Citation:

Alum, A., E. Villegas, S. Keely, K. Bright, L. Sifuentes, AND M. Abbaszadegan. Detection of Protozoa in Surface and Finished Waters. Chapter 316, Manual of Environmental Microbiology. ASM Press, Washington, DC, , 3.1.6-1-3.1.6-25, (2016).

Impact/Purpose:

State of the science review chapter on waterborne protozoa. Chapter includes Cryptosporidium, Giardia, and N. fowleri, the three most important waterborne protozoa contaminating drinking water supplies.

Description:

Humans are known to be the host to approximately 1500 infectious agents, out of which 66 are protozoa and 287 are helminths. Therefore, from a global perspective helminths and protozoan parasites account for approximately one fourth of the total infectious diseases of humans. A similar trend has been observed in waterborne infectious diseases, among which a significant part is caused by enteric parasites.Cryptosporidium and Giardia are the leading cause of waterborne outbreaks of gastroenteritis across the globe, and as such, will be discussed in length in this chapter. These parasites are particularly suited for waterborne transmission as the environmentally resistant cysts and oocysts, respectively are shed in large numbers in feces (108-109 oocysts/gram), have a low infectious dose, and are resistant to disinfection practices.Naegleria fowleri is a pathogenic free-living amoeba found in the environment in both water and soil. There have been over 40 species of Naegleria described to date, but only N. fowleri is pathogenic to humans. N. fowleri was first identified as a human pathogen in 1965 in Australia. The first case in the United States was reported in 1966 and was described as primary meningoencephalitis. Prior to this documented case, free-living amoebae were not considered to be pathogenic. Pathogenic Naegleria fowleri is not easily differentiated from other Naegleria species due to similarities including common morphology when observed microscopically and indistinguishable behavior in cell culture.

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