What could be the cause for prolonged loss if voice and fatigue followung high temperature?

Infection: This might represent an infection of the vocal box (laringitis) and the fever is consistent with the infection. Might need to see a doctor.

Heat exhaustion: A place to start to guess which might be a simple explanation - could be dehydration - that would make one tired, and would make your throat dry. Its important to stay well hydrated in the heat. If high temp occured without outside heat exposure - probably infection - see a doc.