Bacteria
Bacteria are the most prevalent organisms on earth. A cubic centimeter of soil contains more than a million organisms. These tiny organisms or microorganisms, are often composed of single cells shaped like rods, spheres or spiral structures. Once deposited in surface water, they can survive for weeks, awaiting ingestion by a carrier who can support their reproduction.
Coliform bacteria are not disease causing organisms, and are only mildly infectious. They are a natural part of the microbiology of the intestinal tract of warm blooded mammals, including humans. Their presence in drinking water is used as an indicator that the water may contain bacteria that are harmful to humans, such as fecal coliforms and pathogenic Escherichia coli (E. coli). Chlorination is frequently used to treat drinking water, and to control bacteria like Vibrio cholerae, Salmonella typhii and several species of Shigella. These bacteria are responsible for serious diseases such as cholera, typhoid fever and bacillary dysentery. A drinking water outbreak of E. coli in Walkerton, Ontario in 2000, sickened 2,300 residents and killed seven when the municipal water supply was insufficiently treated. The developing world still grapples routinely with these bacterial pathogens in their drinking water. Bacteria that cause everything from ear infections to pneumonia are becoming immune to antibiotics. The primary cause is overuse and misuse by doctors and patients. But significant levels of antibiotics in water supplies could compound the problem. Some common bacterial pathogens are as follows:
Coliform
E-Coli Salmonella
Campylobacter
Viruses
Viruses can reproduce only within living host cells. They can be shaped like rods, spheres or filaments. Viruses are very small and they often pass through filters that will retain bacteria. They are not affected by antibiotics. There are more than 100 enteric viruses that infect the gastrointestinal or respiratory tracts. They are typically excreted in the feces of infected individuals and may contaminate water intended for drinking. Symptoms signifying infection include diarrhea, fever, hepatitis, paralysis, meningitis and heart disease (American Water Works Association, 1999). For more information on enteroviruses see the web page of the CDC.
Hepatitis A
Rotovirus
Noroviruses
Coxsackie B
Parasites
Parasites are organisms that derive nourishment and protection from other living organisms known as hosts. They may be transmitted from animals to humans, from humans to humans, or from humans to animals. Several parasites have emerged as significant causes of foodborne and waterborne disease. These organisms live and reproduce within the tissues and organs of infected human and animal hosts, and are often excreted in feces. For a visual representation of some common parasites, visit Cells Alive. For additional information, see the web site of the Food and Safety Inspection Service or the FDA's web site.
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