Plasmodium 287207 226038004 2008-07-16T15:32:43Z /* Life cycle */ {{copyedit|date=April 2008}} ''A '''plasmodium''' is also the macroscopic form of the [[protist]] known as a [[slime mould]].'' {{Taxobox | color = greenyellow | name = ''Plasmodium'' | image = Malaria.jpg|Plasmodium | domain = [[Eukaryota]] | superphylum = [[Alveolata]] | phylum = [[Apicomplexa]] | classis = [[Aconoidasida]] | ordo = [[Haemosporida]] | familia = [[Plasmodiidae]] | genus = '''''Plasmodium''''' | subdivision_ranks = Species | subdivision = ''[[Plasmodium accipiteris]]''<br/> ''[[Plasmodium achiotense]]''<br/> ''[[Plasmodium achromaticum]]''<br/> ''[[Plasmodium acuminatum]]<br/> ''[[Plasmodium adunyinkai]]''<br/> ''[[Plasmodium aegyptensis]]''<br/> ''[[Plasmodium aeuminatum]]''<br/> ''[[Plasmodium agamae]]''<br/> ''[[Plasmodium alloelongatum]]<br/> ''[[Plasmodium anasum]]''<br/> ''[[Plasmodium anomaluri]]''<br/> ''[[Plasmodium arachniformis]]''<br/> ''[[Plasmodium ashfordi]]''<br/> ''[[Plasmodium atheruri]]''<br/> ''[[Plasmodium audaciosum]]''<br/> ''[[Plasmodium aurulentum]]''<br/> ''[[Plasmodium australis]]''<br/> ''[[Plasmodium attenuatum]]<br/> ''[[Plasmodium azurophilum]]''<br/> ''[[Plasmodium balli]]''<br/> ''[[Plasmodium bambusicolai]]''<br/> ''[[Plasmodium basilisci]]<br/> ''[[Plasmodium beebei]]''<br/> ''[[Plasmodium beltrani]]''<br/> ''[[Plasmodium berghei]]''<br/> ''[[Plasmodium bertii]]''<br/> ''[[Plasmodium bigueti]]<br/> ''[[Plasmodium bitis]]''<br/> ''[[Plasmodium biziurae]]<br/> ''[[Plasmodium booliati]]''<br/> ''[[Plasmodium bouillize]]''<br/> ''[[Plasmodium bowiei]]''<br/> ''[[Plasmodium brodeni]]''<br/> ''[[Plasmodium brasilianum]]''<br/> ''[[Plasmodium brasiliense]]''<br/> ''[[Plasmodium brumpti]]''<br/> ''[[Plasmodium brucei]]''<br/> ''[[Plasmodium brygooi]]''<br/> ''[[Plasmodium bubalis]]''<br/> ''[[Plasmodium bucki]]''<br/> ''[[Plasmodium bufoni]]''<br/> ''[[Plasmodium buteonis]]''<br/> ''[[Plasmodium capistrani]]''<br/> ''[[Plasmodium carinii]]''<br/> ''[[Plasmodium cathemerium]]''<br/> ''[[Plasmodium causi]]''<br/> ''[[Plasmodium cephalophi]]<br/> ''[[Plasmodium cercopitheci]]<br/> ''[[Plasmodium chabaudi]]''<br/> ''[[Plasmodium chalcidi]]''<br/> ''[[Plasmodium chiricahuae]]''<br/> ''[[Plasmodium circularis]]''<br/> ''[[Plasmodium circumflexum]]''<br/> ''[[Plasmodium clelandi]]''<br/> ''[[Plasmodium cordyli]]''<br/> ''[[Plasmodium cnemaspi]]''<br/> ''[[Plasmodium cnemidophori]]''<br/> ''[[Plasmodium coatneyi]]''<br/> ''[[Plasmodium coggeshalli]]''<br/> ''[[Plasmodium colombiense]]''<br/> ''[[Plasmodium columbae]]''<br/> ''[[Plasmodium corradettii]]<br/> ''[[Plasmodium coturnixi]]<br/> ''[[Plasmodium coulangesi]]''<br/> ''[[Plasmodium cuculus]]''<br/> ''[[Plasmodium cyclopsi]]''<br/> ''[[Plasmodium cynomolgi]]''<br/> ''[[Plasmodium diminutivum]]<br/> ''[[Plasmodium diploglossi]]''<br/> ''[[Plasmodium dissanaikei]]''<br/> ''[[Plasmodium divergens]]''<br/> ''[[Plasmodium dominicana]]''<br/> ''[[Plasmodium draconis]]''<br/> ''[[Plasmodium durae]]''<br/> ''[[Plasmodium effusum]]''<br/> ''[[Plasmodium egerniae]]''<br/> ''[[Plasmodium elongatum]]''<br/> ''[[Plasmodium eylesi]]''<br/> ''[[Plasmodium fabesia]]''<br/> ''[[Plasmodium fairchildi]]''<br/> ''[[Plasmodium falciparum]]''<br/> ''[[Plasmodium falconi]]''<br/> ''[[Plasmodium fallax]]''<br/> ''[[Plasmodium fieldi]]''<br/> ''[[Plasmodium fischeri]]''<br/> ''[[Plasmodium foleyi]]''<br/> ''[[Plasmodium formosanum]]''<br/> ''[[Plasmodium forresteri]]''<br/> ''[[Plasmodium floridense]]''<br/> ''[[Plasmodium fragile]]''<br/> ''[[Plasmodium galbadoni]]''<br/> ''[[Plasmodium garnhami]]''<br/> ''[[Plasmodium gallinaceum]]''<br/> ''[[Plasmodium giganteum]]''<br/> ''[[Plasmodium giganteumaustralis]]''<br/> ''[[Plasmodium giovannolai]]<br/> ''[[Plasmodium girardi]]''<br/> ''[[Plasmodium gonderi]]''<br/> ''[[Plasmodium georgesi]]''<br/> ''[[Plasmodium gologoense]]''<br/> ''[[Plasmodium gonatodi]]''<br/> ''[[Plasmodium gracilis]]''<br/> ''[[Plasmodium griffithsi]]''<br/> ''[[Plasmodium guangdong]]''<br/> ''[[Plasmodium gundersi]]''<br/> ''[[Plasmodium guyannense]]<br/> ''[[Plasmodium heischi]]''<br/> ''[[Plasmodium hegneri]]''<br/> ''[[Plasmodium hermani]]''<br/> ''[[Plasmodium herodiadis]]''<br/> ''[[Plasmodium heteronucleare]]''<br/> ''[[Plasmodium hexamerium]]''<br/> ''[[Plasmodium holaspi]]''<br/> ''[[Plasmodium holti]]''<br/> ''[[Plasmodium huffi]]''<br/> ''[[Plasmodium hylobati]]''<br/> ''[[Plasmodium icipeensis]]''<br/> ''[[Plasmodium iguanae]]''<br/> ''[[Plasmodium inconstans]]<br/> ''[[Plasmodium inopinatum]]''<br/> ''[[Plasmodium inui]]''<br/> ''[[Plasmodium japonicum]]''<br/> ''[[Plasmodium jefferi]]''<br/> ''[[Plasmodium jiangi]]''<br/> ''[[Plasmodium josephinae]]''<br/> ''[[Plasmodium joyeuxi]]''<br/> ''[[Plasmodium juxtanucleare]]''<br/> ''[[Plasmodium kempi]]''<br/> ''[[Plasmodium knowlesi]]''<br/> ''[[Plasmodium kentropyxi]]''<br/> ''[[Plasmodium lacertiliae]]''<br/> ''[[Plasmodium lagopi]]''<br/> ''[[Plasmodium lainsoni]]''<br/> ''[[Plasmodium landauae]]''<br/> ''[[Plasmodium leanucteus]]''<br/> ''[[Plasmodium lemuris]]''<br/> ''[[Plasmodium lepidoptiformis]]''<br/> ''[[Plasmodium limnotragi]]''<br/> ''[[Plasmodium lionatum]]''<br/> ''[[Plasmodium lophurae]]''<br/> ''[[Plasmodium loveridgei]]''<br/> ''[[Plasmodium lutzi]]<br/> ''[[Plasmodium lygosomae]]''<br/> ''[[Plasmodium mabuiae]]''<br/> ''[[Plasmodium mackerrasae]]''<br/> ''[[Plasmodium mackiei]]''<br/> ''[[Plasmodium maculilabre]]''<br/> ''[[Plasmodium maior]]''<br/> ''[[Plasmodium majus]]''<br/> ''[[Plasmodium malariae]]''<br/> ''[[Plasmodium marginatum]]<br/> ''[[Plasmodium matutinum]]<br/> ''[[Plasmodium melanoleuca]]''<br/> ''[[Plasmodium melanipherum]]<br/> ''[[Plasmodium mexicanum]]''<br/> ''[[Plasmodium michikoa]]''<br/> ''[[Plasmodium minasense]]''<br/> ''[[Plasmodium modestum]]''<br/> ''[[Plasmodium morulum]]''<br/> ''[[Plasmodium multiformis]]''<br/> ''[[Plasmodium murinus]]<br/> ''[[Plasmodium narayani]]''<br/> ''[[Plasmodium necatrix]]''<br/> ''[[Plasmodium neotropicalis]]''<br/> ''[[Plasmodium neusticuri]]''<br/> ''[[Plasmodium nucleophilium]]''<br/> ''[[Plasmodium octamerium]]''<br/> ''[[Plasmodium odocoilei]]''<br/> ''[[Plasmodium osmaniae]]''<br/> ''[[Plasmodium ovale]]''<br/> ''[[Plasmodium paddae]]''<br/> ''[[Plasmodium papernai]]''<br/> ''[[Plasmodium paranucleophilum]]''<br/> ''[[Plasmodium parvulum]]''<br/> ''[[Plasmodium pedioecetii]]''<br/> ''[[Plasmodium pelaezi]]''<br/> ''[[Plasmodium percygarnhami]]''<br/> ''[[Plasmodium pessoai]]''<br/> ''[[Plasmodium petersi]]<br/> ''[[Plasmodium pifanoi]]''<br/> ''[[Plasmodium pinotti]]''<br/> ''[[Plasmodium pinorrii]]''<br/> ''[[Plasmodium pitheci]]''<br/> ''[[Plasmodium pitmani]]''<br/> ''[[Plasmodium polare]]''<br/> ''[[Plasmodium pulmophilum]]<br/> ''[[Plasmodium pythonias]]''<br/> ''[[Plasmodium quelea]]''<br/> ''[[Plasmodium reichenowi]]<br/> ''[[Plasmodium relictum]]''<br/> ''[[Plasmodium rhadinurum]]''<br/> ''[[Plasmodium rhodaini]]''<br/> ''[[Plasmodium robinsoni]]''<br/> ''[[Plasmodium rousetti]]''<br/> ''[[Plasmodium rousseloti]]''<br/> ''[[Plasmodium rouxi]]''<br/> ''[[Plasmodium sandoshami]]''<br/> ''[[Plasmodium sasai]]''<br/> ''[[Plasmodium saurocaudatum]]''<br/> ''[[Plasmodium schweitzi]]''<br/> ''[[Plasmodium scelopori]]''<br/> ''[[Plasmodium scorzai]]''<br/> ''[[Plasmodium semiovale]]''<br/> ''[[Plasmodium semnopitheci]]''<br/> ''[[Plasmodium shortii]]''<br/> ''[[Plasmodium siamense]]''<br/> ''[[Plasmodium silvaticum]]''<br/> ''[[Plasmodium simium]]''<br/> ''[[Plasmodium simplex]]''<br/> ''[[Plasmodium smirnovi]]''<br/> ''[[Plasmodium stuthionis]]''<br/> ''[[Plasmodium tanzaniae]]''<br/> ''[[Plasmodium tenue]]''<br/> ''[[Plasmodium tejerai]]''<br/> ''[[Plasmodium telfordi]]''<br/> ''[[Plasmodium tomodoni]]''<br/> ''[[Plasmodium torrealbai]]''<br/> ''[[Plasmodium toucani]]''<br/> ''[[Plasmodium traguli]]''<br/> ''[[Plasmodium tribolonoti]]''<br/> ''[[Plasmodium tropiduri]]''<br/> ''[[Plasmodium tumbayaensis]]''<br/> ''[[Plasmodium tyrio]]''<br/> ''[[Plasmodium uilenbergi]]''<br/> ''[[Plasmodium uluguruense]]''<br/> ''[[Plasmodium uncinatum]]''<br/> ''[[Plasmodium uranoscodoni]]''<br/> ''[[Plasmodium utingensis]]''<br/> ''[[Plasmodium uzungwiense]]''<br/> ''[[Plasmodium watteni]]''<br/> ''[[Plasmodium wenyoni]]''<br/> ''[[Plasmodium vacuolatum]]''<br/> ''[[Plasmodium vastator]]''<br/> ''[[Plasmodium vaughani]]''<br/> ''[[Plasmodium vautieri]]''<br/> ''[[Plasmodium venkataramiahii]]''<br/> ''[[Plasmodium vinckei]]''<br/> ''[[Plasmodium vivax]]''<br/> ''[[Plasmodium volans]]''<br/> ''[[Plasmodium voltaicum]]''<br/> ''[[Plasmodium wenyoni]]''<br/> ''[[Plasmodium yoelii]]''<br/> ''[[Plasmodium youngi]]''<br/> ''[[Plasmodium zonuriae]]''<br/> }} '''''Plasmodium''''' is a genus of parasitic [[protozoa]]. Infection with this genus is known as [[malaria]]. The parasite always has two hosts in its [[Biological life cycle|life cycle]]: a [[mosquito]] [[Vector (biology)|vector]] and a [[vertebrate]] host. Of the 200 known species of Plasmodium, at least 10 species infect humans. Other species infect other animals, including [[bird]]s, [[reptile]]s and [[rodent]]s. The [[genus]] ''Plasmodium'' was created in [[1885]] by [[Marchiafava]] and [[Angelo Celli|Celli]]. Currently over 200 species are recognized. New species continue to be described.<ref name="Chavatte2007">Chavatte J.M., Chiron F., Chabaud A., Landau I. (2007) Probable speciations by "host-vector 'fidelisation'": 14 species of ''Plasmodium'' from magpies. Parasite 14(1):21-37</ref> The genus is currently ([[2006]]) in need of reorganization as it has been shown that parasites belonging to the genera ''[[Haemocystis]]'' and ''[[Hepatocystis]]'' appear to be closely related to ''Plasmodium''. It is likely that other species such as ''[[Haemoproteus meleagridis]]'' will be included in this genus once it is revised. == History == The organism itself was first seen by [[Charles Louis Alphonse Laveran|Laveran]] on November 6th [[1880]] at a military hospital in [[Constantine, Algeria]], when he discovered a [[microgametocyte]] exflagellating. [[Manson]] (in [[1894]]) hypothesised that [[mosquito]]es could transmit malaria - an association made considerably earlier in [[India]], possibly as early as 2000BC. This hypothesis was experimentally confirmed independently by the Italian professor [[Giovanni Battista Grassi]] and the British physician [[Ronald Ross]] both in [[1898]]. Ross demonstrated the existence of ''Plasmodium'' in the wall of the [[midgut]] and [[salivary glands]] of a ''[[Culex]]'' mosquito. For this discovery he won the [[Nobel Prize]] in [[1902]]. Grassi showed that human malaria could only be transmitted by ''[[Anopheles]]'' mosquitoes. It is worth noting, however, that for some species the vector may not be a mosquito. Grassi also proposed in [[1900]] the existence of an exerythrocytic stage in the life cycle: this was later confirmed by Short, Garnham, Covell and Shute (in [[1948]]) who found ''[[Plasmodium vivax]]'' in the human liver. == Life cycle == Mosquitoes of the genera ''[[Culex]]'', ''[[Anopheles]]'', ''[[Culiceta]]'', ''[[Mansonia]]'' and ''[[Aedes]]'' may act as vectors. The currently known vectors for human malaria (> 100 species) all belong to the genus ''Anopheles''. Bird malaria is commonly carried by species belonging to the genus ''Culex''. Only female mosquitoes bite. Aside from blood both sexes live on [[nectar]], but one or more blood meals are needed by the female for egg laying as the protein content of nectar is very low. The life cycle of ''Plasmodium'' was discovered by Ross who worked with species from the genus ''Culex''. The life cycle of ''Plasmodium'' is very complex. [[Sporozoite]]s from the saliva of a biting female mosquito are transmitted to either the blood or the lymphatic system<ref name="Lymph">[ HHMI Staff (22 January 2006) "Malaria Parasites Develop in Lymph Nodes" ''HHMI News'' Howard Hughes Medical Institute</ref> of the recipient. The sporozoites then migrate to the [[liver]] and invade [[hepatocyte]]s. This latent or dormant stage of the ''Plasmodium'' sporozoite in the liver is called the [[hypnozoite]]. The development from the hepatic stages to the erythrocytic stages has until very recently been obscure. In 2006<ref name="Sturm2006"> Sturm A., Amino R., van de Sand C., Regen T., Retzlaff S., Rennenberg A., Krueger A., Pollok J.M., Menard R., Heussler V.T. (2006) Manipulation of host hepatocytes by the malaria parasite for delivery into liver sinusoids. Science 313(5791):1287-1290 </ref> it was shown that the parasite buds off the hepatocytes in merosomes containing hundreds or thousands of merozoites. These merosomes have been subsequently shown<ref name="Baer2007"> Baer K., Klotz C., Kappe S.H., Schnieder T., Frevert U. (2007) Release of hepatic ''Plasmodium yoelii'' merozoites into the pulmonary microvasculature. PLoS Pathog. 3(11):e171 </ref> to lodge in the pulmonary capilaries and to slowly disintergrate there over 48-72 hours releasing merozoites. Erythrocyte invasion is enhanced when blood flow is slow and the cells are tightly packed: both of these conditions are found in the alveolar capilaries. Within the erythrocytes the merozoite grow first to a ring-shaped form and then to a larger [[trophozoite]] form. In the [[wiktionary:schizont|schizont]] stage, the parasite divides several times to produce new merozoites, which leave the red blood cells and travel within the bloodstream to invade new red blood cells. The parasite feeds by ingesting haemoglobin and other materials from red blood cells and serum. The feeding process damages the erythrocytes. Details of this process have not been studied in species other than ''[[Plasmodium falciparum]]'' so generalisations may be premature at this time. At the molecular level a set of enzymes known as [[plasmepsin]]s which are [[protease|aspartic acid proteases]] are used to degrade [[hemoglobin]]. Most merozoites continue this replicative cycle, but some merozoites differentiate into male or female sexual forms ([[gametocyte]]s) (also in the blood), which are taken up by the female mosquito. In the mosquito's midgut, the [[gametocyte]]s develop into [[gamete]]s and [[fertilization|fertilize]] each other, forming motile [[zygote]]s called [[ookinetes]]. The ookinetes penetrate and escape the midgut, then embed themselves onto the exterior of the gut membrane. Here they divide many times to produce large numbers of tiny elongated [[sporozoite]]s. These sporozoites migrate to the salivary glands of the mosquito where they are injected into the blood of the next host the mosquito bites. The sporozoites move to the liver where they repeat the cycle. The pattern of alternation of sexual and asexual reproduction which may seem confusing at first is a very common pattern in parasitic species. The evolutionary advantages of this type of life cycle were recognised by [[Mendel]]. Under favourable conditions asexual reproduction is superior to sexual as the parent is well adapted to its environment and its descendents share these genes. Transferring to a new host or in times of stress, sexual reproduction is generally superior as this produces a shuffling of [[genes]] which on average at a population level will produce individuals better adapted to the new environment. Reactivation of the hypnozoites has been reported for up to 30 years after the initial infection in humans. The factors precipating this reactivation are not known. In the species ''[[Plasmodium malariae]]'', ''[[Plasmodium ovale]]'' and ''[[Plasmodium vivax]]'' hypnozoites have been shown to occur. Reactivation does not occur in infections with ''[[Plasmodium falciparum]]''. It is not known if hypnozoite reactivaction may occur with any of the remaining species that infect humans but this is presumed to be the case. A single report of recurrence of ''P. falciparum'' in a patient with [[sickle cell]] anaemia exists <ref name="Greenwood2008"> Greenwood T., Vikerfors T., Sjöberg M., Skeppner G., Färnert A. (2008) Febrile ''Plasmodium falciparum'' malaria 4 years after exposure in a man with sickle cell disease. Clin. Infect. Dis. </ref> but this needs additional confirmation as liver forms are not known to occur in ''P. falciparum'' infections. == Evolution == The life cycle is probably best understood in terms of its [[evolution]]. At the present time (2007) DNA sequences are available from fewer than sixty species of ''Plasmodium'' and most of these are from species infecting either rodent or primate hosts. The evolutionary outline given here should be regarded as speculative and subject to revision as data becomes available. The ''[[Apicomplexa]]'' — the phylum to which ''[[Plasmodium]]'' belongs - are thought to have originated within the [[Dinoflagellate]]s — a large group of photosynthetic protozoa. It is thought that the ancestors of the Apicomplexa were originally prey organisms that evolved the ability to invade the intestinal cells and subsequently lost their photosynthetic ability. Many of the species within the Apicomplexia still possess a plastid (the organelle in which photosynthesis occurs in eukaryotes): some that do not have evidence of plastid genes within their genome. These plastids - unlike those found in [[algae]] - are not [[photosynthetic]]. Its function is not known but there is some suggestive evidence that it may be involved in [[reproduction]]. Some extant dinoflagelates, however, can invade the bodies of [[jellyfish]] and continue to photosynthesize, which is possible because jellyfish bodies are almost transparent. In other organisms with [[Opacity (optics)|opaque]] bodies this ability would most likely rapidly be lost. The recent ([[2008]]) description of a photosynthetic protist related to the Apicomplexia with a functional plastid supports this hypothesis.<ref name="Moore2008">Moore R.B., Oborník M., Janouskovec J., Chrudimský T., Vancová M., Green D.H., Wright S.W., Davies N.W., Bolch C.J., Heimann K., Slapeta J., Hoegh-Guldberg O., Logsdon J.M., Carter D.A. (2008) A photosynthetic alveolate closely related to apicomplexan parasites. Nature 451(7181):959-963.</ref> Current ([[2007]]) theory suggests that the genera ''Plasmodium'', ''[[Hepatocystis]]'' and ''[[Haemoproteus]]'' evolved from one or more ''[[Leukocytozoon]]'' species. Parasites of the genus ''Leukocytozoan'' infect white blood cells ([[leukocytes]]), [[liver]] and [[spleen]] cells and are transmitted by 'black flies' (''[[Simulium]]'' species) — a large genus of flies related to the mosquitoes. It is thought that ''Leukocytozoon'' evolved from a parasite that spread by the orofaecal route and which infected the [[intestinal]] wall. At some point this parasite evolved the ability to infect the [[liver]]. This pattern is seen in the genus ''[[Cryptosporidium]]'' to which ''Plasmodium'' is distantly related. At some later point this ancestor developed the ability to infect [[blood cells]] and to survive and infect [[mosquito]]es. Once vector transmission was firmly established the previous orofecal route of transmission was lost. Leukocytes, [[hepatocyte]]s and most spleen cells actively [[phagocytose]] particulate matter making entry into the cell easier for the parasite. The mechanism of entry of ''Plasmodium'' species into [[erythrocyte]]s is still very unclear taking as it does less than 30 seconds. It is not yet known if this mechanism evolved before mosquitoes became the main vectors for transmission of ''Plasmodium''. The genus ''Plasmodium'' evolved (presumably from its ''Leukocytozoon'' ancestor) about 130 million years ago, a period that is coincidental with the rapid spread of the [[angiosperms]] (flowering plants). This expansion in the angiosperms is thought to be due to at least one [[genomic duplication]] event. It seems probable that the increase in the number of flowers led to an increase in the number of mosquitoes and their contact with vertebrates. Mosquitoes evolved in what is now [[South America]] about 230 million years ago. There are over 3500 species recognised but to date their evolution has not been well worked out so a number of gaps in our knowledge of the evolution of ''Plasmodium'' remain. There is evidence of a recent expansion of ''[[Anopheles gambiae]]'' and ''[[Anopheles arabiensis]]'' populations in the late [[Pleistocene]] in [[Nigeria]].<ref name="Matthews2007"> Matthews S.D., Meehan L.J., Onyabe D.Y., Vineis J., Nock I., Ndams I., Conn J.E. (2007) Evidence for late Pleistocene population expansion of the malarial mosquitoes, ''Anopheles arabiensis'' and ''Anopheles gambiae'' in Nigeria. Med Vet Entomol. 21(4):358-369.</ref> Presently it seems probable that birds were the first group infected by ''Plasmodium'' followed by the reptiles—probably the lizards. At some point primates and rodents became infected. The remaining species infected outside these groups seem likely to be due to relatively recent events. All ''Plasmodium species'' examined to date have 14 [[chromosomes]], one [[mitochondrion]] and one [[plastid]]. The chromosomes whose length is known vary from 500 kilobases to 3.5 megabases in length. It is presumed that this is the pattern throughout the genus. The typical chormosome number of ''Leukcytozoon'' has not yet been established. == Taxonomy == ''Plasmodium'' belongs to the [[family]] [[Plasmodiidae]] (Levine, [[1988]]), [[Order (biology)|order]] [[Haemosporidia]] and [[phylum]] [[Apicomplexa]]. There are currently 450 recognised [[species]] in this order. Many species of this order are undergoing reexamination of their taxonomy with [[DNA]] analysis. It seems likely that many of these species will be re-assigned after these studies have been completed.<ref name="Perkins2002"> Perkins S.L., Schall J.J. (2002) A molecular phylogeny of malarial parasites recovered from cytochrome b gene sequences. J. Parasitol. 88 (5):972-978 </ref><ref name="Yotoko2006"> Yotoko, K.S.C., Elisei C. (2006) Malaria parasites (''Apicomplexa'', ''Haematozoea'') and their relationships with their hosts: is there an evolutionary cost for the specialization? J. Zoo. Syst. Evol. Res. 44(4): 265</ref> For this reason the entire order is outlined here. Order [[Haemosporida]] * Genus [[Bioccala]] Family [[Haemoproteidae]] * Genus [[Haemoproteus]] **Subgenus [[Parahaemoproteus]]</br> **Subgenus [[Haemoproteus]]</br> Family [[Garniidae]] * Genus [[Fallisia]] **Subgenus [[Plasmodioides]]</br> Family [[Leucocytozoidae]] * Genus [[Leukocytozoon]] **Subgenus [[Leucocytozoon]]</br> **Subgenus [[Akiba]]</br> Family [[Plasmodiidae]] * Genus [[Billbraya]] * Genus [[Dionisia]] * Genus [[Hepatocystis]] * Genus [[Mesnilium]] * Genus [[Nycteria]] * Genus Plasmodium **Subgenus Asiamoeba</br> **Subgenus Bennettinia</br> **Subgenus Carinamoeba</br> **Subgenus Giovannolaia</br> **Subgenus Haemamoeba</br> **Subgenus Huffia</br> **Subgenus Lacertaemoba</br> **Subgenus Laverania</br> **Subgenus Novyella</br> **Subgenus Plasmodium</br> **Subgenus Paraplasmodium</br> **Subgenus Sauramoeba</br> **Subgenus Vinckeia</br> * Genus [[Polychromophilus]] * Genus [[Rayella]] * Genus [[Saurocytozoon]] == Diagnostic characteristics of the genus ''Plasmodium'' == * Forms gamonts in erythrocytes * Merogony occurs in erythrocytes and in other tissues * Hemozoin is present * Vectors are either mosquitos or sandflies * Vertebrate hosts include mammals, birds and reptiles '''Notes:''' The genera ''Plasmodium'', ''Fallisia'' and ''Saurocytozoon'' all cause malaria in lizards. All are carried by ''[[Diptera]]'' (flies). Pigment is absent in the ''Garnia''. Non pigmented gametocytes are typically the only forms found in ''Saurocytozoon'': pigmented forms may be found in the leukocytes occasionally. ''Fallisia'' produce non pigmented asexual and gametocyte forms in leukocytes and thrombocytes. == Phylogenetic trees == The relationship between a number of these species can be seen on this graphic from the Tree of Life. Perhaps the most useful inferences that can be drawn from this [[phylogenetic tree]] are: * ''P. falciparum'' and ''P. reichenowi'' (subgenus ''Laverania'') branched off early in the evolution of this genus * The genus ''Hepatocystis'' is nested within (paraphytic with) the genus ''Plasmodium'' * The primate (subgenus ''Plasmodium'') and rodent species (subgenus ''Vinckeia'') form distinct groups * The rodent and primate groups are relatively closely related * The lizard and bird species are intermingled * Although ''Plasmodium elongatum'' (subgenus ''Haemamoeba'') and ''Plasmodium elongatum'' (subgenus ''Huffia'') appear be related here there are so few bird species (three) included, this tree may not accurately reflect their real relationship. * While no snake parasites have been included these are likely to group with the lizard-bird division While this tree contains a considerable number of species, DNA sequences from many species in this genus have not been included - probably because they are not available yet. Because of this problem, this tree and any conclusions that can be drawn from it should be regarded as provisional. Three additional trees are available at These trees agree with the Tree of Life. Because of there greater number of species in these trees, some additional inferences can be made: * The genus ''Hepatocystis'' appears to lie within the primate-rodent clade * The genus ''Haemoproteus'' appears lie within the bird-lizard clade * The trees are consistent with the proposed origin of ''Plasmodium'' from ''Leukocytozoon'' == Subgenera: discussion == The full taxonomic name of a species includes the subgenus but this is often omitted. The full name indicates some features of the morphology and type of host species. The only two species in the sub genus ''[[Laverania]]'' are ''P. falciparum'' and ''P. reichenowi''. The presence of elongated gametocytes in several of the avian subgenera and in ''Laverania'' in addition to a number of clinical features suggested that these might be closely related. This is is no longer thought to be the case. Species infecting [[monkey]]s and [[apes]] (the higher [[primates]]) with the exceptions of ''P. falciparum'' and ''P. reichenowi'' are classified in the subgenus ''Plasmodium''. The distinction between ''P. falciparum'' and ''P. reichenowi'' and the other species infecting higher primates was based on the morphological findings but have since been confirmed by DNA analysis. Parasites infecting other [[mammal]]s including lower primates ([[lemur]]s and others) are classified in the subgenus ''[[Vinckeia]]''. ''Vinckeia'' while previously considered to be something of a taxonomic 'rag bag' has been recently shown - perhaps rather surprisingly - to form a coherent grouping. The remaining groupings are based on the morphology of the parasites. Revisions to this system are likely to occur in the future as more species are subject to analysis of their [[DNA]]. The four subgenera ''[[Giovannolaia]]'', ''[[Haemamoeba]]'', ''[[Huffia]]'' and ''[[Novyella]]'' were created by Corradetti ''et al''<ref name="Corradetti1963"> Corradetti A., Garnham P. C. C. and Laird M. (1963). New classification of the avian malaria parasites. Parassitologia 5, 1–4 </ref> for the known avian malarial species. A fifth - ''[[Bennettinia]]'' - was created in 1997 by Valkiunas.<ref name="Valkiunas1997"> Valkiunas G. (1997). Bird Haemosporidia. Institute of Ecology, Vilnius</ref> The relationships between the subgenera are the matter of current investigation. Martinsen ''et al'' 's recent ([[2006]]) paper outlines what is currently ([[2007]]) known.<ref name="Martinsen"> Martinsen E.S., Waite J.L., Schall J.J. (2006) Morphologically defined subgenera of ''Plasmodium'' from avian hosts: test of monophyly by phylogenetic analysis of two mitochondrial genes. Parasitology 1-8 </ref> The subgenera ''Haemamoeba'', ''Huffia'', and ''Bennettinia'' appear to be monphylitic. ''Novyella'' appears to be well defined with occasional exceptions. The subgenus ''Giovannolaia'' needs revision. <ref name="Martinsen2007">Martinsen E.S., Waite J.L., Schall J.J. (2007) Morphologically defined subgenera of ''Plasmodium'' from avian hosts: test of monophyly by phylogenetic analysis of two mitochondrial genes. Parasitol. 134(4):483-490.</ref> ''P. juxtanucleare'' is currently ([[2007]]) the only known member of the subgenus ''Bennettinia''. Unlike the mammalian and bird malarias those affecting reptiles have been more difficult to classify. In [[1966]] Garnham classified those with large schizonts as ''[[Sauramoeba]]'', those with small schizonts as ''[[Carinamoeba]]'' and the single then known species infecting snakes (''[[Plasmodium wenyoni]]'') as ''[[Ophidiella]]''.<ref name="Garmham1966"> Garnham P.C.C. (1966) Malaria parasites and other haemospordia. Oxford, Blackwell</ref> He was aware of the arbitrariness of this system and that it might not prove to be biologically valid. Telford in [[1988]] used this scheme as the basis for the currently accepted (2007) system.<ref name="Telford1988"> Telford S. (1988) A contribution to the systematics of the reptilian malaria parasites, family ''Plasmodiidae'' (''Apicomplexa: Haemosporina''). Bulletin of the Florida State Museum Biological Sciences 34: 65-96</ref> == Classification criteria for subgenera == Avian species: Species in the subgenus ''[[Bennettinia]]'' have the following characteristics: *[[Schizonts]] contain scant [[cytoplasm]], are often round, do not exceed the size of the host [[Cell nucleus|nucleus]] and stick to it. *[[Gametocytes]] while varying in shape tend to be round or oval, do not exceed the size of the nucleus and stick to it. Species in the subgenus ''[[Giovannolaia]]'' have the following characteristics: *Schizonts contain plentiful cytoplasm, are larger than the host cell nucleus and frequently displace it. They are found only in mature [[erythrocytes]]. *Gametocytes are elongated. *Exoerythrocytic schizogony occurs in the [[mononuclear phagocyte]] system. Species in the subgenus ''[[Haemamoeba]]'' have the following characteristics: *Mature schizonts are larger than the host cell nucleus and commonly displace it. *Gametocytes are large, round, oval or irregular in shape and are substantially larger than the host nucleus. Species in the subgenus ''[[Huffia]]'' have the following characteristics: *Mature schizonts, while varying in shape and size, contain plentiful cytoplasm and are commonly found in immature erthryocytes. *Gametocytes are elongated. Species in the subgenus ''[[Novyella]]'' have the following characteristics: *Mature schisonts are either smaller than or only slightly larger than the host nucleus. They contain scanty cytoplasm. *Gametocytes are elongated. Sexual stages in this subgenus resemble those of ''Haemoproteus''. *Exoerythrocytic schizogony occurs in the mononuclear phagocyte system Reptile species: Species in the subgenus ''[[Carinamoeba]]'' have the following characteristics: *Infect lizards *Schizonts normally give rise to less than 8 merozoites Species in the subgenus ''[[Sauramoeba]]'' have the following characteristics: *Infect lizards *Schizonts normally give rise to more than 8 merozoites '''Notes''' *The erythrocytes of both reptiles and birds retain their nucleus, unlike those of mammals. The reason for the loss of the nucleus in mammalian erythocytes remains unknown. == Species listed by subgenera == {| | ''Plasmodium (Asiamoeba) draconis''<br/> ''Plasmodium (Asiamoeba) vastator''<br/> ''Plasmodium (Bennettinia) juxtanucleare''<br/> ''Plasmodium (Carinamoeba) basilisci''<br/> ''Plasmodium (Carinamoeba) clelandi''<br/> ''Plasmodium (Carinamoeba) lygosomae''<br/> ''Plasmodium (Carinamoeba) mabuiae''<br/> ''Plasmodium (Carinamoeba) minasense''<br/> ''Plasmodium (Carinamoeba) rhadinurum''<br/> ''Plasmodium (Carinamoeba) volans''<br/> ''Plasmodium (Giovannolaia) anasum''<br/> ''Plasmodium (Giovannolaia) circumflexum''<br/> ''Plasmodium (Giovannolaia) dissanaikei''<br/> ''Plasmodium (Giovannolaia) durae''<br/> ''Plasmodium (Giovannolaia) fallax''<br/> ''Plasmodium (Giovannolaia) formosanum''<br/> ''Plasmodium (Giovannolaia) gabaldoni''<br/> ''Plasmodium (Giovannolaia) garnhami''<br/> ''Plasmodium (Giovannolaia) gundersi''<br/> ''Plasmodium (Giovannolaia) hegneri''<br/> ''Plasmodium (Giovannolaia) lophurae''<br/> ''Plasmodium (Giovannolaia) pedioecetii''<br/> ''Plasmodium (Giovannolaia) pinnotti''<br/> ''Plasmodium (Giovannolaia) polare''<br/> ''Plasmodium (Haemamoeba) cathemerium''<br/> ''Plasmodium (Haemamoeba) coggeshalli''<br/> ''Plasmodium (Haemamoeba) coturnixi''<br/> ''Plasmodium (Haemamoeba) elongatum''<br/> ''Plasmodium (Haemamoeba) gallinaceum''<br/> ''Plasmodium (Haemamoeba) giovannolai''<br/> ''Plasmodium (Haemamoeba) lutzi''<br/> ''Plasmodium (Haemamoeba) matutinum''<br/> |''Plasmodium (Haemamoeba) paddae''<br/> ''Plasmodium (Haemamoeba) parvulum''<br/> ''Plasmodium (Haemamoeba) relictum''<br/> ''Plasmodium (Haemamoeba) tejera'' ''Plasmodium (Huffia) elongatum''<br/> ''Plasmodium (Huffia) hermani''<br/> ''Plasmodium (Lacertaemoba) floridense''<br/> ''Plasmodium (Lacertaemoba) tropiduri''<br/> ''Plasmodium (Laverania) falciparum''<br/> ''Plasmodium (Laverania) reichenowi''<br/> ''Plasmodium (Novyella) ashfordi''<br/> ''Plasmodium (Novyella) bertii''<br/> ''Plasmodium (Novyella) bambusicolai''<br/> ''Plasmodium (Novyella) columbae''<br/> ''Plasmodium (Novyella) corradettii''<br/> ''Plasmodium (Novyella) dissanaikei''<br/> ''Plasmodium (Novyella) hexamerium''<br/> ''Plasmodium (Novyella) jiangi''<br/> ''Plasmodium (Novyella) kempi''<br/> ''Plasmodium (Novyella) nucleophilum''</br> ''Plasmodium (Novyella) papernai''<br/> ''Plasmodium (Novyella) paranucleophilum''<br/> ''Plasmodium (Novyella) rouxi''<br/> ''Plasmodium (Novyella) vaughani'' ''Plasmodium (Paraplasmodium) chiricahuae''<br/> ''Plasmodium (Paraplasmodium) mexicanum''<br/> ''Plasmodium (Paraplasmodium) pifanoi''<br/> ''Plasmodium (Plasmodium) bouillize''<br/> ''Plasmodium (Plasmodium) brasilianum''<br/> ''Plasmodium (Plasmodium) cercopitheci''<br/> ''Plasmodium (Plasmodium) coatneyi''<br/> |''Plasmodium (Plasmodium) cynomolgi''<br/> ''Plasmodium (Plasmodium) eylesi''<br/> ''Plasmodium (Plasmodium) fieldi''<br/> ''Plasmodium (Plasmodium) fragile''<br/> ''Plasmodium (Plasmodium) georgesi''<br/> ''Plasmodium (Plasmodium) girardi''<br/> ''Plasmodium (Plasmodium) gonderi''</br> ''Plasmodium (Plasmodium) inui''<br/> ''Plasmodium (Plasmodium) jefferyi''<br/> ''Plasmodium (Plasmodium) joyeuxi''<br/> ''Plasmodium (Plasmodium) knowlei''<br/> ''Plasmodium (Plasmodium) hyobati''<br/> ''Plasmodium (Plasmodium) malariae''<br/> ''Plasmodium (Plasmodium) ovale''<br/> ''Plasmodium (Plasmodium) petersi''<br/> ''Plasmodium (Plasmodium) pitheci''<br/> ''Plasmodium (Plasmodium) rhodiani''<br/> ''Plasmodium (Plasmodium) schweitzi''<br/> ''Plasmodium (Plasmodium) semiovale''<br/> ''Plasmodium (Plasmodium) semnopitheci''<br/> ''Plasmodium (Plasmodium) silvaticum''<br/> ''Plasmodium (Plasmodium) simium''<br/> ''Plasmodium (Plasmodium) vivax''<br/> ''Plasmodium (Plasmodium) youngi''<br/> ''Plasmodium (Sauramoeba) achiotense''<br/> ''Plasmodium (Sauramoeba) adunyinkai''<br/> ''Plasmodium (Sauramoeba) aeuminatum''<br/> ''Plasmodium (Sauramoeba) agamae''<br/> ''Plasmodium (Sauramoeba) beltrani''<br/> ''Plasmodium (Sauramoeba) brumpti''<br/> ''Plasmodium (Sauramoeba) cnemidophori''<br/> ''Plasmodium (Sauramoeba) diploglossi''<br/> |''Plasmodium (Sauramoeba) giganteum''<br/> ''Plasmodium (Sauramoeba) heischi''<br/> ''Plasmodium (Sauramoeba) josephinae''<br/> ''Plasmodium (Sauramoeba) pelaezi''<br/> ''Plasmodium (Sauramoeba) zonuriae'' ''Plasmodium (Vinckeia) achromaticum''<br/> ''Plasmodium (Vinckeia) aegyptensis''<br/> ''Plasmodium (Vinckeia) anomaluri''<br/> ''Plasmodium (Vinckeia) atheruri''<br/> ''Plasmodium (Vinckeia) berghei''<br/> ''Plasmodium (Vinckeia) booliati''<br/> ''Plasmodium (Vinckeia) brodeni''</br> ''Plasmodium (Vinckeia) bubalis''<br/> ''Plasmodium (Vinckeia) bucki''<br/> ''Plasmodium (Vinckeia) caprae'' </br> ''Plasmodium (Vinckeia) cephalophi''<br/> ''Plasmodium (Vinckeia) chabaudi''<br/> ''Plasmodium (Vinckeia) coulangesi''<br/> ''Plasmodium (Vinckeia) cyclopsi''<br/> ''Plasmodium (Vinckeia) foleyi''<br/> ''Plasmodium (Vinckeia) girardi''<br/> ''Plasmodium (Vinckeia) inopinatum''<br/> ''Plasmodium (Vinckeia) lemuris''<br/> ''Plasmodium (Vinckeia) melanipherum''<br/> ''Plasmodium (Vinckeia) odocoilei''<br/> ''Plasmodium (Vinckeia) percygarnhami''<br/> ''Plasmodium (Vinckeia) sandoshami''<br/> ''Plasmodium (Vinckeia) traguli''<br/> ''Plasmodium (Vinckeia) tyrio''<br/> ''Plasmodium (Vinckeia) uilenbergi''<br/> ''Plasmodium (Vinckeia) vinckei''<br/> ''Plasmodium (Vinckeia) watteni''<br/> ''Plasmodium (Vinckeia) yoelli'' |} '''Notes''' ''[[Ophidiella]]'' was a subgenus created by Garnham in [[1966]] for the species infecting snakes. Presently (2007) it is no longer in use. == Host range == Host range among the mammalian orders is non uniform. At least 29 [[species]] infect non human [[primates]]; [[rodents]] outside the tropical parts of [[Africa]] are rarely affected; a few species are known to infect [[bat]]s, [[porcupine]]s and [[squirrel]]s; [[carnivore]]s, [[insectivore]]s and [[marsupial]]s are not known to act as hosts. The listing of host species among the reptiles has rarely been attempted. Ayala in [[1978]] listed 156 published accounts on 54 valid species and subspecies between [[1909]] and [[1975]]. <ref name="Ayala1978"> Ayala S.C. (1978) Checklist, host index, and annotated bibliography of ''Plasmodium'' from reptiles. J. Euk. Micro. 25(1): 87-100 </ref> The regional breakdown was [[Africa]]: 30 reports on 9 species; [[Australia]], [[Asia]] & [[Oceania]]: 12 reports on 6 species and 2 subspecies; [[Americas]]: 116 reports on 37 species. 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]]<br/> *[[Plasmodium species infecting mammals other than primates]]<br/> *[[Plasmodium species infecting birds]]<br/> *[[Plasmodium species infecting reptiles]]<br/> == Species reclassified into other genera == The literature is replete with species initially classified as ''Plasmodium'' that have been subsequently reclassified. With DNA taxonomy some of these may be once again be classified as ''Plasmodium''. Some of these species are listed here for completeness. The following species are currently (2007) regarded as belonging to the genus ''[[Hepatocystis]]'' rather than ''Plasmodium'': *''Plasmodium epomophori'' *''Plasmodium kochi'' *''Plasmodium limnotragi'' Van Denberghe 1937 *''Plasmodium pteropi'' Breinl 1911 *''Plasmodium ratufae'' Donavan 1920 *''Plasmodium vassali'' Laveran 1905 The following species are now considered to belong to the genus ''[[Haemoemba]]'' rather than to ''Plasmodium'': *''Plasmodium praecox'' *''Plasmodium rousseleti'' The following species been reclassified as a species of ''[[Garnia]]'': *''Plasmodium gonatodi'' Host note: ''Hepatocystis epomophori'' infects the [[bat]] (''[[Hypsignathus monstruosus]]'') == Species of dubious validity == The following species are currently regarded as questionable validity (''nomen dubium'') *''[[Plasmodium caprea]]'' *''[[Plasmodium danilweskyi]]'' *''[[Plasmodium gambeli]]'' *''[[Plasmodium malariae raupachi]]'' *''[[Plasmodium struthionis]]'' == General references == The standard reference books for the identification of ''Plasmodium'' species are: *Laird, M. ([[1998]]) Avian Malaria in the Asian Tropical Subregion. Springer, [[Singapore]]. *Garnham P.C ([[1966]]) Malaria Parasites And Other Haemosporidia. Blackwell, [[Oxford]]. This book remains the standard reference work on malarial species classification. *Hewitt ([[1940]]) Bird Malaria. Baltimore, The [[Johns Hopkins University|Johns Hopkins]] Press. Other useful references include * Short, H. E. (1951) ''Life-cycle of the mammalian malaria parasite" ''British Medical Bulletin'' 8(1): pp. 7-9, (PMID 14944807); * Baldacci, Patricia and Ménard, Robert (Oct. 2004) "The elusive malaria sporozoite in the mammalian host" ''Molecular Microbiology'' 54(2): pp. 298-306, (AN 14621725); * [ Bledsoe, G. H. (December 2005) "Malaria primer for clinicians in the United States" ''Southern Medical Journal'' 98(12): pp. 1197-204] (PMID 16440920); == References == {{Reflist}} ==External links== {{Wikispecies|Plasmodium}} Some history of malaria - * [ Malaria Atlas Project] * [ Tree of Life Plasmodium] * [ PlasmoDB: The Plasmodium Genome Resource] [[Category:Apicomplexa]] [[Category:Malaria]] [[ar:متصورة]] [[ca:Plasmodi]] [[cs:Plasmodium]] [[de:Plasmodium]] [[eo:Plasmodio]] [[es:Plasmodium]] [[fr:Plasmodium]] [[he:Plasmodium]] [[hr:Plasmodium]] [[id:Plasmodium]] [[it:Plasmodium]] [[lt:Plazmodis]] [[ms:Plasmodium]] [[pl:Zarodziec]] [[pt:Plasmodium]] [[sr:Plasmodium]] [[sv:Plasmodium (släkte)]] [[ta:பிளாஸ்மோடியம்]] [[th:พลาสโมเดียม]] [[zh:瘧原蟲]]