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Cryptosporidium is a waterborne parasite that sneaks into your intestines with all the grace of a tabloid journalist at a Royal Gala. 

I feel sorry for those living in Devon that have been finding this out the hard way.

This microscopic miscreant thrives in the murky depths of contaminated water, often lurking in pools and water parks, those modern cesspits of chlorine and children’s laughter. 

It strikes with the suddenness of a tax audit, leaving you doubled over in gastrointestinal agony, as if cursed by the ghost of a disgruntled chef.

This ghastly protozoan, with its tenacity to resist even the most rigorous chlorination, is the stuff of nightmares for both public health officials and hapless holidaymakers. 

Once ingested, it sets up camp in your gut, multiplying with a fervour that would make rabbits blush. 

The result? Days of relentless, watery diarrhoea, nausea, and a malaise that transforms your stomach into a gurgling cauldron of woe.

Yet, for all its malevolence, Cryptosporidium often slips through the cracks of public consciousness, overshadowed by more flamboyant pathogens. 

But make no mistake, this insidious bug is a reminder that nature, much like a mugger, can be both unseen and devastating. So next time you take a dip, remember: even the clearest water can hide the darkest secrets.

Cryptosporidium can spread rapidly.  The best way to minimise this in your home is by practicing extremely good hygiene. Wash your hands with soap more often than you usually do, especially after using the toilet, after changing nappies, and a-l-w-a-y-s before eating or preparing food, drink; even when making ice.

There are several forms of Cryptosporidium that afflict a menagerie of beings: humans, household pets, cattle, sheep, rodents, birds, fish, and reptiles. But today, let’s turn our spotlight on Cryptosporidium hominis, the particular scourge that takes an unwholesome interest in us humans.

For the robust among us, the infection may pass unnoticed, though it often manifests as a bout of diarrhoea that graciously resolves itself in a couple of weeks.

However, for those with compromised immune systems, it’s a far grimmer tale.

They may be beset by a deluge of life-threatening, watery diarrhoea that laughs in the face of our most advanced medical treatments.

The transmission route is the faecal-oral highway, with infectious cysts hitching a ride via direct contact with infected individuals or animals, or through contaminated water and food.

These tenacious cysts can hibernate for months in moist soil or water, and endure the harshest of environmental conditions, be it scorching heat or biting cold.

Outbreaks are the stuff of nightmares, cropping up in hospitals, homes, kindergartens, at communal dining events, in the inviting waters of lakes, rivers and pools, and, as we’ve lamentably seen in Devon, within municipal water supplies tainted by this resilient pest.

Water distribution systems are particularly susceptible, as Cryptosporidium can laugh off most disinfection attempts, including chlorination.

But don’t let your guard down just because you’re fixated on Cryptosporidium. Animal parasites are also prolific hitchhikers, spreading from pets through human contact or from farm animals directly via their meat or indirectly through manure fertilising our crops. Fish, too, are no strangers to water-borne parasites.

Research, in its grimly enlightening way, suggests that 85% of us are playing host to parasites – a number that is, distressingly, on the low end of the real estimate.

Another microscopic parasite worth avoiding is Giardia. You can fit about 8000 Giardia onto a pinhead making it difficult to detect them, unless with an electron microscope. 

Just a single cubic inch of prime, organic, Grade A beef can be home to up to 1,000 unhatched parasite larvae. If you have regular bowel movements, you may deny these unwelcome guests the time they need to hatch in your digestive tract.


In the great outdoors, hydrate wisely. Drink from large, fast-flowing streams when possible. Giardia cysts, those other merry pranksters, can be vanquished with iodine-based compounds found in water purification kits.

But a word of caution – iodine, while a valiant warrior, can turn traitorous if overdosed, leading to accidental poisoning.

So, as ever, drink and think smart.

Graeme Dinnen

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