Adapted from "Food and Water Preparation" module, Pre-Service Health Training for Volunteer Binder, Peace Corps Office of Medical Services

BACKGROUND

Food and water-borne diseases are very common among host country populations and among students in many countries. Diarrheal disease is the leading reason for visits to the medical office in many countries.

Students should understand the following:

1. Assume that all untreated water and food that you do not know to be properly prepared is probably contaminated and could be dangerous to your health.
2. Be aware of water and food-borne diseases and how transmission occurs.
3. Know the proper methods of food and water preparation.

FOOD AND WATER-BORNE DISEASES

While diarrhea can be related to many factors, including change in diet, it is often the result of an infection with one of a variety of organisms (viral, bacterial, or parasitic). This subject is covered in the Diarrhea module, which is meant to be used in conjunction with this module.

PREVENTION OF FOOD AND WATER-BORNE DISEASES

The primary strategy in preventing diarrhea is the avoidance of food and water contaminated with fecal pathogens.

It may be useful to contrast the situation in country with measures undertaken in the United States to insure that food and water is free of pathogens:

• FDA (Food and Drug Administration) approves meats and vegetables as meeting standards regarding salmonella, shigella and tuberculosis.
• The consumer is protected by health inspections of restaurants, farms, food servers, and processing plants.
• Water is purified /chlorinated and sewer systems maintained by municipalities.
• Sanitation: toilets are abundant. There are garbage collection and disposal routines.
• Vegetables are not fertilized with night soil.
• Food is refrigerated.
• Food is wrapped and packaged to prevent contamination.
• The population is relatively disease-free, so there is little diarrheal disease to pass person to person.

WATER PREPARATION

Tap water may be contaminated unless it is known to be safe; i.e., potential pathogens are removed or inactivated. Drinking bottled water may be the best advice in much of the world.

More effective

There are two preferred methods of water disinfection.

Both are effective against all pathogens:

Boil for 3 minutes

• A 3-minute boil is adequate at all altitudes even with heavily contaminated water.

Filter using a 1-2 micron pore-size filter FOLLOWED BY treatment with iodine or chlorine

• Chlorine bleach 2 drops/liter, let stand for 15 minutes
• Iodine 2% 5 drops/liter, let stand for 15 minutes
• Iodine tablets 1/2 tablet/liter, let stand for 15 minutes

Filtering removes all protozoa (including cryptosporidium and cyclospora). Iodine or chlorine can then be used at lower doses to kill bacteria and viruses.

Less effective

The following water disinfection methods are effective against all pathogens except cryptosporidium and cyclospora and, since they are less reliable, should be used only when unable to use the preferred methods:

• Iodine tablets: 1 tablet/liter, let stand for 60 minutes
• Iodine 2% liquid: 10 drops/liter, let stand for 60 minutes
• Iodine resin filters: Follow manufacturer directions. Allow water to stand 30 minutes after filtering if cold.

For best results, cloudy water should be filtered before adding iodine or chlorine. The contact times listed are minimum times for cloudy or cold water.

• The use of chlorine bleach alone (4 drops/liter, let stand for 60 minutes) is less effective than the methods described above and should be avoided unless unable to use the other methods.
• Iodine tablets must be kept in a tightly closed bottle and should be grayish blue, not yellow, in color.
• Chlorine bleach must be kept in a tightly closed bottle.
• Alcohol does not disinfect water or other fluids.

FOOD PREPARATION

In some parts of the world, foods purchased (unless canned) or served in restaurants (unless fully cooked and hot) may be contaminated.

Fresh fruits and vegetables

Vegetables may have been fertilized with night soil (human waste), handled by several people, or washed with unclean water. Thorough cooking of vegetables inactivates pathogens but destroys some important nutrients.

• All fruits and vegetables that can be peeled are safe once peeled.
• Any fruits or vegetables that are not or cannot be peeled should be washed and soaked.
• Soak items in a solution of one(1) tablespoon household bleach per gallon for 15 minutes and then rinse in treated water.

Meat preparation

All meats should be cooked thoroughly. Adequate cooking will prevent parasitic (trichinosis and tapeworm) and bacterial infections.

Milk products

Bring all fresh (unpasteurized) milk to boil before consuming. Avoid eating fresh cultured dairy products (such as yogurt) since there is no way of pasteurizing it.

• Canned foods are generally safe.
• Freezing does not disinfect food.
• Food should be eaten immediately after cooking as a delay can allow bacteria to multiply again, and cooked food should be protected from flies and other sources of recontamination.

Adapted from "Food and Water Preparation" module, Pre-Service Health Training for Volunteer Binder, Peace Corps Office of Medical Services