Dr Erica Sox claims that TNR reduces shedding of the parasite Toxoplasma gondii.  What evidence is there of that?  I've never read that in the literature anywhere.  Neutering doesn't affect the number of oocysts shed by an infected cat, so far as I know, but perhaps there is new research out on this.  The oocysts shed by an infected cat are over a million, so that reduction would have to be significant to make any difference.  In lab conditions, a single oocyst can infect a pig, although infecting a marine mammal may be different.  As to alternative to TNR, humane euthanasia of feral cats unsuitable for adoption is acceptable to me and many other people, as is mandatory licensing of dogs and cats alike, mandatory neutering prior to the first litter, and requirements to constrain dogs and cats from movement and defecation in watersheds and wildlife areas.  She does not speak for all biologists or wildlife advocates.