Question
I have read through all the Q&A's about cat feces and soil but haven't found
this one yet.  My yard has become the giant kitty litter box that the feral cat
population uses and as I have begun to clean it out and prepare for planting, I
have found infestations of small white worms in large number underneath the
surface.  I have dug out most of the offending worms and contaminated soil
but am wondering if you think this is roundworm from the cat feces having
lain larvae that hatched?  Or perhaps just live worms passing through the cat
into the feces?  I live in Santa Fe, NM and I have been amending this soil for
several years with leaf compost and some organic matter, so I don't want to
dig most of it out.  I have read all I can about these parasites but have not
found any info anywhere about the worms actually living in the soil.  Do
roundworms live/survive in the soil?  I have a biologist friend who has
suggested buying beneficial nematodes and the local greenhouse has
suggested diatomaceous earth.  But I'm most curious if you think it's from
the cat feces?  Cat related or not?  Ideas?

Answer
Hi Alexandria, I don't think they are from the cat feces but without a positive identification, I can't be sure.  Check someone else's yard for the same worms.  If you find them, then I wouldn't worry.
I'm not aware of any homeowner product labeled to kill true worms.
Beneficial nematodes and diatomaceous earth may help, may not.  Insecticides like Dylox that are labeled for Soil insects are likely to kill them, but are not labeled for worms either.
I'm not aware of any parasitic worms that live as adults outside their host, but I'm not an expert in parasitology.  Your family physician or local veterinarian may have a better answer since he/she should be familiar with parasites in your area.  Jim