Does malaria have a reservoir host?
There are 5 species of Malaria the can infect humans, and Chimpanzees and gorillas have also been found with 5 species, including vivax and falciparum.  https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4089193/

The parasite can go dormant in the liver for days to years, causing no symptoms and remaining undetectable in blood tests. They form what are called hypnozoites (the name derives from "sleeping organisms"), a small form that nestles inside an individual liver cell. The hypnozoites allow the parasite to survive in more temperate zones, where mosquitoes bite only part of the year.

Cows are known to carry falciparum protozoa, which has at least four reservoir species. (cows, chimps, gorillas, humans) Human with sickle cells also act as a reservoir in a different way, perhaps more or less invisible or innocuous, i haven't studied recent research, and sickle cell may also have some effect in cows and chimps and gorillas.