'A fish rots from the head down' proverb with origin and meaning

Origin

This proverb is of ancient origin but precisely which of the ancients coined it is probably beyond our ken at this distant remove.

Many countries lay claim to it. I've seen sources that place it in China, Russia, Poland, England, Greece and so on..., but usually with no evidence to substantiate those claims. A correspondent of mine has asserted that it was written in a Greek text by Erasmus, who died in 1546. That may be the case, but I've not been able to substantiate that claim.

Meaning

When an organization or state fails, it is the leadership that is the root cause.