24---A specter is haunting the nationís drinking water supply:
the specter of Cryptosporidium.
Cryptosporidium parvum is a small, crude and
potentially deadly pathogen. Scientists have known about it since
1907 but were not aware of its effects on humans until 1976. Nine
years later in 1987, cryptosporidium sickened more than 13,000
people in Carrolton, Ga. Scientists traced the outbreak back to the
municipal water supply Ė surprising, considering that the water
met all state and federal safety standards.
The most memorable case occurred 6 years later in
Milwaukee, when an outbreak sickened an estimated 400,000 people,
contributed to the deaths of more than 50 AIDS and chemotherapy
patients and resulted in the loss of more than $37 million in lost
wages and productivity. Like the Carrolton outbreak, the problem was
traced to the local drinking water supply.
Cryptosporidium is like few other waterborne
pathogens, which explains why it can survive rigorous disinfection
and why scientists are so worried about it.
"Cryptosporidium parvum is extremely
troublesome for a number of reasons," says Dr. Jim Hairston, an
Alabama Cooperative Extension System water quality scientist and
Auburn University professor of agronomy and soils.
"It can exist outside its host in a tough
egg-type structure called an oocyst, which can cause infection once
itís been ingested by humans and host species," he adds.
Equally disturbing, Hairston says, is the fact that
scientists are not sure how long these oocysts can survive under a
wide range of environmental conditions.
"They are very resistant to the most common
detergents and disinfectants," he says, adding that even
commonly recommended sanitary procedures will not always prevent
Oocysts, for example, are not killed by many common
household disinfectants, including bleach. In fact, they can survive
for up to two hours in common household bleach at room temperature.
Even chlorination, the method most commonly used by
water treatment plants to cleanse water of potentially harmful
pathogens, will not kill the oocysts. That is why public water
utilities throughout the nation are developing new techniques to
ensure drinking water is safeguarded from this pathogen.
Physical removal of particles has traditionally been
an important step in treating drinking water. Following the Cryptosporidium
outbreak in Milwaukee, water-treatment authorities throughout the
nation stepped up efforts to improve their micro-filtration system
to reduce risk of oocysts turning up in the drinking water supply.
Ozone and ultra-violent light are also effective
against Cryptosporidium oocysts, though these techniques are
very expensive and cannot safeguard the water against additional
exposure that may occur as the water moves beyond the treatment
facility and further along the distribution chain.
Currently, no drug is available to treat
Cryptosporidiosis, the disease that can occur when the oocysts are
ingested. The good news is that Cryptosporidiosis poses no threat to
healthy people, other than a few days of diarrhea, nausea and
People with compromised immune systems are a
different matter. The effects of prolonged diarrhea and dehydration
can be dangerous and, in some cases, even deadly.
The elderly as well as AIDS and chemotherapy
patients need to be especially aware of the risks associated with
The risk of waterborne Cryptosporidiosis from public
drinking water varies depending on the quality of the source water
and the type of water treatment.
People with compromised immune systems should
consult their local health authorities to determine the risk in
In areas where chance of a Crytosporidium
outbreak is relatively high, AIDS patients and others with weakened
immune systems should consider disinfecting their water by bringing
it to a rolling boil for at least one minute. The pathogen also can
be removed with point-of-use filters, although only filters with an
absolute (not minimum) pore size of one micron or smaller will
(Source: Dr. Jim
Hairston, Extension water quality scientist, 334-844-3973.)