Francisella noatunensis subsp. orientalis (Fno) is the etiological agent of francisellosis in cultured warm water fish, such as tilapia. Antibiotics are administered to treat the disease but a better ...understanding of Fno infection biology will inform improved treatment and prevention measures. However, studies with native hosts are costly and considerable benefits would derive from access to a practical alternative host. Here, larvae of Galleria mellonella were assessed for suitability to study Fno virulence.
Larvae were killed by Fno in a dose-dependent manner but the insects could be rescued from lethal doses of bacteria by antibiotic therapy. Infection progression was assessed by histopathology (haematoxylin and eosin staining, Gram Twort and immunohistochemistry) and enumeration of bacteria recovered from the larval haemolymph on selective agar. Fno was phagocytosed and could survive intracellularly, which is consistent with observations in fish. Virulence of five Fno isolates showed strong agreement between G. mellonella and red Nile tilapia hosts.
This study shows that an alternative host, G. mellonella, can be applied to understand Fno infections, which will assist efforts to identify solutions to piscine francisellosis thus securing the livelihoods of tilapia farmers worldwide and ensuring the production of this important food source.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
subsp.
(
) is the causative agent of piscine francisellosis, an emerging infectious disease in Asia and Latin America. In this study two outbreaks of francisellosis were diagnosed in the UK on the ...basis of histopathology, electron microscopy, PCR, bacterial isolation and fulfillment of Koch's postulates. Furthermore, a phenotypic fingerprint based on biochemical analyses, metabolic activity, chemotaxonomic composition, and antimicrobial assays was generated for the novel isolates, the
type strain Ehime-1 from Asia and other
from Latin America. The genetic relatedness between the novel
and other
species was investigated by sequencing and comparing the 16SrRNA gene, 8 housekeeping genes (individually and concatenated) and the 16SrRNA-ITS-23SrRNA sequence. The phenotypic profiling indicated a high degree of similarity among the
strains as all were able to metabolize dextrin, N-acetyl-D glucosamine, D-fructose, α-D-glucose, D-mannose, methyl pyruvate, acetic acid, α-keto butyric acid, L-alaninamide, L-alanine, L-alanylglycine, L-asparagine, L-glutamic acid, L-proline, L-serine, L-threonine, inosine, uridine, glycerol, D L-α-glycerol phosphate, glucose-1-phosphate, and glucose-6-phosphate. The chemotaxonomic analyses indicated that 24:1 (20.3%), 18:1n-9 (16.9%), 24:0 (13.1%) 14:0 (10.9%), 22:0 (7.8%), 16:0 (7.6%), and 18:0 (5.5%) were the predominant structural fatty acids in
. The antimicrobial assays showed little variation between the isolates and high susceptibility to enrofloxacin, gentamicin, neomycin, streptomycin, amikacin, ciprofloxacin, gatifloxacin, nitrofurantoin, tobramycin, kanamycin, tetracycline, oxytetracycline, florfenicol, oxolinic acid, and streptomycin in all the
analyzed. In all the phylogenetic trees the
strains clustered together in independent branches confirming a high degree of homogeneity. Interestingly in five of the 11 trees i.e.,
, 16SrRNA-ITS-23SrRNA, and concatenated sequence the two
ssp. diverged more from each other than from the closely related
(
). The phenotypic and genetic characterization confirmed the
isolates represent a solid phylo-phenetic taxon that in the current context of the genus seems to be misplaced within the species
. We propose the use of the present polyphasic approach in future studies to characterize strains of
and
and verify their current taxonomic rank of
and other aquatic
spp.
Skin conditions, especially those of unknown aetiology, are often reported in rainbow trout (Oncorhynchus mykiss) aquaculture and are a true challenge for the trout industry. Red mark syndrome (RMS) ...is a skin condition affecting cultured rainbow trout, which first appeared in the United States of America (USA) in the late-1960s, then referred to as strawberry disease. It later appeared in Europe in the 1980s and was reported in the United Kingdom (UK) in late 2003. Since then, it has quickly spread to the rest of Europe and more recently has been reported in the Middle East, the Americas and Asia. Due to the downgrading of affected fish, RMS can cause significant economic loss to the rainbow trout industry.
Several papers have described the histology associated with RMS in detail, and there is a good case definition for the disease. Although the aetiology has not yet been confirmed, two pathogens have been associated with the disease: a Rickettsia-like organism (RLO), now identified as a Midichloria–like organism (MLO), and Flavobacterium psychrophilum, however, an association between the latter and RMS has not been supported in subsequent studies. Although the MLO has yet to be isolated, ultrastructural features resembling Rickettsiales order organisms have been observed in affected tissues and a strong positive correlation has been found between the MLO and RMS-affected fish using a variety of techniques. More recently papers have described a reproducible challenge model based on cohabitation, which has been used to investigate the disease dynamics of RMS under controlled conditions. This review aims to examine the current state of knowledge relating to RMS and to highlight where there are gaps in this knowledge.
•Complete overview of current research on red mark syndrome.•Authors interpretation on current publications on red mark syndrome.•Suggestions for research gaps and direct to future work on red mark syndrome.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Red mark syndrome (RMS) is a skin condition in Rainbow trout Oncorhynchus mykiss that has been reported worldwide but was first seen in the United Kingdom (UK) in 2003. The current study was ...conducted to examine if there was an association between a Midichloria-like organism (MLO) and RMS using a statistically appropriate sample set, whilst determining if there is a lack of association with Flavobacterium psychrophilum implicated in disease in previous studies. Fish in this study were obtained from three sites positive for RMS in the UK and United States (US), and three sites in the UK and the Netherlands that had no previous history of this condition. Samples taken from RMS-affected sites were found to show typical RMS pathology. Analysis of the major organs of affected fish by quantitative polymerase chain reaction (qPCR) demonstrated a significantly higher presence of the MLO in the RMS-affected tissues. Although most of the tissues were positive for the MLO, the highest correlation was seen in the skin, whilst the tissues from the unaffected fish were all negative. Thus, a strong positive correlation was found between the MLO and RMS-affected fish, whilst no association was found between the RMS-affected fish and F. psychrophilum other than superficial presence in the skin. The use of immunohistochemistry showed positive staining of what was considered to be MLO-related antigens in the internal organs of most RMS-affected fish. Attempts were made to culture the MLO, but no MLO was isolated.
•The association between a MLO and RMS was examined using a statistically appropriate sample set.•A high association between the MLO and RMS-affected fish was found.•The MLO was mostly associated with the skin lesions as shown by quantitative PCR.•Flavobacterium psychrophilum was superficially present in skin samples and not associated with RMS.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The maturation and reproduction of Pacific whiteleg shrimp, Penaeus vannamei, through the practice of unilateral eyestalk ablation though common is an animal welfare concern. This study assessed the ...resilience of offspring from non-ablated P. vannamei when challenged with an isolate of Vibrio parahaemolyticus (Vp) causing acute hepatopancreatic necrosis disease (VpAHPND), and with white spot syndrome virus (WSSV). VpAHPND and WSSV challenges were conducted using PL and juveniles under controlled conditions, with both trials using four groups (i.e. shrimp from either ablated or non-ablated females and then either challenged with the pathogen or not challenged). For the VpAHPND challenge, ten replicate 20 L tanks (five replicates for each population) each containing 100 PL 17 (average weight 14 mg) in 15 ppt, 29.05 ± 0.13 °C water were challenged with 2 mL of 2.0 × 108 CFU mL−1 culture of V. parahaemolyticus. A further ten replicate tanks (five per population) served as the corresponding non-challenged controls. The shrimp mortalities were assessed every 3 h over the following 96 h. For the WSSV challenge, individual 1.4 g (average weight) shrimp (50 individuals per population) were housed in 1 L tanks and fed 0.1 g WSSV infected tissue (av. 2.02 × 109 WSSV). A further 50 shrimp per population served as non-challenged controls. The shrimp were maintained at 15 ppt, 26.3 ± 0.71 °C water and assessed every 3 h post-infection over the subsequent 168 h and mortalities at each time point noted. Postlarvae from non-ablated females had significantly (p = 2.4E-23) better survival (70.4%) than those from ablated females (38.8%) at 96 h post-challenge with VpAHPND. Both challenged populations had significantly (p ≤1.3E-36) lower survival than the control groups. The survival of the juveniles from non-ablated females (62%) at 168 h post-infection with WSSV was not significantly higher than that of the juveniles from ablated female (48%) although the difference was significantly different at 65 to 75 h. Both challenged populations also had significantly (p ≤1.0E-5) lower survival rates than the control groups. The study demonstrates that postlarvae and juveniles from non-ablated females are more resilient to typical pathogens (VpAHPND and WSSV) and may show higher survival rates during a disease outbreak.
•Non-ablated Penaeus vannamei females produce offspring that are more resilient to commonly encountered pathogens.•Postlarvae from non-ablated female have a significantly higher resistance to VpAHPND.•Juveniles from non-ablated animals have better survival to WSD than their juvenile counterparts from ablated female.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Following on from the Annual Fish Veterinary Society Conference, this symposium was organised with the Laboratory Animal Science Association and brought together experts from ornamental (pond and ...aquarium) fish practice, aquaculture and aquatic-research facilities to discuss good practice of anaesthesia. This proceedings paper gives an overview of relevant experiences involving a range of immersion drugs including tricaine, benzocaine and isoeugenol, as well as a summary of the main topics of discussion. While fish anaesthesia is commonplace, administration methods, drugs and monitoring procedures may often be regarded as antiquated when compared with mammalian practice. These limitations notwithstanding, individual fish will benefit from good anaesthetic monitoring. Although the most common anaesthetic drugs may be perceived as equally efficacious and therefore interchangeable for different settings, challenges are different for the anaesthesia of grouped fish, when determining species-dependent anaesthetic dosing in a multi-species tank, or adapting to farming requirements, nationally licensed products, costs and withdrawal periods. The fish anaesthetic arsenal fails to address premedication, analgesia and issues of averseness. The two latter factors should be part of the evaluation of anaesthetic protocols; therefore, instructions for the analgesic provision of lidocaine to fin clipped zebrafish are proposed. Euthanasia practices could sometimes be refined too. Alternative physical methods such as electrical stunning are options to be considered.
Francisellosis, induced by Francisella noatunensis subsp. orientalis (Fno), is an emerging bacterial disease representing a major threat to the global tilapia industry. There are no commercialised ...vaccines presently available against francisellosis for use in farmed tilapia, and the only available therapeutic practices used in the field are either the prolonged use of antibiotics or increasing water temperature. Recently, an autogenous whole cell-adjuvanted injectable vaccine was developed that gave 100% relative percent survival (RPS) in tilapia challenged with a homologous isolate of Fno. In this study, we evaluated the efficacy of this vaccine against challenge with heterologous Fno isolates. Healthy Nile tilapia, Oreochromis niloticus (∼15 g) were injected intraperitoneally (i.p.) with the vaccine, adjuvant-alone or phosphate buffer saline (PBS) followed by an i.p. challenge with three Fno isolates from geographically distinct locations. The vaccine provided significant protection in all groups of vaccinated tilapia, with a significantly higher RPS of 82.3% obtained against homologous challenge, compared to 69.8% and 65.9% with the heterologous challenges. Protection correlated with significantly higher specific antibody responses, and western blot analysis demonstrated cross-isolate antigenicity with fish sera post-vaccination and post-challenge. Moreover, a significantly lower bacterial burden was detected by qPCR in conjunction with significantly greater expression of IgM, IL-1 β, TNF-α and MHCII, 72 h post-vaccination (hpv) in spleen samples from vaccinated tilapia compared to fish injected with adjuvant-alone and PBS. The Fno vaccine described in this study may provide a starting point for development a broad-spectrum highly protective vaccine against francisellosis in tilapia.
•Efficacy of an injectable vaccine of Francisella noatunensis subsp. orientalis with adjuvant was tested against challenge with three different Fno isolates in Nile tilapia.•The developed vaccine stimulated innate and adaptive immunity post-vaccination and provided protection against homologous and heterologous Fno isolates.•Significantly higher IgM levels and significantly lower bacterial burden following i.p. vaccination and challenge correlated with protection, suggesting a protective role of antibody-mediated immunity against Fno in Nile tilapia.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Francisella noatunensis subsp. orientalis is a pathogen of tilapia and other warm‐water fish for which no vaccines are commercially available. In this study, a whole cell formalin‐inactivated vaccine ...was developed for the first time using the highly virulent isolate STIR‐GUS‐F2f7 and the oil‐based adjuvant Montanide™ ISA 763A VG. The efficacy of the vaccine was assessed in red Nile tilapia via intraperitoneal (i.p.) injection using homologous experimental infection and correlates of protection such as seral antibody production and bacterial loads in the spleen. For immunization, fish were i.p. injected with 0.1 ml of the vaccine, the adjuvant alone or PBS. At 840 degree days post‐vaccination, all fish were i.p. injected with 4.0 × 103 CFU/fish of pathogenic bacteria. The RPS at the end of the trial was 100% in the vaccinated group with significantly higher survival than in the adjuvant and control groups. The RPS in the adjuvant group was 42%, and no significant difference was seen in survival between this and the PBS group. Moreover, significantly higher antibody titres in the serum and significantly lower bacterial loads in the spleen were detected in the vaccinated fish by ELISA and qPCR, respectively. These findings highlight the potential of autogenous vaccines for controlling francisellosis in tilapia.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Over the past 80 years, tilapia have been translocated globally for aquaculture; active production is recorded in >124 countries. Of 7 million tonnes of tilapia produced in aquaculture, 79% is from ...79 countries outside the natural range of tilapia. Capture fisheries account for a further 723,627 tonnes of tilapia, and >47% of this is landed from established invasive populations outside Africa. Tilapias host a rich fauna of parasites, many of which have been translocated with their hosts. This review summarises >2500 host–parasite records from 73+ countries and >820 recorded tilapia translocations (provided in the supplementary materials). This work focuses on the notable pathogens that threaten the health of cultured populations of tilapia, providing a description of their pathology and includes species that also have substantial impacts on wild tilapia populations, where relevant. For each major parasite taxonomic group, we highlight which parasites have been translocated or have been acquired from the new environments into which tilapia have been introduced, together with remarks on standard treatment approaches and research on them and their management and control. Regarding the theme ‘Tilapia health: quo vadis?’, Africa has enormous potential for aquaculture growth, but substantial knowledge gaps about tilapia parasites in many African states remain, which creates associated production and biosecurity risks. For each parasitic group, therefore, the risks of parasite translocation to new regions as tilapia aquaculture industries expand are highlighted.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
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