Piscirickettsia salmonis gen. nov., sp. nov., the Causative Agent of an Epizootic Disease in Salmonid Fishes

Fryer, J. L.; Lannan, C. N.; Giovannoni, Stephen J.; Wood, N. D.

doi:10.1099/00207713-42-1-120

Cited by 233 publications

(227 citation statements)

References 18 publications

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“…At present the molecular phylogenetic placement of Piscin'ckettsia salmonis has been based on the 16s rRNA gene sequence of a single isolate, LF-8gT the type strain (Fryer et al 1992). This analysis showed that P salmonis is a member of the gamma subdivision of the Proteobacteria, as are the genera Coxiella and Francisella.…”

Section: Introductionmentioning

confidence: 99%

Phylogenetic analysis of Piscirickettsia salmonis by 16S, internal transcribed spacer (ITS) and 23S ribosomal DNA sequencing

Mauel¹,

Giovannoni²,

Fryer³

1999

Dis. Aquat. Org.

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Piscinckettsia salrnonis, the etiologic agent of piscirickettsiosis, is a systemic disease of salmonid fish. Variations in virulence and mortality have been observed during epizootics at different geographical regions and in laboratory experiments with isolates from these different locations. This raises the possibility that biogeographical patterns of genetic variation might be a significant factor with this disease To assess the genetic variabihty the 16s ribosomal DNA, the internal transcribed spacer (ITS) and the 23s ribosomal DNA of isolates from 3 different hosts and 3 geographic origins were amplified using the polymerase chain reaction (PCR). Results of this analysis confirm that P. salmonis is a member of the gamma subgroup of the Proteobacteria and show that the isolates form a tight monophyletic cluster with 16s rDNA similarities ranging from 99.7 to 98.5%. The ITS regions were 309 base pairs (bp), did not contain tRNA genes, and varied between isolates (95.2 to 99.7 % similarity). Two-thirds of the 23s rRNA gene was sequenced from 5 of the isolates, yielding similarities ranging from 97.9 to 99.8%. Phylogenetic trees were constructed based on the 16s rDNA, ITS and 23s rDNA sequence data and compared. The trees were topologically similar, suggesting that the 3 types of molecules provided similar phylogenetic information. Five of the isolates are closely related (:,99.4 % 16s rDNA s d a r i t y , 99.1 to 99.7 % ITS and 99.3 to 99.8 % 23s rDNA slrmlarities). The sequence of one Chilean isolate, EM-90, was unique, with 16s rDNA similarities to the other isolates ranging from 98.5 to 98.9%, the ITS from 95.2 to 96.9% and the 23s rDNA from 97.6 to 98.5%.

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Section: Introductionmentioning

confidence: 99%

Phylogenetic analysis of Piscirickettsia salmonis by 16S, internal transcribed spacer (ITS) and 23S ribosomal DNA sequencing

Mauel¹,

Giovannoni²,

Fryer³

1999

Dis. Aquat. Org.

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“…13 The tilapia disease agent (0.57 ϫ 0.8 m) is smaller than the reported size of P. salmonis (0.5 ϫ 1.5 m). 9 The combination of characteristics-different host species, smaller cell size, no response to P. salmonis-specific PCR and P. salmonis-specific fluorescent antibody assays-indicates that the bacterium causing epizootics in tilapia in these cases is not P. salmonis.…”

mentioning

confidence: 99%

“…About half of these were reported in the United States (G. S. Visvesvara, personal communication). Although CNS infections due to Acanthamoeba and Balamuthia have been recorded in animals, such as dogs, sheep, cattle, primates, and horses, 1,4,[9][10][11]15,16 there has been only 1 report of naturally acquired PAM in animals, namely in a South American tapir at a zoo in Arizona. 6 Primary amoebic meningoencephalitis has been experimentally induced in mice, sheep, and monkeys.…”

mentioning

confidence: 99%

“…Since the identification of Piscirickettsia salmonis as the first rickettsia-like organism recognized as a fish pathogen, 9 a number of Piscirickettsia-like organisms (PLOs) have been observed microscopically or isolated in cell culture from a variety of marine and fresh-water piscine species from locations worldwide. 5,11,12,16 Piscirickettsiosis or piscirickettsiosis-like syndromes can be severe, resulting in high mortality and significant economic losses.…”

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confidence: 99%

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Occurrence of Piscirickettsiosis-Like Syndrome in Tilapia in the Continental United States

et al. 2005

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Abstract. From 2001to 2003 farms in Florida, California, and South Carolina experienced epizootics of a systemic disease causing mortality. The fish exhibited lethargy, occasional exophthalmia, and skin petechia. The gills were often necrotic, with a patchy white and red appearance. Grossly, the spleen and kidneys were granular with whitish irregular nodules throughout. Granulomatous infiltrates were observed in kidney, spleen, testes, and ovary tissues, but not in the liver. The granulomas contained pleomorphic coccoid bacteria, measuring 0.57 Ϯ 0.1 ϫ 0.8 Ϯ 0.2 m, that were Giemsa-positive, acid-fast-negative, and Gram-negative. The bacteria had a double cell wall, variable electron-dense and -lucent areas, and were present in the cytoplasm and within phagolysosomes. The syndrome was associated with cold stress and poor water conditions. These findings are consistent with an infectious process caused by a Piscirickettsia-like bacterium described previously in tilapia in Taiwan and Hawaii. This report involves the first identified cases of a piscirickettsiosis-like syndrome affecting tilapia in the continental United States.Key words: Piscirickettsiosis; Piscirickettsia-like organisms; piscirickettsiosis-like syndrome; Tilapia.Since the identification of Piscirickettsia salmonis as the first rickettsia-like organism recognized as a fish pathogen, 9 a number of Piscirickettsia-like organisms (PLOs) have been observed microscopically or isolated in cell culture from a variety of marine and fresh-water piscine species from locations worldwide. 5,11,12,16 Piscirickettsiosis or piscirickettsiosis-like syndromes can be severe, resulting in high mortality and significant economic losses.The number of reports of piscirickettsiosis, with significant associated economic losses, have been increasing for the last 5-10 years in British Columbia, 2,8 Ireland, 16 and Scotland. 10 PLOs have also been observed in and isolated from seabass in Europe 1,7 and California 3 during epizootics characterized by high mortality and severe economic losses. Tilapia in Taiwan 4,6 and Hawaii 15 have also been severely affected by PLO epizootics. Here we report on the first identified cases of PLO epizootics in tilapia in the continental United States.Between 2001 and 2003, 3 facilities in the continental United States (California, South Carolina, and Florida) reported epizootics with signs consistent with a piscirickettsiosis-like syndrome. All 3 facilities had increased mortalities during times of fish stress due to lowered temperature or water quality. The fish appeared lethargic, with darkened color, and would crowd toward the middle of the pond or tank. Occasionally, petechia were observed on the sides of the fish. Fins had light fraying, some exophthalmia was observed, and gills were necrotic, with a patchy white and red appearance. Internally, the spleen and kidneys were extremely granular with whitish irregular nodules throughout. The liver was a pale reddish tan with patchy lighter areas.In hematoxylin and eosin (HE) sections, the spl...

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“…9 This disease causes high mortality rates and significant economic losses to the salmon industry. 10 Salmonid rickettsial septicemia was first reported in coho salmon, Oncorhynchus kisutch Walbaum, in Chile 2 and has since been observed in other salmonid species, including rainbow trout, Oncorhynchus mykiss Walbaum; Chinook salmon, Oncorhynchus tshawytscha Walbaum; and Atlantic salmon, Salmo salar Linnaeus. 7 Similar rickettsia-like organisms (RLO) have been reported in Atlantic salmon held in salt water in western Canada, 4 Ireland, 17 and Norway.…”

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confidence: 99%

Pathogenesis of Liver Lesions Caused by Experimental Infection with Piscirickettsia Salmonis in Juvenile Atlantic Salmon, Salmo Salar L

2000

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Abstract. Piscirickettsia salmonis, the etiologic agent of salmonid rickettsial septicemia (SRS), or piscirickettsiosis, causes substantial economic losses to the salmon industry. The pathogenesis of the disease has not been fully characterized. The aim of this study is to describe the hepatic lesions associated with experimental P. salmonis infection in Atlantic salmon juveniles. Fish were maintained in fresh water and inoculated intraperitoneally (IP), orally, or on the gill surface with P. salmonis. A group of uninfected fish was kept as control. Liver samples from 5 fish in each inoculated group and 3 controls were collected weekly and processed for histological and immunohistochemical examination. Thickening of the liver capsule by inflammatory cells was a characteristic histologic feature of IP inoculated fish. Three weeks post-IP inoculation, 8 fish had died and 2 fish were sampled. Histological changes at this time consisted of vasculitis, presence of fibrin thrombi, vacuolated hepatocytes and focal areas of necrosis. Leukocytes containing intracytoplasmic basophilic microorganisms were seen within hepatic sinusoids. Vasculitis and intracytoplasmic vacuoles were prominent features in fish inoculated orally and on the gill surface. The presence of P. salmonis within hepatocellular vacuoles, endothelial cells, and leucocytes was confirmed by immunohistochemistry. The intracellular location of P. salmonis and the vascular damage seen in infected fish are characteristic of rickettsial infections. Histological lesions induced by experimental infection with P. salmonis using the oral and gill surface routes were similar to those observed in natural outbreaks of piscirickettsiosis. The tropism of P. salmonis for endothelial cells explains the vascular lesions observed in SRS, whereas hepatic lesions are due to ischemic necrosis and direct injury by intracytoplasmic organisms.

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Piscirickettsia salmonis gen. nov., sp. nov., the Causative Agent of an Epizootic Disease in Salmonid Fishes

Cited by 233 publications

References 18 publications

Phylogenetic analysis of Piscirickettsia salmonis by 16S, internal transcribed spacer (ITS) and 23S ribosomal DNA sequencing

Phylogenetic analysis of Piscirickettsia salmonis by 16S, internal transcribed spacer (ITS) and 23S ribosomal DNA sequencing

Occurrence of Piscirickettsiosis-Like Syndrome in Tilapia in the Continental United States

Pathogenesis of Liver Lesions Caused by Experimental Infection with Piscirickettsia Salmonis in Juvenile Atlantic Salmon, Salmo Salar L

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