Food and Water borne Enteric Protozoa: Current considerations for Environmental Health

Enteric protozoa continue to contribute to the burden from preventable infectious diseases affecting humans and animal health in industrialized settings. Giardia, Cryptosporidium and Entamoeba sp., are the most commonly reported protozoa associated with enteric infections, and are mainly associated with food and waterborne outbreaks. Others such as Cyclospora, Dientamoeba fragilis, Balantidium coli, Cystoisospora belli, and Blastocystis hominis are emerging as important causes of illness, with serious implications for travellers to developing regions, immuno-compromised populations and young children. Although public health measures in most developed countries are more stringent than in developing settings, minority groups, institutionalized persons and the immuno-compromised remain at extremely high risk. In an era where environmental health interventions has reversed the burden from communicable diseases, globalization, explosion of urban populations and the
emerging effects of climate change, are predicted to have unprecedented effects on the risk and transmission of infectious intestinal illnesses, threatening previous gains. Furthermore, the challenges of protozoan diseases transmitted by food, water and animals are expected to increase as a result of complex interactions between the human and animal hosts, and the need to increase food production, international food trade and the demand for alternate water sources.

Enteric protozoa have been implicated in several large water-bone outbreaks in
the USA, Norway, and Australia. Giardia intestinalis was the most common cause of parasitic drinking water outbreaks and Cryptosporidium was responsible for the majority of individual cases, while Entamoeba histolytica and Cyclospora have caused fewer cases in the USA. Cryptosporidium, C. cayetanensis, Giardia and Toxoplasma gondii are the main protozoa associated with food-borne infections in developed countries. While the majority of laboratory confirmed cases of foodborne parasitic diseases are due to G. intestinalis, Toxoplasma is the major cause of reported illness, the fourth highest cause of hospitalization and the second leading cause of deaths from overall foodborne illnesses in the USA.  This paper discusses food and waterborne transmission of enteric protozoa, highlights emerging technologies for their diagnosis and molecular epidemiology, and emerging water and waste water quality issues and technologies, to aid in their surveillance, prevention and control.