Can giardiasis be misdiagnosed as chronic fatigue syndrome (CFS) or IBS?

My colleagues and I published a study of two hundred patients with Chronic Fatigue Syndrome and demonstrated active Giardia infection in 46 per cent. (Giardia is a digestive tract parasite.) 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.

I also 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."