South Cumbria reservoir given crypto all-clear

Although Thirlmere is the largest single source serving the area, at the time of going to press, North West NHS communicable disease control scientists had found no evidence of cryptosporidium actually entering water supplies.

One sample taken from the reservoir did show an unusually high count of the microorganism, but North West Water said that follow-up tests showed no traces of the organism.

Water from the reservoir is piped to 400,000 households – 217 cases were reported last month in the north-west, mainly in the Greater Manchester areas of Salford, Trafford, Wigan and Bolton. Dr Paul Hunter, leader of the NHS investigation, advised people in the area “not to boil their water, but to seek medical advice” if suffering from persistent diarrhoea.

Cryptosporidium can be carried by a number of animals, has a long incubation period and is highly resistant to disinfection chemicals such as chlorine.

Several cases are known to have arisen following the contamination of boreholes and reservoirs with run-off from livestock farms.