My Dad got a strain of Malaria in the Philippines during WWII.
Believe it or not, he got one 24-48 hour attack every February, just once a year, until he died almost 50 years later. I never understood the February thing, it wasn't because of cold weather (Miami). ???
I was on Guadalcanal for 2 years. At the time there were two basic strains: falciparum and vivax. I got the falci after blowing off the meds for 6 months and relying solely on G&Ts (much more fun).
The vivax won't typically kill you outright, but it stays in your liver forever and keeps coming back. That's probably what your dad had.
The falci can kill you, but once it's gone, it's gone. I hammered it with chloriquine and did okay. Super high fever and hallucinations, but not too bad.
I was there during the 50th anniversary of the battle for GC and met many vets, US, Solis, and Japanese. After seeing all the holes blown in hundreds of palm trees and imagining working my way through that kind of steel blizzard at 19 - I had nothing but respect for all of them.
(The prophylax sucks. I won't take it. But I'm willing to take my chances in places I sail. And I won't be sailing to Mali.)