Aquatic Animal Diseases Research Articles

Aquatic animal diseases with awareness and perception of freshwater fish farmers on aquatic animal health management practices in tropical archipelago of India

Aquatic animal diseases with awareness and perception of freshwater fish farmers on aquatic animal health management practices in tropical archipelago of India

Antibacterial effects against pathogens of Vibrio genus using 5-aminolevulinic acid produced from recombinant Escherichia coli

BackgroundVibrio genus comprises a group of notorious pathogens that cause diseases in aquatic animals, leading to a reduction in seafood production. With climate change, Vibrio spp. pose an increasingly severe threat to the growing aquaculture industry, thereby affecting global food production. This study explored the use of 5-aminolevulinic acid (5-ALA) as a biocompatible antibacterial agent due to the inducibility of antibacterial properties by light and in vivo conversion to photosensitizing protoporphyrin IX (PPIX). Methods5-ALA were produced by recombinant E. coli was introduced as a photodynamic therapy against three Vibrio strains; namely, Vibrio parahaemolyticus (Vp), Vibrio alginolyticus (Va), and Vibrio damsela (Vd). The effect of 5-ALA on the three Vibrio species was investigated at a neutral pH, considering various factors such as reaction time and concentration under both light and dark conditions. Significant findingsThe antimicrobial photodynamic therapy (aPDT) utilizing 0.5 % (w/v) 5-ALA was effective against Vibrio sp. only at pH < 5.5. In a neutral pH environment and without light exposure, antimicrobial activity was still observed against V. alginolyticus and Vibrio parahaemolyticus when the concentration of 5-ALA was increased to 1 % and 2 %, respectively. The bactericidal effect was only 39 % for Vibrio damsela, indicating a slower biosynthesis of PPIX. Nonetheless, this also suggests the potential of 5-ALA as an in vitro antibacterial agent under acidic conditions. The bactericidal effect of crude and pure 5-ALA was found to be similar, indicating the potential of using cost-effective crude extracts as aPDT agent.

Development and validation of a multiplex quantitative polymerase chain reaction assay for detecting and genotyping red sea bream iridoviral disease

Megalocytiviruses are responsible for severe mortality in various marine and freshwater fish species worldwide. Specifically, the red sea bream iridovirus (RSIV) and infectious spleen and kidney necrosis virus (ISKNV) genotypes are known to cause the red sea bream iridoviral disease (RSIVD). Although several quantitative polymerase chain reaction (qPCR) assays have been developed for diagnosing RSIVD, these methods fail to differentiate between viral genotypes within Megalocytivirus. The present study introduces an innovative multiplex qPCR assay for the precise detection of RSIVD. This diagnostic method targets the histidine triad motif (HIT)-like protein and ORF080L genes, which are unique markers for the RSIV and ISKNV genotypes. The assay exhibited high analytical sensitivity, expressed as the 95% limit of detection (LoD95%), of 8.69 copies/5 μL for RSIV and 19.07 copies/5 μL for ISKNV. Notably, the assay exhibited no cross-reactivity and was unaffected by common inhibitory substances. The diagnostic sensitivity and specificity were 100% for both RSIV and ISKNV, demonstrating the reliability of the assay. The multiplex qPCR assay was 100–1000 times more sensitive than conventional PCR methods, emphasizing its importance in early-stage infection detection. The repeatability and reproducibility of the assay were confirmed through extensive testing, showing low variation and high correlation across different technicians and laboratory settings. Furthermore, the ability of the assay to selectively detect and differentiate between RSIVD genotypes represents a significant advancement in aquatic animal disease diagnostics. This multiplex qPCR assay offers a rapid, specific, sensitive, and quantitative diagnostic tool for global RSIVD surveillance efforts and contributes to the prevention and understanding of disease progression in the aquaculture industry.

Emerging technologies revolutionising disease diagnosis and monitoring in aquatic animal health

AbstractIn recent years, aquaculture has seen tremendous growth worldwide due to technological advancements, leading to research and development of various innovations. Aquaculture farmers prioritise early diagnosis for timely treatment to achieve better productive and economic performance. Aquatic animal health experts still employ traditional diagnostic methods using visual diagnosis, cell culture, media culture, histopathology and serology. However, the developments of technologies in aquamedicine, such as sequencing, biosensors and CRISPR, have enabled rapid disease detection within minutes. Furthermore, integrating sensors, drones, artificial intelligence and the internet in aquaculture farm monitoring has helped farmers take decisive actions to improve production. Advancements in diagnostic techniques have significantly enhanced the efficient detection of bacterial, viral, parasitic and fungal diseases in aquatic animals. Moreover, monitoring water quality, aquatic animal health and animal behaviour on farms has become exceptionally streamlined with cutting‐edge tools like drones, sensors and artificial intelligence. Summarising research and development in aquatic animal health and monitoring aids efficient technology adoption in aquaculture. With these advanced technologies' continued development and adoption in developed countries, the aquaculture industry is experiencing growth and increased efficiency, benefiting farmers and consumers in these regions. However, farmers and educators in developing countries lack information about these technologies. Training of agricultural educators and efficient dissemination of knowledge and technologies through advertising and publication in collaboration with companies is essential. This review delves into emerging technologies capable of replacing the conventional diagnostic and monitoring methods utilised in aquaculture. We also explore their strengths, limitations and potential future applications within aquaculture settings.

First Report of Viral Nervous Necrosis in Asian Sea Bass, Lates Calcarifer Cultured in Sri Lanka

Viral Nervous Necrosis (VNN) caused by Betanodavirus is a devastating disease in aquatic animals. The virus infects both marine and freshwater fish worldwide. Vacuolating necrosis of neural cells of the brain, the retina of the eye, and the spinal cord of the infected fish are the primary histological lesions of the condition. It causes up to 100% mortality in larvae and juvenile fish and can cause significant death in adult fish. The present study detected viral nervous necrosis in larvae and fry of Asian sea bass (Lates calcarifer) with progressive mortality of up to 95% in one week during the Northeast monsoon when the mean water temperature was 27 to 29°C. Histopathological examination of the moribund fish revealed extensive vacuolation and gliosis in the olfactory bulb, the optic lobe of the forebrain, and the inner and outer layer of the retina. Furthermore, tissues of the brain and the retina had intracellular inclusion bodies suggesting viral etiology, further justified by the negative results of the bacterial and parasitic examinations. The Reverse Transcriptase Polymerase Chain Reaction (RT-PCR) test additionally confirms the etiology diagnosis using specific primers designed previously. The histopathology and RT-PCR results suggest that the mortalities of Asian sea bass were due to the VNN. The present finding is the first report of the VNN associated with mass mortalities in Asian seabass cultured in Sri Lanka. These crucial findings emphasize the need for quarantine and control strategies to prevent the spread of the virus and outbreak of the disease.

Gut bacterial consortium enriched in a biofloc system protects shrimp against Vibrio parahaemolyticus infection

BackgroundShrimp cultured in a biofloc system (BFS) have a lower disease incidence than those farmed in a water exchange system (WES). Although a number of studies have reported that the gut bacterial community induced by BFS is highly associated with shrimp disease resistance, the causal relationship remains unknown. Here, the promotive roles of gut bacterial community induced by BFS in pathogenic Vibrio infection resistance and its potential micro-ecological and physiological mechanisms were investigated by gut bacterial consortium transplantation and synthetic community (SynCom) construction.ResultsThe BFS induced a more stable and resistant gut bacterial community, and significantly enriched some beneficial bacterial taxa, such as Paracoccus, Ruegeria, Microbacterium, Demequina, and Tenacibaculum. Transplantation of a gut bacterial consortium from BFS shrimp (EnrichBFS) greatly enhanced the stability of the bacterial community and resistance against pathogenic V. parahaemolyticus infection in WES shrimp, while transplantation of a gut bacterial consortium from WES shrimp significantly disrupted the bacterial community and increased pathogen susceptibility in both WES and BFS shrimp. The addition of EnrichBFS in shrimp postlarvae also improved the pathogen resistance through increasing the relative abundances of beneficial bacterial taxa and stability of bacterial community. The corresponding strains of five beneficial bacterial taxa enriched in BFS shrimp were isolated to construct a SynComBFS. The addition of SynComBFS could not only suppress disease development, but also improve shrimp growth, boost the digestive and immune activities, and restore health in diseased shrimp. Furthermore, the strains of SynComBFS well colonized shrimp gut to maintain a high stability of bacterial community.ConclusionsOur study reveals an important role for native microbiota in protecting shrimp from bacterial pathogens and provides a micro-ecological regulation strategy towards the development of probiotics to ameliorate aquatic animal diseases.1NpdyYjfCEzGqNeY6CWHQHVideo

The Pathogenic Yeast Metschnikowia bicuspidata var. bicuspidata in the Aquacultured Ecosystem and Its Biocontrol.

M. bicuspidata var. bicuspidata is a pathogenic yeast which can affect aquacultured and marine-cultured animals such as brine shrimp, ridgetail white prawn, chinook salmon, giant freshwater prawn, the Chinese mitten crab, marine crab, the mud crab, the mangrove land crab, the Chinese grass shrimp, sea urchins, sea urchins, Daphnia dentifera and even snails, causing a milky disease, and it has caused big economic losses in aquacultural and marine-cultural industries in the past. However, the detailed mechanisms and the reasons for the milky disease in the diseased aquatic animals are still completely unknown. So far, only some antimycotics, killer toxins and Massoia lactone haven been found to be able to actively control and kill its growth. The ecofriendly, green and renewable killer toxins and Massoia lactone have high potential for application in controlling the milky disease.

Farm level bio-economic modelling of aquatic animal disease and health interventions

A farm level bio-economic model, for aquatic animal production, of the relationships between inputs (e.g. purchased animals), outputs (e.g. harvested animals) and gross margin (GM) was developed to assess ex-ante the economics of disease and animal health interventions. Feed costs were calculated from estimates of food conversion ratio (FCR), animals harvested and mortality. The model was applied to a typical grow-out rainbow trout (Oncorhynchus mykiss) farm on Lake Titicaca, Peru and a typical shrimp (Paenus vannamei) farm in the Mekong Delta, Vietnam. The model was used in two analyses. Firstly, an approach to assess the burden of disease developed by the Global Burden of Animal Diseases (GBADs) project was adopted. Output under conditions of ‘ideal health’ was estimated by reducing mortality to zero and removing health costs. GM in both systems increased by approximately 25% when production was kept constant (and stocking rates reduced) and more than doubled if production was allowed to rise (and initial stocking increased). The increase in GM under conditions of ideal compared with current production provided an estimate of the maximum possible benefit from improved health management. Secondly, break-even analysis was used to assess the economics of vaccination against infectious pancreatic necrosis (IPN) vaccine (rainbow trout - RBT) and probiotics (shrimp). If initial stocking was kept constant, and production allowed to rise, break-even points for the intervention (when GM was the same with and without the intervention) were achieved when mortality was reduced by 16% in RBT fry and juvenile and 28% in shrimp. If production was kept constant and benefit realised by reduced initial stocking, the break-even point was achieved for i) vaccination of RBT when mortality in fry and juveniles was reduced by 39%, and ii) probiotics in shrimp production when there was a 15% reduction in mortality (nursery and grow-out), 10% increase in shrimp weight at harvest and 10% improvement in FCR. The results demonstrate how relatively simple models, parameterised with basic farm production data, can assess the burden of disease and quantify ex-ante the potential benefit of interventions. In the absence of trial data, these analyses support decision-making by farmers. The models can be adapted for many aquaculture systems. Farm level results can be extrapolated to estimate disease burden, and benefits of interventions, at regional or national level and thus support informed decision-making and allocation of resources to health management.

Aeromonas hydrophila infection in acute myeloid leukemia: A case report

Rationale: Aeromonas hydrophila, a bacterium commonly found in a variety of soils, aquatic habitats, and other natural environments, is known for causing infections and hemorrhagic diseases in both aquatic and terrestrial animals. Patients with leukemia, when infected by Aeromonas hydrophila following chemotherapy, face an increased risk of developing necrotizing fasciitis. Patient concerns: A 48-year-old male with a history of acute myeloid leukemia presented with swelling and pain in his right hand after being stabbed by a grass carp two days ago. The injury occurred on the fifth day after his last chemotherapy session when he was accidentally punctured in the right thumb and ring finger by a carp while fishing. Two days following the injury, the skin isurrounding the wound turned black immediately, while the rest of his hand was reddened, swollen, and bleeding. Diagnosis: Aeromonas hydrophila infection in the soft tissue of the right hand. Interventions: Intravenous antibiotics and local debridement. Outcomes: The patient experienced an alleviation of systemic poisoning symptoms, effective control of the local wound infection. Lessons: It is important for physicians to appreciate the potential for highly unusual and life-threatening infections in patients with acute myeloid leukemia. Early diagnosis and prompt treatment can prevent the development of necrotizing fasciitis and save patients' lives.

A Novel RAA Combined Test Strip Method Based on Dual Gene Targets for Pathogenic Vibrio vulnificus in Aquatic Products.

Vibrio vulnificus can cause disease in aquatic animals and humans, therefore, rapid and simple field detection of pathogenic V. vulnificus is important for early disease prevention. In this study, a novel recombinase-aided amplification (RAA) combined test strip with double T-lines (RAA-TS-DTL) was developed for the rapid detection of V. vulnificus in aquatic products. Pathogenic V. vulnificus was detected using the virulence vvhA gene and the housekeeping gene gyrB gene as the dual target of the test strip. The RAA-TS-DTL method showed 100% specificity for V. vulnificus, and no cross-reaction was observed with Vibrio spp. or other bacteria (n = 14). Furthermore, sensitive detection of V. vulnificus in oysters was achieved. The LODs of the gyrB and vvhA genes were 6 CFU/mL and 23 CFU/mL, respectively, which was about five times higher than that of the commercial test strip. The method was validated with spiked samples (n = 60) of fish, shrimp and oyster. The consistency between RAA-TS-DTL and the traditional culture method was 97.9%. In addition, the entire process of detection, including preparation of the sample, could be completed within 50 min. Our results indicated that the developed RAA-TS-DTL was a reliable and useful tool for rapid screening or on-site detection of pathogenic V. vulnificus in aquatic products and aquaculture water.

Application of Predatory Bacteria in the Prevention and Control of Aquaculture Diseases

The green and healthy development of aquaculture is an important guarantee for food security. Pathogenic bacteria are a major factor constraining the development of aquaculture. Predatory bacteria are a class of potentially beneficial bacteria that can be used as an alternative to antibiotics for the prevention and control of aquatic animal diseases. This article reviews the application of predatory bacteria in the prevention and control of aquaculture diseases, discusses their potential as probiotics, and also points out some unresolved issues, including limited bacterial resources, insufficient studies on biological and ecological properties, lack of systematic safety and

Pathogenicity and inactivated vaccine treatment of Aeromonas veronii JW-4 on crucian carp

Aeromonas veronii is a common bacterium found in a variety of aquatic environments, capable of causing a diverse array of diseases in both aquatic animals and humans. Therefore, evaluating the pathogenicity of A. veronii and implementing measures to control its spread are essential. In this study, a strain JW-4, identified as A. veronii, was isolated from diseased Scaphesthes macrolepis, a grade Ⅱ protected animal in China. To investigate the pathogenicity of the strain, fish were fed with serial levels JW-4 supplemented diet or basal diet (control group 1, CG1) for 28 days (d). Results showed that JW-4 stimulated an immune response, evidenced by an increase in immune-related enzyme activities (GOT and GPT) of serum and liver and an upregulation of genes expression levels (TNF-α and IFN-γ) of liver and spleen, and these effects gradually decreased over time. Histopathological examination revealed that JW-4 could alter the tissue structure of immune organs, such as liver and kidney. These changes were accompanied by vacuolar degeneration, nuclear dissolution, and an increased lymphocyte count. To assess protective effects of a vaccine against this strain, fish were injected with an inactivated vaccine (immunization group, IG) or 0.85% sterile saline (control group 2, CG2) for 28-day observation period, then challenged with JW-4 on the 28th day. The inactivated vaccine enhanced total and specific IgM to A. veronii levels of the fish, resulting in a relative percentage survival of 75% in IG. These findings provide a foundation for identifying pathogenic bacteria and developing more effective prophylactic strategies in aquaculture.

A review on the application of chicken immunoglobulin Y in aquaculture

AbstractThe widespread use of antimicrobial drugs in aquaculture has led to antibiotic residues in aquatic animals. Food safety problems caused by the misuse of antibiotics and antibiotic residues have caused widespread global concern. Consequently, there is an urgent need to develop an alternative to antibiotics for use in aquaculture. Immunoglobulin Y (IgY) has attracted significant attention over recent years because it is readily available, simple to prepare, effective in inhibiting pathogenic microorganisms, free from environmental contamination and free from other toxic side effects. In this paper, we review the research progress relating to the basic structure, physicochemical properties and mechanism of action of IgY. We also highlight the applications of IgY in the control of aquatic animal disease, immunological diagnosis and the preservation of aquaculture products, thus providing a reference for future research and the wider application of IgY in aquaculture.

Establish and apply ISI pathological method to evaluate the intestinal health of largemouth bass (Micropterus salmoides) and channel catfish (Ictalurus punctatus) challenged with Aeromonas hydrophila

Gut health is essential for animal growth because it can absorb nutrients more efficiently, promote growth, and protect the body from invasion by pathogenic microorganisms. Temperature, dissolved oxygen, water quality, nutrition level, pathogen, net fishing, and so on will affect the gut health of aquatic animals. Intestinal diseases in aquatic animals were often not easily detected, making them difficult to prevent and control. Therefore, establishing a stable and scientific evaluation standard of gut health was of great significance. This study evaluated the effects of gross pathological and histological parameters of largemouth bass and channel catfish infected by Aeromonas hydrophila. A total of 150 largemouth bass and 150 channel catfish were randomly divided into 5 groups: 1 control group (NC) and 4 challenge groups (CH, fish were infected with A. hydrophila by intraperitoneal injection with a concentration of 200 µL 1x108 CFU/mL, 1x107 CFU/mL, 1x106 CFU/mL, and 1x105 CFU/mL, respectively). After the challenge, largemouth bass’ gross pathological and histological changes were observed on the 2nd, 6th, 9th, 12th, and 14th days. In contrast, channel catfish’s gross pathological and histological changes were observed on the 3rd, 6th, 9th, 12th, and 15th day. In this study, regarding the “I See Inside” (ISI) methodology of poultry, a pathological evaluation method of fish intestinal health was established to comprehensively evaluate the intestinal health status of fish by gross pathological and histopathological score. In gross pathology, it was scored by the body surface and intestinal lesions. In histology, it was a metric evaluation of histological alterations in the intestine, converting macroscopic and microscopic alterations into numbers and then scoring. Each evaluation parameter sets up an “influence factor” (IF) according to the degree of influence of its pathological changes on intestinal function. The final score was the sum of the IF product and this parameter’s score. The results of two kinds of fish showed that the gross pathological and histopathological scores correlated with the infection dose and time. And the significant difference in the score between the enteritis and control groups was observed. The results showed that the higher score, the more serious the pathological changes of fish infected by A. hydrophlia. From this, it can be concluded that the pathological evaluation method established can be used to evaluate the gut health of fish.

Editorial: The transmission and prevention of infectious diseases in aquatic animals

Editorial: The transmission and prevention of infectious diseases in aquatic animals

Bacteriophage applications in aquaculture

Aquaculture has grown tremendously due to the big demand for its products. However, diseases affecting aquaculture and economic losses are worldwide problems and it needs low cost, sustainable, highly efficient, specific and eco-friendly therapeutants. Due to the rising up antibiotic resistant-microorganism, bacteriophage therapy has reinvigorated to replace antibiotics in agriculture, medicine, food safety and the environment. Likewise, it also holds great promise to avoid, control and treat bacteria in aquaculture to decrease the mortality level of different aquatic animal diseases. The isolation and characterization of new phages and phage application therapy to eliminate bacterial fish and shellfish pathogens such as Vibrio, Aeromonas, Pseudomonas, Lactococcus, Yersinia, Flavobacterium, and Streptococcus was gradually reported in aquaculture literature. The present review summarizes large-scale reports in vitro or in vivo use of aquaphage studies and applications in fish diseases from the 1980s to 2022 and future directions.

Correlation of Atmospheric Temperature with the Prevalence of White Spot Disease (WSD) and Acute Hepatopancreatic Necrosis Disease (AHPND) in the Philippines

The growing crustacean aquaculture industry in the Philippines is a significant contributor to the seafood production sector. However, several problems hinder the growth and overall market production, the main factor being diseases. Previous studies observed that temperature changes affect shrimp’s physiological and immunological responses to different pathogens and parasites; hence, this meta-analysis examined the correlation of white spot disease (WSD) and acute hepatopancreatic necrosis disease (AHPND) with atmospheric temperature changes. The analysis was conducted using the available data from the Quarterly Aquatic Animal Disease report of the Network of Aquaculture Centres in Asia Pacific, the Bureau of Fisheries and Aquatic Resources, and the Philippine Atmospheric, Geophysical, and Astronomical Services Administration. Results indicated that temperatures ranging from 27–28 °C generally cause higher disease occurrences in the Philippines, as it facilitates optimum conditions for the infectivity of the causative agents of both diseases. Statistical analysis also has shown a positive correlation of temperature to the disease occurrence, indicating that temperature monitoring is crucial, especially in the culture of shrimps in a controlled environment. This information will serve as a guide to the fish health and aquaculture industry in mitigating possible disease outbreaks.

Dysbiosis of intestinal homeostasis contribute to Whitmania pigra edema disease.

Whitmania pigra is widely used in traditional Chinese medicine. However, W. pigra is being threatened by an edema disease with unknown causes (WPE). In this study, a comprehensive exploration of virome, microbiome, and metabolome aberrations in the intestine of W. pigra was performed to address the aetiology of WPE. Virome analysis indicated that eukaryotic viruses did not contribute to WPE, whereas an expansion of Caudovirales was observed in WPE. Compared to the control, the microbial richness and diversity in diseased W. pigra decreased remarkably. Nine genera, including Aeromonas, Anaerotruncus, Vibrio, Proteocatella, Acinetobacter, and Brachyspira were overrepresented in WPE, whereas eleven genera, including Bifidobacterium, Phascolarctobacterium, Lactobacillus, Bacillus and AF12, were enriched in healthy individuals. Furthermore, certain metabolites, especially amino acids, short-chain fatty acids, and bile acids, were found to be linked to intestinal microbiota alterations in WPE. An integration of the microbiome and metabolome in WPE found that dysbiosis of the gut microbiota or metabolites caused WPE. Notably, W. pigra accepted intestinal microbiota transplantation from WPE donors developed WPE clinical signs eventually, and the dysbiotic intestinal microbiota can be recharacterized in this recipient W. pigra. Strikingly, pathological features of metanephridium and uraemic toxin enrichment in the gut indicated a putative interconnection between the gut and metanephridium in WPE, which represents the prototype of the gut-kidney axis in mammals. These finding exemplify the conservation of "microecological Koch's postulates" from annelids to insects and other vertebrates, which provides a direction of prevention and treatment for WPE and opens a new insight into the pathogenesis of aquatic animal diseases from an ecological perspective.

Current Knowledge on Epizootic Haemorrhagic Disease in China.

Epizootic haemorrhagic disease (EHD) is an infectious, non-contagious viral disease of ruminants caused by epizootic haemorrhagic disease virus (EHDV) and is transmitted by insects of the genus Culicoides. In 2008, EHD was listed on the World Organization for Animal Health (WOAH) list of notifiable terrestrial and aquatic animal diseases. This article reviews the distribution of EHD in China and relevant studies and proposes several suggestions for the prevention and control of EHD. There have been reports of positivity for serum antibodies against EHDV-1, EHDV-2, EHDV-5, EHDV-6, EHDV-7, EHDV-8 and EHDV-10 in China. Strains of EHDV-1, -5, -6, -7, -8 and -10 have been isolated, among which the Seg-2, Seg-3 and Seg-6 sequences of serotypes -5, -6, -7 and -10 belong to the eastern topotype. The emergence of western topotype Seg-2 in EHDV-1 strains indicates that EHDV-1 strains in China are reassortant strains of the western and eastern topotypes. A novel serotype strain of EHDV named YNDH/V079/2018 was isolated in 2018. Chinese scholars have successfully expressed the EHDV VP7 protein and developed a variety of ELISA detection methods, including antigen capture ELISA and competitive ELISA. A variety of EHDV nucleic acid detection methods, including RT-PCR and qRT-PCR, have also been developed. LAMP and the liquid chip detection technique are also available. To prevent and control EHD, several suggestions for controlling EHD transmission have been proposed based on the actual situation in China, including controlling the number of Culicoides, reducing contact between Culicoides and hosts, continued monitoring of EHDV and Culicoides in different areas of China and further development and application of basic and pioneering research related to EHD prevention and control.

Whole spectrum of Aeromonas hydrophila virulence determinants and the identification of novel SNPs using comparative pathogenomics

Aeromonas hydrophila is a ubiquitous fish pathogen and an opportunistic human pathogen. It is mostly found in aquatic habitats, but it has also been isolated from food and bottled mineral waters. It causes hemorrhagic septicemia, ulcerative disease, and motile Aeromonas septicemia (MAS) in fish and other aquatic animals. Moreover, it might cause gastroenteritis, wound infections, and septicemia in humans. Different variables influence A. hydrophila virulence, including the virulence genes expressed, host susceptibility, and environmental stresses. The identification of virulence factors for a bacterial pathogen will help in the development of preventive and control measures. 95 Aeromonas spp. genomes were examined in the current study, and 53 strains were determined to be valid A. hydrophila. These genomes were examined for pan- and core-genomes using a comparative genomics technique. A. hydrophila has an open pan-genome with 18,306 total genes and 1620 genes in its core-genome. In the pan-genome, 312 virulence genes have been detected. The effector delivery system category had the largest number of virulence genes (87), followed by immunological modulation and motility genes (69 and 46, respectively). This provides new insight into the pathogenicity of A. hydrophila. In the pan-genome, a few distinctive single-nucleotide polymorphisms (SNPs) have been identified in four genes, namely: d-glycero-beta-d-manno-heptose-1,7-bisphosphate 7-phosphatase, chemoreceptor glutamine deamidase, Spermidine N (1)-acetyltransferase, and maleylpyruvate isomerase, which are present in all A. hydrophila genomes, which make them molecular marker candidates for precise identification of A. hydrophila. Therefore, for precise diagnostic and discrimination results, we suggest these genes be considered when designing primers and probes for sequencing, multiplex-PCR, or real-time PCR.