: 3. Disease Causing Agents
causing agents include viruses
and bacteria, protozoa, worms and now dinoflagellates and diatoms that
either enter from domestic sewage and animal wastes or thrive in conditions
which give them a competitive edge.
The extent of
More than one
billion people worldwide drink unsafe water, A total of 3.4 million
people, mostly children, die every year from water-related diseases
from drinking, swimming in or washing clothes in polluted water.
Diseases include malaria, diarrhea and guinea worm.
This is to
be expected in LDC's, but does the US also have problems with parasites?
read the article below...
CONCLUDES MICROBES ENDANGER U.S. WATERS
have been busy protecting their waters from chemical pollution,
but microbes such as viruses and bacteria pose a much greater threat.
dangerous organisms include E. coli O157, cryptosporidium,giardia,
hepatitis A and pfiesteria, the report, from the American Society
for Microbiology, said. "Control of water pollution in the United
States over the past two decades has focused on chemical risks,
overshadowing the significant risks associated with microbial pollutants,"
to the Centers for Disease Control and Prevention, as many as 900,000
people get sick and 900 die every year in the United States because
of waterborne microbial infections.
coli bacteria can kill, as can legionella, which causes Legionnaire's
disease, a respiratory illness. Cholera, salmonella and shigella
are all bacteria that cause diarrhea and sometimes death. Parasites
such as Giardia cause diarrhea and can lead to lactose intolerance
and severe joint pain, while cryptosporidium, which also causes
diarrhea, can kill weak victims.
range from hepatitis A, which can cause liver failure, to coxsackieviruses,
which can cause a deadly heart inflammation and sometimes even diabetes,
while echoviruses cause meningitis.
of the contamination comes from the practice of pumping human waste
into rivers or oceans, or letting them filter into groundwater.
"A small drop of fecal matter can contain millions of these microorganisms,"
the report said. "There are approximately 25 million septic
tanks in the United States, receiving 175 billion gallons of wastewater
that could contaminate ground and surface waters with viruses and
other pathogens," it added. It said viruses had been found in
20 percent of groundwaters tested nationwide.
also pollutes waters. "Cattle can excrete millions of E. coli O157,
cryptosporidium, giardia and other microbes," he report said. "Chicken
wastes carry the pathogenic bacteria salmonella and campylobacter."
report points out that the EPA's standards for drinking water name
at least 70 chemicals, but only one microbe -- coliform bacteria,
which include the E. coli family.
treatment plants are supposed to filter out or destroy microorganisms,
but do not always succeed, the report adds. "Thus the wastewaters
released could still contain enough pathogenic microorganisms to
threaten human health," it says. Joan Rose, a marine biologist at
the University of South
who helped write the report, said she found nasty bugs sometimes
present in feces wind up right offshore within 12 to 24 hours of
being flushed. The report called for coordinated national action
by the EPA, the Food and Drug Administration and other agencies.
"There is a critical need for an integrated national initiative
on the microbial quality of water and on risk assessment as related
to public health," it concluded. Source: Reuters
if that isn't enough..........
WELL WATER LINKED TO STOMACH ULCERS
reported Wednesday they have found the first direct link between
drinking water and stomach ulcers. The finding came from tests done
on wells and other water sources in Pennsylvania where the bacteria
Helicobacter pylori was found. The bacteria is known to cause certain
report from Pennsylvania State University in Harrisburg said interviews
with residents who consumed the water found a statistically significant
correlation between presence of the bacteria and cases of stomach
ulcers. Katherine Baker who led the research said drinking water
is generally considered safe when coliform bacteria is not present.
But the ulcer-causing bacteria was found in coliform-free water
samples, she said.
this really means is that our current methods for testing drinking
water may be saying that water is fine while H. pylori may actually
be present," she said. Baker said the study involved private, untreated
water supplies ( approx. 25% of US water supplies are considered
rural) and not municipal water sources, which are less likely to
contain the organism. .......Source: Reuters
: Specific noted cases of outbreaks in the US include:
Examples: In 1993
the worst outbreak of a water born disease in modern US history occurred
in Milwaukee, Wisconsin. Severe bouts of watery diarrhea struck an estimated
August 1998 An estimated
1,300 people in a suburban area north of Austin may have been infected
with a potentially fatal parasite that could have been distributed through
the public drinking water system for as long as a week, health officials
say. The parasite comes from the feces of wild and domestic animals and
is found in up to 87 percent
of untreated water supplies. Rain runoff carries the parasite to surface
water supplies. Official estimate that crypto is in about one third of
the country's finished drinking water supplies.
The parasite causes
severe diarrhea and nausea. Healthy individuals recover in about 10 days,
but the virus can be deadly for children, the elderly or anyone with a
weak immune system, such as those affected by AIDS.
cypto, other parasites of concern include:
Diarrhea. severe vomiting enlarged spleen,inflamed; often fatal if untreated
- Cholera: Diarrhea,
severe vomiting dehydration often fatal if untreated
- Bacterial dysentery:
Diarrhea; rarely fatal except in infants without proper treatment
- Enteritis: Severe
stomach pain, nausea, vomiting; rarely fatal
Other major bacterial
diseases frequently linked to consumption of drinking water are caused
by Shigella spp., Salmonella spp., pathogenic E. coli, and Campylobacter
spp. All have multiple routes of infection and may be transmitted
through water, food, soil, or person-to-person contact. However, in
each case, major outbreaks of these diseases have been linked to consumption
of contaminated water. Morris and Levin (2) have estimated that within
the United States,contaminated water is responsible for 35,000
cases of shigellosis, 59,000 cases of salmonellosis, 150,000 cases
of infection with pathogenic E. coli, and 320,000 cases of campylobacteriosis.
- Infectious Hepatitis:Fever,
severe headache loss of appetite abdominal pain, jaundice enlarged liver
rarely fatal but may cause permanent liver damage
- Polio: High
fever severe headache sore throat, stiff neck, deep muscle pain, severe
weakness, tremors, paralysis in legs, arms, and body; can be fatal
In many ways,
viruses are the most poorly understood area of research on waterborne
disease. A number of authors have suggested that Norwalk virus and
Norwalk-like viruses are the major causes of both food- and waterborne
illnesses worldwide (143).
There is also
strong epidemiologic evidence that hepatitis A (HAV) and rotaviruses
are frequent causes of waterborne disease (147). HAV is reported to
be the first virus definitively shown to be transmitted by water,
and numerous outbreaks have been documented .HAV is one of the most
prevalent waterborne viral pathogens. Rotaviruses are also frequently
reported in outbreaks and, together with enteroviruses, have been
isolated from chlorinated drinking water systems (149,150). These
viruses are a primary cause of traveler's diarrhea. They are also
a major cause of infantile gastroenteritis and have been reported
to be responsible for 50% of hospitalized cases of diarrheal illness
in temperate climates (148,151).
Bennett et al.'s
analysis (84) suggested that 300,000 cases of waterborne infection
were caused annually by Norwalk virus in the United States. Rose
and Gerba's 1986 review of viruses in treated drinking water (148)
listed more than 110 types of enteric viruses capable of environmental
transmission. Morris and Levin (2) provide a point estimate of 6.5
million annual cases of waterborne viral disease in the United States,
with an estimated mortality of 0.005%. As previously discussed, many
assumptions necessarily made in these estimates may dramatically underestimate
or overestimate burden of disease.
- Amoebic dysentery:
Severe diarrhea, headache, abdominal pain, chills fever; if not treated
can cause liver abscess, bowel perforation and death
- Giardia (
now fairly common in US) Diarrhea, abdominal cramps flatulence belching,
fatigue. Increasing number of pets are picking up this parasite as well
parvum oocysts and Giardia lamblia (intestinalis) cysts imaged together
for purposes of comparison. In the photomicrograph, the C. parvum oocysts
are distinguished from neighboring G. lamblia cysts by their smaller
size. Bar = 10 microns.
G. lamblia and C.
Smith and Lloyd
(111) have recently reported that these two protozoa are responsible
for more than 600 million infections worldwide, of which a significant
proportion are waterborne. For example, 60% of Giardia cases are estimated
to be waterborne in the United States (84), with a point estimate of
the annual incidence of giardiasis of 260,000 cases (2). Until recently,
giardiasis was the most frequently reported waterborne disease (112,113).
Cryptosporidiosis has now overtaken giardiasis, with a point estimate
of 420,000 annual waterborne cases in the United States (2).
Over the past 10
years, there has been considerable emphasis on C. parvum research. This
is partly because of the scale of waterborne outbreaks seen in 1989
(116) (estimated 13,000 cases) and again in 1993 (117) (estimated >400,000
cases) but also because the outbreaks were associated with filtered
water supplies apparently meeting all appropriate standards for that
Outbreaks are reported with increasing frequency not only in the United
States (116-118) but also globally in both developed (119,120) and developing
countries (121,122). It is probable that reporting of cryptosporidiosis
infections will increase dramatically as awareness of this disease increases.
indicate that exposure to C. parvum is widespread and that asymptomatic
infection occurs frequently. In a study of 803 children in Oklahoma,
13% of children under 5 years of age, 38% of children 5 to 13 years
of age, and 58% of adolescents 14 to 21 years of age were seropositive
has been directed toward understanding the etiology of cryptosporidiosis,
in particular, its transmission from animal host through the water supply
to the human host. As with Giardia and many of the other pathogens described
in this review, C. parvum has a broad host range, making elimination
of this pathogen from the watershed virtually impossible. Both Giardia
cysts and infectious C. parvum oocysts recently have been shown to be
disseminated by waterfowl (125).
Abdominal pain, skin rash, anemia, chronic fatigue, and chronic general
- "Recently, considerable
interest has been focused on the plant plankton genus called Pseudonitzchia,
diatoms in which some species produce domoic acid, a potent neurotoxin
which causes short-term memory loss and death.
of this Pseudonitzchia were first discovered in 1987 when people who
had eaten mussels on Prince Edward Island in Canada began experiencing
short-term memory loss. Since that time another toxic species of this
genus, P. australis, was found to be responsible for the death of
pelicans off the California coast. Psuedonitzschia has also been found
in New England waters where health officials now monitor the mussels
for the presence of the toxin, domoic acid."
Locally we are
dealing with Pfeisteria:
Human Health Impacts
Thirteen people who worked with dilute toxic cultures of Pfiesteria
sustained mild to serious adverse health impacts through water contact
or by inhaling toxic aerosols from the cultures.
The effects include
a suite of symptoms such as narcosis (a "drugged"effect), development
of sores (in areas that directly contact water containing toxic cultures
of P. Piscicida, and also on the chest and face), uniform reddening
of the eyes, severe headaches, blurred vision, nausea/vomiting, sustained
difficulty breathing (asthma-like effects), kidney and liver dysfunction,
acute short-term memory loss, and severe cognitive impairment (= serious
difficulty in being able to read, remember one's name, dial a telephone
number, or do simple arithmetic beyond 1 + 2 = 3).Most of the acute
symptoms proved reversible over time, provided that the affected
people were not allowed near the toxic cultures again.
Some of these effects have recurred (relapsed) in people following
strenuous exercise, thus far up to six years after exposure to these
toxic fish-killing cultures.
In LDC countries,
simple techniques such as drinking water which has been stored in plastic
bottles, whose bottoms were painted black, and exposed to intense sunlight
for at least five minutes is enough to kill most of the parasites in the
which encourage people to share their water supplies with domestic animals
or to use the same water supplies for drinking and waste increases diseases
transmission. Here better education can have a major impact.
Funding or help for
towns to build wells for drinking water may be more important than expensive
water treatment plants. Estimated costs of $500-1000 per village well
is enough to significantly reduce infant/child mortality.
In MDC ( more developed
countries) upgrading their old, antique water purifications centers, better
training of personnel in this centers, and decreasing nutrients which
come from fertilization of fields, domestic animal production centers
( especially chicken, hog) would all help reduce disease transmission.
to introduction 1. Go to sediments
2. Go to inorganics: 3.
Go to disease vectors 4. Go to
plant nutrients: 5. Got to organics
6. Go to Oxygen-demanding wastes
7. Go to radioactive & thermal