Feral cats should NOT be TESTED for FeLV/FIV unless they are not healing/recovering from treatment for injury/illness. This is a nationally recognized standard of care for feral/community cat colonies. Few exceptions to this rule exist. Killing a cat that is NOT sick or that has something that can be treated is NOT euthanasia . Ringworm is a minor skin fungus, ear mites are easily treated, even FIV is not a reason to kill a cat.
“Alley Cat Allies does not support testing feral cats for FIV and FeLV for multiple reasons...” “Alley Cat Allies does not support the euthanasia of healthy cats who test positive for FeLV and FIV. The American Association of Feline Practitioners agrees, recommending against routine euthanasia of healthy FeLV- and FIV-positive cats. Euthanasia should only be used to relieve suffering from a terminal or incurable condition. Cats showing signs of illness or injury should be trapped and taken to a veterinarian for medical treatment. Learn more about the difference between euthanasia and killing at www.alleycat.org/Euthanasia." https://www.alleycat.org/resources/protocols-testing-feline-immunodeficiency-virus-fiv-and-feline-leukemia-virus-felv/
Neighborhoodcats.org - "The "guilt trip" isn't true. Among the small minority of TNR programs which still test every cat, the main argument advanced is that, by returning a cat who is FIV or FeLV positive, you are responsible for the deaths of any other cats who catch the diseases from him or her. We don't agree, even if a positive cat should end up transmitting the virus to another. Practicing TNR does not mean creating a world without risk for community cats - it's about making the situation better, not perfect. The viruses were in the environment before you, the caretaker, came along and will continue to be there. By getting the cats fixed and providing for their care, you are vastly improving their lives. No one has cause to criticize you for deciding to allow a cat, positive or not, to return to his family and home instead of euthanizing him." http://www.neighborhoodcats.org/how-to-tnr/veterinary/fiv-felv-testing "Neighborhood Cats opposes euthanizing any feral cat simply because he or she tests positive for FIV (feline immuno-deficiency virus) or FeLV (feline leukemia virus). If the cat shows no active signs of ill health, we believe he should be released back into his colony regardless of the test results. Because this is our policy, we don't test in the first place unless the cat does show signs of ill health and our veterinarian believes test results would be useful in diagnosis and treatment, or unless the cat is a candidate for adoption. The reasons for these policies include the following...” http://www.neighborhoodcats.org/HOW_TO_RELEASING_FIV_FELV_POSITIVE_CATS
San Diego - “Currently the Feral Cat Coalition (FCC) does not routinely test or vaccinate for FeLV, FIP, or FIV. There are several reasons why this is not done at our monthly clinics:” http://www.feralcat.com/tpolicy.html
ASPCA NY - “...no healthy cat should be euthanized based upon the results of one single test...” © 2004 ASPCA https://www.petfinder.com/cats/cat-health/feline-leukemia-virus/
BestFriends.org - “FIV and FeLV testing should never be used as standard practice to determine which cats are eligible for a CCP [community cat program].” http://bestfriends.org/resources/working-veterinarians-and-veterinary-clinics
MaddiesFund.org - “Our take-home message for this is that if the cats look healthy, they are no more likely to be infected than a pet cat is. We should not have different standards for them, and no one is forcing pet owners to test their cats. No one is forcing pet owners to kill their cats if they are positive. So, in our program, we have made the strategic decision to put all of our resources into neutering more cats, and we no longer test. We will say that we have tests on hand, in case we want to use the test as a tiebreaker in a cat that we are on the fence about.” http://www.maddiesfund.org/assets/documents/Institute/Community%20Cats%20QA%20Transcript.pdf