Common infections •
Plasmodium falciparum (the cause of malignant tertian malaria) •
Plasmodium vivax (the most frequent cause of benign tertian malaria) •
Plasmodium ovale curtisi (another, less frequent, cause of benign tertian malaria) •
Plasmodium ovale wallikeri (another, less frequent, cause of benign tertian malaria) •
Plasmodium malariae (the cause of benign quartan malaria) •
Plasmodium knowlesi (the cause of severe quotidian malaria in Southeast Asia)
Rare cases While infection of humans by other species is known, they are quite rare, in some instances, only a single case. In a number of the cases, the means of infection is unknown, and may be due to accident, i.e. infection by laboratory equipment or a bite by an animal. With the use of the
polymerase chain reaction additional species have been and are still being identified that infect humans. •
Plasmodium cynomolgi (spp.
cynomolgi,
bastianellii) •
Plasmodium inui •
Plasmodium schwetzi •
Plasmodium semiovale •
Plasmodium simium (
Plasmodium brasilianum and
Plasmodium rhodiani which have been reported to infect humans, are likely synonymous with
P. malariae) One possible experimental infection has been reported with
Plasmodium eylesi. Fever and low grade parasitemia were apparent at 15 days. The volunteer (Dr Bennett) had previously been infected by
Plasmodium cynomolgi and the infection was not transferable to a
gibbon (
P. eylesi 's natural host) so this cannot be regarded as definitive evidence of its ability to infect humans. A second case has been reported that may have been a case of
P. eylesi but the author was not certain of the infecting species. A possible infection with
Plasmodium tenue has been reported. This report described a case of malaria in a three-year-old black girl from Georgia, United States, who had never been outside the US. She suffered from both
P. falciparum and
P. vivax malaria and while forms similar to those described for
P. tenue were found in her blood even the author was skeptical about the validity of the diagnosis. Confusingly
Plasmodium tenue was proposed in the same year (1914) for a species found in birds. The human species is now considered to be likely to have been a misdiagnosis and the bird species is described on the
Plasmodium tenue page.
Former names Taxonomy in parasitology until the advent of DNA based methods has always been a problem and revisions in this area are continuing. A number of synonyms have been given for the species infecting humans that are no longer recognised as valid. Since perusal of the older literature may be confusing some currently defunct species names are listed here.
Plasmodium shortii and
Plasmodium osmaniae are now considered to be junior synonyms of
Plasmodium inui.
Notes ;Falciparum Until recently the only known host of
P. falciparum was humans but this species has also been described in gorillas (
Gorilla gorilla) and
bonobos There has been a single report of
P. falciparum in a brown howler monkey (
Alouatta guariba) and in black howler monkeys (
Alouatta caraya) but until this is confirmed its validity should be considered dubious. A possible report of
P. falciparum in a greater spot-nosed monkeys (
Cercopithecus nictitans) has not been confirmed in a large survey. A species that clusters with
P. falciparum and
P. reichenowi has been identified in
Gabon, Africa in chimpanzees (
Pan troglodytes). This appears to have diverged from these two species about 21 million years ago. It has only been identified from the sequence of its mitochondrion to date and further work is needed to characterise the species. A second report has confirmed the existence of this species in chimpanzees. Night monkeys (
Aotus nigriceps) can be infected with
P. falciparum. This infection may occur naturally. Their potential role - if any - as a source of human infection is unknown. Two additional species within the subgenus
Laverania have been identified on the basis of DNA sequences alone:
Plasmodium billbrayi and
Plasmodium billcollinsi. The presence of
P. malaria in chimpanzees has been reported in Japan suggesting that this species may be able to act as a host. A second paper has described the presence of
P. malaria in wild chimpanzees. Another paper has confirmed the presence of
P. malaria in chimpanzees. The existence of multiple independent reports seem to suggest that the chimpanzee and possibly other species may act as a host to
P. malaria at least occasionally. ; Vivax
P. vivax will infect chimpanzees. Infection tends to be low grade but may be persistent and remain as source of parasites for humans for some time.
P. vivax is also known to infect
orangutans and the brown howler monkey (
Alouatta guariba clamitans) ;Ovale Like
P. vivax,
P. ovale has been shown to be transmittable to chimpanzees.
P. ovale has an unusual distribution pattern being found in
Africa,
Myanmar the
Philippines and
New Guinea. In spite of its admittedly poor transmission to chimpanzees given its discontigous spread, it is suspected that
P. ovale may in fact be a
zoonosis with an as yet unidentified host. If this is actually the case, the host seems likely to be a primate. A report has been published suggesting that
P. ovale may be a natural parasite of chimpanzees but this needs confirmation.
P. ovale has since been described from chimpanzees living in the wild. These two species separated between 1.0 and 3.5 million years ago. ; Knowlesi
Plasmodium knowlesi has a natural reservoir in the macaques of Southeast Asia, and was only in 1965 identified as being transmissible to humans. ;Other species The remaining species capable of infecting humans all have other primate hosts. ==
Plasmodium taxonomy ==