Tetracapsuloides bryosalmonae

:"PKX redirects here. For the company, see POSCO."Taxobox
name = "Tetracapsuloides bryosalmonae"
regnum = Animalia
phylum = Cnidaria
unranked_classis = Myxozoa
classis = Malacosporea
ordo = Malacovalvulida
familia = Saccosporidae
genus = "Tetracapsuloides"
species = "T. bryosalmonae"
binomial = "Tetracapsuloides bryosalmonae"
binomial_authority = Canning "et al.", 1999
synonyms = "Myxosporidium bryozoides?" "Glugea bryozoides?" "Nosema bryozoides?" "PKX Organism" "Tetracapsuloides renicola" "Tetracapsula bryosalmonae"

"Tetracapsuloides bryosalmonae" is a myxozoan parasite of salmonid fishes, which causes Proliferative kidney disease (PKD), one of the most serious parasitic diseases of salmonid populations in Europe and North AmericaRef|Hedrick, which causes losses of up to 90% in infected populations.

Taxonomy

Until the late 1990s, the organism which caused PKD was enigmatic. The "PKX organism", the causative agent of the disease, had been recognized as some form of myxozoanRef|Kent1, but the absence of mature spores in salmonid hosts, the lack of fish to fish transmission, and seasonality of the disease suggest that the life cycle of PKX was completed in another host and that infection of salmonids could be accidental.Korotneff observed a myxozoan in the bryozoan, "Plumatella fungosa", in 1892, which he described as "Myxosporidium bryozoides"Ref|Korotneff. Myxozoan infection of bryozoans were not reported again until 1996. Ecological investigations of freshwater bryozoans in North America discovered parasitic sacs of a myxozoan species, freely floating in the body cavities of several bryozoans. Molecular analyses indicated that the 18S rDNA sequences of these sacs were indistinguishable from those of PKXRef|Anderson, and the PKX organism was scientifically described as "Tetracapsuloides bryosalmonae" Canning, Curry, Feist, Longshaw & Okamura 1999Ref|Canning1, which has been assigned to a new class, the Malacosporea within the phylum MyxozoaRef|Canning2. Around the same time, another group described the PKX organism from Arctic char, "Salvelinus alpinus", as "Tetracapsuloides renicola" Kent, Khattra, Hedrick & Devlin 2000Ref|Kent2, but the first given name has priority according to the rules of the binomial nomenclature.

Life cycle

"T. bryosalmonae" is highly unusual amongst the myxosporea, in that it uses a bryozoan as an alternate host, rather than an oligochaete or polychaete worm. To date, T. bryosalmonae has been found to parasitize five bryozoan species belonging to the genera Fredericella and Plumatella, all considered to be primitive generaRef|Anderson.Problems have occurred in determining the fish host for this species. However, recent work has demonstrated that the parasite cycles between bryozoa and native salmonid species.

Pathology

Proliferative Kidney Disease is characterised by a swollen kidney and spleen, bloody ascites, and pale gills, which indicate the fish is anaemic. Note that these symptoms are common amongst many diseases of fish and do not specifically indicate an infection with "Tetracapsuloides bryosalmonae".

Distribution

"T. bryosalmonae" has been recorded in Europe and North America. Phylogenetic analyses of internal transcribed spacer 1 sequences revealed a clade composed of all North American sequences plus a subset of Italian and French sequences. High genetic diversity in North America and the absence of genotypes which are characteristic of the North American clade in the rest of Europe implies that southern Europe was colonized by immigration from North America; however, sequence divergence suggests that this colonization substantially pre-dated human movements of fish. Furthermore, the lack of southern European lineages in the rest of Europe, despite widespread rainbow trout farming, indicates that "T. bryosalmonae" is not transported through fisheries activities. This result contrasts with the commonness of fisheries-related introductions of other pathogens and parasites such as "Myxobolus cerebralis" and "Ceratomyxa shasta"Ref|Henderson.

Cited literature

#cite journal | author= Hedrick R., McConnell E., de Kinkelin P | title=Proliferative kidney disease of salmonid fish | journal=Annual Review of Fish Diseases | year=1993 | pages=277–290 | doi=10.1016/0959-8030(93)90039-E | volume=3
#cite journal | author=Kent, M.L., and R.P. Hedrick | title=PKX the causative agent of proliferative kidney disease (PKD) in Pacific salmonid fishes and its affinities with the Myxozoa | year=1985 | journal=Journal of Protozoology | volume=32 | pages=254 260
#cite journal | author= Korotneff, A. | title=Myxosporidium bryozoides | year=1892| journal=Zeitsch. Wiss. Zool.| volume=53 | pages=591–596
#cite journal | author=Anderson, C.L., Canning, E.U. & Okamura, B. | year=1999 | title=18S rDNA sequences indicate that PKX organism parasitizes Bryozoa | journal=Bulletin of the European Association of Fish Pathologists | volume=19 | pages=94–97
#cite journal | author=Canning, E.U., Curry, A., Feist, S.W., Longshaw, M., & Okamura, B. | year=1999 | title=Tetracapsula bryosalmonae n.sp. for PKX organism the cause of PKD in salmonid fish | journal=Bulletin of the European Association of Fish Pathologists | volume=19| issue=2 |pages=203–206
#cite journal | author=Canning, E.U., Curry, A., Feist, S.W., Longshaw, M., & Okamura, B. | year=2000 | title=A new class and order of myxozoans to accommodate parasites of bryozoans with ultrastructural observations on Tetracapsula bryosalmonae (PKX organism) |journal=Journal of Eukaryotic Microbiology| volume=47| pages=456–468 | doi=10.1111/j.1550-7408.2000.tb00075.x
#cite journal | author=Kent, M.L. J. Khattra, R.P. Hedrick, and R.H. Devlin |year=2000| title=Tetracapsula renicola (Myxozoa: Saccosporidae); the PKX myxozoan – the cause of proliferative kidney disease of salmonid fishes| journal= Journal of Parasitology | volume=86 | pages=103–111| doi=10.1645/0022-3395(2000)086 [0103:TRNSMS] 2.0.CO;2
#cite journal | author=Anderson, C.L., Canning, E.U. & Okamura, B. | year=1999 | title=18S rDNA sequences indicate that PKX organism parasitizes Bryozoa | journal=Bulletin of the European Association of Fish Pathologists | volume=19 | pages=94–97
#cite journal| author= Henderson, M. & Okamura, B. | title=The phylogeography of salmonid proliferative kidney disease in Europe and North America| journal=Proceedings of the Royal Society Series B | year= 2004| volume=271| issue=1549 |pages=1729–1736 | doi=10.1098/rspb.2004.2677