Dog bites are reaching "epidemic proportions," a well-known TV dog trainer said Thursday, as video of a cat fearlessly chasing off a dog that bit a small boy in California went viral.

Every year more than 4.5 million Americans -- more than half of them children -- are bitten by dogs, said the American Humane Association ahead of National Dog Bite Prevention Week, which begins Sunday.

Insurers paid more than $483 million in dog bite claims in 2013. Plastic surgeons performed 26,935 operations to repair injuries caused by dog bites. And the US Postal Service said 5,581 of its employees were attacked last year.

"The dog bite situation in America is at epidemic proportions -- in Europe less so, but still a huge issue," British-born dog trainer and television presenter Victoria Stilwell, host of the reality series "It's Me or the Dog," told AFP.

"Everywhere needs to take the situation very seriously," said Stilwell at a media event in Washington attended by Elle, a mellow therapy dog that happens to be a pit bull.

Stiwell appealed for greater education and awareness among dog owners and the public -- as well as better-trained dogs.

In a surveillance video going viral on YouTube, four-year-old Jeremy Triantafilo of Bakersfield, California is seen being attacked and badly bitten in the leg by a pit bull-looking dog.

But the dog immediately turns tail when Tara, the Triantafilo family cat since 2008, leaps to the defense of the mildly autistic lad, who was playing on bicycle on the sidewalk.

"Our cat saved our son!" his mother Erica Triantafilo, who was close by watering a tree, told ABC television affiliate KERO in Bakersfield, north of Los Angeles.

"It was truly amazing. She's my hero."

The boy needed several stitches to close the wound. The dog, which belonged to neighbors, was taken away by local authorities for quarantine. Tara was unhurt.