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Sporodic outbreak


Your news item on the Cryptosporidium outbreak in Galway (News last week) describes Cryptosporidium as a 'bacterial disease'. It is, in fact, a protozoan parasite, rather like an amoeba.

It does not 'lay eggs'; it reproduces asexually by forming a hard shell around itself, an oocyst, inside which it divides into four new Cryptosporidia. Once ingested by a potential host, the oocyst splits releasing the new Cryptosporidia to infect the gut of the host.

The UK Cryptosporidium regulations are not to be tightened, as your article suggests. The Drinking Water Inspectorate is currently consulting on the possibility of a change in the regulations which would allow ultra violet as a treatment option, inactivating the Cryptosporidia.

Oocysts are resistant to traditional chlorine disinfection of drinking water, so current regulations insist on physical removal down to a level below 1 oocyst per 10 litres.

The ability to use inactivation by UV, rather than physical removal, would have to be accompanied by a relaxation of the current treatment standard, which does not differentiate between viable and dead oocysts.

David Shore (M), operations director, South East Water, uk

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