Preventing Diarrheal Disease in Developing Countries
The health consequences of inadequate water and sanitation services include an estimated 4 billion cases of diarrhea and 1.9 million deaths each year, mostly among young children in developing countries. Diarrheal diseases lead to decreased food intake and nutrient absorption, malnutrition, reduced resistance to infection, and impaired physical growth and cognitive development. Water and sanitation interventions to reduce diarrheal disease incidence in developing countries fall into four general categories: water provision, household water treatment, handwashing promotion, and sanitation. Each of these interventions is proven to reduce diarrheal disease incidence. Organizations are often faced with the difficult decision of where to focus limited resources in order to improve water and sanitation conditions. Selecting the most appropriate intervention for a specific location depends on existing water and sanitation conditions, cultural acceptability, hydrology and water quality, implementation feasibility, and local conditions.
Table of Contents
Water Provision
Currently, 1.1 billion people worldwide lack access to safe water supplies. The Millennium Development Goal (MDG) target is to “halve, by 2015, the proportion of people without sustainable access to safe drinking water,” as measured by access to an improved supply. The world is on schedule to meet the MDG target; however, success will leave over 600 million people without access to improved water supplies in 2015 and the target does not address safety of the water. Improved supplies include household connections, public standpipes, boreholes and protected dug wells, protected springs, and rainwater collection. Understanding local hydrological conditions is key to selecting the appropriate improved water supply. Water from improved supplies can be treated at the community level to ensure it is safe to drink.
Improved Well in Haiti (D. Lantagne)
Household Water Treatment
Household water treatment and safe storage (HWTS) interventions are proven to improve water quality and reduce diarrheal disease incidence in developing countries. Five HWTS options – chlorination, solar disinfection, ceramic and slow sand filters, and PUR – are proven to be effective at treating untreated unimproved and improved water supplies to improve the microbiological safety of the water during transport and storage. Successful HWTS programs select a high-quality, culturally appropriate option, distribute the products reliably, and work with trusted local community educators to encourage healthy water practices. http://www.who.int/household_water
A Woman Using HWTS (P. Vidot)
Hand Washing Promotion
Handwashing with soap is critical to reduce transmission of many infectious diseases. Successful handwashing promotion programs focus on establishing a reliable soap supply in the community or region; teaching people to wash hands correctly at critical times through demonstration; and motivational activities. Critical handwashing times include before eating and cooking, after using the toilet, and after changing a baby. Handwashing education can be included in all health programming and curricula.
Washing Hands with Soap (A. Parker)
Sanitation
Currently, 2.4 billion people worldwide lack access to improved sanitation. The Millennium Development Goal target is to “halve, by 2015, the proportion of people without sustainable access to safe sanitation”, as measured by access to an improved sanitation facility. Improved sanitation facilities include public sewer connections, septic system connections, pour-flush latrines, pit latrines, and ventilated pit latrines. Many organizations now focus on step-wise sanitation improvements, working with communities to move from open defecation and poor hygiene toward total sanitation. Successful programs focus on educating communities to use local resources and knowledge to cost-effectively improve sanitation throughout the community.
Latrine (D. Lantagne)
Proven Household Water Treatment Options
Since 1996, a large body of work has been published that has examined the health impact of interventions to improve water quality at the point-of-use through household water treatment and safe storage (HWTS). Five interventions – chlorination, solar disinfection, ceramic filtration, slow sand filtration, and PUR – have been proven to reduce diarrhea in users in developing countries and improve the microbiological quality of stored household water and are discussed below. The most appropriate HWTS option for a location depends on existing water and sanitation conditions, water quality, cultural acceptability, implementation feasibility, availability of HWTS technologies, and other local conditions. For more information, contact safewater@cdc.gov. Photos courtesy: PSI, PFP, Hydraid, EAWAG, P&G.
Household Chlorination
Household chlorination includes water treatment with chlorine solution at the point-of-use, storage of water in a safe container, and behavior change communication. Users add one cap of solution to their storage container . Diarrhea reduction is 22-84%. Product cost is 0.01-0.05 US cents per liter treated. Benefits are residual protection against recontamination, acceptability to users, ease-of-use, scalability, and low cost. Drawbacks include potential user taste and odor objections, and lower protection against some organisms and in turbid water. www.cdc.gov/safewater
Ceramic Filtration
Ceramic filters depend on mechanical processes to remove contaminants. Users simply pour water through the filters. Diarrhea reduction is 60-70% in commercially manufactured filters in conjunction with safe storage. Product cost is 0.034-0.14 US cents per liter treated. Benefits include user acceptability because of ease-of-use, long life if the filter remains unbroken, and potential for local production. Drawbacks include unknown effectiveness against viruses, lack of residual protection that can lead to recontamination, the need for user education to keep the filter and receptacle clean, and slow flow rates. www.pottersforepeace.org
Slow Sand Filtration
The Slow Sand Filter (SSF) is a sand filter adapted for household use. To use the SSF, users simply pour water into the SSF, and collect finished water out of the outlet pipe into a bucket. Diarrhea reduction is 44-47%. Product and program costs over a 10 year life span is 0.068 cents per liter treated in one NGO program. Benefits include turbidity removal, high flow rate, ease of use, long-life, low maintenance requirements, and local production. Drawbacks include unknown effectiveness against viruses, lack of residual protection that can lead to recontamination, the need for user education to keep the filter and storage container clean, and heavy weight. http://www.cawst.org
Solar Disinfection – SODIS
SODIS uses increased temperature, UV light, and oxidative chemistry to inactivate disease-causing organisms. Users are trained to place bottles in the sun for 6 hours-2 days, depending on climate. Diarrhea reduction is 9-86%. Aside from initial bottles, SODIS is a zero-cost option. Benefits include acceptability to users because of the minimal cost and ease-of-use. Also, recontamination is unlikely because water is consumed directly from the bottles in which it is treated. Drawbacks include the need for pretreatment of turbid water, limited volume of water that can be treated at once, length of time required to treat water, and the plastic bottles supply required. www.sodis.ch
Flocculant / Disinfectant Powder - PUR Purifier of Water™
Procter & Gamble developed the combined flocculant/disinfectant PUR® for sale at no-profit to users and NGOs. To use, one sachet is added to 10 liters of water, and users stir, let the solids settle, strain the water through a cloth, and wait 20 minutes. Diarrhea reduction is 16->90%. Product cost is 1 cent per liter treated. Benefits include high quality water due to dual process treatment even in turbid waters, residual protection against contamination, and visual improvement in the water. Drawbacks are multiple steps for correct use, the need for users to have two buckets, a cloth, and a stirrer, and the higher relative cost per liter of water treated. http://www.pghsi.com/pghsi/safewater/
Resources
The issues in this article are addressed on the USAID Environmental Health web pages. For more topics relating to environmental health, visit the web site at: http://www.ehproject.org
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