The genome of the zoonotic malaria parasite Plasmodium simium reveals adaptions to host-switching

Plasmodium simium, a parasite of various species of Platyrrhini monkeys whose range is restricted to the Atlantic Forest of Brazil, is genetically and morphologically similar to P. vivax. Based on this similarity, it appears likely that P. simium originated as a parasite of monkeys in Brazil following a host switch from humans carrying P. vivax. The 2015 outbreak of P. simium in the local human population raised questions about the degree of divergence that has occurred between P. vivax and P. simium, and whether adaptation to monkeys has led to the evolution of a parasite with clinical relevance to human health that differs from that of P. vivax. The degree and nature of adaptation to a non-human primate host and a sylvatic transmission cycle that has occurred in P. simium following its anthroponotic origin is of relevance to the understanding of how malaria parasites adapt to new hosts. It is also of interest to determine whether the current, human-infecting P. simium parasites have recently undergone changes at the genomic level that have allowed them to infect people in this region, as it has previously been suggested that P. simium has historically lacked the ability to infect man.