Anet A8 (Prusa i3) Power Supply Fuse
The fuse rating is same as described on the board - so that shall be no issue with it.

My main concern is why the fuse is down?

Was there a short-circuit? As this is mains fuse - that suggest a big-bang, so, please check carefully hot-end and bed heater connections before restarting the device, to avoid replacing another fuse.