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    Frequency of Giardia species in groundwater samples and giardiasis in children during the rainy season in Xochimilco, Mexico City, 2001. N = well; SL = San Luis.

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    Frequency of Giardia species in groundwater samples and giardiasis in children during the dry season in Xochimilco, Mexico City, 2000–2001. N = well; SL = San Luis.

  • 1

    Hancock CM, Rose JB, Callahan M, 1997. The prevalence of Giardia and Cryptosporidium in US groundwater. Proceedings of the International Symposium on Waterborne Cryptosporidum. Newport Beach, CA: American Water Works Association, 147–152.

  • 2

    Levy DA, Bens MS, Craun CF, Calderon RL, Herwaldt BL, 1998. Surveillance for waterborne-disease outbreaks—United States, 1995–1996. MMWR Morb Mortal Wkly Rep 47 :1–33.

    • Search Google Scholar
    • Export Citation
  • 3

    WHO, 1995. World Health Report: Bridging the Gaps. Geneva, World Health Organization.

  • 4

    Guerrant R, 1994. Twelve messages from enteric infections for science and society. Am J Trop Med Hyg 51 :26–35.

  • 5

    Bartone C, 1994. Urban sanitation, sewerage and wastewater management: responding to growing household and community demand. Second Annual Meeting. The World Bank: Environmentally Sustainable Development. Washington, DC: The World Bank.

  • 6

    INEGI, 2000. Información Estadística y Geográfica Municipal. Mexico City: Instituto Nacional de Geografía e Informática, Mexico, VI.

  • 7

    National Research Council, 1995. Mexico City Water Supply. Washington, DC: National Academy Press.

  • 8

    Ezcurra E, Mazari-Hiriart M, 1996. Are megacities viable? A cautionary tale from Mexico City. Environment 38 :6–35.

  • 9

    Anteproyecto de Norma Local NOM, 2002. Requerimientos para la Recarga Artificial del Sistema Acúifero de la Ciudad de Mexico. Mexico City: Secretaría del Medio Ambiente. Dirección General de Regulación y Gestión Ambiental del Agua, Suelo y residuos. Mexico.

  • 10

    Kirkwood B, 1988. Essentials of Medical Statistics. Oxford, United Kingdom: Blackwell Scientific Publications.

  • 11

    García LS, Bruckner DA, 1997. Diagnostic Medical Parasitology. Third edition. Washington, DC: American Society for Microbiology Press.

  • 12

    Pipes WO, 1990. Microbiological methods and monitoring of drinking water. McFeters, ed. Drinking Water Microbiology. New York: Springler-Verlag, 428–445.

  • 13

    American Public Health Association, 1995. Standard Methods for the Examination of Water and Wastewater. Washington, DC: American Public Health Association. 19th edition.

  • 14

    Diggle P, Zeger S, Liang K, 1994. Analysis of Longitudinal Data. Oxford, United Kingdom: Oxford University Press.

  • 15

    Hosmer D, Lemeshow S, 1989. Applied Logistic Regression. Wiley Series in Probability and Mathematical Statistics. New York: John Wiley & Sons.

  • 16

    Blum D, Feachem R, 1983. Measuring the impact of water supply and sanitation investments on diarrhoeal diseases: problems of methodology. Int J Epidemiol 12 :357–365.

    • Search Google Scholar
    • Export Citation
  • 17

    STATA, 1997. Statistical Data Analysis: A Users Perspective. Version 5.0. College Station, TX: Stata Company.

  • 18

    SPSS, 1999. Statistical Program. Version 9.0.1. Chicago: SPSS, Inc.

  • 19

    MapInfo, 1995. MapInfo Professional. Version 4.0. Troy, NY: MapInfo Corporation.

  • 20

    Morrow AL, Reves R, West MS, Guerrero L, Ruiz Palacios G, Pickering LK, 1992. Giardia lamblia in a cohort of Mexican infants. J Pediatr 121 :363–370.

    • Search Google Scholar
    • Export Citation
  • 21

    Cifuentes E, Blumenthal U, Gomez M, Tellez MM, Romieu I, Ruiz Palacios G, 2000. The risk of Giardia intestinalis infection in agricultural villages practicing wastewater irrigation, México. Am J Trop Med Hyg 62 :388–392.

    • Search Google Scholar
    • Export Citation
  • 22

    Harvey RW, Kinner NE, Bunn A, MacDonald D, Metge D, 1995. Transport behavior of groundwater protozoa and protozoan sized microspheres in sandy aquifer sediments. Appl Environ Microbiol 61 :209–217.

    • Search Google Scholar
    • Export Citation
  • 23

    Atherholt TB, Lechevallier MW, Norton WD, Rosen JS, 1998. Effect of rainfall on Giardia sp and Cryptosporidium.J Am Water Works Assoc 90 :66–80.

    • Search Google Scholar
    • Export Citation
  • 24

    VanDerslice J, Briscoe J, 1995. Environmental interventions in developing countries: interactions and their implications. Am J Epidemiol 141 :135–144.

    • Search Google Scholar
    • Export Citation
  • 25

    Esrey S, 1996. Water waste and well being; a multicountry study. Am J Epidemiol 143 :608–612.

  • 26

    Esrey S, Collett J, Miliotis MD, Kornhoff HJ, Makhales P, 1989. The risk of infection due to drinking water supply, use of water and latrines in rural Lesotho. Int J Epidemiol 18 :248–253.

    • Search Google Scholar
    • Export Citation
  • 27

    Gyorkos T, Mc Lare D, Law C, 1989. Absence of significant differences in intestinal parasite prevalence estimates after examination of either one or two stool specimens. Am J Epidemiol 130 :976–982.

    • Search Google Scholar
    • Export Citation

 

 

 

 

RISK OF GIARDIA INTESTINALIS INFECTION IN CHILDREN FROM AN ARTIFICIALLY RECHARGED GROUNDWATER AREA IN MEXICO CITY

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  • 1 Instituto Nacional de Salud Pública, Cuernavaca, Mexico; Patología Experimental, Centro de Investigación y Estudios Avanzados del Instituto Politécnico Nacional, Zacatenco, Mexico

The objective of this study was to assess the risk of infection with Giardia intestinalis in children living in an area with artificial groundwater recharge and potable water reuse in Mexico City. Eligible wells and surrounding homesteads were defined by using a geographic information system. Five wells were tested for G. intestinalis cysts per 400 liters of water. A total of 750 eligible households were visited during two cross-sectional surveys. Stool samples were provided by 986 children in the rainy season study and 928 children during the dry season survey for parasitologic tests. Their guardians provided information on water, sanitation, hygiene, and socioeconomic variables. The prevalence rates of G. intestinalis infection were 9.4% in the rainy season and 4.4% in the dry season. Higher rates of infection were observed in older individuals (9.5% and 10.6%) and girls had a lower risk of infection than boys (odds ratio [OR] =0.55, 95% confidence interval [CI] = 0.34, 0.88 in the rainy season and OR = 0.47, 95% CI = 0.25, 0.90 in the dry season). During the wet season survey, a health risk was detected among those storing water in unprotected receptacles (OR = 4.00, 4.69, and 5.34 for those using uncovered jars, cisterns or tanks, and buckets, respectively), and bathing outside the dwelling, i.e., using a tap (OR = 1.93, 95% CI = 1.10, 3.39). A health risk was also detected among children from households with unsafe food hygiene practices (OR =2.41, 95% CI =1.10, 5.30) and those with no hand-washing habits (OR = 2.27, 95% CI = 1.00, 5.20). Groundwater reserves are at risk of fecal pollution, as indicated by the presence of G. intestinalis cysts. However, the endemic pattern of intestinal infection reflects low standards of personal hygiene and unsafe drinking water storage and food-related practices at household level. Prevention activities must address health education and environmental protection policies.

INTRODUCTION

Excreta disposal practices and water pollution are leading causes of disease worldwide. Even in industrialized societies, which already have sophisticated water treatment technology in place, an increasing number of waterborne outbreaks have fueled the debate concerning public health protection measures.1,2 In less developed countries, the excess burden of diarrhea is likely to reflect multiple modes of transmission of pathogens.3 Global exposure to fecal pollution is on the increase as a result of population growth, economic driving forces, and weak institutions.4,5 The population of the Mexico City Metropolitan Area (MCMA) is 18 million individuals,6 for whom water is obtained mainly (70%) from underground reserves.7 Water extracting rates during the last five decades have resulted in soil subsidence, cracking of pipes, and downward migration of pollutants.8 Pilot water reclamation projects are being evaluated in the MCMA,9 some of which will rely on a series of advanced wastewater treatment plants; the effluents may be reused for artificial recharge of groundwater or cropland irrigation. Given the water quality indicators currently used, chlorination is included as an additional protection measure. However, both the indicators and the rationale for such a policy is increasingly questioned on the grounds of actual health risk and preventive actions needed. This may be the case of protozoan infections (e.g., Giardia intestinalis), the cysts of which resist common water disinfection practices, and remain viable for several weeks in the environment.1,2 The purpose of this investigation was to evaluate the risk of groundwater pollution with G. intestinalis, as well as the risk of infection with G. intestinalis, in children living in an area with artificial groundwater recharge and potable water reuse in Mexico City.

POPULATION AND METHODS

The study area was located on the southern boundaries of Mexico City (i.e., Xochimilco). The water reclamation project currently in place consists of a series of advanced wastewater treatment plants. The effluent of these plants flows through a network of canals and is subsequently reused for cropland irrigation and greenbelts and for recharging of groundwater reserves for subsequent extraction (i.e., pumping wells).

Eligible study units were defined by using a geographic information system that allowed for the overlapping of layers containing hydrologic and demographic data. Site visits facilitated the detection of non-residential units (e.g., farming plots), which were excluded from further consideration (Figures 1 and 2).Only households with children less than six years of age were numbered, spatially located and included in the census. A random sampling technique was used,10 and after informed consent was obtained, 750 eligible households were included in two cross-sectional surveys. The dry season study was conducted November–May 2000–2001, whereas the rainy season survey was conducted in June–October 2001. Households thus acted as the sampling units, whereas the unit of analysis was the individual; siblings were involved if complying with the required criteria. The study was reviewed and approved by the Ethics Committee of the National Institute of Public Health.

Trained field workers used structured questionnaires to gather data on the drinking water supply, sanitation,and hygiene-related variables. At the end of the interview, barcode-labeled flasks containing 25 mL of 2.5% potassium dichromate in phosphate buffer were delivered to the guardian, who received face-to-face explanations and written instructions for the collection of stool samples from each child. Approximately two grams of these fecal samples were gathered the following day, bar coded (i.e., identification, age, location), and immediately transported to the laboratory at the Center of Infectious Diseases in Cuernavaca, Mexico. After vortexing, 500 μL of stool dichromate buffer mixture were centrifuged at 12,000 × g for five minutes, decanted, washed with ethyl acetate, and resuspended in 100 μL of phosphate buffer. One drop of sediment was spread into the wells of glass slides, air-dried, and fixed with methanol before staining with the MERIFLUOR direct immunofluorescence detection kit (Meridian Diagnostics, Inc., Cincinnati, OH); positive and negative controls were stained simultaneously.11 Each well was scanned at a magnification of × 100 under a fluorescence microscope, while confirmation was performed at × 400, using an epifluorescence microscope (excitation filter = 450-490 nm, mirror = 510 nm, barrier filter = 520 nm; Carl Zeiss, Inc., Thornwood, NY).

A trained technician collected 30 water samples from five wells (i.e., three replicates from each well, and 15 in each season), which were tested for G. intestinalis cysts. Briefly, 400 liters of water from each well were filtered through 1.0-μm porosity, wound polypropylene yarn cartridge filters (A-01508-77; Cole-Parmer, Vernon Hills, IL), kept on ice at 4°C, and transported to the laboratory for immediate analysis.12,13 Cartridge filters were cut down to the plastic core and rinsed with 4 liters of deionized water. Giardia intestinalis cysts were recovered following elution and centrifugation procedures. Samples were then concentrated by centrifugation in a Percoll-sucrose gradient and placed on a nitrocellulose filter, stained with fluorescein isothiocyanate-conjugated monoclonal antibody against G. intestinalis cysts (Aqua-Glo; Water-borne, Inc., New Orleans, LA) for microscopic observation.

Data management and analysis.

Both population and environmental data were entered twice and corrected for error using IBM 486 (International Business Machines, Yorktown Heights, NY) compatible processors. Case children were defined on the basis of presence of G. intestinalis oval cysts (diameter = 10–14 μm; fluorescence = 2+ to 3+) in stool smears. Contaminated wells were defined as those showing positive results for G. intestinalis cysts. Those consistently showing negative results were included as “clean” wells. Every child was allocated to one well water quality category, and this exposure remained constant throughout the analysis. Multiple logistic regression was used for bivariate analyses, and since person-to-person transmission was not excluded, an intrafamily correlation structure was examined as a source of bias. Generalized estimation equations were developed to account for autocorrelation within the data, while allowing for the use of time-dependent covariates.14 Potentially confounding factors (e.g., sex, age) were controlled for, and after adjusting for the effect of water quality, the final model included only statistically significant associations.15,16 Measurements used included prevalence rates, odds ratios (ORs), 95% confidence intervals (CIs), and P values, all of which were obtained by the use of STATA17 and SPSS.18 The interpretation of the regression coefficients followed the usual conventions. The use of a geographic information system (MapInfo software)19 allowed for the overlapping of both health and environmental data.

RESULTS

The rates of G. intestinalis infection were 9.4% in the rainy season and 4.4% in the dry season. As shown in Table 1, more than 70% of the children came from households with piped water supplies; however, one-third of these households reported water supply interruptions (12 or more hours a day), and 8% reported water from taps with an unpleasant taste and some color. Half of the interviews provided positive answers on water treatment before ingestion, while 20–25% reported purchasing commercially bottled water, particularly during the driest time of the year. Nearly all of the dwellings had excreta disposal facilities; however, 15% were discharging waste into rudimentary tanks into the backyard soil. Wells N1, N2, and N3 showed positive results for the presence of G. intestinalis cysts, whereas wells N6 and SL 19 showed consistently negative results (Figures 1 and 2). Bivariate analysis (Table 2) showed no statistical association between the presence of G. intestinalis cysts in water samples and G. intestinalis infection in these children (OR = 1.77 in the dry season and 0.73 in the rainy season). Data from the wet season shown that older children had higher rates of infection than infants (OR = 6.83, 95% CI = 0.92, 50.52 and OR = 7.58, 95% CI = 1.11, 51.82, respectively). Girls had a lower prevalence of infection than boys (OR = 0.47, 95% CI = 0.25, 0.89 in the dry season and OR = 0.55, 95% CI = 0.34, 0.86 in the rainy season). The health risk was higher in individuals from households without piped water than those with piped water (OR = 2.08, 95% CI = 1.25, 3.48), and individuals from households storing water in jars, cisterns or tanks, and buckets had higher rates of infection than those purchasing commercially bottled water (OR =5.44, 95% CI =1.60, 18.52, OR =7.49, 95% CI =2.25, 24.85, and OR =7.51, 95% CI =2.12, 26.57, respectively). Children from households complaining of an unpleasant taste in the water had a higher risk of infection than those without this complaints (OR = 4.07, 95% CI = 1.51, 10.99). Individuals using water for feces disposal (i.e., flush toilet) had a higher risk of infection than those who did not (OR = 1.97, 95% CI = 1.18, 3.29). Increasing rates of infection were also observed if sewage was disposed in a septic tank or directly on the soil when compared with sewage that was disposed into the public drainage system (OR = 2.05, 95% CI = 1.10, 3.83 and OR = 3.12, 95% CI = 1.23, 7.91). A health risk was also observed among children bathing outside the dwelling (e.g., tap, backyard), instead of inside in a bathroom (OR = 2.64, 95% CI = 1.53, 4.57). Individuals with higher rates of infection were more likely to live in crowded dwellings (two or more families per home; OR = 1.84, 95% CI = 1.08, 3.13), and a two-fold higher risk was detected in children from dwellings with corrugated roofs (OR = 2.34, 95% CI = 1.40, 3.94). A risk was observed in children from households with low standards of food hygiene i.e., washing vegetables only with soap or water, compared with those who used chlorine for more than five minutes (OR =2.73, 95% CI =1.27, 5.89 and OR =2.57, 95% CI =1.20, 5.56, respectively). In the dry season study, a two-fold higher risk of infection was found among those with no hand washing habits (OR = 2.18, 95% CI = 0.97, 4.91).

Logistic regression analysis is summarized in Tables 3 and 4. No statistical association was detected between the presence of G. intestinalis cysts in groundwater samples and the risk of G. intestinalis infection in these children. The wet season data show a health risk among children from household storing water in jars, cistern or tanks, and buckets (OR = 4.00, 95% CI = 1.14, 14.03, OR = 4.69, 95% CI = 1.35, 16.28, and OR = 5.34, 95% CI = 1.46, 19.58). In addition, children bathing outside the dwelling (i.e., backyard) had a higher risk of infection than those taking a shower inside their home (OR = 1.93, 95% CI = 1.10, 3.39). Finally, a two-fold higher risk was observed in children from households in which vegetables were usually washed solely with tap water or water and soap before consumption (OR = 2.41, 95% CI = 1.10, 5.30 and OR = 2.15, 95% CI = 0.98, 4.71, respectively). Older children had an increased risk of infection (OR =7.04, 95% CI = 1.10, 46.16 in the 1–4-year-old group and OR = 8.48, 95% CI = 1.31, 54.96 in the oldest children). However, in both surveys, girls showed a lower health risk than boys (OR = 0.55, 95% CI = 0.34, 0.88 in the wet season and OR = 0.47, 95% CI = 0.25, 0.90 in the dry season). Dry season data confirmed that children with no hand washing habits had a two-fold higher risk of infection (OR = 2.27, 95% CI = 1.00, 5.20).

DISCUSSION

This investigation suggested an endemic pattern of G. intestinalis infection, rather than a waterborne outbreak because the rates of infection were not substantially different from the ones recently reported for Mexico as a whole.20,21 Despite the lack of statistical associations between ground-water quality and health risk, it is worth emphasizing that fecal pollution is finding its way into underground water sources; this is the actual meaning of the presence of highly resistant protozoa cysts in groundwater samples.22 However, following our methods, closer socio-cultural risk factors were observed: unsafe water and food-related practices, as well as poor standards of personal hygiene (i.e., behavior); seasonal differences may explain different risk factors.23–25 The health risk detected in the oldest children, and the lower risk observed in girls when compared with boys, reinforce the potential role of behavior and recreational exposure.26 Again, this epidemiologic picture may be different from waterborne disease outbreaks reported in communities in North America outside Mexico.1,2

Our data provides original information on the risk of G. intestinalis infection in children from an artificially recharged groundwater project in Mexico City. However, several limitations must be taken into account. First, eligible households were confined to less than 500 meters around each well, under the assumption that children were not exposed to distant wells (> 10 blocks), which may or may not be the case. Second, and of equal importance, financial and logistical constraints prevented sampling from recipients or house-to-house taps; therefore, our results did not directly reflect the quality of water reaching the consumers. Furthermore, as the data showed, more than one-fourth of this population reported regular purchase of bottled water, while direct ingestion from the tap (without previous “disinfection”) was seldom recorded. Methodologic shortcomings may also result from the study design, which does not prove cause and effect. However, it is important to note that more than 70% of the individuals involved in this investigation were repeatedly evaluated during two seasons (the rest were replacements within the same compound). The inclusion of a control group, the blinding of both water quality data and the health outcome (i.e., cysts passing) to interviewers and respondents, along with the procedures used for controlling potentially confounding factors during the analysis, were all strategies that reduced the chance of bias. It is worth noting that identical parasitologic procedures were used for both the exposed and control groups to reduce bias.27

Finally, both public health and groundwater reserves urgently require broader protection policies, and this may be, in our view, a central issue in groundwater recharge programs in Mexico City; a cautious approach resulted from technical gaps that have limited our ability to make baseline health recommendations. Clearly, further research is needed, but safe water reclamation projects must always include a code of safe practices and evidence-based research. This study provided original data from which we may suggest basic and “novel” interventions: households and individuals should assume empowerment self care and common sense activities, community health promotion including use of narrow-mouth flasks (i.e., drinking water), safer food related practices, hand washing, and ecologic sanitation toilets. This may be the core of behavior “simple” and cost-effective interventions.

Table 1

General characteristics of the study population in Xochimilco, Mexico City

Dry season (n = 986)Rainy season (n = 928)
VariableNo.%No.%
Prevalence of Giardia intestinalis infection434.4879.4
Piped water supply inside the dwelling
    Yes71572.568673.9
    No27127.524226.1
Water availability days/week
    4 or less767.7707.5
    5 or more91092.385892.5
Full day water supply
    No31131.532735.2
    Yes67568.560164.8
Taste in the water
    Yes34034.536439.2
    No64665.556460.8
Color in the water
    Yes787.9768.2
    No90892.185291.8
Drinking water treatment
    Yes52853.549753.5
    No45846.543146.4
Drinking water storage
    Commercially bottled23924.218820.3
    Jar30831.227429.5
    Cistern or tank30230.631533.9
    Bucket13713.915116.3
Place for bathing
    Shower, bathroom54955.744047.4
    Tap, yard outside43744.348852.6
Hard-washing habits
    No15115.315016.2
    Yes83584.777883.8
Excreta disposal facilities
    Yes97799.190897.8
    No90.9202.2
Sewage
    Public system83285.274980.7
    Septic tank10510.712813.8
    On soil404.1353.8
Vegetables hygiene practices
    Disinfection, chlorine for 5 minutes28629.024626.5
    Water and soap33534.031734.2
    Only water36537.036539.3
Animal pets
    Yes63164.058462.9
    No35536.034437.1
Number of families per dwelling
    >247147.852556.6
    151552.240343.4
Table 2

Bivariate analysis of Giardia intestinalis infection in children in Xochimilco, Mexico City*

Dry seasonRainy season
No.%nOR95% CIPNo.%nOR95% CIP
* OR = odds ratio; CI = confidence interval.
Groundwater quality (Giardia intestinalis)
    Negative3453.211146610.348
    Contaminated6415.0321.770.77, 4.070.184628.4390.730.44, 1.210.21
Sex of children
    Male5105.126148411.6561
    Female4763.6170.470.25, 0.890.024447.0310.550.35, 0.860.009
Age of children (years)
    < 1981.011691.411
    1–44964.6233.60.66, 20.030.134739.5456.830.92, 50.520.06
    ≥ 53924.8193.50.61, 19.640.1638610.6417.581.11, 51.820.03
Piped water inside the dwelling
    Yes7153.52516867.6521
    No2716.6181.870.91, 3.850.0824214.4352.081.25, 3.480.005
Drinking water storage
    Commercially bottled2394.21011881.631
    Jar3084.5141.040.41, 2.650.942749.1255.441.60, 18.520.007
    Cistern or tank3024.3130.830.31, 2.220.7031512.4397.492.25, 24.850.001
    Bucket1374.461.050.33, 3.380.9315113.2207.512.12, 26.570.002
Taste in drinking water
    Chlorine3124.21313339.0301
    Unpleasant287.122.360.43, 12.960.323129.094.071.51, 10.990.006
Place for bathing
    Shower, bathroom5493.82114405.2231
    Tap, backyard4375.0221.280.63, 2.600.4948813.1642.641.53, 4.570.000
Availability of water/flushing toilet
    No5953.72214856.4311
    Yes3815.0191.370.67, 2.810.3942312.8541.971.18, 3.290.01
Sewage
    Public drainage8323.73117498.1611
    Septic tank986.161.610.58, 4.460.3612814.8192.051.10, 3.830.02
    Soil (backyard)405.021.100.18, 6.810.913520.073.121.23, 7.910.01
Hand washing
    Yes8353.73117788.7681
    No1517.9122.180.97, 4.910.0615012.7191.580.86, 2.900.14
Vegetables hygiene pactices
    Disinfection, chlorine for 5 minutes2864.51312464.5111
    Water and soap3353.9130.900.37, 2.180.8131711.7372.731.27, 5.890.01
    Only water3654.7170.960.40, 2.310.9336510.7392.571.20, 5.560.01
Number of families per dwelling
    15153.71914036.5261
    ≥ 24715.1241.220.60, 2.490.5752511.6611.841.08, 3.130.02
Housing/roof
    Cement7023.62516397.2461
    Corrugated2506.4161.740.83, 3.650.1426414.4382.341.40, 3.940.001
Table 3

Logistic regression analysis of Giardia intestinalis infection in children in Xochimilco, Mexico City during the rainy season, 2001*

VariablesNo.%nOR†95% CIP
* OR = odds ratio; CI = confidence interval.
† Adjusted for all variables in the table.
Groundwater quality (Giardia intestinalis)
    Negative46610.3481
    Contaminated4628.4390.960.57, 1.620.888
Sex of children
    Male48411.6561
    Female4447.0310.550.34, 0.880.01
Age of children (years)
    < 1691.511
    1–44739.5457.041.10, 46.160.04
    ≥ 538610.6418.481.31, 54.960.02
Storage of drinking water
    Commercially bottled1881.631
    Jar2749.1254.001.14, 14.030.03
    Cistern or tank31512.4394.691.35, 16.280.01
    Bucket15113.3205.341.46, 19.580.01
Place for bathing
    Shower, bathroom4405.2231
    Tap, backyard48813.1641.931.10, 3.390.02
Vegetable hygiene
    Disinfection, chlorine for 5 minutes2464.5111
    Water and soap31711.7372.411.10, 5.300.02
    Only water36510.7392.150.98, 4.710.05
Table 4

Logistic regression analysis of Giardia intestinalis infection in children in Xochimilco, Mexico City during the dry season, 2000–2001*

VariablesNo.%nOR†95% CIP
* OR = odds ratio; CI = confidence interval.
† Adjusted for all variables in the table.
Groundwater quality (Giardia intestinalis)
    Negative3453.2111
    Contaminated6415.0321.880.82, 4.280.134
Sex of children
    Male5105.1261
    Female4763.5170.470.25, 0.900.02
Hand-washing habits
    Yes8353.7311
    No1518.0122.271.00, 5.200.04
Figure 1.
Figure 1.

Frequency of Giardia species in groundwater samples and giardiasis in children during the rainy season in Xochimilco, Mexico City, 2001. N = well; SL = San Luis.

Citation: The American Journal of Tropical Medicine and Hygiene Am J Trop Med Hyg 71, 1; 10.4269/ajtmh.2004.71.65

Figure 2.
Figure 2.

Frequency of Giardia species in groundwater samples and giardiasis in children during the dry season in Xochimilco, Mexico City, 2000–2001. N = well; SL = San Luis.

Citation: The American Journal of Tropical Medicine and Hygiene Am J Trop Med Hyg 71, 1; 10.4269/ajtmh.2004.71.65

Authors’ addresses: Enrique Cifuentes, Leticia Suárez, and Luis Juárez-Figueroa, Instituto Nacional de Salud Pública CENSA/CISP, Av. Universidad 655, Sta. María Ahuacatitlán, Cuernavaca, CP 62508 Mexico, Telephone: 177-73-29-30-60, Fax: 177-71-01-29-37, E-mail: ecifuent@correo.insp.mx. Martha Espinosa and Adolfo Martínez-Palomo, Laboratorio de Patología Experimental, Centro de Investigación y Estudios Avanzados, Avenue Instituto Politécnico Nacional 2508, Zacatenco, Mexico, Telephone: 155-57-47-38-00, E-mail: mespinosa@mail.cinvestav.mx.

Acknowledgments: We thank the staff of the Dirección General Construcción Obras Hidráulicas for their logistical support and willingness to participate in the study, M. Solano for data management, and R. Santos for help with the geographic information system.

Financial support: This study was supported by the CONSERVA Program (Gobierno Distrito Federal) and CONACyT, Mexico.

REFERENCES

  • 1

    Hancock CM, Rose JB, Callahan M, 1997. The prevalence of Giardia and Cryptosporidium in US groundwater. Proceedings of the International Symposium on Waterborne Cryptosporidum. Newport Beach, CA: American Water Works Association, 147–152.

  • 2

    Levy DA, Bens MS, Craun CF, Calderon RL, Herwaldt BL, 1998. Surveillance for waterborne-disease outbreaks—United States, 1995–1996. MMWR Morb Mortal Wkly Rep 47 :1–33.

    • Search Google Scholar
    • Export Citation
  • 3

    WHO, 1995. World Health Report: Bridging the Gaps. Geneva, World Health Organization.

  • 4

    Guerrant R, 1994. Twelve messages from enteric infections for science and society. Am J Trop Med Hyg 51 :26–35.

  • 5

    Bartone C, 1994. Urban sanitation, sewerage and wastewater management: responding to growing household and community demand. Second Annual Meeting. The World Bank: Environmentally Sustainable Development. Washington, DC: The World Bank.

  • 6

    INEGI, 2000. Información Estadística y Geográfica Municipal. Mexico City: Instituto Nacional de Geografía e Informática, Mexico, VI.

  • 7

    National Research Council, 1995. Mexico City Water Supply. Washington, DC: National Academy Press.

  • 8

    Ezcurra E, Mazari-Hiriart M, 1996. Are megacities viable? A cautionary tale from Mexico City. Environment 38 :6–35.

  • 9

    Anteproyecto de Norma Local NOM, 2002. Requerimientos para la Recarga Artificial del Sistema Acúifero de la Ciudad de Mexico. Mexico City: Secretaría del Medio Ambiente. Dirección General de Regulación y Gestión Ambiental del Agua, Suelo y residuos. Mexico.

  • 10

    Kirkwood B, 1988. Essentials of Medical Statistics. Oxford, United Kingdom: Blackwell Scientific Publications.

  • 11

    García LS, Bruckner DA, 1997. Diagnostic Medical Parasitology. Third edition. Washington, DC: American Society for Microbiology Press.

  • 12

    Pipes WO, 1990. Microbiological methods and monitoring of drinking water. McFeters, ed. Drinking Water Microbiology. New York: Springler-Verlag, 428–445.

  • 13

    American Public Health Association, 1995. Standard Methods for the Examination of Water and Wastewater. Washington, DC: American Public Health Association. 19th edition.

  • 14

    Diggle P, Zeger S, Liang K, 1994. Analysis of Longitudinal Data. Oxford, United Kingdom: Oxford University Press.

  • 15

    Hosmer D, Lemeshow S, 1989. Applied Logistic Regression. Wiley Series in Probability and Mathematical Statistics. New York: John Wiley & Sons.

  • 16

    Blum D, Feachem R, 1983. Measuring the impact of water supply and sanitation investments on diarrhoeal diseases: problems of methodology. Int J Epidemiol 12 :357–365.

    • Search Google Scholar
    • Export Citation
  • 17

    STATA, 1997. Statistical Data Analysis: A Users Perspective. Version 5.0. College Station, TX: Stata Company.

  • 18

    SPSS, 1999. Statistical Program. Version 9.0.1. Chicago: SPSS, Inc.

  • 19

    MapInfo, 1995. MapInfo Professional. Version 4.0. Troy, NY: MapInfo Corporation.

  • 20

    Morrow AL, Reves R, West MS, Guerrero L, Ruiz Palacios G, Pickering LK, 1992. Giardia lamblia in a cohort of Mexican infants. J Pediatr 121 :363–370.

    • Search Google Scholar
    • Export Citation
  • 21

    Cifuentes E, Blumenthal U, Gomez M, Tellez MM, Romieu I, Ruiz Palacios G, 2000. The risk of Giardia intestinalis infection in agricultural villages practicing wastewater irrigation, México. Am J Trop Med Hyg 62 :388–392.

    • Search Google Scholar
    • Export Citation
  • 22

    Harvey RW, Kinner NE, Bunn A, MacDonald D, Metge D, 1995. Transport behavior of groundwater protozoa and protozoan sized microspheres in sandy aquifer sediments. Appl Environ Microbiol 61 :209–217.

    • Search Google Scholar
    • Export Citation
  • 23

    Atherholt TB, Lechevallier MW, Norton WD, Rosen JS, 1998. Effect of rainfall on Giardia sp and Cryptosporidium.J Am Water Works Assoc 90 :66–80.

    • Search Google Scholar
    • Export Citation
  • 24

    VanDerslice J, Briscoe J, 1995. Environmental interventions in developing countries: interactions and their implications. Am J Epidemiol 141 :135–144.

    • Search Google Scholar
    • Export Citation
  • 25

    Esrey S, 1996. Water waste and well being; a multicountry study. Am J Epidemiol 143 :608–612.

  • 26

    Esrey S, Collett J, Miliotis MD, Kornhoff HJ, Makhales P, 1989. The risk of infection due to drinking water supply, use of water and latrines in rural Lesotho. Int J Epidemiol 18 :248–253.

    • Search Google Scholar
    • Export Citation
  • 27

    Gyorkos T, Mc Lare D, Law C, 1989. Absence of significant differences in intestinal parasite prevalence estimates after examination of either one or two stool specimens. Am J Epidemiol 130 :976–982.

    • Search Google Scholar
    • Export Citation
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