Abstract
We applied a sensitive diagnostic test for Giardia lamblia infection to 218 patients with a chief complaint of chronic fatigue. Sixty-one patients were infected with Giardia. All had minor gastrointestinal symptoms: bloating (61%), flatulence (62%), loose bowel movements (56%) and constipation (50%). All patients also complained of other systemic symptoms: depression (61%), myalgia (34%), headache (41%), muscle weakness (46%) and flu-like feelings (34%). The median duration of the illness was 3.2 years. Treatment of giardiasis produced a complete cure of fatigue in 13/48 patients, marked improvement in 21/48 patients, some benefit in 8/48 and no benefit in 6/48 patients. ‘Viral’ symptoms such as fever, myalgia and sore throat were much more common in fatigued patients with giardiasis than in fatigued patients without giardiasis. Giardia infection may be an important cause of chronic fatigue and myalgic encephalomyelitis (ME) in patients with minor digestive disturbances. Dysfunctional immune activation or transport of RNA viruses by the parasite may account for systemic symptoms being predominant.
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