A study of variation in serological markers for Cryptosporodium exposure over time associated with the introduction of enhanced filtration treatment of drinking water from Loch Katrine

Cryptosporidium is a protozoan parasite that causes the clinical illness cryptosporidiosis in humans, presenting as a diarrhoeal illness, which can be prolonged but is usually self-limiting. The infectious oocysts are carried and transmitted by a wide variety of animal species including humans. Zoonotic transmission occurs from animal carriers to man,as well as person-to-person transmission between humans. Infection can also be acquired indirectly through the exposure to contaminated food or water. Consumption of contaminated drinking water is a well-recognised risk factor for human cryptosporidiosis,presenting both as sporadic cases and as waterborne outbreaks. The first recorded waterborne outbreak in the UK occurred in Ayrshire, Scotland in 1988.A number of additional high profile waterborne Cryptosporidium outbreaks occurred in Scotland and elsewhere in the UK, associated with unfiltered tap water consumption, failures of filtration treatment or post-treatment contamination of treated supplies. This lead to a Government enquiry, chaired by Sir John Badenoch. The report of this enquiry and subsequent (Bouchier) groups recommended a series of measures to reduce the risks of waterborne cryptosporidiosis. This, in turn, lead to significant investment in improved standards of water treatment, especially for unfiltered supplies.Scotland had several large examples supplying the Glasgow area (Loch Lomond, Loch Katrine)