ATLANTA — Findings of a new Centers for Disease Control and Prevention (CDC) study about the prevalence of Cryptosporidium and other parasites in swimming pool filter backwash suggest that there is a need for continued emphasis on improving swimming pool operation and maintenance, such as preventive hyperchlorination or routine flocculation, combined with supplementary inline disinfection systems such as ultraviolet light (UV) or ozone.

The study, “Prevalence of Cryptosporidium spp. and Giardia intestinalis in swimming pools, Atlanta, Georgia,” was published in the June 2008 issue of the journal Emerging Infectious Diseases.

UV and ozone are known to inactivate Giardia sp. and Cryptosporidium spp., both gastrointestinal parasites spread through the fecal-oral route, according to the study’s authors, Joan M. Shields, et al.

According to the study’s abstract, “Cryptosporidium spp. and Giardia intestinalis have been found in swimming pool filter backwash during outbreaks. To determine baseline prevalence, we sampled pools not associated with outbreaks and found that of 160 sampled pools, 13 (8.1 percent) were positive for 1 or both parasites; 10 (6.2 percent) for Giardia sp.; 2 (1.2 percent) for Cryptosporidium spp.;, and 1 (0.6 percent) for both.”

While the authors write that the study is “a snapshot of contamination at the end of the swim season,” they conclude that “the finding of swimming pool filter contamination by Giardia sp. and Cryptosporidium spp. is key,” reinforcing the need for improved pool operation and maintenance. UV and ozone are both listed as supplementary inline disinfection systems that should be considered.

The authors also write that the general public, especially immunocompromised persons, need to understand recreational water–associated illness transmission and adopt healthy swimming habits that are needed to reduce the risk for pathogen transmission.

To read the full study, click here.

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