Cysts - Real Pests in our Drinking Water
Cryptosporidium, "Beaver Fever", Giardia Lambia
This organic sporozoan, first described in 1907, wasn't recognized
as a cause of human illness until 1976. It is a protozoan parasite
that can infect a variety of animals. In the environment, Cryptosporidium
exists as a resilient, infectious, round oocyst about four to six
microns in diameter. The cyst is a "suitcase" for the
infectious material inside.
Cryptosporidium is widespread in the environment. Oocysts (cysts)
have been found in rivers, streams, lakes, reservoirs, sewage, and
treated surface water. Once introduced to water, the oocyst can
survive for weeks, even at low temperatures. The organism has been
found in humans, cattle, sheep, swine, goats, cats, and dogs as
well as deer, raccoons, foxes, coyotes, beavers, muskrats, rabbits
and squirrels. Oocysts infecting certain species can infect another
(referred to as cross-transmission). For example, organisms from
domestic animals (cattle, dogs, eats, etc.) are able to infect humans,
Conversely, organisms from humans can infect animals. Consequently,
animals which typically reside in or around watersheds may serve
as hosts to the cysts and continuous sources of infection. This
is where the nick name "Beaver Fever" was born. Beavers
carry the organisms and through their feces spread it throughout
surface water supplies without becoming ill themselves. Moreover,
infection can occur not only from drinking contaminated water but
also from eating contaminated food and from exposure to fecally
contaminated environmental surfaces.
When ingested, the Oocysts pass through the stomach into the small
intestine. There the Oocysts split open, releasing sporozoites which
invade the cells lining the gastrointestinal tract. Infected cells
lining the intestine appear normal, but their ability to absorb
water and nutrients is severely impaired. The water and food ingested
simply passes through the digestive system. Additional Oocysts are
formed in the intestine and either split open to release additional
sporozoites to continue the infection or are excreted in the feces.
The Cryptosporidium infection causes an illness called cryptosporidiosis.
After the Oocysts are ingested, the incubation period typically
varies from two to 12 days with an average of seven days. Disease
symptoms include diarrhea, abdominal cramps, nausea, occasional
vomiting and low grade fever.
The number of Oocysts that must be ingested to cause infection
in humans is not conclusively known. Studies indicate that as few
as ten and perhaps as many as 500 Oocysts are required to initiate
infections in mammals. The infectious dose for humans is thought
to be fewer than ten.
Cryptosporidiosis typically last 10 to 14 days. However, it may
linger off and on for up to 30 days and infrequently can persist
for extended periods. Children may be the most susceptible, particularly
six year olds and under. A rapid cure for Cryptosporidiosis has
not been found. Recovery depends on the patient's overall health
and immune system. The disease can be fatal for those who are already
in a fragile state such as someone with AIDS or any others weakness
to their immune system.
There are two varieties of the oocyst; (1) a sphere of about 4.5
micron in diameter and (2) an ellipse of about 7 x 5 micron. The
thick walls of the Oocysts make it difficult, almost impractical,
to kill with the UV systems in most domestic water treatment systems.
Also, the cyst is much more difficult to kill using chlorine than
normal coliform bacteria found in water supplies.
Since Doulton ceramic filter elements are manufactured so that
they remove pathogenic bacteria down to 1 micron in size; they are
100% effective in the removal of Cryptosporidium.