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2003
RIVER
RESCUERS
UM'S NEW RIVERINE SCIENCE CENTER
POISONED
HEARTS
ARSENIC EFFECTS ON CARDIOVASCULAR HEALTH
WATER
WIZARDRY
BIO STATION'S NEW FLOOD PLAIN MODEL
RIVERS
THAT TIME FORGOT
AN UNDISTURBED RUSSIAN WILDERNESS
SODIUM
SOLUTIONS
COALBED METHANE IN EASTERN MONTANA
HEAVY
METAL
SCIENTISTS STUDY IMPACT OF METALS ON MICROBES
COTTONWOOD
CONUNDRUM
MONTANA'S DISAPPEARING RIVER TREES
WATER
WARDENS
UM'S WATERSHED HEALTH CLINIC
TALLYING
TADPOLES
STUDYING MONTANA AMPHIBIANS
FISH
FINDERS
DNA IN WATER REVEALS LOCATION OF FISH
WET
AND WILD
A PRIMER ON MONTANA AQUATIC LIFE
WATER
THAT WAS
THE SECRETS OF GLACIAL LAKE MISSOULA
NEWS
TO USE
THE WEIRD LIFE CYCLE OF SWIMMER'S ITCH
BACKTALK
GIARDIA: A WATER DRINKER'S GUT-WRENCHING SURPRISE
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| Two microscopic views of giardia lamblia. |
Backtalk
Giardia:
a water-drinker's gut-wrenching surprise
By
HOLLY FOX
You've heard it before -- don't drink the water!
That mantra holds true whether you're siteseeing in another country or exploring the wilderness of your own backyard. While the water in Montana's lakes, rivers and streams may look refreshingly clear, just one sip could make you a very unhappy camper.
The
culprit? Giardia lamblia, one of the most common intestinal parasites in
the world. The waterborne parasite can be found anywhere from remote areas
to high-density, high-dollar resort towns — anywhere there's water
and a host.
Hosts can be people or any mammal. Beavers have taken the brunt of the
blame for spreading giardiasis, which is often called "Beaver Fever."
"While beavers can carry the parasite, I think they have been blamed excessively for spreading the disease," says UM Professor Bill Granath. "Most mammals — dogs, sheep, cows, any livestock — can carry and spread the parasite. I think beavers have probably been blamed because the water in beaver ponds can look clean, leading people to drink from them."
Giardia lamblia has two life stages — trophozoite and cyst. In the trophozoite stage, the parasite latches on to the small intestines where it feeds and reproduces. As it nears the large intestine, the parasite forms an outer covering — a cyst — which is excreted from the body into the environment. People contract giardiasis when they drink water that has been contaminated with giardia cysts.
"People used to think giardia cysts were dormant," Granath says, "but actually, the parasite divides twice in the cyst, so for every cyst ingested, you actually get four trophozoites."
Classified as a protozoan and a non-invasive parasite, giardia doesn't feed on its host's tissue like other such bugs. Instead the teardrop-shaped organisms attach to the intestinal lining where they feed on mucus and other secretions. Their attachment to the intestinal wall prevents the host from absorbing water or nutrients from food.
Giardiasis is rarely fatal and the symptoms can vary widely. Half of infected people show no symptoms, while others experience mild diarrhea. In the worst cases, people infected with giardia can develop malabsorption syndrome — dehydration so severe that hospitalization is required. Severe dehydration can lead to an electrolyte imbalance, which can lead to shock or death.
Granath says that humans have a difficult time killing the parasite because as soon as we have developed enough antibodies to fight it off, giardia changes form just enough to require a different antibody.
"When the antibodies reach a certain level, the parasite changes and we have to start making new antibodies all over again," he says. "All the while, the parasites are feeding and reproducing."
Luckily, the ailment can be treated with any one of three prescription drugs, all of which have good rates of success.
So how do you avoid getting giardiasis in the first place?
Forget any type of chemical treatment — including the chlorine tablets many campers use to purify their water in the woods — the amount of chemicals needed to kill this parasite is not safe for human consumption.
"The cysts can't survive freezing or drying out, so freezing or boiling water will kill the parasite," Granath says. "Also, water filtration kits for campers and hikers will remove the parasite."
Campers, hikers and outdoor enthusiasts of all kinds: Get out there and enjoy Montana's natural beauty — just remember to think before you drink.