Human Health, Environmental Health, and Hog Manure
Ron Fleming, Ridgetown College, University of Guelph
(From Proceedings of Swine Production and the Environment Seminar "Living With Your Neighbours", March 26, 1997, Shakespeare, Ontario)

Part A - A Soil Macro-what?

You have heard by now of soil macropores - those cracks, openings, continuous pores in the soil that help aerate and drain the soil. They also can provide a direct link between the soil surface and tile drains. Unfortunately liquid manure can follow this pathway, under certain conditions, and contaminate surface water. Ten years of Ontario research looking at this problem has told us:

1. Macropores exist - By blowing smoke into tile drains, it is very apparent that there are connections to the surface. Smoke puffs out of the ground over the drains.

2. Liquid manure can travel through macropores and enter tile drains -We aren't talking about a large volume compared to the total applied to the land, but even a small amount can cause damage to some streams, depending on stream flow. Ammonium, bacteria, and organic matter are the culprits.

3. Macropore flow occurs within 24 hours of spreading (or after a rainfall) - The studies have shown that manure can be found running out of drains within 20 minutes of spreading. If there has been no flow by the time 24 hours has elapsed, there likely won't be any, unless there is a heavy rainfall quite soon.

4. If the drains aren't running there is no problem - This sounds obvious, but it may be a spreading strategy for some farmers.

5. If the soil has been worked recently, no problem - The most effective way to prevent flow to tile drains is to till the soil before spreading manure. It doesn't seem to take much to break up the macropores (pathways) at the soil surface.

6. Plugging drains works for some people - This involves plugging the drain outlets at spreading time and leaving them plugged for at least a week. We have found that you can get a considerable reduction in the ammonium and bacteria by holding the water in the tile system. The only trouble is, you need fairly flat land so that you don't create too much pressure in the drain system, forcing water up to the surface at locations other than the outlet. Also, if it rains within the week, and there is still field work remaining, the soil may not dry out fast enough with the system plugged. The practice of plugging drains has rather limited usefulness.

7. Monitor tile drains during and after spreading - While this isn't a pollution prevention strategy, it at least keeps you on top of the situation. It is possible that you have never had this problem and never will, but keeping an eye on the outlet is good insurance. It is quite easy to tell if you have a problem - the odour and colour are unmistakable.

Part B - Cryptosporidium and Pigs

We are running a study that is looking at a relatively recent problem, but one that is getting a lot of attention - crytosporidium in drinking water. Since we are just now compiling laboratory results, we do not have much hard data, but a background understanding would be useful.


Cryptosporidium (crip-toe-spor-ID-ee-um) is a protozoan, a single-celled parasite, that lives in the intestines of animals and people. This microscopic pathogen causes a disease called cryptosporidiosis. The dormant (inactive) form of Cryptosporidium, called an oocyst (O-o-sist), is excreted in the feces (stool) of infected humans and animals. The tough-walled oocysts survive under a wide range of environmental conditions.

How spread?

You can get infected with Cryptosporidium when you put anything in your mouth that has been in contact with feces from an infected animal or person. Cryptosporidiosis can be easily spread among people in close social groups such as families, day care centers, and nursing homes. People who work with animals, especially young animals or animals with diarrhea, have greater chance of exposure to the parasite. You can also get cryptosporidiosis by drinking water or eating food that has been contaminated with oocysts.

Oocysts are not killed by typical household disinfectants, including bleach, but are killed at temperatures over 160 F. Thorough drying in a clothes dryer will kill oocysts by desiccating them.


Cryptosporidiosis has long been a problem in young farm animals, such as calves. Cryptosporidium was first recognized as a cause of human disease in 1976 but was rarely reported in humans until 1982. There have been major outbreaks in several US cities (eg. Milwaukee) and in Canadian communities (eg Collingwood, spring 1996).


Is it runoff from fields receiving manure that is the problem? Or is the source of crypto in surface water septic system effluent reaching surface water, or sewage treatment plant discharge, or runoff from fields receiving sewage sludge, or simply wildlife? Our study aims to find answers for at least part of this question.


1. To investigate the prevalence of Cryptosporidium parvum in typical livestock manure storages and in sewage sludge in Southwestern Ontario;

2. To compare the prevalence of C. parvum in tile drainage discharge water from 2 different areas - those having a high concentration of livestock in the drainage basin, and those having no livestock in the drainage basin.

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