Now that authorities say a rabid cat bit two people in Northwest Roanoke last week, the resulting anxiety might tempt pet owners to search the Internet for bargain rabies vaccine to protect their pets and any close-at-paw humans.

You'll find rabies vaccine online at a fraction of the price charged by many veterinarians. The material does not require a prescription to purchase.

But injecting your own pet against rabies is strongly discouraged. Even though rabies vaccine sells online for a couple of dollars a shot, veterinarians and public officials say medical safety, common sense and state law call for employing a licensed professional to direct the needle.

That's not to say that pet owners can't successfully administer other pet medications, such as vaccines for pet diseases such as distemper or therapeutic treatments such as insulin for diabetes.

Rabies, though, is a special case.

"Never, never self-administer rabies vaccine to a cat or a dog," warned Dr. Sharon Harris, proprietor of the Copper Hill Animal Clinic in Floyd County.

Rabies is a virus that an infected wild animal such as a skunk, raccoon, fox or bat can pass to a pet through a bite. The pet's bite can infect a human. Untreated rabies is often fatal in both animals and people. Virginia confirms more than 500 cases of infected animals yearly, though human deaths are rare.

Virginia requires every cat and dog be vaccinated against rabies by a licensed veterinarian or a technician working under one. The vaccine, when given every three years, is considered highly effective in preventing infection even if an animal comes in contact with the rabies virus. And 30 doses are available for $11.95 at Jeffers Pet, a national discount pet supply company with a catalog and Web site.

But a pet owner-administered rabies shot is "not going to be recognized by the authorities," Harris said.

The pet owner won't have a veterinarian-issued rabies certificate with which to purchase a municipal pet license, where required.

Of more concern, perhaps, if the animal bites someone, authorities would consider the animal unvaccinated, Harris said. They would place the animal under observation or, if rabies is suspected, kill it to procure brain matter for a rabies test. It's necessary for the safety of the human bite victim to determine as rapidly as possible if the biting animal had rabies so treatment can begin as soon as possible, the veterinarian said.

And the pet owner could be subject to a ticket for failing to properly vaccinate his or her pet. That will cost an estimated $10 to $20 plus court costs, said Officer M.W. Quesenberry with Roanoke police.

There are other, practical considerations. Internet vendors of unknown reputation might supply vaccine that has not been properly refrigerated, Harris said. Or, the pet owner might not administer the shot correctly to achieve protection, the veterinarian said.

If it's time to get your pet a professional rabies vaccination, there a few things to consider.

If the animal is due for a regular checkup, the checkup and injection can be done at the same time. Southern Hills Animal Hospital in Roanoke, for instance, charges $41 for the examination and $12 to $15 for the rabies shot.

But if price is an issue, and if a full exam isn't needed or desired, a pet owner who shops around can save. That's because some veterinary practices do not require a complete examination to give the shot.

Copper Hill Animal Clinic, Harris' practice, sells the rabies shot alone for $15. Salem Animal Hospital charges $16. Furry Friends, a practice in Bedford County, charges $15.37.