Environmental Engineering Reference
In-Depth Information
that the highest U.S. level ever reported was 1000—and that those U.S. reports included the
1995 Milwaukee outbreak, where hundreds of thousands of people fell ill. He also pointed
out that other common fecal bacteria should be present in the sample as well, but were not
(Anon., 1998).
The moral of the story? Know your stuff. Be sure of your technique and do everything
you can to ensure the accuracy of your samples and test results. As a water control technolo-
gist, you may have to turn in test results that open a similar can of worms at some point—or
announce unsafe water supplies to the press.
Cryptosporidiosis
Cryptosporidium parvum
is an important emerging pathogen in the United
States and a cause of severe, life-threatening disease in patients with
AIDS. No safe and effective form of specific treatment for cryptospo-
ridiosis has been identified to date. The parasite is transmitted by inges-
tion of oocysts excreted in the feces of infected humans or animals. The
infection can therefore be transmitted from person-to-person, through
ingestion of contaminated water (drinking water and water used for rec-
reational purposes) or food, from animal to person, or by contact with
fecally contaminated environmental surfaces. Outbreaks associated with
all of these modes of transmission have been documented. Patients with
human immunodeficiency virus infection should be made more aware
of the many ways that
Cryptosporidium
species are transmitted, and they
should be given guidance on how to reduce their risk of exposure.
—Dennis D. Juranek (1995)
Since the Milwaukee outbreak, concern about the safety of drinking water
in the United States has increased, and new attention has been focused on
determining and reducing the risk of contracting cryptosporidiosis from
community and municipal water supplies (CDC, 1995). Cryptosporidiosis
is spread by putting something in the mouth that has been contaminated
with the stool of an infected person or animal. In this way, people swallow
the
Cryptosporidium
parasite. As we pointed out earlier, a person can become
infected by drinking contaminated water or eating raw or undercooked food
contaminated with
Cryptosporidium
oocysts, by direct contact with the drop-
pings of infected animals or stool of infected humans, or by hand-to-mouth
transfer of oocysts from surfaces that may have become contaminated with
microscopic amounts of stool from an infected person or animal.
The symptoms may appear 2 to 10 days after infection by the parasite.
Although some persons may not have symptoms, others experience watery
diarrhea, headache, abdominal cramps, nausea, vomiting, and low-grade
fever. These symptoms may lead to weight loss and dehydration. In other-
wise healthy persons, these symptoms usually last 1 to 2 weeks, at which
time the immune system is able to stop the infection. In persons with sup-
pressed immune systems, such as persons who have AIDS or who recently
have had an organ or bone marrow transplant, the infection may continue
and become life threatening.
