Generally research follows funding, not intellectual curiousity. So the single-celled eukaryotic malaria parasite is pretty well-studied. This also highlights

Generally research follows funding, not intellectual curiousity. So the single-celled eukaryotic malaria parasite is pretty well-studied. This also highlights the often arbitrary nature of division of labor in academics - all viruses and many eubacteria could reasonably be classified as parasites, but are instead handed off to virology and infectious microbiology (which tends to exclude parasitic eukaryota, even single-celled protists, from its domain). Out in nature, things get more complicated - there are many reports of viruses infecting parasites which in turn infect animals, for example. https://schaechter.asmblog.org/schaechter/2011/07/viruses-that-infect-parasites-that-infect-us-the-matryoshka-dolls-of-human-pathogens.html https://schaechter.asmblog.org/schaechter/2011/07/viruses-th...