Can warm blooded vertebrates other than humans act as reservoir hosts for malaria parasites? I'm mainly interested in Plasmodium vivax and possible reservoir hosts in the wider area of Europe/ Eurasia.
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.
From Wikipedia Plasmodium spp. have a huge range of hosts, including: human, primates, mammals, reptiles and birds.
Four important points to note:
- The Plasmodium genus contains about 200 species.
- Further important to note is that P. falciparum, P. vivax, P. ovale, and P. malariae are responsible for almost all of human malaria infections, and the distribution of Plasmodium species varies between different animals.
- Humans are not in fact the definitive host of Plasmodium species. Vertebrate hosts simply serve as a site for the parasite to replicate asexually, and the sexual replication occurs in the mosquitoes.
- To act as a reservoir, the host needs to suffer a long term infection. P. vivax is one species noted for its ability to form a dormant stage in the liver, and cause relapses.
So I think it would certainly be possible for there to be other vertebrate hosts (warm blooded or not) aiding in the spread of malaria to humans, but I think it's unlikely to be occurring at an epidemiologically significant rate. I think if that did happen, we would already know about it, given the considerable study that has been done on malaria.