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The general rule for the number of litterboxes in the house, should be the number of cats, plus one, as many cats do not like to use a litterbox that has already been used by another. If your cat is an only-cat, you should have at least two boxes in different areas of the house. The boxes should be in low traffic, quiet areas.
A cat that was using the litterbox in the past and then suddenly starts eliminating inappropriately, is often due to stress or anxiety. Stress can be caused by any changes in the cat's environment and is often difficult to determine. However, because you are getting ready to move, the increased activity, boxes around, perhaps strangers in and out of the house, may be contributing to her anxiety and stress.
If this stress is successfully treated, the house soiling should be controlled. A very good, over the counter product. is "Feliway". This is a synthetic feline calming pheromone--a hormone that makes cats feel good--and is very effective in treating inappropriate elimination caused by anxiety. It is available in both a spray and a plug-in diffuser; the diffuser is easy to use, as it covers a large area, like an air freshener, but it is only detectable by cats; it has no scent to humans.
It's also very important that you clean the areas where she's been soiling, with an enzyme-based cleaner like Nature's Miracle, Zero Odor or Odor Mute, available in pet supply stores, with many others of the same type. Once you clean the areas with this type of cleaner, if she can no longer smell where she's gone, and also, if you lightly spray some Feliway over the spots after they dry from the cleaning, and allow the Feliway to dry for about 30 minutes before allowing her access, it will deter her from doing it there, again.
If your Calico still continues to soil inappropriately, despite the above suggestions, the next step would be trying a behavior modification medication, such as Clomicalm. Here is more information:
You would need to see your vet for a prescription for this medication and a routine senior blood and urine panel, plus a fecal analysis, is always a good idea, especially in an older cat, to eliminate any underlying health issues that may be causing this problem.
If the above doesn't help, try placing her food bowl on the area where she is soiling. Cats generally will not eliminate where they eat.
I would also suggest placing the Feliway diffusers in the new house before you bring her over there, when you move in, as a precaution and deterrent.
I hope this helped and all will be well with your furry girl! Also, much good luck on your upcoming move!
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