Hello there.
I would suggest you run the source stream through the Wowza Transcoder and add key-frames to the stream with the Video/KeyFrameInterval tag.
How to set up and run Wowza Transcoder for live streaming
Alternatively, you can use FFMPEG to do the same thing. You can find example code for setting the GOP (Key-frame interval) here:
Frequently requested FFMPEG command examples for Wowza
Regards,
Salvadore