arsenic and uranium levels that often exceed EPA drinking water standards (Murphy et al. ).
In Alaska, an ecologic study reported an association between lack of in-home water service and rates of infectious disease hospitalization among rural Alaska Natives (Hennessy et al. ). A dose-response relationship was described whereby communities with the lowest in-home water service availability experienced the highest hospitalization rates. These hospitalization rates decreased with improved access to in-home water. In the Alaska study population, 27% of homes overall did not have access to in-home water, a rate similar to that seen on the Navajo Nation.
Despite high rates of diarrheal disease and challenges to the access of safe potable water on the Navajo Nation, there is a dearth of published information regarding water quality, availability, use patterns and associated health outcomes among Navajo people. The objective of this pilot study was to describe water use, availability, and quality among those who presented for care for AGE at two Indian Health Service hospitals on the Navajo Reservation as well as Navajo who presented for care and did not have AGE. We also aimed to evaluate the feasibility of conducting a case-control study of the association of water and AGE. The information from this study can begin to fill gaps in understanding the importance and potential health benefits of improved access to safe, regulated water for inhabitants of this region and help direct future research on this topic.

Study subjects
American Indian patients of any age residing within the boundaries of the Fort Defiance and Chinle Service Units of the Navajo Nation who presented for care to the Fort Defiance or Chinle Hospitals with clinician-diagnosed AGE were recruited for enrollment as case patients from May 2010 to June 2011. These hospitals provide service to approximately 40% of the population residing on the Navajo Reservation (Navajo Epidemiology Center ). In order to have a study population that spanned the entire age spectrum, investigators attempted to enroll equal numbers of participants in the following age strataless than 5 years; 6 to less than 18; 18 to less than 65; and 65 and older. Controls admitted with conditions other than AGE were matched to case patients on date of service, age strata, and Service Unit of residence. Study subjects were evenly enrolled over the wet (July through December) and the dry (January through June) seasons. Case patients and controls were excluded if they had any other known noninfectious acute or chronic disease that may include symptoms of AGE (e.g., abdominal or colorectal cancer, gastric reflux or gastrointestinal ulcers, HIV/AIDS, inflammatory bowel disease, food allergies, pregnancy, and anxiety disorder). Written informed consent was obtained from all participants 18 years or older. Written parental permission was obtained for individuals under 18 years of age at recruitment; subjects 7 to 17 years of age provided written assent.
For participants who were illiterate or non-English speaking, informed consent was obtained after verbal review with the aid of a translator. For these participants, an additional witness signature was obtained on the consent form. The study protocol was reviewed and approved by Institutional Review Boards (IRBs) at the Centers for Disease Control and Prevention (CDC), Johns Hopkins University, and the Navajo Nation prior to implementation. Study subjects were surveyed by study personnel using a standardized questionnaire. This survey included questions regarding demographic information, clinical information including characteristics and duration of symptoms (for case patients), and household water use practices including water source, volume collected and stored, transport methods and handling practices, and personal and household hygiene practices. If another household member (e.g., parent) was more knowledgeable about these household water use practices, that individual could provide responses on behalf of the study participant. Individuals who participated in the study were reimbursed up to $10 for their time.
Clinical specimen collection and laboratory testing methods At least 10 g of stool was collected from study subjects. Specimens were collected in sterile containers and refrigerated at 4 to 8 C and overnight shipped on ice on a weekly basis to CDC laboratories. An aliquot (at least 3 g) of the stool was stored in 10% formalin for routine examination of ova and parasites. Once received at CDC, stool specimens were tested for bacterial, parasitic, and viral pathogens. Viral Water sample collection and laboratory testing methods Study staff visited the home of each case patient and control to sample the primary residence drinking water within 1 week of study enrollment. Three drinking water samples were collected during the home visits: a 10 mL sample for residual chlorine testing; a 250 mL grab sample for total coliform and E. coli testing; and approximately 100 liters of water were sampled by dead-end ultrafiltration (UF).
Residual chlorine was assessed during the home visit using the Hach Chlorine Colorimeter II Kit (Lampoc, CA, USA), in which at least 10 mL of drinking water was placed into a glass vial, followed by dissolution of free chlorine reagent into the vial and analysis of the sample via the colorimeter.
The grab sample of water was collected following residual chlorine testing and stored in a chilled cooler after collection and during transit to the laboratory for testing.
Coliform and E. coli testing were conducted at a laboratory on the Navajo Reservation using membrane filtration and culture on MI Agar per procedures in EPA Method 1604 (United States Environmental Protection Agency ).
Analysts were proficiency-tested in the membrane filtration method prior to the start of the study. Approximately 100 liters of drinking water was filtered through a REXEED 25SX dialysis filter (i.e., ultrafilter) (Asahi Kasei Medical Company, Tokyo, Japan) using a standard protocol. The UF procedure has been demonstrated to be effective for recovering a wide range of waterborne bacterial, viral, and protozoan pathogens (Smith & Hill ; Mull & Hill ; Hill ). The filtered effluent was collected hygienically into portable containers and returned to the household, if desired. Ultrafilters were sealed in a leakproof bag following UF and stored in a chilled cooler until shipment to CDC for processing and analysis. Ultrafilters were backwashed with a Tween 80-based solution to generate a ∼500-mL sample for secondary concentration, nucleic acid extraction, and molecular analysis (Smith & Hill ).
All stool specimen and water sample results were shared with the study subjects once testing was completed.
Additionally, positive stool results were reported to the subject's IHS health care provider and positive water sample results were reported to the IHS, the Navajo Nation Environmental Protection Agency (NNEPA), and the NTUA, if the positive sample was from a municipal water source.
Statistical differences between cases and controls were assessed by calculating odds ratios and 95% confidence intervals. Statistical differences between categorical characteristics were assessed using Chi-square or Fisher's exact test; differences between discrete variables were assessed using the Wilcoxon rank sum test. Significant differences were assessed at the p ¼ 0.05 level.

RESULTS
A total of 72 individuals were contacted to participate in the study. Seven (10%) refused to participate; additionally, investigators were unable to collect stool specimens and/ or water samples from four (6%) individuals. Thus, data were analyzed from 61 individuals; 32 (52%) were case patients and 29 (48%) were controls.
Mean age of study participants was 39 years (range: 10 months-87 years; Table 1); 36 (59%) participants were female. Forty-two (69%) participants reported living in a framed house; households included a median of five individuals who regularly slept in primary residences (range: 1-11 people). Case patients were similar to controls with respect to age, sex, residence type, and household size.

Case-control analysis
Case patients and controls were not significantly different with respect to their primary residences' connections to community water systems, opinions of community water systems, history of drinking hauled water (i.e., water brought to one's primary residence from an outside source), hauled water sources, opinions of hauled water, or problems with aesthetic water quality (Table 2). Therefore, the descriptive

Water use and availability
Seventy-nine percent (n ¼ 48) of study participants lived in primary residences that were connected to community water systems (Table 2). Overall, 31% (n ¼ 19) of participants reported drinking hauled water in the last 4 weeks. Of these, 47% (n ¼ 9) reported living in a residence with a connection to a community water system. Common sources of hauled water included water that was regulated, such as bottled water from grocery stores or trading posts (n ¼ 6), Chapter houses or watering points (n ¼ 5), and a Navajo Housing Authority apartment building. In addition, sources of hauled water included water that presumably had not been treated or regulated, such as windmill-driven or private wells (typically untreated and shallow water sources) (n ¼ 7).
Respondents who drank hauled water also reported obtaining water from sources for which treatment or regulation was unknown, such as a relative's residences (n ¼ 3). Participants who reported drinking hauled water were, on average, older

Opinions and perceptions of water quality
Forty-one percent (n ¼ 25) of study participants reported having a 'bad' opinion of their community water system (Table 3) Thirty-nine percent (n ¼ 24) of the 61 study participants reported having problems with the aesthetic quality of their drinking water (Table 3). Of the respondents who reported aesthetic water quality problems, 71% (n ¼ 17) reported having problems with the color of their drinking water; aesthetic water quality problems such as taste, color, or smell were also not associated with being connected to community water systems. Seven of the 19 (37%) respondents who reported drinking hauled water reported having problems with the aesthetic quality of their drinking water, and they were not more likely to have aesthetic drinking water quality problems when compared to respondents who did not drink hauled water (p ¼ 1.000; OR ¼ 0.88, 95% CI ¼ 0.29, 2.75). Of the 9 respondents who were connected to a community water system and drank hauled water, 44% (n ¼ 4) reported problems with aesthetic drinking water quality.
Fifty-four percent (n ¼ 33) of all respondents reported being generally concerned about water quality (Table 3), and cases were more likely to report a concern about water quality when compared to controls (p ¼ 0.009; OR ¼ 6.33, 95% CI ¼ 2.05, 19.54). Among cases, being connected to a community water system or drinking hauled water were not associated with general concerns about water quality. Eighty-nine percent (n ¼ 54) of all respondents reported being willing to pay for higher quality water; being connected to a community water system or drinking hauled water was not associated with willingness to pay for higher quality water.

Laboratory testing
Water samples collected at households were drawn from taps (n ¼ 46, 75%), a bucket, an outdoor garden hose, a barrel, and bottled water. Eight (13%) households provided water samples from wells. Of the 13 residences reportedly not connected to community water systems, water samples were collected from 6 (46%) wells, 4 (31%) taps, a tank, a bucket, and an unnamed source. Forty-six percent (n ¼ 27) of water samples tested positive for coliform bacteria (Table 4)   were not more likely to report general or aesthetic (i.e., color, taste, smell) issues with water quality. Eleven of 18 (61%) study participants who reported drinking hauled water in the past 4 weeks had drinking water that was contaminated with coliforms. Of the 11 water sources obtained from participants who drank hauled water and had coliforms present in their drinking water, 6 (55%) were well water sources; 3 (27%) were from tap water sources; a bucket water source; and a garden hose. Study participants with water samples that had low (<0.2 mg/L) residual chlorine levels were more likely to report having concerns with water quality (p ¼ 0.031; OR ¼ 3.43, 95% CI ¼ 1.09, 10.78), but aesthetic water quality issues were not associated with low residual chlorine levels in water samples.
Fourteen percent (n ¼ 8) of study participants were infected with diarrheagenic E. coli as determined through stool specimen testing ( This study also did not examine human waste disposal or handwashing practices that might be associated with AGE. Furthermore, this study did not assess the level of arsenic, which is a known water contaminant on the Navajo Nation and can be associated with gastroenteritis (Hoover et al. ).
This is the first study examining water sources, quality, and availability among Navajo people that also examines the association of these factors and infection with pathogens that cause AGE. Our results highlight a need for additional detailed examinations concerning the use of unregulated hauled water for drinking, including drinking hauled water when community water sources are available. A detailed evaluation of the quality and integrity of existing community water systems and remedying any deficiencies in disinfection may be necessary.