Disease caused by Yersinia ruckeri serotype O2b found in Chilean-farmed coho salmon, Oncorhynchus kisutch (Walbaum, 1792)

Artículo que describe Yersiniosis por Yersinia ruckeri serotype O2b en salmones de Chile.During September and October 2015, farmed coho salmon (Oncorhynchus kisutch [Walbaum, 1792]) suffered outbreak mortalities. For all outbreaks, cumulative losses of the affected population reached up to 15%. Three representative bacterial isolates were recovered with the objective of antigenically identifying and characterizing the causative microorganism of the ERM outbreaks in Chilean coho salmon. The obtained micro-organisms were characterized as Y. ruckeri O2b, making this the first report of a mortality-associated isolate in coho salmon farmed in Chile.Work was supported by the Grants CONICYT/ FONDAP/15110027 and FONDECYT No 1150695, awarded by the Comisión Nacional de Investigación Científica y Tecnológica (CONICYT, Chile)

Confirmation of spring viremia of carp virus in wild common carp (Cyprinus carpio L.) in Mexico

Abstract del trabajo exposición en conferencia eafp-2019This study confirms the presence of spring viremia of carp virus (SVCV) in wild common carp (Cyprinus carpio L) in central Mexico. Fish exhibited lesions suggestive of SVC, and samples were analyzed by cell culture, molecular techniques, gene sequencing, and electronic microscopy, resulting in the isolation and identification of SVCV.FONDAP 15110027 and FONDECYT 1150695 from CONICYT, Chile. Research Projects 4489/2018/CI from SIEA‐UAEM and Ciencia Básica CONACYT México: reference 287537

First identification and characterization of Streptococcus iniae obtained from tilapia (Oreochromis aureus) farmed in Mexico

Estudio de cuadros septicémicos por Streptococcus iniae en tilapias de cultivo de México.This is the first study to isolate, identify and characterize Streptococcus iniae as the causative disease agent in two tilapia (Oreochromis aureus) populations. The populations were geographically isolated, of distinct origins, and did not share water sources. Affected fish showed various external (e.g., exophthalmia and cachexia, among others) and internal (e.g., granulomatous septicaemia and interstitial nephritis, among others) signs. All internal organ samples produced pure cultures, two of which (one from each farm, termed S-1 and S-2) were subjected to biochemical, PCR and 16S rRNA sequencing (99.5% similarity) analyses, confirming S. iniae identification. The two isolates presented genetic homogeneity regardless of technique (i.e., RAPD, REP-PCR and ERIC-PCR analyses). Pathogenic potentials were assessed through intraperitoneal injection challenges in rainbow trout (Oncorhynchus mykiss) and zebrafish (Danio rerio). Rainbow trout mortalities were respectively 40% and 70% at 104 and 106 CFU per fish with the S-1 isolate, while 100% mortality rates were recorded in zebrafish at 102 and 104 CFU per fish with the S-2 isolate. The obtained data clearly indicate a relationship between intensified aquaculture activities in Mexico and new disease appearances. Future studies should establish clinical significances for the tilapia industry.Universidad Autónoma del Estado de México, Grant/Award Number: 3675/2014/CID and 4489/2018/CI. Comisión Nacional de Investigación Científica y Tecnológica, Grant/Award Number: FONDAP 15110027, FONDECYT 115069

Serological diversity in Flavobacterium psychrophilum: A critical update using isolates retrieved from Chilean salmon farms

International audienceChile is currently the second largest producer of farmed salmon worldwide, but Flavobacterium psychrophilum, as one of the most detrimental pathogens, is responsible for major losses during the freshwater culturing step in salmonid fish farms. An antigenic study conducted 10 years ago reported four serological groups using 20 F. psychrophilum Chilean strains. To reduce disease outbreaks and to develop vaccine candidates, antigenic knowledge needs to be regularly updated using a significant number of additional recent F. psychrophilum isolates. The present study aimed at investigating the serological diversity of 118 F. psychrophilum isolates collected between 2006 and 2018 from farmed Atlantic salmon (Salmo salar), rainbow trout (Oncorhynchus mykiss) and coho salmon (Oncorhynchus kisutch). The current study supports an expansion of the known antigenic groups in Chile from 4 to 14. However, the use of the slide-agglutination technique for serotyping is costly, is labour-intensive and requires significant technical expertise. Addressing these points, the mPCR-based procedure was a very useful tool for serotyping the collected Chilean F. psychrophilum isolates. This technique revealed the presence of diverse mPCR serotypes (i.e. types 0, 1, 2 and 4). Therefore, mPCR should be employed to select the bacterial strain(s) for vaccine development and to conduct follow-up, selective breeding or epidemiological surveillance in Chilean fish farms. Given the presented findings, changes to Chilean fish-farming practices are vital for ensuring the continued productivity and well-being of farmed salmonids

Disease caused by Yersinia ruckeri serotype O2b found in Chilean-farmed coho salmon, Oncorhynchus kisutch (Walbaum, 1792)

Artículo que describe Yersiniosis por Yersinia ruckeri serotype O2b en salmones de Chile.During September and October 2015, farmed coho salmon (Oncorhynchus kisutch [Walbaum, 1792]) suffered outbreak mortalities. For all outbreaks, cumulative losses of the affected population reached up to 15%. Three representative bacterial isolates were recovered with the objective of antigenically identifying and characterizing the causative microorganism of the ERM outbreaks in Chilean coho salmon. The obtained micro-organisms were characterized as Y. ruckeri O2b, making this the first report of a mortality-associated isolate in coho salmon farmed in Chile.Work was supported by the Grants CONICYT/ FONDAP/15110027 and FONDECYT No 1150695, awarded by the Comisión Nacional de Investigación Científica y Tecnológica (CONICYT, Chile)

Isolation characterization, virulence potential of Weissella ceti responsible for weissellosis outbreak in rainbow trout (Oncorhynchus mykiss) cultured in Mexico

Artículo que describe el diagnóstico y caracterización de la enfermedad emergente weissellosis en trucha arcoíris de MéxicoWeissella ceti, a Gram‐positive nonmotile bacterium, is currently an emerging pathogen within rainbow trout (Oncorhynchus mykiss) farms in China, Brazil, the United States, and Japan. This study is the first to isolate, identify, and characterize W. ceti isolates from rainbow trout farmed in Mexico. In late 2015, a severe disease outbreak caused a 60% mortality rate among 20,000 fish. The diseased rainbow trout (100–300 g average) exhibited severe cachexia, body darkening, abdominal distension, exophthalmia, haemorrhages, and corneal opacity. Internally, diseased fish had pale gills; multifocal, disseminated whitish spots on the liver; haemorrhages in the swim bladder, ovary, and on the parietal surface of the muscle; and hearts with pseudo‐membrane formation. Histologically, lesions were characterized by corneal oedema, degenerative and necrotic hepatitis, and meningitis. A brain (W‐1) and kidney (W‐2) isolate were identified as W. ceti through polyphasic taxonomy, which included phenotypic characterization and 16S rRNA sequencing. RAPD and ERIC‐PCR analyses demonstrated genetic homogeneity among the Mexican isolates. Virulence tests in rainbow trout through intraperitoneal W. ceti injections at concentrations of 1 × 104, 1 × 105, and 1 × 106 CFU per fish resulted in cumulative mortality rates of 25%, 62.5%, and 87.5%, respectively, as well as the same clinical signs of hemorrhagic septicaemia as were recorded for the natural outbreak. The present report is the first to confirm the presence of W. ceti in Mexico, thus extending the known geographical distribution of this pathogen across the Americas.Conacyt, UAEMe

Identification and expression analysis of two steamer-like retrotransposons in the Chilean blue mussel (Mytilus chilensis)

Abstract Background Disseminated neoplasia (DN) is a proliferative cell disorder of the circulatory system of bivalve mollusks. The disease is transmitted between individuals and can also be induced by external chemical agents such as bromodeoxyuridine. In Mya arenaria, we have cloned and characterized an LTR-retrotransposon named Steamer. Steamer mRNA levels and gene copy number correlates with DN and can be used as a marker of the disease. So far, the only mollusk where a retrotransposon expression relates to DN is Mya arenaria. On the other hand, it has been reported that the Chilean blue mussel Mytilus chilensis can also suffers DN. Our aim was to identify retrotransposons in Mytilus chilensis and to study their expression levels in the context of disseminated neoplasia. Results Here we show that 7.1% of individuals collected in August 2018, from two farming areas, presents morphological characteristics described in DN. Using Steamer sequence to interrogate the transcriptome of M. chilensis we found two putative retrotransposons, named Steamer-like elements (MchSLEs). MchSLEs are present in the genome of M. chilensis and MchSLE1 is indeed an LTR-retrotransposon. Neither expression, nor copy number of the reported MchSLEs correlate with DN status but both are expressed at different levels among individual animals. We also report that in cultured M. chilensis haemocytes MchSLEs1 expression can be induced by bromodeoxyuridine. Conclusions We conclude that SLEs present in Mytilus chilensis are differentially expressed among individuals and do not correlate with disseminated neoplasia. Treatment of haemocytes with a stressor like bromodeoxyuridine induces expression of MchSLE1 suggesting that in Mytilus chilensis environmental stressors can induce activation of LTR-retrotransposon