Lesson 3: Foodborne and Waterborne Diseases
The faecal–oral mechanism for transfer of infection often includes food as a mechanism
of infection, but in addition, there are other diseases that are only transmitted by food. These can infect foods in general, such as with food poisoning, or be very specific in a particular food, such as certain helminth infections. As the method of infection is very specific so are its methods of control, which include food hygiene, the proper cooking of foods and sanitary methods to prevent the food from being contaminated.
Waterborne diseases are caused by people ingesting water contaminated by human or animal faeces containing pathogens. Such diseases can also be caused by food that has been prepared using water contaminated with pathogens. The diseases are caused only when the infectious agent enters the body. Waterborne diseases include most of the enteric (related to the intestine) and diarrhoeal diseases caused by bacteria and viruses. Bacteria are unicellular organisms (made of one cell) and are very small, ranging from 0.5 to 5.0 micrometres (µm) in size. When seen under a microscope, they have different shapes, such as spheres, rods, or spirals. Viruses are microscopic infectious particles, much smaller than bacteria, that can only reproduce when inside the living cells of organisms. Waterborne diseases also include some caused by protozoa (single-celled micro-organisms that are much larger than bacteria, usually between 10 and 50 µm) and helminths. Helminths is a general term for worms, usually applied to those that are parasites on humans and other animals.