Divorced, wife not taking care of father's child, child sick! help?

can a father go to the authorities if his wife who's got custody but doesn't seem to be taking care of his child properly, as the boy is having symptoms of Pellagra. he's got severe depression, insomnia, red limbs, doesn't eat for days, can't control his urine, has hypo activity, standing in one place for days - not moving, doesn't want to leave the bathroom or go to doctors. she got help from psychologists, but they said to wait. should he really? if the child has no vitamins he won't get any better. he's been like this for 4 months now. what should the father do? if u ask me - force him out to hospital and force him to eat - he's not much different to an anorexic.