Uhhh...
The hold for pets has always been pressurized and climate controlled. Direct flights are the best to eliminate intermediate spots.
Even at intermediate spots some airlines will exercise the pet - not many.
Our Chow travelled via Chicago and Tokyo to
Singapore and survived well.
The season is a big deal to me and I would not send a pet in the heat of summer or dead of
winter. In fact many airlines have blackout dates.
If you are bent on travelling to Brazil by
boat maybe you can find a cargo ship that takes passengers headed that way.
My sister found one between
Sydney and Long Beach.