androin Trojan (RAT) infection

[phonetrip]

Hello, I have few questions about trojans called RAT (remote access trojan).

As I understand RAT can be inflitrated to an android by installing app that contains also hidden RAT code.

My question is: can android be infected by RAT only by istalling infected app? Or can android also get infected by RAT that is hidden in a ordinary jpg file? As I know RATS can be hidden in jpg file to infect PC computers. Can be like that also with android?

So: can android get infected with RAT by opening infected jpg file? Or can android get RAT infected only by installing app with RAT in it?

Thanks