WASHINGTON: French researchers have found that extremely chlorine-resistant parasites called Cryptosporidium, which cause a diarrhoeal disease in humans and can lead to significant mortality in immunodeficient patients, become virtually inactive when exposed to industrial UV reactors.

Human contamination of the waterborne disease called cryptosporidiosis occurs by ingestion of the resistant form of the parasite, either directly through person-to-person and animal-to-person routes or indirectly through environmental vehicles including water, food or soil.

Contamination of water resources for drinking water supplies, as well as inadequate water treatment can be responsible for large cryptosporidiosis outbreaks. There has been no efficient curative treatment for this to date.

However, collaborators from the University Denis Diderot in Paris and the VEOLIA Research Center in Maisons-Laffitte have now shown the efficacy of UV light in large-scale tests with pilot equipment.

The researchers spiked the water with large amounts of Cryptosporidium oocysts, and then passed it through the UV reactors.

Thereafter, they assessed the efficacy of medium-pressure and low-pressure UV reactors used in the water industry by using a sensitive cell culture method in the Denis Diderot's University Laboratory of Parasitology.

The experiments successfully achieved inactivation rate of 99.998 per cent with both reactors.

According to the researchers, their findings confirm the remarkable efficacy of both polychromatic medium-pressure and monochromatic low-pressure UV lamps in conditions that are close to that of many small or medium size water distribution units.

"These tests, made in near real conditions, confirm that these industrial UV reactors could prevent waterborne outbreaks and secure water supply to customers," said Dr. Cedric Feliers, who led the study conducted for the VEOLIA Research Center.

The study has been published in FEMS Immunology & Medical Microbiology, a journal of the Federation of European Microbiological Societies.