Do Intestinal Parasites Explain Your Post-Vacation Slump?

After traveling, it's time to get your GI tract back on track, because you may have brought home a parasite on your vacation.

Your bowel disturbances may have already told you that parasites had arrived in your digestive tract.

Parasites Can Be Acquired Anywhere

You don't need to travel to get a parasitic infection. The gastrointestinal tract is vulnerable to getting parasites anywhere, as I will explain below.

Last year I saw a patient who had returned from her Christmas vacation complaining of persistent dizziness and fatigue that had not improved for over a year.

Before visiting my office she had consulted three other doctors but no cause for the dizziness was found.

When I questioned her about the vacation, which took place at a Caribbean resort, I discovered that she had experienced a transient episode of diarrhea there and since returning home had been unusually constipated and gassy.

She had never mentioned these intestinal symptoms to a doctor before, because it was dizziness and fatigue that bothered her the most.

Testing for Parasites

I've seen many patients with chronic fatigue caused by intestinal parasites, so I had this woman tested at a specialized laboratory. The test revealed infection with a parasite called Giardia lamblia, a condition called giardiasis.

Healing the GI Tract

After treatment with anti-parasitic medication, her gastrointestinal symptoms slowly resolved, along with her main complaints of dizziness and fatigue.

Two Types of Parasites

There are two general groups of parasites that infect the digestive tract. The first consists of worms - tapeworms and roundworms - which attach themselves to the lining of the small intestine, causing internal bleeding and loss of nutrients. People infested with gastrointestinal tract worms may have no symptoms or may slowly become anemic.

The second category of digestive tract parasites is the protozoa, one-celled organisms like Giardia, which can cause bowel health symptoms such as acute or chronic diarrhea or can cause symptoms that are not ordinarily associated with parasitic infection like constipation, fatigue, dizziness, joint pain or hives.

Parasite Outbreaks

Epidemics of giardiasis have occurred at ski resorts in the dead of winter because of drinking water contamination. They commonly occur at day care centers that serve toddlers who wear diapers. Twenty to thirty per cent of workers in day care centers harbor Giardia. Most have no symptoms; they are merely carriers.

Parasites at the Salad Bar

Eating at a salad bar increases your risk of food-borne infection. Just observe the unhygienic habits of patrons or the way in which handles of serving spoons and tongs fall into the food.

A study at Johns Hopkins medical school demonstrated antibodies against Giardia in 20 per cent of randomly chosen blood samples from patients in the hospital. This means that at least twenty per cent of these patients had been infected with Giardia at some time in their lives and had mounted an immune response against the parasite. Most were unaware of having been infected.

Parasites: From the Water to the GI Tract

Giardia contaminates streams and lakes throughout North America and has caused epidemics of diarrheal disease in several small cities by contaminating their drinking water.

One epidemic, in Placerville, California, was followed by an epidemic of Chronic Fatigue Syndrome, which swept through the town's residents at the time of the Giardia epidemic. Possibly, this epidemic was due to failure of some people to eradicate the parasite.

Another protozoan that's achieved notoriety in the U.S. is Cryptosporidium parvum, which contaminated Milwaukee's water supply in the 1990's, causing the largest epidemic of diarrhea in U.S. history, infecting about 400,000 people and causing over one hundred deaths. Most municipal water supplies in the U.S. today are home to protozoa like Giardia and Cryptosporidium and one in five Americans drinks water that violates Federal health standards. Every year, almost a million North Americans become sick from water-borne diseases.

A Study on Chronic Fatigue Syndrome and Giardia

In 1991, my colleagues and I published a study of two hundred patients with Chronic Fatigue Syndrome and demonstrated active Giardia infection in 46 per cent. Most of the patients with giardiasis had only minor gastrointestinal symptoms but were really ill with muscle pain, muscle weakness, flu-like feelings, sweats and enlarged lymph nodes. In fact, 61 per cent of fatigued patients with giardiasis had been diagnosed elsewhere as suffering from chronic fatigue immune dysfunction syndrome (CFIDS), compared to only 19 per cent of fatigued patients without giardiasis. Cure of giardiasis resulted in clearing of fatigue and related 'viral' symptoms (muscle pain, sweats, flu-like feelings) in 70 per cent of cases, some reduction of fatigue in 18 per cent, and was of no benefit in only 12 per cent.

In 1990 I presented a paper before the American College of Gastroenterology which demonstrated Giardia infection in about half of a group of two hundred patients with chronic diarrhea, constipation, abdominal pain and bloating. Most of these patients had been told they had irritable bowel syndrome, which is commonly referred to as "nervous stomach". I reached two conclusions from this study: (1) Parasitic infection can be a common event among patients with chronic gastrointestinal symptoms. (2) Many people are given a diagnosis of irritable bowel syndrome without a thorough evaluation.

My presentation was reported by numerous magazines and newspapers, including the New York Times. My office was flooded with hundreds of phone calls from people who were suffering with chronic gastrointestinal complaints. Most of them had been given a diagnosis of Irritable Bowel Syndrome (IBS) by their physicians. The standard treatment for this syndrome had not helped them. All they had received was a label. Many had been told there was no cure.

In evaluating these patients, I found that the majority had intestinal parasites, food intolerance or a lack of healthy intestinal bacteria. (For more information about intestinal bacteria, see Probiotics or Friendly Bacteria)

These conditions were not mutually exclusive. Many patients had more than one reason for chronic gastrointestinal problems. Treating these abnormalities as they occurred in various patients produced remarkably good therapeutic results. A year later, researchers in the Department of Family Medicine at Baylor University in Houston reported findings similar to mine.

Despite the research and the news reports about parasites, I still find that intestinal parasites are a common and often unsuspected cause of mystery illness.

For more info on a gastrointestinal health, see my article Do you Have Leaky Gut Syndrome?

And to learn how to stay healthier next time you travel, read my article Pills for Your Upcoming Trip.

Resolving parasites and other digestive problems and improving gastrointestinal health are vitally important to healing. Learn how to assess your digestive function and the presence of intestinal toxicity in my book Power Healing.


Galland L, "Intestinal Protozoan Infestation and Systemic Illness", in Textbook of Natural Medicine, 3rd Edition, Volume 2, J. Pizzorno and M. Murray, editors, Churchill Livingstone Elsevier, St. Louis, 2005, pp. 655-660.

Galland L. "The Effect of Systemic Microbes on Intestinal Immunity" Post-Viral Fatigue Syndrome (Myalgic Encephalomyelitis) R. Jenkins and J. Mowbray, editors. John Wiley & Sons Ltd. London. 1991. pp 405-430.

Galland, L., Lee M., Bueno H. and Heimowitz C. (1990) "Giardia lamblia infection as a cause of chronic fatigue." Journal of Nutritional Medicine, 2, 27-32.

Galland, L. (1989) "Intestinal protozoan infection is a common unsuspected cause of chronic illness." Journal of Advancement in Medicine, 2, 529-552.