Although the majority of Chicago pet owners have dogs, most do not register their canines, which is a growing problem city officials are working to address.

Chicago Municipal Code requires all dogs four months and older to be registered, but the number of dog licenses issued accounts for only 6 percent of the city’s 600,00-plus dogs, according to the American Veterinary Medical Association.

The majority of dog owners do not register their pets because they are not aware that they should, said Anna Johnson, manager of the Chicago Canine Rescue Shelter.

“I’m sure some folks just don’t want to spend the money or haven’t spayed or neutered their pets,” Johnson said.

Dog licensing and registration is important to assure all animals are properly vaccinated, said Frank Shuftan, public information officer for the Cook County Bureau of Administration.

“Vaccination and registration must go hand in hand,” Shuftan said in an email. “In order for public health officials to protect the public against instances of rabies, we need to be able to establish a protocol to determine the number of animals properly vaccinated.”

Whether dogs are stray or not, unregistered dogs that are not up to date on vaccinations pose a health threat, said David Kirkpatrick, spokesman for the American Veterinary Association.

“By getting a rabies vaccination and by registering your dog, you are certainly contributing to the betterment of the public health in your area,” Kirkpatrick said. “Any dog that is not vaccinated for rabies is a public health risk.”

Dog registration costs $5 per year or $50 for a dog that is not spayed or neutered and requires a current rabies vaccination. Chicagoans can register their dog online or by visiting one of three City Hall offices.

Animal-related service calls are a high priority and are the primary way Chicago Animal Care and Control can enforce dog registration, said Brad Powers, CACC spokesman. CACC receives 60,000 reports a year ranging from animal bites to cruelty and neglect cases, Powers said. Any time responders interact with dog owners, they ask for a proof of dog license and current rabies vaccination.

CACC works with the Chicago Police Department to enforce registration laws by ticketing offenders with fines of up to $200. In 2013, 720 tickets were issued, a 78 percent increase from 2011, according to Powers.

In 2011, the city added 11,600 dog licenses during a two-year push, according to the Chicago City Clerk’s office. Last year, CACC processed 2,000 dog license applications from adoptions, low cost vaccine clinics and animal redemptions, which generated $30,000 in revenue for the city, Powers said. The CACC works with alderman offices to remind Chicagoans that dog registration is a requirement.

“Registration is verifying the source and means of vaccination against rabies,” Shuftan said. “Therefore memorializing the date officially for the protection of your pet and all of the citizens of the county.”