Abalone withering syndrome: distribution, impacts, current diagnostic methods and new findings.

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Abalone withering syndrome: distribution, impacts, current diagnostic methods and new findings.

Dis Aquat Organ. 2014 Apr 3;108(3):261-270

Authors: Crosson LM, Wight N, Vanblaricom GR, Kiryu I, Moore JD, Friedman CS

Abstract
Withering syndrome (WS) is a fatal disease of abalone caused by a Rickettsiales-like organism (WS-RLO). The causative agent, ‘Candidatus Xenohaliotis californiensis’, occurs along the eastern Pacific margin of North America in California, USA, and Baja California, Mexico. However, as infected abalones have been transported to Chile, China, Taiwan, Iceland, Ireland, Israel, Spain, Thailand and Japan, the geographical range of the etiological agent is suspected to be broad, especially where California red abalones Haliotis rufescens are cultured or in areas where native species have been exposed to this species. Susceptibility varies among species, with up to 99% losses of black abalone H. cracherodii in laboratory and field studies in the USA to no losses among the small abalone H. diversicolor supertexta in Thailand. Some populations that have suffered catastrophic losses due to WS have developed resistance to the disease. In addition, a newly identified phage hyperparasite of the WS-RLO may reduce pathogenicity and dampen associated losses. Diagnosis of WS requires the identification of infection with the pathogen (WS-RLO detected via in situ hybridization or histology coupled with PCR and sequence analysis) accompanied by morphological changes that characterize this disease (e.g. pedal and digestive gland atrophy, and digestive gland metaplasia). A quantitative PCR assay was developed and may be useful in quantifying pathogen DNA. Confirmation of infection cannot be done by PCR analysis alone but can be used as a proxy for infection in areas where the agent is established and is recommended for inclusion in health examinations. Avoidance of WS is best accomplished by the establishment of a health history and multiple health examinations prior to movement of animals.

PMID: 24695239 [PubMed – as supplied by publisher]

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Validation of a quantitative PCR assay for detection and quantification of ‘Candidatus Xenohaliotis californiensis’.

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Validation of a quantitative PCR assay for detection and quantification of ‘Candidatus Xenohaliotis californiensis’.

Dis Aquat Organ. 2014 Apr 3;108(3):251-9

Authors: Friedman CS, Wight N, Crosson LM, White SJ, Strenge RM

Abstract
Withering syndrome (WS), a serious disease affecting abalone Haliotis spp., is caused by infection from an intracellular Rickettsia-like organism (WS-RLO). Diagnosis of the disease currently relies on a combination of histological examination and molecular methods (in situ hybridization, standard PCR, and sequence analysis). However, these techniques only provide a semi-quantitative assessment of bacterial load. We created a real-time quantitative PCR (qPCR) assay to specifically identify and enumerate bacterial loads of WS-RLO in abalone tissue, fecal, and seawater samples based on 16S rDNA gene copy numbers. The qPCR assay designed to detect DNA of the WS-RLO was validated according to standards set by the World Organisation for Animal Health. Standard curves derived from purified plasmid dilutions were linear across 7 logs of concentration, and efficiencies ranged from 90.2 to 97.4%. The limit of detection was 3 gene copies per reaction. Diagnostic sensitivity was 100% and specificity was 99.8%. The qPCR assay was robust, as evidenced by its high level of repeatability and reproducibility. This study has shown for the first time that WS-RLO DNA can be detected and quantified in abalone tissue, fecal, and seawater samples. The ability to detect and quantify RLO gene copies in a variety of materials will enable us to better understand transmission dynamics in both farmed and natural environments.

PMID: 24695238 [PubMed – in process]

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Reduced disease in black abalone following mass mortality: phage therapy and natural selection.

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Reduced disease in black abalone following mass mortality: phage therapy and natural selection.

Front Microbiol. 2014;5:78

Authors: Friedman CS, Wight N, Crosson LM, Vanblaricom GR, Lafferty KD

Abstract
Black abalone, Haliotis cracherodii, populations along the NE Pacific ocean have declined due to the rickettsial disease withering syndrome (WS). Natural recovery on San Nicolas Island (SNI) of Southern California suggested the development of resistance in island populations. Experimental challenges in one treatment demonstrated that progeny of disease-selected black abalone from SNI survived better than did those from naïve black abalone from Carmel Point in mainland coastal central California. Unexpectedly, the presence of a newly observed bacteriophage infecting the WS rickettsia (WS-RLO) had strong effects on the survival of infected abalone. Specifically, presence of phage-infected RLO (RLOv) reduced the host response to infection, RLO infection loads, and associated mortality. These data suggest that the black abalone: WS-RLO relationship is evolving through dual host mechanisms of resistance to RLO infection in the digestive gland via tolerance to infection in the primary target tissue (the post-esophagus) coupled with reduced pathogenicity of the WS-RLO by phage infection, which effectively reduces the infection load in the primary target tissue by half. Sea surface temperature patterns off southern California, associated with a recent hiatus in global-scale ocean warming, do not appear to be a sufficient explanation for survival patterns in SNI black abalone. These data highlight the potential for natural recovery of abalone populations over time and that further understanding of mechanisms governing host-parasite relationships will better enable us to manage declining populations.

PMID: 24672512 [PubMed]

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Genomic resource development for shellfish of conservation concern.

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Genomic resource development for shellfish of conservation concern.

Mol Ecol Resour. 2013 Mar;13(2):295-305

Authors: Timmins-Schiffman EB, Friedman CS, Metzger DC, White SJ, Roberts SB

Abstract
Effective conservation of threatened species depends on the ability to assess organism physiology and population demography. To develop genomic resources to better understand the dynamics of two ecologically vulnerable species in the Pacific Northwest of the United States, larval transcriptomes were sequenced for the pinto abalone, Haliotis kamtschatkana kamtschatkana, and the Olympia oyster, Ostrea lurida. Based on comparative species analysis the Ostrea lurida transcriptome (41 136 contigs) is relatively complete. These transcriptomes represent the first significant contribution to genomic resources for both species. Genes are described based on biological function with particular attention to those associated with temperature change, oxidative stress and immune function. In addition, transcriptome-derived genetic markers are provided. Together, these resources provide valuable tools for future studies aimed at conservation of Haliotis kamtschatkana kamtschatkana, Ostrea lurida and related species.

PMID: 23280275 [PubMed – indexed for MEDLINE]

via pubmed: school of aquatic an… http://www.ncbi.nlm.nih.gov/pubmed/23280275?dopt=Abstract

Putative phage hyperparasite in the rickettsial pathogen of abalone, “Candidatus Xenohaliotis californiensis”.

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Putative phage hyperparasite in the rickettsial pathogen of abalone, “Candidatus Xenohaliotis californiensis”.

Microb Ecol. 2012 Nov;64(4):1064-72

Authors: Friedman CS, Crosson LM

Abstract
Studies on the ecology of microbial parasites and their hosts are predicated on understanding the assemblage of and relationship among the species present. Changes in organismal morphology and physiology can have profound effects on host-parasite interactions and associated microbial community structure. The marine rickettsial organism, “Candidatus Xenohaliotis californiensis” (WS-RLO), that causes withering syndrome of abalones has had a consistent morphology based on light and electron microscopy. However, a morphological variant of the WS-RLO has recently been observed infecting red abalone from California. We used light and electron microscopy, in situ hybridization and16S rDNA sequence analysis to compare the WS-RLO and the morphologically distinct RLO variant (RLOv). The WS-RLO forms oblong inclusions within the abalone posterior esophagus (PE) and digestive gland (DG) tissues that contain small rod-shaped bacteria; individual bacteria within the light purple inclusions upon hematoxylin and eosin staining cannot be discerned by light microscopy. Like the WS-RLO, the RLOv forms oblong inclusions in the PE and DG but contain large, pleomorphic bacteria that stain dark navy blue with hematoxylin and eosin. Transmission electron microscopy (TEM) examination revealed that the large pleomorphic bacteria within RLOv inclusions were infected with a spherical to icosahedral-shaped putative phage hyperparasite. TEM also revealed the presence of rod-shaped bacteria along the periphery of the RLOv inclusions that were morphologically indistinguishable from the WS-RLO. Binding of the WS-RLO-specific in situ hybridization probe to the RLOv inclusions demonstrated sequence similarity between these RLOs. In addition, sequence analysis revealed 98.9-99.4 % similarity between 16S rDNA sequences of the WS-RLO and RLOv. Collectively, these data suggest that both of these RLOs infecting California abalone are “Candidatus Xenohaliotis californiensis,” and that the novel variant is infected by a putative phage hyperparasite that induced morphological variation of its RLO host.

PMID: 22729142 [PubMed – indexed for MEDLINE]

via pubmed: school of aquatic an… http://www.ncbi.nlm.nih.gov/pubmed/22729142?dopt=Abstract

Genomic resource development for shellfish of conservation concern.

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Genomic resource development for shellfish of conservation concern.

Mol Ecol Resour. 2012 Dec 27;

Authors: Timmins-Schiffman EB, Friedman CS, Metzger DC, White SJ, Roberts SB

Abstract
Effective conservation of threatened species depends on the ability to assess organism physiology and population demography. To develop genomic resources to better understand the dynamics of two ecologically vulnerable species in the Pacific Northwest of the United States, larval transcriptomes were sequenced for the pinto abalone, Haliotis kamtschatkana kamtschatkana, and the Olympia oyster, Ostrea lurida. Based on comparative species analysis the Ostrea lurida transcriptome (41 136 contigs) is relatively complete. These transcriptomes represent the first significant contribution to genomic resources for both species. Genes are described based on biological function with particular attention to those associated with temperature change, oxidative stress and immune function. In addition, transcriptome-derived genetic markers are provided. Together, these resources provide valuable tools for future studies aimed at conservation of Haliotis kamtschatkana kamtschatkana, Ostrea lurida and related species.

PMID: 23280275 [PubMed – as supplied by publisher]

via pubmed: school of aquatic an… http://www.ncbi.nlm.nih.gov/PubMed/23280275?dopt=Abstract