Giardiasis: a common and underrecognized enteric pathogen.

Until the early 1940s, Giardia lamblia was considered by virtually all to be a simple intestinal commensal that benignly fed on small amounts of ingested food, never to cause symptoms or invade tissue. In the past 35 years this organism has established itself, through epidemics in which other pathogens were ruled out, as a fairly common cause of human enteropathology. The most common forms of symptomatic giardial illness present initially to primary care physicians and invariably are diagnosed as "gastroenteritis" with a symptom complex of abdominal upset, diarrhea, cramping, flatulence, and belching. Unlike most enteritides, giardiasis may become chronic and cause severe weight loss, malabsorption, or generalized discomfort. Also, unlike most, the organism is quite sensitive to antimicrobials and may be simply eradicated. Therefore, it is crucial that the index of suspicion for this illness be raised among family physicians, since it may be treated at the primary care level instead of remaining unsuspected until eventually being referred for a major gastrointestinal evaluation.