First Report of an Eosinophilic Rickettsia-like Organism in Diseased Oysters <i>Crassostrea gigas</i>

Carvalho-Saucedo, Liliana; Dimitrov, Ilie Sava Racotta; Rodrı́guez-Jaramillo, Cármen; García‐Gasca, Alejandra; Gutiérrez‐Rivera, Jesús Neftalí

doi:10.2983/035.037.0306

Cited by 4 publications

(2 citation statements)

References 30 publications

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“…There are some reports of eosinophilic IVs (Buchanan, 1978; Wu & Pan, 1999a; Wu & Pan, 2000; Sun & Wu, 2004; Zhu et al, 2012). Interestingly, eosinophilic inclusions described as RLOs in the cuticular cells, gill epithelia and connective tissue of Pinctada maxima (Wu & Pan, 1999a), the mantle cells of Crassostrea ariakensis (Sun & Wu, 2004), the gills, mantle and digestive epithelia of Tegillarca granosa (Zhu et al, 2012), the gill epithelia of Crassostrea rivularis (Zhang et al, 2017) and the epithelial cells of the digestive tract of Crassostrea gigas (Carvalho‐Saucedo et al, 2018) closely resemble what have typically been described as neutral mucopolysaccharides in marine molluscs produced by mucocytes (Dufour & Beninger, 2001). Histochemistry, TEM and appropriate in situ hybridization may aid in the differentiation of true RLOs from natural intracytoplasmic secretions.…”

Section: Histologymentioning

confidence: 99%

Rickettsiales‐like organisms in bivalves and marine gastropods: a review

Cruz‐Flores

Cáceres-Martı́nez

2020

Reviews in Aquaculture

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Rickettsiales‐like organisms (RLOs) are intracellular bacteria that have been reported to be symbionts of over 60 species of bivalves and marine gastropod molluscs of aquaculture importance around the world. Morphologically, some of these prokaryotes are similar to bacteria from the order Rickettsiales, and in most cases, they form intracytoplasmic inclusions similar to those observed in bacteria of the family Anaplasmataceae. Genetically, only Candidatus Xenohaliotis californiensis (CXc), a parasite of several abalone species, has been classified as a member of the order Rickettsiales. The other two characterized RLOs are distantly related; one belongs to the same class (α‐proteobacteria), and the other belongs to the γ‐proteobacteria. Hyperparasitism of RLOs by bacteriophages has been reported in several species of mollusc and appears to have a negative effect on RLOs. The intracellular lifestyle of RLOs has been associated with cell alterations including hypertrophy and compression of the cytoplasmic organelles, and in most cases, no host reaction is observed by histology. In some cases, a high infection intensity of RLOs has been related to dysfunction of the affected organs that can result in disease, and in other cases, high burdens of RLOs have been associated with mortality, but most of these cases have yet to be confirmed. To date, only CXc has been confirmed as the aetiological agent of a chronic and potentially lethal disease of several abalone species known as withering syndrome. This disease is listed by the World Organization of Animal Health. With the ever‐increasing interest in preserving fisheries and expanding the aquaculture production of mollusc species, more efforts should be focused on the characterization and study of RLOs to elucidate the type of symbiosis they maintain with their host and determine when they are acting as true pathogens that should be subjected to control in aquaculture. This review provides an overview of the literature on RLOs that infect bivalves and gastropods of aquaculture importance, and we discuss the most important aspects of these unique prokaryotes.

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Section: Histologymentioning

confidence: 99%

Rickettsiales‐like organisms in bivalves and marine gastropods: a review

Cruz‐Flores

Cáceres-Martı́nez

2020

Reviews in Aquaculture

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“…During the 1950s and 60s, nocardiosis -a disease caused by the bacteria Nocardia crassostreae, was observed during summer mortalities of POs in Japan, Canada, and the USA [31][32][33][34]. Ricksettsia-like bacteria have also been implicated in PO SM [35]. Yet, species within the Vibrio genus have most often been associated with reports of SM and POMS [27,29].…”

Section: Introductionmentioning

confidence: 99%

Phylogenomic diversity of Vibrio species and other Gammaproteobacteria isolated from Pacific oysters (Crassostrea gigas) during a summer mortality outbreak

et al. 2022

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The Pacific oyster (PO), Crassostrea gigas, is an important commercial marine species but periodically experiences large stock losses due to disease events known as summer mortality. Summer mortality has been linked to environmental perturbations and numerous viral and bacterial agents, indicating this disease is multifactorial in nature. In 2013 and 2014, several summer mortality events occurred within the Port Stephens estuary (NSW, Australia). Extensive culture and molecular-based investigations were undertaken and several potentially pathogenic Vibrio species were identified. To improve species identification and genomically characterise isolates obtained from this outbreak, whole-genome sequencing (WGS) and subsequent genomic analyses were performed on 48 bacterial isolates, as well as a further nine isolates from other summer mortality studies using the same batch of juveniles. Average nucleotide identity (ANI) identified most isolates to the species level and included members of the Photobacterium , Pseudoalteromonas , Shewanella and Vibrio genera, with Vibrio species making up more than two-thirds of all species identified. Construction of a phylogenomic tree, ANI analysis, and pan-genome analysis of the 57 isolates represents the most comprehensive culture-based phylogenomic survey of Vibrios during a PO summer mortality event in Australian waters and revealed large genomic diversity in many of the identified species. Our analysis revealed limited and inconsistent associations between isolate species and their geographical origins, or host health status. Together with ANI and pan-genome results, these inconsistencies suggest that to determine the role that microbes may have in Pacific oyster summer mortality events, isolate identification must be at the taxonomic level of strain. Our WGS data (specifically, the accessory genomes) differentiated bacterial strains, and coupled with associated metadata, highlight the possibility of predicting a strain’s environmental niche and level of pathogenicity.

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