The boy, from Cambridgeshire, had been visiting the zoo with his family when the incident took place.
His family said he received injuries to his arms, neck, head, face and suffered broken bones after the attack and his most recent surgery involved completing “a nerve graft on his arm”.
The family recalled arriving at Addenbrooke’s Hospital and experiencing “the worst 12 hours” of their lives after the attack, which involved “signing consent forms involving resuscitation and amputation”.
The understands the arrested man, who did not know the child, has learning disabilities and was on a trip with carers.
He was released on bail until 18 September and police said he was “assessed as not being fit for interview”.
The Care Quality Commission has launched an investigation into the care of the man arrested.
Norfolk County Council – which did not provide any care for the man – has also launched an inquiry under the Care Act 2014.
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