USING DOG & CAT MANURE ON HOME GARDENS
There have been several requests from home gardeners asking about the advisability of using pet wastes for fertilizer. There are no studies that we could find to document the pros or cons for this method of waste disposal. We have two major concerns to bring to your attention: Public Health Aspect, Fertilizer Values.
Is there any human health danger to this practice?
Yes, both dog and cat manure may contain organisms that cause human health problems.
What is the hazard in dog manure?
The common large roundworm, called Toxocara canis can also infect humans.
How common is this worm in dogs?
It is estimated that 90% of young puppies are infected with ascarids or large roundworms.
How do humans become infected?
They get the infective eggs in their mouth. The eggs are transferred to mouth by the person's fingers, food, or other objects contaminated by dog feces.
What kind of symptoms would a person have who is infected by dog worms?
1) A condition called Visceral Larval Migrans. The ascarid eggs hatch in a person's small intestine. The little worms or larvae get into the blood stream and float to the liver. They migrate in the liver and get to the blood stream that goes to the lungs. Some may enter the general circulation and end up in different parts of the body. They have been found in the human heart, brain, spinal cord, skin, and other tissues. The symptoms would vary depending on where the larvae become attached.
2) Another condition is called Ocular Larval Migrans. The immature ascarid worms or larvae can affect the human eye. The larvae attack the retina and cause blindness. Many eyes of children have had to be removed which until recently was the only treatment for this problem.
How long can ascarid eggs live in the soil?
They can live for many months, or many years depending on soil conditions.
How common are these infections in humans?
Probably more common than the figures show. It's a difficult disease to specifically diagnose. Physicians are not required to report this disease so there are no accurate statistics. A test in 1978 used by the U.S. Public Health Service on 2,606 human samples showed 30% positive. In a pediatric hospital 37% of all the retinal diseases of children's eyes were positive for dog ascarid larvae. This is definitely a potential human health hazard.
What problem does cat feces pose as a human health problem?
The principal disease transmissible to humans is called Toxoplasmosis.
What is Toxoplasmosis?
This is an intestinal parasitic disease of cats and other animals. It affects the intestines and other tissues and the cysts are shed in the feces.
How does it affect humans?
It is associated with abortion and malformation of the unborn child in pregnant women. How common is this disease in Wisconsin cats? About 45% of the cats tested at the Central Animal Health Laboratory were positive.
How long do cats spread this organism?
They spread this organism for about 7-10 days after they become infected. They then become resistant, and fewer eggs are shed.
How is Toxoplasmosis spread to humans?
The eggs are usually placed in the mouth by fingers or objects contaminated with cat feces. Garden produce contaminated with cat feces containing infective eggs could be a human health hazard for pregnant women.
What is the fertilizer value of cat and dog manure?
The composition of cat and dog manure is similar. The feces contain about 0.7% nitrogen (N), 0.25% phosphate (P2O5) and 0.02% potash (K2O). The urine contains about 1.1% N, 0.01% P2O5 and 0.5% K2O.
How does this compare with cattle manure?
Cat and dog manure, as excreted, contains about 2-1/2 times as much N, the same amount of P2O5 and half as much K2O as cattle manure. However, the fertilizer value depends on the kind and amount of associated litter or bedding as well as on the manure itself.
Since the urine from dogs is not normally collected, how does the composition of the feces compare with cattle manure with bedding?
Assuming no bedding or litter associated with dog feces, the feces would have about 40% more N, the same amount of P2O5 and 1/20 as much K2O as cattle manure.
What would be a recommended rate of application of dog manure?
As application of 20 lb per 100 square feet would provide most of the N and P2O5 needed for a lawn and about half of that for gardens. Owing to the potential problems with parasites indicated above, however, the use of dog and cat manure on lawns and gardens is not recommended.
With normal "kitty litter," what is the fertilizer value of cat manure?
Since both the urine and feces are collected, cat manure with litter will contain about 0.85 lb N, 0.2 lb P2O5 and 0.15 lb K2O per 100 lb of manure. If the litter is sawdust or wood shavings, the N will be temporarily "locked up" by the bacteria and fungi in decomposing the litter and little, if any, will be available to plants for several weeks.
Will composting dog and cat manure make it safe for use on gardens?
Composting would sterilize the manure and make it safe for use if the temperature of the compost heap exceeds 165oF for about five days. Unfortunately, backyard compost heaps rarely reach this temperature, and the outer several inches never do.
Can pet manure be sterilized chemically to make it safe?
There are chemical sterilants such as methyl bromide and others that could be used, but the cost and bother is probably not worth the value of the manure. Also, the average homeowner probably is not equipped to handle chemical sterilants. CONCLUSIONS
The health hazards associated with cat and dog manure are greater than the potential benefit from its fertilizer value. Cat and dog manure should be disposed of by flushing down the toilet, burying deep in the soil (six inches or more) or by placement in tight plastic bags for garbage collection.