Intestinal Protozoa: Their Role as Human Pathogens and Zoonoses

Abstract

Intestinal protozoa are single-celled eukaryotic microorganisms with nearly 10,000 species being parasitic in many invertebrates and most vertebrates. Intestinal protozoan infections are among the most common worldwide and contribute significantly to the burden of infectious diseases. While the morbidity and mortality caused by parasitic diseases affect people mainly in developing countries, protozoa also cause significant illness (e.g., outbreaks) in developed countries. These diseases are much more common in the tropics, including Southeast Asia, wherever sanitation is poor, making them a major health problem. Hence, it is crucial to have an enhanced understanding of the current status of the epidemiology of intestinal protozoan infections. In this review we provide an update on intestinal protozoan infections in Southeast Asian countries covering the diseases caused by Giardia duodenalis, Entamoeba histolytica, Cryptosporidium, and Blastocystis sp. Among them Giardia duodenalis is the best-known cause of protozoan gastrointestinal disease, producing significant but not life-threatening gastrointestinal distress and diarrhea. Dysentery, however, caused by E. histolytica is probably the most dangerous intestinal protozoan infection, although Cryptosporidium and Blastocystis sp. may cause diarrhea in healthy individuals and result in intractable, life-threatening illness in patients with acquired immunodeficiency syndrome or other immunosuppressive diseases.KeywordsProtozoa parasites Giardia Cryptosporidium Entamoeba Blastocystis