It is produced under very high standards of hygiene. If it weren't for the 'meat' that goes into it, it would be perfectly safe for human consumption. Even so, if I were starving and that's all there was, I'd have no hesitation in eating it!
You can seems to have been 'blown'. It very occasionally happens (and to human food too). Tinning is a very reliable way of preserving and distributing food. The maggots are very unlikely to have been in the can when it was made and sealed.
I'm sure if you contact the suppliers, they will be mortified and as well as apologising and recompensing you, you may well get some additional samples.