Feral cat care is not the same as domestic cat care, although one is dealing with the same animal. It is the social structure that differs, and humans who take care of feral cats need to be aware of how to reduce populations and disease risk to both domestic cats and humans in the area.
The first rule of feral cat care is to take precautions to protect oneself from diseases that might transmit from cat to human. Protect against rabies, infections from bites, cat scratch fever, Chlamydiosis, Lyme Disease, Campylobacter, Salmonella, Ringworm, and Toxoplasmosis are easily handled with a little foresight and planning. Simply donning padded or thick gloves, a heavy long sleeved shirt or jacket (possibly re-enforced, even), long pants and leather shoes goes a long way. If you intend to be trapping feral cats to take for neutering/spaying, then get a pre-exposure rabies vaccination. That said, the chances of getting one of these infections is extremely low.
You can reduce the chances further by doing a few things where the colony has taken up residence. This part of feral cat care is good common sense anyhow. Make sure that old food is not left about and that the colony knows food is there for them at certain times only. Spray for fleas in the environment, thus reducing one way that Lyme Disease can spread. Keep the “litter” areas cleaned up from feces to reduce risk of Campylobacter, Salmonella, and Toxoplasmosis. Become involved in a trap/sterilize/release program to reduce overall population over time. Get those members who are sterilized vaccinated against rabies.
Once you have determined that you do want to be involved in a trap/sterilize/release program, and have gotten community support for it, you can improve the overall health of the colony and further feral cat care with a few extra steps. Begin with testing a few of the animals for Feline Leukemia and Feline Immunodeficiency Virus. Any animal that is positive should be humanely put to sleep to reduce spread of these viral born diseases. If the first few come up negative, this step can be skipped for the rest of those trapped. Cats trapped for sterilization should be vaccinated for Distemper, treated for fleas, ticks, and ear mites, roundworms, hookworms, tapeworms and other internal parasites. In most cases, use of cheaper cattle deworming medications can be used for this in small doses. Ivermectin will treat both internal parasites and ear mites with one injection.
Young feral cats treated for the first time as part of a feral cat care program may develop upper respiratory issues. If the animal will eat while being held, these can be treated usually in a couple of days. It is well known that male cats can be re-released back into the population within 24 hours of castration. Female cats benefit from the use of flank incisions coupled with absorb-able sutures and surgical glue to reduce the time they are held from 5-6 days to much less than that.