Waterborne transmission of protozoan parasites: Review of worldwide outbreaks – An update 2004–2010

Abstract

The present update gives a comprehensive review of worldwide waterborne parasitic protozoan outbreaks that occurred and were published globally between January 2004 and December 2010. At least one hundred and ninety-nine outbreaks of human diseases due to the waterborne transmission of parasitic protozoa occurred and were reported during the time period from 2004 to 2010. 46.7% of the documented outbreaks occurred on the Australian continent, 30.6% in North America and 16.5% in Europe. Cryptosporidium spp. was the etiological agent in 60.3% (120) of the outbreaks, Giardia lamblia in 35.2% (70) and other protozoa in 4.5% (9). Four outbreaks (2%) were caused by Toxoplasma gondii, three (1.5%) by Cyclospora cayetanensis. In two outbreaks (1%) Acanthamoeba spp. was identified as the causative agent. In one outbreak, G. lamblia (in 17.6% of stool samples) and Cryptosporidium parvum (in 2.7% of stool samples) as well as Entamoeba histolytica (in 9.4% of stool samples) and Blastocystis hominis (in 8.1% of stool samples) were detected. In those countries that are likely affected most a lack of surveillance systems is noticeable. However, countries that established surveillance systems did not establish an international standardization of reporting systems.

Introduction

Waterborne parasitic protozoan diseases have a worldwide distribution and are, in both developed and developing countries, reasons for epidemic and endemic human suffering (Cotruva et al., 2004). They are one of the main reasons for 4 billion cases of diarrhea that causes annually 1.6 million deaths (www.who.int) and 62.5 million Disability Adjusted Life Years (DALYs) worldwide (Wright and Gundry, 2009). Diarrhea belongs to the five most common disease causes of death (www.who.int) and is responsible for 21% of deaths of children younger than five years of age (Kosek et al., 2003). The most prevalent waterborne parasitic infections producing diarrhea are cryptosporidiosis and giardiasis, already the appearance of infections caused by Giardia lamblia account 2.8 × 10^8 cases yearly (Lane and Lloyd, 2002). Other parasitic protozoa with a waterborne transmission that cause human infections are Toxoplasma gondii, Entamoeba histolytica, Acanthamoeba spp., Cyclospora cayetanensis, Microsporidia, Isospora, Blastocystis hominis, Sarcocystis spp., Naegleria spp. and Balantidium coli. Since most of these protozoa use the faecal-oral way of transmission they can infect humans through sewage and contamination of land and rivers by animal or human feces (Lanata, 2003). Efficient sanitation and improved water supplies are the main safety measures against parasitic protozoan hazards. The United States created organizations like the Center for Disease Control and Prevention (CDC) and the US Environmental Protection Agency (USEPA) that enforced waterborne disease outbreak surveillance since 1971 (WBDOSS). In 1980 Sweden established a surveillance system (Stanwell-Smith et al., 2003) and in 1981 Japan started the National Epidemiological Surveillance of Infectious Diseases (NESID). The National Notifiable Diseases Surveillance System (NNDSS) in Australia was founded in 1990, the Health Protection Agency (HPA) of the United Kingdom in 2003, and furthermore, the Public Health Agency of Canada (PHAC) in 2004. Following the example of the USA European Countries created the European Center for Disease Control and Prevention (ECDC) in 2005. From most of these centers highly qualified information and documentations of waterborne parasitic protozoan outbreaks are approachable. In developing countries, governmental systems to register incidence and prevalence of protozoan infections or waterborne outbreaks are not established. Consequently there is a lack of documentation of waterborne parasitic protozoan outbreaks in developing countries.

In 2007, the Journal of Water and Health published a review of worldwide waterborne outbreaks caused by parasitic protozoa (Karanis et al., 2007: Waterborne transmission of protozoan parasites: A worldwide review of outbreaks and lessons learnt) which spans a time period of almost hundred years from the beginning of the previous century. The aim of the present work is to update worldwide waterborne outbreaks of pathogenic protozoa during the time period of 2004–2011 and to figure out their worldwide distribution pattern.