What are the dangers of letting my cat outdoors?

A snoozing tabby, stretched out in the sun-dappled backyard, may appear to be an example of the good life, feline-style. Yet cats that spend time outdoors have lives filled with risks, from minor ones such as ticks to serious threats from cars or dogs. You may believe cats living only indoors are deprived of a chance at freedom, and that they miss the call of the wild. But what cats that go outdoors are actually deprived of is the consistent safety and contentment of a comfortable life at home. In fact, the American Society for the Prevention of Cruelty to Animals estimates that cats who are allowed outdoors live about one-quarter as long as cats that live indoors exclusively.
Do all cats long for outdoor life?
A cat’s hunting instincts, like those of his larger relatives in the wild, are inborn. Mother cats teach kittens to chase and catch prey. While cats who go outdoors will naturally stalk birds or rodents in the area, cats don’t need to be outside killing neighborhood blue jays to satisfy their instincts. They can display their stalking instincts by racing around your home, chasing down imaginary prey, or treating a catnip mouse like a prized kill. Many toys permit cats to act out their hunting rituals without endangering either the cats or smaller animals.
Cats’ mating drives are strong, and if an indoor-only cat is not spayed or neutered, the mating urge will prompt it to do anything to escape and find a mate. Cats that are allowed to go outside should always be spayed or neutered to prevent them from mating.
Allowing a cat outdoors
There are aspects of letting a cat live outdoors that seem positive but aren't really so. Cat owners who dislike cleaning a litter box may be thrilled that their cats do their business outdoors. They can save money on cat food since their cats will be hunting birds or rodents. Their cats will also get plenty of exercise roaming the neighborhood and satisfy their sense of curiosity exploring yards and garages, or climbing fences and trees. And if the pets have not been neutered or spayed, indoor furniture and walls won't be affected by spraying.
Dangerous realities
These "benefits" obscure the harmful realities. A cat that goes outdoors risks being struck by a car, because no cat can outrun a motor vehicle. Even on a quiet street, a driver may not see a cat or kitten playing in his path, and cats hit by cars rarely survive. If your cat spends any time outdoors, he is vulnerable to weather extremes and injuries, as well as ticks and fleas, which he’ll bring indoors to your home and kids. He may be poisoned by rodent bait, pesticide-treated lawns or leaked antifreeze.
Cats going outdoors may fight with raccoons or other cats, and can contract diseases that include rabies, roundworms, Feline Leukemia Virus (FeLV), feline distemper (FPV) or upper respiratory infections. Dogs pose a threat to cats, and foxes and coyotes are also feline predators. A cat could also get locked in a garage or other building, or abused or even killed by humans who do not like cats.  An outdoor cat may sometimes be mistaken for a stray and end up in an animal shelter or taken in by someone else.
Further, if your outdoor female cat is not spayed, her behavior will be loud and annoying as she cries to attract a male and tries to get pregnant.  Meanwhile, your unneutered male will continue his caterwauling and spraying of urine marks around your garden and the neighbors'. With all these dangers, it is actually kinder to have your cat live indoors full-time.
Teaching an outdoor cat to live indoors
Converting an outdoor cat into an indoor pet begins with a vet exam and spaying or neutering.  A spayed/neutered feline will be less interested in an outside life because the mating instinct will be reduced.
Provide a good-sized litter box in a private, comfortable area. If the cat has ever used a box, memory will kick in, or his natural inclination to cover his waste will give him the right idea. Offer him a scratching post and opportunities to exercise and play with toys that simulate prey. Ease the cat’s transition to his new world with plenty of social interaction.
Some formerly outdoor cats, fearful and stressed in their old lives, want nothing to do with the great outdoors after coming inside. Others may long for the wild. If you’re concerned that the cat will miss the sunshine and fresh air, train him to wear a leash and harness (not a collar) and walk him outdoors. Or build a catio, a screened, secured outside space that allows the cat to experience the outdoors while safely confined. Practice patience, and he’ll eventually forget an existence spent dodging dogs and cars while looking for his next meal.