The detriments to humans are more of cost and inconvenience than anything else. Feral cats put pressure on local government budgets for control and cause strong disagreements between those who believe in eradication of the animals rather than the non-harmful trap-neuter-return (TNR) program.
According the Humane Society of the United States the following list includes many of the problems associated with Feral Cat Colonies:
- frequent and loud noise from fighting and mating behavior
- strong foul odors from un-neutered male cats spraying to mark their territory
- flea infestations
- visible suffering from dying kittens and injured adults.
The pressure on animal shelters is high as well and can include:
- higher intake rates of cats into shelters due to the rescue of feral kittens and the capture of feral adults
- higher euthanasia rates for all cats due to the unadoptability of feral adults and the necessity to euthanize adoptable animals due to limited cage space
- higher animal control costs due to trapping efforts and/or costs associated with caring for and euthanizing feral cats
- a constant rate of nuisance complaints about feral cats.
In addition, according to experts, Feral cats may carry and spread many human and wildlife diseases. These included cat scratch fever, distemper, histoplasmosis, leptospirosis, mumps, plague, rabies, ringworm, salmonellosis, toxoplasmosis, tularemia, and various endo- and ectoparasites.