second estimate put the earliest date of the evolution of p. vivax at 265,000 years. an estimate of the date of origin of p. vivax has placed it at 768,000 years ago. an estimate of the time of origin of p. vivax based on nuclear genes suggests that it originated between 232,228 and 303,030 years ago. it may have appeared in india between 79,235 and 104,008 years ago. a study of p. vivax in the americas suggests that the strains in venezuela and northeastern brazil diverged from the others ~30,000 years ago. this separation may have occurred before the parasite was introduced into south america. the most recent common ancestor of the extant p. knowlesi strains has been estimated to have appeared 257,000 (95% credibility interval 98,000–478,000) years ago. p. knowlesi underwent a rapid population growth between approximately 30,000 and 40,000 years ago. this era follows the growth in the human population in this area (~50,000 years ago). branching order p. coatneyi and p. inui appear to be closely related to p. vivax. p. vivax and p. knowesli appear to have diverged 25–30 million years ago. p. gonderi appears to be basal in this clade. this is consistent with its african distribution rather than the mainly asian distribution of the other species in this group. several of the 'asian' clade - plasmodium coatneyi, plasmodium cynomolgi, plasmodium fragile, plasmodium inui, plasmodium fieldi, plasmodium hylobati, plasmodium inui, plasmodium knowlesi and plasmodium simiovale and an african species plasmodium gonderi - have a single s-type-like gene and several a-type-like genes. it seems likely that these species form a clade within the subgenus plasmodium. the 'asian' species form a clade with p. simium and p. vivax being clearly closely related as are p. knowseli and p. coatneyi and p. fragile; similarly p. brazillium and p. malariae are related. p. hylobati and p. inui are closely related. p. fragile and p. gonderi appear to be more closely related to p. vivax than to p. malariae. an analysis of four apicoplast genome-encoded genes (small subunit rrna, large subunit rrna and caseinolytic protease c) of nine 'asian' species (p. coatneyi, p. cynomolgi, p. fieldi, p. fragile, p. hylobati, p. inui, p. knowlesi, p. simiovale and p. vivax) and the african species p. gonderi suggests that p. coatneyi and p. knowlesi are closely related and that p. fragile is the species most closely related to these two. also p. vivax and p. cynomolgi appear to be related. the pattern emerging from this data suggests that the ancestor of p. gonderi and the 'asian' clade (p. coatneyi, p. cynomolgi, p. fieldi, p. fragile, p. hylobati, p. inui, p. knowlesi, p. simiovale and p. vivax) infected a primate host - perhaps the ancestor of the extant rhesus monkey - and migrated with its vertebrate host from africa to asia via the middle east. the asian branch then gave rise to several clades - p. fragile-p. coatneyi/p. knowlesi, p. hylobati/p. inui and p. cynomolgi - p. simium/p. vivax. p. fieldi, p. simiovale and p. vivax appear to be relatively early diverging species within this clade. p. fieldi and p. simiovale appear to be each other's closest relations. a summary of the currently understood branching order is as follows: p. gondori - asian clade p. fieldi, p. simiovale, p. vivax, p. simium, p. cynomolgi, p. inui - p. fragile, p. coatneyi, p. knowlesi, p. hylobati p. vivax/p. simium - p. fieldi, p. simiovale, p. cynomolgi, p. inui p. cynomolgi/p. inui - p. fieldi/p. simiovale p. fragile/p. coatneyi - p. knowlesi/p. hylobati this branching order may have to be revised as more data becomes available. the timing of these events is still rather uncertain. the african species p. georgesi appears to be a close relation of p. gondori. another paper suggests that p. coatneyi and p. knowlesi are sister species while p. hylobati and p. inui are also sister species. this analysis supports the grouping of p. fieldi and p. semiovale as sister species with their closest relation being p. cynomogli. it also agrees with previous analyses that place p. simium and p. vivax as sister species. it also agrees that p. gondori is the african species most closely related to the asian clade. this branching order may have some difficulties. a deletion of the ls1 rrna gene of p. gonderi p. cynomolgi and p. simiovale has been reported. this mutation was not found in the other species of this group that were examined - p. fragile, p. knowelsi, p. simiae and p. vivax. these mutations are rare and suggest a relationship between the first three species to the exclusion of the others. host relations p. cynomolgi, p. inui and p. knowlesi infect primates of the genus presbytis. p. cynomolgi, p. fieldi, p. inui, p. knowlesi and p. semiovale infect primates of the genus macaca. p. georgesi and p. gondori infect primates of the genus cocerebus. p. gondori infects primates of the genus mandillus. additional species within the 'asian' clade are three unnamed potential species. one infects each of the two chimpanzee subspecies included in the study (pan troglodytes troglodytes and pan troglodytes schweinfurthii). these appear to be related to the p. vivax/p. simium clade. a new species - yet to be formally described - has been reported from orangutans (pongo pygmaeus) in indonesia. this species was identified from mitochondrial dna in the blood of the hosts. it appears to be related to the other members of the asian clade. another as yet unnamed species likely to belong to this group has been identified in the mandrill (mandrillus sphinx). plasmodium: african clade the species infecting old world monkeys (subgenus plasmodium) seem to form a clade. p. ovale is more closely related to p. malariae than to p. vivax. plasmodium ovale has recently been shown to consist of two cocirculating species - plasmodium ovale curtisi and plasmodium ovale wallikeri. these two species can only be distinguished by genetic means and they separated between 1 million years ago and 3.5 million years ago. a second estimate has placed the separation of these species at 4.5 million years ago (95% confidence interval 0.7-7.7 mya) p. ovale, based on an analysis of the apicoplast genome, appears to be related to the rodent species suggesting an ancestral host switch. the relationship between the p. ovale species and those with rodent hosts has been confirmed by sequencing the genomes of both p. ovale species. one paper has reported a strain of malaria in a chimpanzee with a mitochondrial sequence identical to that of p. ovale and a second closely related to it. it seems likely as has been proposed earlier that p. ovale may have an animal reservoir. two unnamed potential species infect the bonobo (pan paniscus) and these are related to the p. malariae/p. brazillium clade. the species p. gonderi appears to be the closest relation to the asian clade. plasmodium malariae plasmodium malariae has been considered to be closely related to plasmodium brasilianum and plasmodium rhodiani. these species may be a single species with multiple hosts. because the number of strains that have examined to date remains small, retirement of the brasilianum and rhodiani species names to junior synonym status should probably be delayed. rodent species although the branching order among the mammalian clades has not yet been determined the branching order in the rodent infections species has been studied. the rodent parasites (p. berghei, p. chabaudi, p. vinckei and p. yoelii) seem to form a distinct clade. p. berghei and p. yoelii appear to be sister species as do p. chabaudi and p. vinckei. the separation dates between p. berghei and p. yoelii has been estimated to be 4.5 million years ago (95% credibility interval 2.5 - 6.0); that between p. chabaudi and p. vinckei has been estimated to be 9 million years ago (95% credibility interval 5.5 - 12.6); and that between the p. berghei/p. yoelii and p. chabaudi/p. vinckei clades to be 12.5 million years ago (95% credibility interval 9.0 - 17.5). these estimates are consistent with those from another paper that included a number of primate infecting species. p. atheruri appears to be the sister species of p. vinckei. notes a recently (2009) described species (plasmodium hydrochaeri) that infects capybaras (hydrochaeris hydrochaeris) may complicate the phylogentics of this genus. this species appears to be most similar to plasmodium mexicanum a lizard parasite. further work in this area seems indicated. unlike other eukaryotes studied to date plasmodium species have two or three distinct ssu rrna (18s rrna) molecules encoded within the genome. these have been divided into types a, s and o. type a is expressed in the asexual stages; type s in the sexual and type o only in the oocyst. type o is only known to occur in plasmodium vivax at present. the reason for this gene duplication is not known but presumably reflects an adaption to the different environments the parasite lives within. it has been reported that the c terminal domain of the rna polymerase 2 in the primate infecting species (other than p. falciparum and probably p. reichenowei) appears to be unusual suggesting that the classification of species into the subgenus plasmodium may have an evolutionary and biological basis. it is known from many written historical sources that p. vivax malaria was endemic in the wetlands of england from the 1500s until the 20th century. it is suspected that this disease was introduced by the romans sometime before 400 ad. it seems likely that it remained endemic in these areas at least up to 1000 ad. a study in senegal of 25 strains isolated there suggests that p. falciparum underwent a major (60-fold) population expansion of ~20,000-40,000 years ago. a population study based on isolates from several countries suggests that distinct clustering of continental populations - africa, southeast asia and oceania - has occurred. within these grouping there has been some further clustering - west africa versus east africa, thailand versus cambodia. no distinction was identified between isolates from mali and burkina faso. host range because of the number of species parasited by plasmodium further discussion has been broken down into following pages: plasmodium species infecting humans and other primates plasmodium species infecting mammals other than primates plasmodium species infecting birds plasmodium species infecting reptiles criteria used for speciation the vertebrate host is the first criterion used for speciation and may be sufficient alone to determine the subgenus as in ophidiella and vinckeia. the morphological features of the parasite itself most commonly used to describe a species include the number of pigment granules, the degree of encirclement of the host nucleus, the size of the parasite, the degree of host nucleus displacement and the degree of host cell enlargement. list of species plasmodium accipiteris plasmodium achiotense plasmodium achromaticum plasmodium acuminatum plasmodium adleri plasmodium aegyptensis plasmodium aeuminatum plasmodium agamae plasmodium alaudae plasmodium alloelongatum plasmodium anasum plasmodium anomaluri plasmodium arachniformis plasmodium ashfordi plasmodium atheruri plasmodium audaciosum plasmodium auffenbergi plasmodium aurulentum plasmodium australis plasmodium attenuatum plasmodium azurophilum plasmodium billbrayi plasmodium billcollinsi plasmodium balli plasmodium bambusicolai plasmodium basilisci plasmodium beaucournui plasmodium beebei plasmodium beltrani plasmodium berghei plasmodium bertii plasmodium bigueti plasmodium bioccai plasmodium biziurae plasmodium blacklocki plasmodium booliati plasmodium bouillize plasmodium brodeni plasmodium brasilianum plasmodium brumpti plasmodium brygooi plasmodium bubalis plasmodium bucki plasmodium buteonis plasmodium caloti plasmodium capistrani plasmodium caprae plasmodium carmelinoi plasmodium cathemerium plasmodium caucasica plasmodium cephalophi plasmodium cercopitheci plasmodium chabaudi plasmodium chiricahuae plasmodium circularis plasmodium circumflexum plasmodium clelandi plasmodium cnemaspi plasmodium cnemidophori plasmodium coatneyi plasmodium coggeshalli plasmodium coluzzii plasmodium colombiense plasmodium columbae plasmodium cordyli plasmodium coturnixi plasmodium coulangesi plasmodium cuculus plasmodium cyclopsi plasmodium cynomolgi bastianelli plasmodium cynomolgi ceylonensis plasmodium cynomolgi cynomolgi plasmodium delichoni plasmodium dherteae plasmodium diminutivum plasmodium diploglossi plasmodium dissanaikei plasmodium dominicana plasmodium dorsti plasmodium draconis plasmodium durae plasmodium egerniae plasmodium elongatum plasmodium eylesi plasmodium fairchildi plasmodium falciparum plasmodium fallax plasmodium fieldi plasmodium fischeri plasmodium foleyi plasmodium formosanum plasmodium forresteri plasmodium floridense plasmodium fragile plasmodium gaboni plasmodium gabaldoni plasmodium garnhami plasmodium gallinaceum plasmodium gemini plasmodium georgesi plasmodium ghadiriani plasmodium giganteum plasmodium giovannolai plasmodium ginsburgi plasmodium girardi plasmodium globularis plasmodium gloriai plasmodium gologoense plasmodium golvani plasmodium gonatodi plasmodium gonderi plasmodium gracilis plasmodium griffithsi plasmodium guangdong plasmodium gundersi plasmodium guyannense plasmodium heischi plasmodium hegneri plasmodium hermani plasmodium heroni plasmodium heteronucleare plasmodium hexamerium plasmodium hispaniolae plasmodium hoionucleophilum plasmodium holaspi plasmodium holti plasmodium homocircumflexum plasmodium homopolare plasmodium huffi plasmodium hydrochaeri plasmodium hylobati plasmodium