Leukocytozoon

"Leukocytozoon" is a genus of parasitic protozoa belonging to the phylum Apicomplexia. The parasites were first seen by Danilewsky in 1884. The genus was created by Ziemann in 1898. This taxon was revised by Berestneff in 1904 and then by Sambon in 1908.

The species of this genus use blackflies ("Simulium" species) as their definitive host and birds as their intermediate host. There are over 100 species in this genus. Over 100 species of birds have been recorded as hosts to these parasites.

Taxobox | color = khaki
name = "Leukocytozoon "


image_caption = "Leukocytozoon smithi" in a stained blood smear from a turkey
domain = Eukaryota
unranked_phylum = Alveolata
phylum = Apicomplexa
classis = Aconoidasida
ordo = Haemosporida
familia = Plasmodiidae
genus = "Leukocytozoon "
subdivision_ranks = Species
subdivision ="Leukocytozoon acridotheris"
"Leukocytozoon alcedinis"
"Leukocytozoon alcedis"
"Leukocytozoon anatis"
"Leukocytozoon andrewsi"
"Leukocytozoon anellobiae"
"Leukocytozoon apiaster"
"Leukocytozoon ardeolae"
"Leucocytozoon artamidis"
"Leucocytozoon anseris"
"Leukocytozoon atkinsoni"
"Leukocytozoon balmorali"
"Leukocytozoon beaurepairei"
"Leukocytozoon bennetti"
"Leukocytozoon berestneffi"
"Leukocytozoon bishopae"
"Leukocytozoon bishopi"
"Leukocytozoon bisi"
"Leukocytozoon bonasae"
"Leukocytozoon bouffardi"
"Leucocytozoon brimonti"
"Leukocytozoon bucerotis"
"Leukocytozoon cambournaci"
"Leukocytozoon capitonis"
"Leukocytozoon caprimulgi"
"Leukocytozoon caulleryi"
"Leukocytozoon centropi"
"Leukocytozoon chloropsidis"
"Leukocytozoon coccyzus"
"Leukocytozoon colius"
"Leukocytozoon communis"
"Leukocytozoon coraciae"
"Leukocytozoon costai"
"Leukocytozoon dacelo"
"Leukocytozoon danewskyi"
"Leukocytozoon debreuili"
"Leukocytozoon deswardti"
"Leukocytozoon dinizi"
"Leukocytozoon dubreuili"
"Leukocytozoon dubreuili"
"Leukocytozoon dutoiti"
"Leukocytozoon enriquesi"
"Leukocytozoon eurystomi"
"Leukocytozoon francae"
"Leukocytozoon francai"
"Leukocytozoon francolini"
"Leukocytozoon frascai"
"Leukocytozoon fringillinarum"
"Leukocytozoon galli"
"Leukocytozoon gallinarum"
"Leukocytozoon gentili"
"Leukocytozoon giovannolai"
"Leukocytozoon greineri"
"Leukocytozoon grusi"
"Leukocytozoon hamiltoni"
"Leukocytozoon huchzermeyeri"
"Leukocytozoon ibisi"
"Leukocytozoon icteris"
"Leukocytozoon iowense"
"Leukocytozoon irenae"
"Leukocytozoon jakamowi"
"Leukocytozoon kerandeli"
"Leukocytozoon lairdi"
"Leukocytozoon lanium"
"Leukocytozoon laverani"
"Leukocytozoon leboeufi"
"Leukocytozoon leitaoi"
"Leukocytozoon liothricis"
"Leukocytozoon lovati"
"Leukocytozoon maccluri"
"Leukocytozoon macleani"
"Leukocytozoon major"
"Leukocytozoon majoris"
"Leukocytozoon mansoni"
"Leukocytozoon marchouxi"
"Leukocytozoon martini"
"Leukocytozoon mathisi"
"Leukocytozoon mcclurei"
"Leukocytozoon melloi"
"Leukocytozoon mesnili"
"Leukocytozoon molpastis"
"Leukocytozoon muscicapa"
"Leukocytozoon mutus"
"Leukocytozoon neavei"
"Leukocytozoon nectariniae"
"Leukocytozoon numidae"
"Leukocytozoon oriolis"
"Leukocytozoon otidis"
"Leukocytozoon pittae"
"Leukocytozoon pogoniuli
"Leukocytozoon rimondi
"Leucocytozoon roubaudi"
"Leukocytozoon sabrezi"
"Leukocytozoon sakharoffi"
"Leukocytozoon schoutedeni"
"Leukocytozoon schuffneri"
"Leukocytozoon simondi"
"Leukocytozoon struthionis"
"Leukocytozoon smithi"
"Leukocytozoon squamatus"
"Leukocytozoon sunibdu"
"Leukocytozoon tawaki"
"Leukocytozoon timaliae"
"Leukocytozoon toddi"
"Leucocytozoon trachyphoni"
"Leukocytozoon whitworthi"
"Leukocytozoon ziemanni"

Life cycle

Sporozoites are found in the salivary glands of an infected "Simulium" fly and are transmitted to the bird when the fly bites the bird to feed on its blood. The injected sporozoites find their way to the liver where they infect hepatocytes and develop initially into trophozoites and subsequently into schizonts. These schizonts divide into merozoites after 4-6 days. The duration of this stage depends in part upon the species.

The newly released merozoites infect either erythrocytes, leukocytes, macrophages or endothelial cells. Those infecting the macrophages or endothelial cells develop into megaloschizonts. The megaloschizonts divide into primary cytomeres, which in turn multiply into smaller cytomeres, which mature into schizonts, which in turn divide into merozoites.

In erythrocytes or leukocytes, merozoites develop into gametocytes. Two gametocyte forms are recognised: an elongated (sail-like) form and a compact spherical form. These are usually 12-14 microns long. The large gametocytes tend to grossly distort the infected cells and make cell identification difficult.

The gametocytes mature in the insect midgut into macrogametocytes (female) with red-staining nuclei and microgametocytes (male) with pale-staining diffuse nuclei: these fuse to form an ookinete.

The ookinete penetrates an intestinal cell of the fly and matures into an oocyst. After several days the oocyst produces sporozoites that leave and migrate to the salivary glands of the fly.

Diagnostic criteria

Form gamonts in white blood cells and/or erythrocytes. No merogony occurs in either leucocytes or erythrocytes.

Merogony occurs in the parenchyma of liver, heart, kidney, or other organs. Meronts may form large bodies divided into cytomeres.

Hemozoin deposits are not formed.

Oocysts develop rapidly in 3 - 5 days. The oocysts are small and nonexpanding, reaching 13 micrometres in diameter and typically have less than 100 short, thick sporozoites.

The vectors are "Simulium" or "Culicoides" species.

The vertebrate hosts are birds.

Type species: "Leucocytozoon ziemanni"

Pathology

The typical pathology of infection with these parasites includes anaemia and enlargement of the liver and spleen. Gross lesions also include pulmonary congestion and pericardial effusion.

Megaloschizonts appear as grey-white nodules found in the heart, liver, lung or spleen. Microscopically there is ischemic necrosis and associated inflammation in the heart, brain, spleen and liver due to occlusion of blood vessels by megaloschizonts in endothelial cells. Ruptured schizonts may induce granulomatous reactions in the surrounding tissues.

Clinically the majority of birds affected with leucocytozoonosis exhibit no signs. Among those that do the signs include mild to severe signs of anorexia, ataxia, weakness, anemia, emaciation and difficulty breathing.

The excess mortality due to "Leukocytozoon" in adult birds seems to occur as a result of debilitation and increased susceptibility to secondary infection.

Epidemiology

"L. simondi" is suspected to be a major parasite of Canadian geese in some areas, including the upper Midwestern United States and Canada. "L. smithi" affects turkey farms in the southeastern United States.

Host range

Bird hosts

*"L. anatis" - ducks
*"L. andrewsi" - chickens ("Gallus gallus domesticus") Atchley F.O. (1951) "Leucocytozoon andrewsi" n. sp., from chickens observed in a survey of blood parasites in domestic animals in South Carolina. J. Parasitol. 37(5:1):483-488.]
*"L. anseris" - geese
*"L. artamidis" - wood-swallows ("Artamidae" species) Peirce M.A., Adlard R.D., Lederer R. (2005) A new species of "Leucocytozoon" Berestneff, 1904 (Apicomplexa: Leucocytozoidae) from the avian family Artamidae. Syst. Parasitol. 60(2):151-154.]
*"L. atkinsoni" - Old World babblers ("Timaliidae" species) Savage A.F., Ariey F.,Greiner E.C. (2006) "Leucocytozoon atkinsoni" n. sp. (Apicomplexa: Leucocytozoidae) from the avian family "Timaliidae". Syst. Parasitol. 64(2):105-109]
*"L. balmorali" - bushshrikes ("Malaconotidae" species), the "Laniidae"
*"L. bennetti" - hook-billed vanga ("Vanga curvirostris")
*"L. berestneffi" - yellow-billed magpie ("Pica nuttalia")
*"L. bishopi" - parrotbills ("Paradoxornithidae" species)
*"L. bonasae" - ruffed grouse ("Bonasa umbellus"), spruce grouse ("Canachites canadensis"), ptarmigan
*"L. bouffardi" - weaver birds - ("Ploceidae" species)
*"L. brimonti" - bulbuls ("Pycnonotus" species)
*"L. caprimulgi" - nightjars ("Caprimulgidae")
*"L. caulleryi" - chickens ("Gallus gallus domesticus")
*"L. coracinae" - avian family "Campephagidae" Barraclough R.K., Robert V., Peirce M.A. (2008) New species of haematozoa from the avian families Campephagidae and Apodidae. Parasite 15(2):105-110]
*"L. danilewskyi" - owls ("Strix occidentalis")
*"L. deswardti" - the "Promeropidae"
*"L. dubreuili" - American robin ("Turdus migratorius")
*"L. dutoiti" - the "Fringillidae"
*"L. frascai" - rufous-headed ground-roller ("Atelornis crossleyi") Savage A.F., Greiner E.C. (2004) Hematozoa of the avian family "Brachypteraciidae" (the ground-rollers). J. Parasitol. 90(6):1468-1472.]
*"L. fringillinarum" - house sparrows ("Passer domesticus biblicus") Gill H., Paperna I.(2005) Leucocytozoonosis in the Israeli sparrow, "Passer domesticus biblicus" Hartert 1904. Parasitol. Res. 96(6):373-377. ] , yellow wagtails ("Motacilla flava"), dark-eyed Juncos ("Junco hyemalis"), the "Fringillidae"
*"L. gentili" - house sparrows ("Passer domesticus")
*"L. greineri" - common sunbird asity ("Neodrepanis coruscans"), velvet asity ("Philepitta castanea")Savage A.F. (2004) Hematozoa of the avian family "Philepittidae" (the asities and sunbird asities). J. Parasitol. 90(6):1473-1474 ]
*"L. grusi" - sandhill crane ("Grus canadensis") Bennett G.F., Khan R.A., Campbell, A.G. (1974) "Leucocytozoon grusi" sp. n. (Sporozoa: Leucocytozoidae) from a sandhill crane, "Grus canadensis" (L.). J Parasitol. 60(2):359-363.]
*"L. hamiltoni" - Bukharan great tit ("Parus bokharensis") Valkiünas G., Iezhova T.A., Mironov S.V. (2002) "Leucocytozoon hamiltoni" n. sp. (Haemosporida, Leucocytozoidae) from the Bukharan great tit "Parus bokharensis". J Parasitol. 88(3):577-581]
*"L. lairdi" - blue vanga ("Cyanolanius madagascarinus") Savage A.F., Ariey F., Greiner E.C. (2004) Hematozoa of the avian family "Vangidae" (the vangas). J Parasitol. 90(6):1475-1479]
*"L. liothricis" - Old World babblers ("Timaliidae" species)
*"L. lovati" - hawks, greater sage-grouse ("Centrocercus urophasianus"), blue grouse ("Dendragapus obscurus"), willow ptarmigan ("Lagopus lagopus"), wild rock ptarmigan ("Lagopus mutus")
*"L. maccluri" - Thailand thrush ("Zoothera marginata") Greiner E.C. (1976) "Leucocytozoon maccluri" sp. n. (Haemosphorida: Leucocytozoidae) from a Thailand thrush, "Zoothera marginata" Blyth. J. Parasitol. 62(4):545-547. ]
*"L. macleani" - chickens ("Gallus gallus domesticus")
*"L. majoris" - yellow wagtails ("Motacilla flava")
*"L. marchouxi" - Pink Pigeon ("Columba mayeri")Bunbury N., Barton E., Jones C.G., Greenwood A.G., Tyler K.M., Bell D.J. (2007) Avian blood parasites in an endangered columbid: Leucocytozoon marchouxi in the Mauritian Pink Pigeon "Columba mayeri". Parasitology 134(6):797-804. ] and doves
*"L. nectariniae" - sunbird ("Nectarinia olivacea")
*"L. neavei" - guinea fowl
*"L. pogoniuli" - tinker barbets ("Pogoniulus atroflavus", "Pogoniulus subsulphureus") Jones H.I., Sehgal R.N., Smith T.B. (2005) "Leucocytozoon" (Apicomplexa: Leucocytozoidae) from West African birds, with descriptions of two species. J. Parasitol. 91(2):397-401.]
*"L. pycnonoti" - the "Pycnonotidae"
*"L. roubaudi" - estrildid finches ("Estrildidae" species)
*"L. sabrazesi" - chickens ("Gallus gallus domesticus")
*"L. schoutedeni" - chickens ("Gallus gallus domesticus")
*"L. shaartusicum" - redstart ("Phoenicurus phoenicurus")
*"L. simondii" - wood duck ("Aix sponsa"), white Pekin duck ("Anas bochas"), Mexican duck ("Anas diazi"), mallard duck ("Anas platyrhynchos"), black duck ("Anas rubripes"), geese ("Branta canadensis"), Emperor Goose ("Chen canagica"), mergansers ("Mergus merganser"), eider duck ("Somateria mollissima")
*"L. smithi" - turkeys ("Meleagris" species)
*"L. sturni" - the "Sturnidae"
*"L. tawaki" penguins ("Spheniscidae")
*"L. timaliae" - Old World babblers ("Timaliidae" species)
*"L. toddi" - grouse, Coopers hawk ("Accipiter cooperii"), sharp-shinned hawks ("Accipiter striatus"), bald eagles ("Haliaeetus leucocephalus"), Chimango Caracara ("Milvago chimango")
*"L. trachyphoni" - barbet ("Trachyphonus purpureus") Jones H.I., Sehgal R.N., Smith T.B. (2005) "Leucocytozoon" (Apicomplexa: Leucocytozoidae) from West African birds, with descriptions of two species. J. Parasitol. 91(2):397-401.]
*"L. ziemanni" - eagle owl ("Bubo bubo") Ortego J., Cordero P.J. (2008) PCR-based detection and genotyping of haematozoa (Protozoa) parasitizing eagle owls, "Bubo bubo". Parasitol Res. ] , great horned owls ("Bubo virginianus"), snowy owls ("Nyctea scandiaca"), spotted owls ("Strix occidentalis")
*"L. zosteropis" - the "Zosteropidae"

"Simulium" hosts

*"L. bonasae" - "Simulium aureum" and "Simulium latipes"
*"L. caulleryi" - "Culicoides arakawae"
*"L. lovati" - "Prosimulium hirtipes", "Simulium japonicum" and "Simulium uchidai" Sato Y., Tamada A., Mochizuki Y., Nakamura S., Okano E., Yoshida C., Ejiri H., Omori S., Yukawa M., Murata K. (2008) Molecular detection of "Leucocytozoon lovati" from probable vectors, black flies (Simuliudae) collected in the alpine regions of Japan. Parasitol. Res.]
*"L. simondi" - "Cnephia ornithophilia" and "Simulium rugglesi"

Notes

Like many protist species and genera this genus is subject to ongoing revision especially in the light of DNA based taxonomy. Described species may be subject to revision.

"L. andrewsi" and "L. schoutedeni" are considered to be synonyms.

"L. bonasae", "L. jakamowi" and "L. mansoni" are considered to be synonyms of "L. lovati".

"L. brimonti" is considered to be a synonym of "L. fringillinarum".

"L. caulleryi" is spread by biting midges of the genus "Ceratopogonidae" and is now (2007) considered to belong not to this genus but to the genus "Akiba".

"L. costai" and "L. numidae" are considered to be synonyms of "L. neavei".

"L. francolini", "L. kerandeli", "L. martini", "L. mesnili", "L. sabrazesi" and "L. schuffneri" are considered to be synonyms of "L. macleani".

The species "L. galli" is open to some doubt.

"L. molpastis" is considered to be a synonym of L. "brimonti"

"L. monardi" is considered to be a synonym of "L. gentili"

"L. toddi" seems likely to be a cryptic species complex.

"L. turtur" and its subspecies "L. turtur orientalis" are considered a synonym of "L. marchouxi"

External links

*Vetinary notes [http://merckvetmanual.com/mvm/index.jsp?cfile=htm/bc/200106.htm]

*Illustrated life cycle [http://parasitology.informatik.uni-wuerzburg.de/login/b/me14223.png.php]

*Black fly image [http://microbewiki.kenyon.edu/index.php/
]

*Leukocyozoon in thrombocyte [http://bio.winona.edu/bates/images/project/Leucocytozoan.jpg]

*Leukocyotozoon image [http://microbewiki.kenyon.edu/index.php/
]

*Leukoctozoon image [http://www.jwildlifedis.org/cgi/content/full/40/4/804/F1]

*Leukoctyozoon - elongate forms [http://www.k-state.edu/parasitology/625tutorials/Apicomplexa01.html]

*Megaloschizont in lung [http://www.afip.org/vetpath/WSC/WSC95/images/c25c4.jpg]

*Gametocyte images [http://www.diaglab.vet.cornell.edu/clinpath/modules/heme1/av-para.htm]

*Gametocyte images [http://diaglab.vet.cornell.edu/clinpath/modules/rbcmorph/lc.htm]

References