Resolving the phylogeny of malaria parasites

Regardless of what aspect of malaria one might discuss, superlatives will always be abundant in the conversation. That is because human malaria parasites are among the deadliest scourges of our species, have been recorded farther back in our recorded history than any other pathogen, and are among the first pathogens to be identified and studied in a modern public health context. However, despite the extreme significance to the health of our species, malaria has been a most elusive subject of scientific inquiry, and hence a persistent challenge for those seeking to interrupt its transmission. In PNAS, Outlaw and Ricklefs (1) present a unique insight on the phylogenetic relationships among these parasites. To appreciate the relevance of these findings fully, it is necessary to contextualize them in light of the past 130 y of malaria research. Before discovery of its protozoan agent by Laveran in 1880, malaria was believed to be caused by noxious fumes emanating from swamps. Nearly 2 decades after that, British and Italian scientists working separately would demonstrate that the parasite was transmitted by the bite of a mosquito. By the time the mosquito-borne etiology of malaria was published, it was known that malaria in humans was a disease caused not by one but several different species of parasite. At least five of these species are now thought to be of public health significance, and one of these, Plasmodium knowlesi, was only very recently appreciated as a legitimate human threat (2). There are, in fact, hundreds of species of parasites that might broadly be described as malaria parasites infecting mammals, birds, and reptiles (3). Coatney and Roudabush (4) pointed to another malaria superlative in 1949 when they noted that “the nomenclature of malaria parasites is one of the most confusing in all zoologic literature.” This confusion …