Parasites: Little Bugs, Big Trouble

By Catherine Guthrie, Experience Life

Two weeks after kayaking on the Tennessee River, Kathryn Gage doubled over with a sharp, stabbing sensation in her gut. When the pain morphed into severe diarrhea and nausea, she saw a gastroenterologist.

The 40-year-old Knoxville resident told him she’d downed some river water while rolling her kayak, and she suspected her illness was related. Her intuition was fed by a friend who’d suffered from a parasite she’d picked up overseas and whose symptoms were strikingly similar. But after learning that Gage hadn’t been globetrotting, the specialist dismissed her theory and ordered upper and lower endoscopies instead. Both tests came back normal.

Meanwhile, Gage’s health deteriorated. Usually bubbling over with energy, the entrepreneur and mother of two refused to leave the house for fear she’d have a bathroom emergency. “When I did go out, everyone told me how green I was,” she recalls. Within a month, she dropped 20 pounds, leaving just 115 pounds on her 5-foot, 10-inch frame. Weak and dehydrated, she revisited the doctor, begging him again to test her for parasites. Her fears were unfounded, he said, and he ordered a colonoscopy.

The test didn’t find anything amiss, but during the procedure, the doctor removed a benign polyp and didn’t seal the wound completely. Several days later, Gage’s husband rushed her to the emergency room with life-threatening bleeding. Her physician finally agreed to check her for parasites, and sure enough, she tested positive for Giardia, one of the most common waterborne parasites in the United States. “One quick round of antibiotics and I was completely cured,” she says. “I couldn’t believe it, after all I’d gone through.”

The complications that ensued from Gage’s illness were unusual, but her doctor’s refusal to ponder parasites was not. “Most doctors think parasites only infect people who live in or travel to the tropics,” says Omar Amin, PhD, professor of parasitology and founder of Parasitology Center, a research and testing facility in Tempe, Ariz. “People with this mindset are up for a rude awakening.”

The Bug Boom 

The Centers for Disease Control and Prevention (CDC) estimates that millions of Americans are sickened by parasites each year and admits the problem is vastly under-reported. “Since many of the conditions are not reportable, we don’t have an accurate estimate of all the cases,” says Monica Parise, MD, chief of the CDC’s Division of Parasitic Diseases.

Amin and other experts believe as many as one in three Americans is hosting parasites. As evidence, he points to his 2002 study published in the American Journal of Tropical Medicine and Hygiene. Of the 2,896 patients who submitted stools for testing, 32 percent tested positive for parasitic infections. And the infection rate, Amin notes, is actually underestimated, since many patients don’t get tested for parasites.

Parasites are a big reason why one in four Americans has digestive trouble, Amin says, and many alternative practitioners agree. They note that the diagnosis and treatment of many GI troubles like gallstones are routine, while conditions like irritable bowel syndrome, and inflammatory bowel disease, which includes Crohn’s disease and ulcerative colitis, are tough to explain. The symptoms of these more mysterious ailments – stomach upset, gas, bloating, bleeding and diarrhea – mimic those of a GI parasitic infection.

Just coincidence? Skye Weintraub, ND, doesn’t think so. A naturopathic physician in Eugene, Ore., and author of The Parasite Menace: A Complete Guide to the Prevention, Treatment and Elimination of Parasitic Infection (Woodland Publishing, 1998), Weintraub finds underlying parasitic infections in roughly half of her patients who suffer from chronic GI troubles. “People come to me after they’ve been labeled as having irritable bowel syndrome, Crohn’s disease or ulcerative colitis,” she says. “Their doctors tell them they may need drugs for the rest of their lives, but I can often get rid of a parasite, and in a month or two, their symptoms are gone.”

Clinical nutritionist Ann Louise Gittleman, PhD, CNS, author of Guess What Came to Dinner? Parasites and Your Health (Avery, 1993), sees a similar trend. “Parasites are an unsuspected cause of many people’s health problems,” she says. “You can only find what you know how to look for, and most conventionally trained doctors don’t know how to look for parasites.”

Both Weintraub and Gittleman admit their specialized knowledge attracts patients with hard-to-treat parasitic infections, which skews their perspectives. But the question they pose is a valid one: Are parasites bugging us more than we think?

Parasites 101

A parasite is simply an organism that leeches nutrients from another, and humans can host hundreds of them. They range in size from the invisible, single-celled pests, like protozoa, to the more biologically complex worms, which are ingested as larvae and can grow to several feet in length.

Crossing paths with a parasite is easy. Contaminated water, undercooked meat, and poorly washed fruits and vegetables are all common pathways not to mention picking them up from animals and other people. (See “Seven Ways to Avoid Parasites at Home,” below.)

Parasites are linked to foreign travel for good reason. Of the 50-million-plus people who travel to the developing world each year, 22 to 64 percent report a travel-related health problem, and up to 8 percent seek medical care during or after their trip, according to a 2006 study published in the New England Journal of Medicine. Many of these illnesses can be linked to parasites. The three buggiest travel destinations? Central America, South America and South Central Asia.

But staying home won’t necessarily keep you pest-free. Gage, after all, was nearly undone by a parasite without ever leaving Tennessee. And, 40 percent of Amin’s patients get their parasites without pulling out their passports. “With all the foreign travel, parasites move easily from continent to continent,” he says. “There are no barriers anymore.”

So how does a tourist in Bolivia bring a pest back to Boise? Most bugs hopscotch around the world by fecal-oral transmission. Yes, that’s about as disgusting as it sounds, but it happens all the time.

To infect hundreds of people, it takes just one person to get infected abroad, come home and get careless with his personal hygiene, says John Christie, PhD, MD, a medical professor at the Brody School of Medicine at East Carolina University in Greenville, N.C.

Christie, who studies and teaches parasitology, notes that with global tourism, immigration and even military deployment on the rise, we should expect increases in parasitic infections.

NEXT: How to prevent getting sick at work

Immunity at Work

But if parasites are everywhere, why aren’t we all praying to the porcelain god all day? Fortunately, most people can host a parasite, or even two or three, without getting sick. A healthy immune system can keep most critters in check. In Amin’s 2002 study, for example, almost a third of the people infected with the Blastocystis hominis parasite felt perfectly normal.

People with the highest risk of being felled by a parasite are those whose immune systems aren’t up to snuff. When an outbreak strikes, it takes a toll on the elderly, the young and those with immune-compromising illnesses, such as HIV and AIDS. In some cases, a weakened immune system leaves the door open for either a new parasitic infection or an allergy to a parasite’s waste. Skin breakouts can be the body’s attempt to expel a parasite’s byproducts, says Amin. “A lot of people develop allergic reactions to the waste of a GI parasite.”

A dormant parasite also can be activated or reactivated when the body’s shields go down, says Christie. Such is the case with toxoplasmosis, a disease caused by the parasite Toxoplasma gondii. Humans can get the bug from indirect contact with cat feces or direct contact with contaminated raw meat. Roughly 22 percent of Americans age 12 and up have been infected with Toxoplasma gondii, according to a 2001 study by the CDC.

While most people’s immune systems take care of it, says Parise, the parasite can be lethal when a person is immuno-compromised. About 375 people die from food-borne toxoplasmosis each year, according to the CDC, making it the country’s third-leading cause of death due to food-borne illness.

Luckily, in the United States, parasites like Toxoplasma gondii are the exception, not the rule. Most parasites are content to nestle into Americans’ colons and hang out for weeks, months, even years, which is where ornery digestive disorders come into the picture.

Kelly Phillips (not her real name), a New Jersey stay-at-home mom, believes she has been harboring a parasite in her gut for a long time she thinks perhaps since childhood. But until about five years ago, the bug had never given her any trouble. Suddenly, Phillips, 47, began experiencing inflammation, bloating and a leaky gut – despite her strict adherence to a whole-foods diet and a disciplined yoga practice.

“I’ve spent 30 years leaning toward the holistic, healthy lifestyle,” she says, “but I still wasn’t maximizing my results.” She tried everything from acupuncture to aroma-therapy, but nothing helped. Finally, her doctor asked for a stool sample and discovered that Phillips was carrying a parasite called Dientamoeba fragilis. She began a 10-day regimen of Flagyl, an antiparasitic drug, that gradually began to reduce her inflammation and bloating. “I thinned out,” she says. “My body came into a sort of balance.”

But as soon as Phillips stopped taking the drug, the symptoms returned. So she went back to the doctor and learned that she was now suffering from the Epstein-Barr virus perhaps, she thinks, as a result of her weakened immune system. (She recently retested negative for the parasite, but she’s still suffering from Epstein-Barr.)

Whether parasites actually cause such gut-grabbing ills as irritable bowel syndrome, Crohn’s disease or ulcerative colitis, or just prey on people with poor digestion and compromised immunity, is impossible to say, but Western-trained doctors often are too quick to overlook parasites as a possible source of this suffering.

Elizabeth Lipski, PhD, clinical nutritionist and author of Digestive Wellness: How to Strengthen the Immune System and Prevent Disease Through Healthy Digestion (McGraw-Hill, 2005), sees parasites most often misdiagnosed as irritable bowel syndrome. As a result, she says, people take drugs to suppress stomach symptoms without ever addressing the cause.

Who Should Get Tested? 

If you’ve been diagnosed with a chronic digestive disorder but don’t feel like the label fits, and you suspect you might have a parasite, tell your doctor you’d like to be tested. If he or she balks, find a practitioner who specializes in infectious diseases, or tropical or travel medicine. Or find a qualified naturopath. Naturopaths are taught to take a holistic approach to health, which includes testing for parasites.

Parasites are notoriously difficult to diagnose, so be prepared to invest time and money. The best test for gastro-intestinal parasites is the tried-and-true stool exam (also called an O&P for ova and parasite test). Newer testing methods exist, but some experts, like Amin, don’t find them as accurate. Your healthcare practitioner may ask you to provide several stool samples, either over consecutive days or when symptoms are at their worst.

If the test comes back positive, prescription meds may be your best bet although, for nonsevere infections, some natural-health practitioners prefer to try herbal remedies first. Whatever you’re prescribed, take the full dose and then ask to be tested again to ensure the parasite is gone for good.

Parasites are tenacious, and that’s why many pros including Lipski think they are generally most effectively treated using Western medicine. “I’m a big proponent of natural health,” says Lipski, “but if you have a serious parasite, don’t mess around with herbs.”

Since taking antibiotics to wipe out her Giardia, Kathryn Gage hasn’t given parasites much thought. “I just feel like lightning isn’t going to strike twice,” she says. But she did make one parasite-induced promise to herself: “I will never set foot in the Tennessee River again.”

Catherine Guthrie is a freelance writer based in Bloomington, Ind.

NEXT: Reduce the risk of parasites invading your home

7 Ways to Avoid Parasites at Home

1. Keep your mitts clean, especially before preparing and eating food, and after going to the bathroom, diapering children and handling pets. Hand washing is the No. 1 thing people can do to protect themselves from a parasitic infection, says Monica Parise, MD, chief of the Division of Parasitic Diseases at the Centers for Disease Control and Prevention.

2. Drink treated water only. Tap water is a good starting place, because all municipalities treat water for parasites, but outbreaks do happen. Home filtration systems, especially reverse-osmosis filters, can add protection. If you prefer bottled water, look for one that’s labeled “filtered through an absolute 1-micron or smaller filter,” “1 micron absolute,” “distilled,” or “reverse-osmosis treated.”

3. Scoop cat litter boxes daily. As feces age, they acquire more parasites. If you are pregnant or your immune system is weak, ask someone else to clean the cat box for you.

4. Cook meat to 160 degrees F. Undercooked and raw meat, fish, and shellfish can harbor parasite larvae. After working with raw meat, use hot soapy water to wash hands, cutting boards and utensils.

5. Avoid ingesting water from pools and hot tubs. Between 1989 and 1998, 32 outbreaks of waterborne disease which were associated with 10,000 cases of diarrhea were linked to fecal contamination in pools in the United States. Two of the most common waterborne parasites, Cryptosporidium and Giardia, are growing increasingly resistant to the levels of chlorine found in most swimming pools.

6. Wash, peel or cook fresh fruits and vegetables before eating.

7. Don’t fertilize your vegetable garden with untreated manure.
5 Common Bugs in the United States

Blastocystis hominis
What? A microscopic organism that causes the infection blastocystosis

Who? In a 2002 study published in the American Journal of Tropical Medicine and Hygiene, 23 percent of the 2,896 individuals with gastrointestinal complaints tested positive for Blastocystis hominis.

How? Poor hygiene and unsanitary conditions

Symptoms? Watery or loose stools, diarrhea, stomach pain, gas

What? A microscopic parasite that causes the infection cryptosporidiosis

Who? One of the most common causes of waterborne disease in the United States. In 1993, cryptosporidium-tainted water sickened more than 400,000 people in Milwaukee, Wis.

How? Contaminated food or water

Symptoms? Dehydration, diarrhea, stomach cramps, weight loss, fever, nausea, vomiting

What? A single-celled, microscopic organism that causes giardiasis

Who? Found in every part of the United States. The CDC estimates 2 million Americans get giardiasis each year.

How? Eating or drinking contaminated food or water; indirect contact with animal or human feces

Symptoms? Diarrhea, gas, cramps, bloating, nausea, upset stomach, greasy stools that tend to float

Trichomonas vaginalis
What? A single-celled organism found in women’s vaginas, and occasionally in men’s urethras, that causes trichomoniasis, a common sexually transmitted disease

Who? The CDC estimates that more than 8 million people get trichomoniasis every year; it’s the most common, curable STD in young women.

How? Genital contact

Symptoms? A foul-smelling, yellow-green vaginal discharge, vaginal itching or redness; men often don’t have any symptoms.

Toxoplasma gondii
What? A microscopic parasite often carried by cats and found in contaminated meats and water that causes the human disease toxoplasmosis

Who? The CDC estimates that up to one-quarter of Americans may be infected with this parasite.

How? By touching your mouth or your food after cleaning a cat’s litter box, petting a cat or gardening in soil dotted by cat droppings; eating or drinking contaminated meats or water

Symptoms? Most people who have toxoplasmosis don’t even know it. The infection causes flu-like symptoms and usually goes away without treatment. The disease is most dangerous to people with compromised immune symptoms and pregnant women.

Experience Life magazine is an award-winning health and fitness publication that aims to empower people to live their best, most authentic lives, and challenges the conventions of hype, gimmicks and superficiality in favor of a discerning, whole-person perspective. Visit to learn more and to sign up for the Experience Life newsletter.

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Ami Jacobson
Ami Jacobson6 years ago

to GypsyGlory
yes constipation can be a sign of serious infection parasites can multiply quickly esp. if your constipated. they produce 100s 1000s of eggs A DAY not weeks or years but DAILY some stay and others are eliminated during a bowel movement. If you are not going then those destined for the tolit hatch and mature into adults who lay eggs. etc. the cycle continues. they in large numbers can make it difficult or impossible to have a bowel movement.There are so many "common" symptoms that get misdiagnosed as other "diseases". Parasites can and do mimick the body in order not to be detected by either the body or test leaving the host to suffer. I had and am still fighting a serious unknwn infection and went a whole year where I had to have enema's and laxatives every day or I didnt produce any bm. that has gotten better but at times when I dont zap I get constipated again real bad. If I let it go for more than 2 days Im in trouble. Sometimes only thing that works is a epsom salt solution that I drink with lots and lots of water. sometimes it takes a couple of those to get me moving. If you are always having a problem and have tried diet changes and increased your water intake added some exercise to your life with no improvement then you had better talk to a dr or better yet send off for the kit at Dr.Omar Amin office and let them test your feces. It will save you a lot of time and money if you do. good luck

Carol H.
Past Member 6 years ago

When I was a child I was living in Central America b/n/a The Panama, Canal Zone and I fell into a manhole five (5) feet down when I was three (3) years old.
There was dirty water on the bottom of it and on the way down I fell against the wall of the manhole and all of clothes was peeled off so when I landed I had no clothes on and when the water splashed it went into my rectum along with amebas (sp). It took a while but my mother noticed I wasn't gaining weight and when I would eat I bent over in pain and noticed white things in bowl movement so she took me to the doctor.
The only way in those days was to inject stricnine poison (sp) into me every Saturday for an entire year to kill the warms and their eggs without killing me. The only thing I can tell you it worked but as I was growing up I scared to death of shots but from the experience not much really effected me as far as childhood deceases I really didn't get anything except measles (sp) and all of got that at one time.
I am sorry for my bad spelling I hope I got my story over to all of you.

Adam R.
Past Member 6 years ago

I recently came accross your blog and have been reading along. I thought I would leave my first comment. I dont know what to say except that I have enjoyed reading. Nice blog. I will keep visiting this blog very often.


Emily Button
Emily Button6 years ago

It's interesting to read something about parasites in the U.S. I've been living in South America for 2 years, and parasites are as prevalent here as the common cold, but I've never thought about them being rampant in the U.S. Now I have amo against my germ-a-phobic sister who always makes fun of me when I come back to the U.S., saying she doesn't want me to contaminate her!!!

Tamara A.
Tamara A.6 years ago

The other night on TV I also heard that there were Weapons Of Mass Distraction in Iraq.

If _you_ want to try and catch something nasty in hopes of boosting your immune system, be my guest and tell me how it went...but please don't pass any whatever-it-is on to the rest of us :-p

Babak R.
Babak R.6 years ago

as a physician, i would be shocked for a physician not to have tested for giardia lamblia if she indeed gave him the history of drinking river water.

Gypsy Glory
Gypsy Glory6 years ago

Ok, all this info is well and good, but I have a question; can one of the symptoms of infection be constipation instead of diarrhea?
If anyone can answer, that'd be swell! (No pun intended. ;)

Annelise Howes
Annelise Howes6 years ago

Giardia is common....I've contracted it several times travelling through outback Australia and am now more careful about drinking local water in remote areas. It's misery - but easily fixed and I have never had any problems with doctors who readily prescribed the medicine needed.
About parasites: the other night on TV it was claimed that infesting people with hookworm (a parasite quite harmless to humans) helped activate their immune systems and that some asthma & coeliac sufferers improved...??? It appears that we are too sterile for oue own good!

Pamela C.
Pamela C.6 years ago

Wow! I had no idea how prevalent these parasites are. Thank you for this information.

Pam H.
Pamela H.6 years ago

Ah yes the colonoscopy. It's the latest fad. Methinks that drs are getting generous kickbacks for sending people off to have these things. They do them for everything from a headache to an ingrown toenail these days. The dr and his mates got in a few unnecessary tests as usual. Honestly, how unprofessional to send her off for a colonoscopy before doing a simple test for parasites.