The boy suffered abdominal injuries and fractured ribs and was flown to Christchurch Hospital, the spokesman said.
Animal-related injuries cost ACC about $70 million in both 2017 and 2018. Dogs, horses, cattle and sheep were some of the most common animals involved.
There have been more than 20,000 dog-related injury claims in each of the past three years, according to ACC statistics.
Chatham Islands woman Rose Page was attacked by a family pig hunting dog on November 14.
She tried to break up a group of dogs fighting and one grabbed onto her arm.
In the same month, three dogs attacked a woman in Opotiki, leaving her battling critical injuries.
The dogs, who belonged to her brother, left cuts on her head, neck, abdomen and legs.
In July last year, Oliver Beaumont was mauled by two rottweilers in Winton in an attack that lasted about five minutes and left extensive cuts on his face.
Beaumont, who is autistic, had been approached by the dogs while walking near his family's home.