Guardiasis in Paradise

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So what do you do about it? How can you keep from getting giardiasis . . . or get rid of a case you do contract? To answer these questions, you first need to understand what both the organism and the ailment are.

SMILING FACES

Giardia lamblia is a microscopic, one-celled protozoan that can exist in two different forms: one a dormant, tough-walled cyst and the other a mobile, vegetative trophozoite that can swim around with four pairs of flagella and adhere to your intestinal lining with a sucking disk. The trophozoite is very distinctive (see illustration). Its two nuclei and organelles make it look like a happy face . . . a tiny happy face: It's only 10 to 12 microns long by 7 to 10 microns wide. About 8,000 trophozoites can fit on the head of a pin.

The ovoid cyst is less jovial-looking, but it has a sterner function: This form helps the parasite survive hard times. The cyst can live for four days in 98.6°F (body temperature) water and more than two months at 39°F (for example, in the bottom of a winter pond). And taken into a host with food or drink, the hardwalled, dormant invader can survive the acid digestive juices of its host's stomach.

Once the cyst gets to the safety of the intestines, its tough wall breaks down and it "hatches" into a trophozoite, which attaches itself to the intestinal mucosa. There the little giardia feeds and multiplies (by simple fission), producing enormous numbers of progeny, which are passed as cysts in the feces, enhancing the organism's chances of getting to another host. (One estimate places the number at 14 billion protozoa per defecation!)

GIARDIASIS

The most surprising thing about giardiasis is the variation in host response to infection, which covers the spectrum from no symptoms at all to serious disease. Many people who carry giardiasis appear to be completely asymptomatic. That probably explains why the pathogenic nature of the organism has been recognized only in the last 40 years, even though the giardia itself has been known for 300 years—since the inventor of the nicroscope, Anton van Leeuwenhoek, spied the smiling trophozoite in 1681. ( Giardia lamblia was previously thought to be a harmless com mensal resident of the gut . . . merely "eating at the same table" as its host.)

Those who do become ill don't experience symptoms until the trophozoites have multiplied enough to have effects; this incubation period is usually around 6 to 20 days. The malady then experienced varies from mild—but often reoccurring—diarrhea to severely debilitating malabsorption and weight loss. The results can include painful illness and weakness (I could hardly drag myself out of bed), dehydration, lactase and vitamin deficiencies, and electrolyte imbalance. The Pandora's box of complaints goes on: abdominal pain, cramps, nausea, flatulence, belching, anorexia, fever, diarrhea alternating with constipation, and stools that often contain unusual amounts of mucus.

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