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Water '101' |
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Clinical Features: A range of syndromes, including acute dehydrating diarrhea (cholera), prolonged febrile illness with abdominal symptoms (typhoid fever), acute bloody diarrhea (dysentery), and chronic diarrhea (Brainerd diarrhea). Common agents: include Vibrio cholerae, Campylobacter, Salmonella, Shigella, and the diarrheogenic Escherichia coli. Incidence: each year, an estimated 3-5 billion episodes
of diarrhea result in an estimated 3 million deaths, mostly among children.
Waterborne bacterial infections may account for as many as half of
these episodes and deaths. Many deaths among infants and young Transmission: Contaminated surface water sources and large poorly functioning municipal water distribution systems contribute to transmission of waterborne bacterial diseases. Chlorination and safe water handling can eliminate the risk of waterborne bacterial diseases. Risk Groups: Over 2 billion persons living in poverty
in the developing world are at high risk. Sporadic cases are under-reported.
CDC surveillance may detect a small proportion of outbreaks in the
United States; outbreaks abroad are often missed. Centralized water treatment and distribution systems are expensive and take years to complete. To provide the under-served with potable water in the short term requires innovative practical solutions such as point-of-use disinfection and safe water storage vessels. Parasitic AgentsGiardia lamblia is a one-celled agent that is commonly found
in rivers and streams, but may also be found in conventional sources
of drinking water. The agent enters the environment from the feces
of infected animals or other people. The organism lives in the intestine,
but because it has a protective shell, it can survive for long periods
of time outside the body. Infections may occur through accidental ingestion
of the agent when it is in food, soil, or water. Symptoms may take
one to two weeks to appear after infection and may persist for two
to six weeks.
Cryptopsoridium is a microscopic parasite that lives in the
intestines of its hosts. It is protected by a hard outer shell that
provides it some protection from chemical water treatment systems and
allows it to live outside the body for extended periods. It may be
found in recreational and drinking water almost anywhere in the United
States. Cryptopsoridium may be found in soil, food, water,
or any surface that has come into contact with either human or animal
feces infected with it.
Cyclosporiasis has been observed only since 1979. It is a
one-celled parasite that may be spread by ingesting contaminated food
or water contaminated with feces. One possible way the infection is
spread is through contaminated fresh fruit and vegetables that have
been handled improperly or washed with contaminated water. Person-to-person
transmission is unlikely. Recent outbreaks have included cases resulting
from consumption of contaminated raspberries imported from Guatemala.
While the precise mechanism of contamination is unknown, Nelson (2004)
states, “… it is likely that rinsing of the implicated
raspberries with contaminated water prior to their export had occurred.”
Bacterial AgentsEscherichia coli is a very common bacterium that exists in
many varieties. Harmless varieties live in human (and animal) large
intestines and are essential to normal digestion. Some types are harmful
(E. coli O157:H7), producing a potentially fatal toxin when
ingested through contaminated food or water. One well-publicized outbreak
in 1993 involved contaminated hamburgers sold through a popular western
food chain. It was later determined that the hamburgers had not been
cooked to 155 degrees Farenheit, the temperature which effectively
kills E. coli that often are found in ground beef. Person-to-person
transmission may occur and it may be spread through drinking raw milk
or drinking or swimming in contaminated water.
Salmonella is a bacterium that is most commonly associated
with eating undercooked meat, poultry, and eggs, but can affect water
supplies. It can be acquired directly from animals (not just reptiles).
It can be spread by food workers who have not practiced good hygiene
or through washing fruits and vegetables in contaminated water. Failure
to properly wash plates and utensils used to prepare meats and poultry
may also cause infection. Salmonella is also commonly associated
with reptiles. The illness is usually uncomfortable but not dangerous,
except for young children, the elderly, and the immuno-compromised,
who may become dangerously dehydrated. Onset of symptoms begins within
12 to 72 hours of infection and illness may last five to seven days.
Laboratory testing to establish correct antibiotic treatment may be
necessary. Many cases of salmonellosis probably go undetected.
Campylobacter is a spiral-shaped bacterium that is spread
and causes illness in a manner very similar to salmonella—it
is commonly associated with poultry and can be contracted by improper
cooking and handling of food and improper washing of dishes, utensils,
and cutting boards. It can also be acquired directly from animals.
Contaminated water and raw milk are also potential culprits. It is
one of the most common bacterial causes of diarrheal illness in the
United States. Onset of symptoms begins within two to five days of
exposure and typically last a week to 10 days. Treatment including
antibiotics is usually unnecessary, but some victims suffer serious,
long-term complications, including arthritis and Guillain-Barré syndrome.
Guillain-Barré is a condition in which gradually progressive
paralysis overtakes the subject, but the paralysis usually reverses.
It is estimated that one in 1,000 cases of Campylobacter infection
will result in Guillain-Barré and that 40 percent of Guillain-Barré cases
are associated with Campylobacter.
Shigella is a family of bacteria that causes illness very
similar to salmonella and campylobacter, but is usually
spreads differently—through the fecal-oral route, facilitated
by improper hand washing. Most of the types of Shigella found
in the United States cause an uncomfortable illness that is not dangerous,
but in the developing world Shigella dysenteriae type 1 causes
deadly epidemics. As with several other bacterial infections, Shigella may
necessitate hospitalization of the very young or elderly because of
profound diarrhea. Some infected individuals show no symptoms but easily
pass the illness on to others. Onset of symptoms begins within one
or two days after exposure and usually last five to seven days. Treatment
with antibiotics is usually done, but antibiotic-resistant strains
of Shigella have evolved. About 3 percent of victims of Shigella
flexneri suffer a serious, long-term complication known as Reiter’s
syndrome, which causes painful joints, irritation of the eyes, painful
urination, and perhaps long-term arthritis. The syndrome may last months
or years.
Vibrio cholerae, causative agent of cholera (see discussion
of John Snow above) has been almost completely eliminated from the
United States for the past 100 years or so. The United States has been
spared except for imported cases, or clusters of infections from imported
food. During 1993 and 1994, 69 cholera cases were reported to CDC,
and 65 were associated with foreign travel (Todar, 2002). There was
a major outbreak in 1991 in South America that affected several countries,
as well as an outbreak in Bangladesh in 1992. Despite the history of
serious illness and death associated with cholera, illness may be mild
or asymptomatic, but in severe cases dehydration and shock may lead
to death within hours without treatment. The organism is usually spread
by eating contaminated seafood (usually shellfish) and drinking contaminated
water. Antibiotics may shorten the duration of illness but re-hydration
is critical to reducing the chance of death.
ConclusionMore disease-causing agents than these exist, mainly affecting people
in developing nations. Many medical scientists have recently thought
infectious diseases had been conquered by the advent of antibiotics.
What they failed to recognize was that bacteria develop resistance
to antibiotics, and viruses can mutate in such a way as to render vaccines
ineffective. In addition to these forces, modern travel has enabled
microbes that normally were confined to remote, isolated populations
to spread beyond their normal habitats. It behooves us to exercise
care in choosing drinking water sources, particularly when traveling,
and to invest resources at home to assure safe municipal water supplies. ReferencesBlackburn, B.G., Craun, G.F., Yoder, J.S., Hill, V., Calderon, R.L.,
Chen, N., et al. Surveillance for Waterborne-Disease Outbreaks Associated
with Drinking Water—United States, 2001–2002. Morbidity
and Mortality Weekly Report, October 22, 2004/53(SS08); 23–45. OSU Extension embraces human diversity and is committed to ensuring that all educational programs conducted by Ohio State University Extension are available to clientele on a nondiscriminatory basis without regard to race, color, age, gender identity or expression, disability, religion, sexual orientation, national origin, or veteran status. Keith L. Smith, Associate Vice President for Agricultural Administration and Director, OSU Extension TDD No. 800-589-8292 (Ohio only) or 614-292-1868 Source of information: |
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