Researchers at the University of Zaragoza have detected cysts of Cryptosporidium and Giardia in potable water, two protozoa that cause outbreaks of diarrhea in humans. The levels recorded are deficient and do not pose a health risk, but according to the study, the ubiquity of these parasites and the ineffectiveness of conventional treatments to eliminate them can lead to a public health problem.

Cryptosporidium and Giardia

The protozoa of the genus Cryptosporidium and Giardia are the parasites that cause more waterborne diarrhea outbreaks in developed countries.

People can accidentally ingest them when they drink water at playgrounds or even at home if it is not completely clean.

Now scientists from the University of Zaragoza have analyzed the presence of cysts - stains of resistance and dispersion of these parasites - in Water Treatment plants in the 20 most populated towns of Aragon. They took samples between 2013 and 2015, both of the 'raw' water that enters the Water Treatment Plants and the treatment that comes ready to drink, and analyzed using techniques employed by the US Environmental Protection Agency.

The results, published in the journal Science of The Total Environment, show that in potable water delivered eleven of the plants were protozoa, with an average concentration of 88 oocysts of Cryptosporidium and 37 Giardia cysts per 100 liters of Water.

Less in autumn and more in winter

In this study, 55% Cryptosporidium detected in the water treatment plants and 70% Giardia, with nine plants positive for both protozoa and only four in which none meant to register. Both pathogens were found in the entry water throughout the year, with a lower frequency in autumn and a maximum in winter - especially Giardia, with 1.25 cysts per liter.

  • The uncountable techniques are not entirely effective to remove them from the water or inactivate them in case the corresponding filters pass, as they resist chlorination.

The United Kingdom is the only EU country where the presence of these pathogens has been systematically being analyzed by water supply companies for some years.

It is also the European country, along with Ireland, where more cases of Cryptosporidium and Giardia infections have reported.

The cases of Bergen and Milwaukee

The diarrheal outbreaks that produce these parasites can affect large population groups, such as the Beaver Fever that made about 2,500 people sick in Bergen (Norway) in 2004, or the massive outbreak of cryptosporidiosis that in 2003 affected more than 400,000 citizens in Milwaukee (USA).