Water-borne diseases strike thousands of people every year.
“There are about 1,000 cases per year in Calgary,” said microbiologist Merle Olson.
While most people don’t suffer tragedies similar to the Walkerton, Ont., case of E. coli-contaminated water that killed nine people, the threat is always there.
Symptoms like diarrhea and stomach cramps can be the result of an infection caused by a parasite or bacteria in food or water.
During a recent workshop held in Calgary, more than 400 farmers and scientists met to discuss the safe handling of manure.
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Manure is often blamed as a source of fatal diseases but human waste is also dangerous. Failure to process human sewage can pose a greater threat to human health than intensive agriculture. However, when there is a disease outbreak, it is often impossible to detect the source of contamination.
“Perhaps treatment of sewage has not been gold standard,” said Olson of the department of microbiology and infectious diseases at the University of Calgary.
No one is entirely sure what is in human waste but scientists know the contents of animal manure. There are as many as 10 billion bacteria per gram of manure. Some are good bacteria and others are resilient pathogens.
All animal species carry a variety of flora in their guts and when that bacteria is passed in their feces, it can be harmful in water or food that is not cleaned and cooked properly.
Holding manure as slurry, as a solid or compost, reduces pathogen concentrations. Most pathogens survive freezing or low temperatures for extended periods so manure should not be spread on fields where there is potential for runoff.
The most common pathogens include salmonella, E. coli, giardia and cryptosporidium.
There are low levels of salmonella in cattle and feedlot studies could not find it. However, “salmonella is endemic in poultry flocks,” said Olson.
Survival rate
Salmonella can survive up to three weeks in manure and up to five weeks in liquid manure. It is eliminated from composted cattle manure within a few days once the temperature exceeds 35 C.
There are several strains of E. coli but O157:H7 is one of the most potent.
E. coli has extended survival in water, feces and soil. Low infection rates are possible. Chlorination can kill it. Foods should be thoroughly washed and meat well cooked.
Water animals like beavers have been implicated in some water-borne infections like giardia, an intestinal parasite found in humans and animals.
An infection includes acute or chronic diarrhea, abdominal pain, dehydration and weight loss.
Giardia has protective carbohydrate walls that make them resistant to environmental destruction. They can be killed by dessication, heat, UV radiation and high concentrations of biocides like bleach.
Cryptosporidium is a pathogen found in most mammals. It is more common in dairy calves than in beef cattle.
The infection starts when infective oocysts are ingested. Once they reach the stomach they develop, multiply and colonize the entire small intestine.
Watery diarrhea is the most common symptom in humans and animals. Bacteria are only destroyed by drying, heat, UV radiation and high concentrations of some biocides.
Giardia and cryptosporidium can survive for months in cold water.
Chlorination kills campylobacter, frequently found in poultry manure. It can survive for weeks in a frozen state but is inactivated by desiccation. Composting kills it but it can survive several weeks in manure.
There is substantial risk of ingesting campylobacteriosis from drinking unprocessed surface water.
