Changes in the Small Intestinal Mucosa in Giardiasis

Giardia lamblia is the most common protozoal parasite affecting the small intestine in man. The illness caused by infection with Giardia may be acute and self-limiting or chronic; it may be asymptomatic or the cause of a severe enteropathy with malabsorption. At present the reasons for this extreme variation in host susceptibility are not well understood. Many of the clinical studies in the literature concern unusual presentations or highly selected groups of patients. In general, these reports concentrate on particular aspects of the infection, rather than attempting to correlate clinical features with intestinal pathology or with other host factors such as nutritional status, systemic immune competence, or mucosal immunity. In this chapter we have attempted to produce a synthesis of the many changes in small intestinal structure and function reported to occur in human giardiasis. By comparing such detail with information obtained using the mouse model of the disease, where more extensive investigation is possible, we have also analyzed the various effects of the parasite on the intestinal mucosa.