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This study was important to improve proper biosecurity measures and controlling the spread of Aeromonas to prevent future outbreaks. This research sought to determine whether virulent Aeromans species were present in morbid rainbow trout, their resistance and their genetic relatedness. A total number of 542 tissue lesion specimens were collected from gill, liver, heart and kidneys in morbid domesticated fish in Duhok province, Iraq. The gyrB DNA sequence analysis was used to determine the species classification. Drug susceptibility testing was conducted for all isolated strains using disc diffusion technique. The genotyping analysis was carried out using enterobacterial repetitive intergenic consensus-polymerase chain reaction. Thirty-four isolates were found and they were classified into three species (Aeromonas veronii, Aeromonas sorbia, and Aeromonas allosaccharophila), where A. veronii stand as one of the most prevalent species. The most frequently affected organ by Aeromonas was the gills among four different organs. The detection frequencies of the virulence genes aerolysin, outer membrane protein, glycerophospholipid-cholesterol acyltransferase, elastase, flagella, serine protease, cytotonic heat-labile, and hemolysin were 100%, 100%, 79.41%, 64.70%, 76.47%, 67.64%, 70.58%, and 41.17, respectively. None of the strains possessed all of the virulence markers. All isolates were completely resistant to ceftazidime, amoxicillin and doxycycline. All isolates were found to be multi-drug-resistant. Regardless of the nearest geographic source area of samples and the same Aeromonas species, there was a high genetic diversity. The results of this study could help farmers and researchers make informed decisions about measures of biosecurity and proper therapeutic drugs to apply to prevent current outbreaks and prevent them from recurring again. [ABSTRACT FROM AUTHOR]

Simple Summary: Hemorrhagic septicemia (HS) is an acute, fatal, and septicemic bacterial disease of cattle and buffaloes caused by Pasteurella multocida (P. multocida). The present study aimed to carry out HS surveillance through multi-stage random sampling constituting 692 cattle and buffalo serum samples sourced from two Indian states, four districts, eight clusters, 56 epiunits, and 306 households (HHs) by indirect enzyme-linked immunosorbent assay (iELISA). Significantly higher (p < 0.0001) iELISA positives were observed in Gujarat compared to Karnataka state. Of the 306 households visited, 9 of 27 epiunits (33.33%) in Karnataka and 24 out of 29 epiunits in Gujarat were iELISA positive (82.75%) and an association was found to be significant (p = 0.0002). However, a non-significant association to species, age, or lactation was recorded, although indigenous cattle breeds had a higher HS sero-prevalence compared to crossbreeds. This study highlights important baseline data on HS sero-prevalence in two major milk-producing states of India at different strata. Hemorrhagic septicemia (HS) is a highly contagious and fatal disease of cattle and buffaloes caused by P. multocida. Both conventional and molecular methods are applied in parallel for rapid diagnosis of HS outbreaks and the periodical surveillance strategy to identify risk areas for HS is ignored. The current cross-sectional study aimed to estimate sero-prevalence and associated risk factors for HS in cattle and buffaloes in non-vaccinated regions of two Indian states. HS surveillance was carried out through the multi-stage random sampling technique at different strata. The study employed a questionnaire incorporating host factors (species, breed, sex, age, and lactation) and demographic parameters (state, district, block/cluster and village/epiunits, and household). First, two Indian states known for high milk production were selected followed by two districts within each state, subsequently four clusters within each district, finally 5–10 epiunits within clusters and 5–8 households within clusters were randomly selected to collect cattle and buffalo samples. The chi-square/p values and maps were prepared to represent disease prevalence and to correlate disease risk factors at different strata. A total of 692 cattle and buffalo serum samples were sourced from two states of the country (Karnataka-285 and Gujarat-407). In the first strata, antibodies to P. multocida were high in Gujarat (14.49%, CI: 11.22–18.30) compared to Karnataka (3.85%, CI: 1.94–6.80) with significant (p < 0.0001) association between the states. In the second strata, one of the four districts investigated revealed the highest sero-prevalence (18.61%, CI: 13.81–24.24) with statistical significance (p = 0.01) between the districts. Among clusters, one out of eight clusters showed the highest sero-prevalence (23.02%, CI: 16.59–30.54) with statistical significance (p = 0.03) between the clusters in the third strata. At epiunit level (fourth strata), 9 out of 27 epiunits (33.33%) visited in Karnataka and 24 out of 29 epiunits sampled in Gujarat were sero-positive (82.75%) in iELISA. At the household level, out of 306 HH visited, 40 HH had at least one positive animal (13.07%) and the p value between HH in the two states was highly significant (p = 0.0002). Chi-square analysis did not find any association of HS sero-prevalence to species, age, and lactation. However, significantly higher (p < 0.05) sero-prevalence was recorded in indigenous cattle breeds (16.56%) compared to crossbreeds (6.59%). Various immunoprophylactics and antibiotic therapies are effective against HS, but inappropriate disease reporting and failure to implement adequate vaccination control measures are the gaps identified. The present study highlights the current scenario of HS sero-prevalence in two of the high milk-producing states of India, which will be useful for stakeholders for undertaking the implementation of surveillance and control strategies for the regions. [ABSTRACT FROM AUTHOR]

Background: Pasteurella multocida is a bacterial pathogen that causes a variety of infections across diverse animal species, with one of the most devastating associated diseases being hemorrhagic septicemia. Outbreaks of hemorrhagic septicemia in cattle and buffaloes are marked by rapid progression and high mortality. These infections have particularly harmful socio-economic impacts on small holder farmers in Africa and Asia who are heavily reliant on a small number of animals kept as a means of subsistence for milk and draft power purposes. A novel vaccine target, PmSLP-3, has been identified on the surface of hemorrhagic septicemia–associated strains of P. multocida and was previously shown to elicit robust protection in cattle against lethal challenge with a serogroup B strain. Methods: Here, we further investigate the protective efficacy of this surface lipoprotein, including evaluating the immunogenicity and protection upon formulation with a variety of adjuvants in both mice and cattle. Results: PmSLP-3 formulated with Montanide ISA 61 elicited the highest level of serum and mucosal IgG, elicited long-lasting serum antibodies, and was fully protective against serogroup B challenge. Studies were then performed to identify the minimum number of doses required and the needed protein quantity to maintain protection. Duration studies were performed in cattle, demonstrating sustained serum IgG titres for 3 years after two doses of vaccine and full protection against lethal serogroup B challenge at 7 months after a single vaccine dose. Finally, a serogroup E challenge study was performed, demonstrating that PmSLP-3 vaccine can provide protection against challenge by the two serogroups responsible for hemorrhagic septicemia. Conclusion: Together, these data indicate that PmSLP-3 formulated with Montanide ISA 61 is an immunogenic and protective vaccine against hemorrhagic septicemia-causing P. multocida strains in cattle. [ABSTRACT FROM AUTHOR]

P. multocida B: 2 is a Gram-negative, small, non-flagellated, pleomorphic coccobacillus. It does possess different types of outer membrane proteins (OMP’s) which assist in interaction with host cells. The outer membrane protein H (OmpH) of Pasteurella multocida B:2 is a major transmembrane porin that can be used as a subunit vaccine and development of diagnostic kit against hemorrhagic septicemia (HS) because of its immunogenic nature. Pasteurella multocida has economic importance because of endemic and epizootic diseases in domestic and wild animals. This bacterium is an opportunistic pathogen of upper respiratory tracts of wild and domestic animals and birds as well as in livestock . The ompH gene was amplified with in-house designed primers, the amplified gene (1002 bp) was cloned into pET 40-b (+) vector and transformed into E. coli BL21 (DE3) competent cells using heat shock transformation method to get expression. The product size was confirmed by restriction digestion. The rOmpH protein was purified by immobilized metal affinity chromatography by using His-Ni resins to get desired protein and characterized qualitatively by SDS-PAGE by using His antibodies and western blotting. Once purified the immunogenicity of rOmpH was evaluated in BALB/c mice. The expression of recombinant OmpH protein (rOmpH) resulted in its accumulation in cytosol. The purified rOmpH protein had a molecular weight of 36 kDa and concentration around 0.973 mg/mL. The BALB/c mice group injected with 100 ng of purified rOmpH exhibited significant protection (80%) when challenged with LD50 of P. multocida B:2. From the obtained results it is evident that rOmpH can be used as subunit vaccine against P. multocida B:2 and the purified rOmpH can also be further used to develop diagnostic test i.e., ELISA to screen and assess the immune response of cattle and buffaloes against P. multocida B:2 in developing countries like Pakistan. [ABSTRACT FROM AUTHOR]

BackgroundPasteurella multocida is a bacterial pathogen that causes a variety of infections across diverse animal species, with one of the most devastating associated diseases being hemorrhagic septicemia. Outbreaks of hemorrhagic septicemia in cattle and buffaloes are marked by rapid progression and high mortality. These infections have particularly harmful socio-economic impacts on small holder farmers in Africa and Asia who are heavily reliant on a small number of animals kept as a means of subsistence for milk and draft power purposes. A novel vaccine target, PmSLP-3, has been identified on the surface of hemorrhagic septicemia–associated strains of P. multocida and was previously shown to elicit robust protection in cattle against lethal challenge with a serogroup B strain.MethodsHere, we further investigate the protective efficacy of this surface lipoprotein, including evaluating the immunogenicity and protection upon formulation with a variety of adjuvants in both mice and cattle.ResultsPmSLP-3 formulated with Montanide ISA 61 elicited the highest level of serum and mucosal IgG, elicited long-lasting serum antibodies, and was fully protective against serogroup B challenge. Studies were then performed to identify the minimum number of doses required and the needed protein quantity to maintain protection. Duration studies were performed in cattle, demonstrating sustained serum IgG titres for 3 years after two doses of vaccine and full protection against lethal serogroup B challenge at 7 months after a single vaccine dose. Finally, a serogroup E challenge study was performed, demonstrating that PmSLP-3 vaccine can provide protection against challenge by the two serogroups responsible for hemorrhagic septicemia.ConclusionTogether, these data indicate that PmSLP-3 formulated with Montanide ISA 61 is an immunogenic and protective vaccine against hemorrhagic septicemia-causing P. multocida strains in cattle.

Hemorrhagic septicemia (HS) is a highly contagious and fatal disease of cattle and buffaloes caused by P. multocida. Both conventional and molecular methods are applied in parallel for rapid diagnosis of HS outbreaks and the periodical surveillance strategy to identify risk areas for HS is ignored. The current cross-sectional study aimed to estimate sero-prevalence and associated risk factors for HS in cattle and buffaloes in non-vaccinated regions of two Indian states. HS surveillance was carried out through the multi-stage random sampling technique at different strata. The study employed a questionnaire incorporating host factors (species, breed, sex, age, and lactation) and demographic parameters (state, district, block/cluster and village/epiunits, and household). First, two Indian states known for high milk production were selected followed by two districts within each state, subsequently four clusters within each district, finally 5–10 epiunits within clusters and 5–8 households within clusters were randomly selected to collect cattle and buffalo samples. The chi-square/p values and maps were prepared to represent disease prevalence and to correlate disease risk factors at different strata. A total of 692 cattle and buffalo serum samples were sourced from two states of the country (Karnataka-285 and Gujarat-407). In the first strata, antibodies to P. multocida were high in Gujarat (14.49%, CI: 11.22–18.30) compared to Karnataka (3.85%, CI: 1.94–6.80) with significant (p < 0.0001) association between the states. In the second strata, one of the four districts investigated revealed the highest sero-prevalence (18.61%, CI: 13.81–24.24) with statistical significance (p = 0.01) between the districts. Among clusters, one out of eight clusters showed the highest sero-prevalence (23.02%, CI: 16.59–30.54) with statistical significance (p = 0.03) between the clusters in the third strata. At epiunit level (fourth strata), 9 out of 27 epiunits (33.33%) visited in Karnataka and 24 out of 29 epiunits sampled in Gujarat were sero-positive (82.75%) in iELISA. At the household level, out of 306 HH visited, 40 HH had at least one positive animal (13.07%) and the p value between HH in the two states was highly significant (p = 0.0002). Chi-square analysis did not find any association of HS sero-prevalence to species, age, and lactation. However, significantly higher (p < 0.05) sero-prevalence was recorded in indigenous cattle breeds (16.56%) compared to crossbreeds (6.59%). Various immunoprophylactics and antibiotic therapies are effective against HS, but inappropriate disease reporting and failure to implement adequate vaccination control measures are the gaps identified. The present study highlights the current scenario of HS sero-prevalence in two of the high milk-producing states of India, which will be useful for stakeholders for undertaking the implementation of surveillance and control strategies for the regions.

Outer membrane proteins (OMPs) of Pasteurella multocida play an important role in virulence and are important for vaccine development due to immunogenicity. Here, we evaluated immunoprotection in mice, immunized with native OmpH, recombinant OmpH and HS alum precipitated vaccine of P. multocida P52 against P. multocida challenge. Protection studies were performed in mice of groups I (OmpH); II (recombinant OmpH); and III (HS alum precipitated vaccine). Group IV was control group administered with sterile PBS. The protection percentage was recorded as 83.33% protection in Gr. I & III, and 66.66% in Gr. II. The control group (Gr. IV) showed 100% mortality. The mean antibodies titers were detected at day 7, 14, 21 and 28 postimmunization, and compared with the control group. All immunized groups showed significantly high immune protection compared to the control group. [ABSTRACT FROM AUTHOR]

Outer membrane proteins (OMPs), usually found in Gram-negative bacteria, have long been shown to elicit immune responses in infected hosts. This tendency of OMPs to generate immune reactions makes them ideal candidates for vaccine development against pathogenic bacteria. Pasteurella multocida is a Gram-negative pathogen responsible for the economically significant veterinary disease, hemorrhagic septicemia (HS). HS is an endemic and highly fatal disease affecting buffaloes and cattle. In Malaysia, outbreaks of this disease cost about half a million USD each year. Thus, despite current treatment and prevention measures, HS is a prevalent issue that needs to be overcome. Pasteurella multocida subsp. multocida PMTB2.1, a Malaysian strain of the pathogen, has recently had its entire genome sequenced after being isolated from HS outbreaks in the region. Antigenic OMPs from this strain have since been identified and published for further characterisation. LptD, Wza, and TbpA are integral membrane proteins, while Pal is a peripheral membrane protein that has not been characterised in-depth. This study, therefore, aims to analyse these OMPs through in silico methods. First, protein homology modelling was performed using SWISS-MODEL, whereafter, the structures generated were validated using the SWISS-MODEL structure assessment page, PROCHECK, ERRAT, and PROSA programs. The Pal, Wza, and TbpA structures were good models, while the LptD structure was found to be a near-good model based on the validation performed. Analyses using BCPREDS, NetMHCpan4.1, and NetBoLAIIpan1.0 revealed that these four OMPs could potentially elicit humoral and cellular immune responses. [ABSTRACT FROM AUTHOR]

Pasturella multocida (P. multocida) , a gram-negative bacterium, has long been a focus of interest in animal health because of its capacity to cause different infections, including hemorrhagic septicemia. Yaks, primarily found in high-altitude environments, are among the several livestock animals affected by these bacteria. Yaks are essential to the socioeconomic life of the people who depend on them since they are adapted to the cold and hypoxic conditions of highland environments. Nevertheless, these terrains exhibit a greater incidence of P. multocida despite the severe environmental complications. This predominance has been linked to the possible attenuation of the yak's immunological responses in such circumstances and the evolution of some bacterial strains to favor survival in the respiratory passages of the animals. Moreover, these particular strains threaten other cattle populations that interact with yaks, which might result in unanticipated outbreaks in areas previously thought to be low risk. Considering these findings, designing and executing preventative and control strategies suited explicitly for these distinct biological environments is imperative. Through such strategies, yaks' health will be guaranteed, and a larger bovine population will be safeguarded against unanticipated epidemics. The current review provides thorough insights that were previously dispersed among several investigations. Its distinct method of connecting the ecology of yaks with the dynamics of infection offers substantial background information for further studies and livestock management plans. [Display omitted] • P. multocida threatens yak health in high-altitude areas due to weakened immune responses. • Unique strains of the bacterium adapt to yak respiratory passages, posing risks to other cattle. • Environmental factors exacerbate P. multocida prevalence despite harsh conditions. [ABSTRACT FROM AUTHOR]

The present study was conducted to determine the antibacterial resistance profile of Aeromonas hydrophila (n = 42) isolated from the 100 hemorrhagic septicemia‐suspected carp in Gilan, Iran. The prevalence of class 1 and 2 integrons, antibiotic resistance genes (ARG) and virulence factor genes (VFG) among these isolates was investigated using PCR. Also, the possible association between the presence of VFGs and the antibiotic resistance profile of isolates was assessed. The majority of A. hydrophila isolates (83·33%) exhibited multi‐drug resistance (MDR) profile, and all isolates were resistant to clindamycin, while all isolates were susceptible to amikacin. intI1 and intI2 gene was found in 26·2 and 4·8% isolates, respectively. This is the first report of the presence of the intI2 gene in A. hydrophila isolates in Iran. The blaTEM (40·5%) and tetA (33·3%) genes were found as the predominant ARGs. The most frequently detected VFGs were lip and ahh1(90·5%), while the examined isolates carrying at least three VFGs and the most prevalent VFGs profile was ast+, act+, alt+, ahhl+, aerA+, ahyB+ and lip+. The results of this study indicate a positive association between the presence of VFGs and antibiotic resistance, and most MDR A. hydrophila isolates showed high frequencies of VFGs. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the concurrent infection of Pasteurella multocida (P. multocida) type B:2, which causes Hemorrhagic Septicemia (HS), with cases of Foot and Mouth Disease (FMD) outbreaks in cattle in Bangladesh between March and December 2023. Samples were collected from 11 distinct outbreak areas, totaling 102 samples. These included 54 FMD samples (saliva, tissue epithelium, and morbid tissues such as lung, spleen, and heart) and 54 HS samples (nasal swabs and morbid tissues) from 50 cattle of various ages and sexes, all showing clinical signs of suspected concurrent HS and FMD infection. After sample processing, molecular detection of FMDV and its serotypes was performed using Reverse Transcriptase PCR (RT-PCR) with universal and serotype-specific primers. The HS-causing agent, P. multocida type B:2, was initially identified through cultural and morphological characteristics on various media, followed by Gram's and methylene blue staining, biochemical tests, and pathogenicity tests through inoculation of isolates into mice. Finally, molecular detection of P. multocida type B:2 was confirmed using PCR with specific primers. Forty-five (83 %) of the 54 FMD suspected samples tested positive for FMDV, with 53 % of these positive for serotype 'O,' 17 % for serotype 'A,' and 6 % for mixed serotypes 'O' and 'A.' Among the FMDV-positive samples, 17 (38 %) of the HS-suspected samples tested positive for concurrent infection with P. multocida type B:2. The study reveals that FMDV-induced acute immunosuppression in cattle can lead to complications from concurrent infections, particularly those caused by P. multocida type B:2, resulting in HS alongside FMD., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Ltd.)

Hemorrhagic septicemia (pasteurellosis) in animals, caused by Pasteurella multocida Trevisan 1887, is a significant but previously undocumented disease in Mongolian camels. Pasteurella multocida , a small Gram-negative coccobacillus, typically exists commensal in the nasopharynx of camels but can cause severe illness under certain environmental stressors. This study reports the first case of cameline hemorrhagic septicemia in Gobi region of Mongolia, specifically in Umnugobi province, where acute septicemia affected 26 camels, resulting in 10 deaths within 24-48 hours. Clinical signs included depression, inappetence, lethargy, increased rectal temperature, and paralysis of the lower lip. Surviving camels responded to treatment with Lactate Ringer solution and antibiotics. Postmortem examinations revealed acute pulmonary congestion and necrotic liver. Molecular diagnostic test, PCR, confirmed the presence of P. multocida with the identification of the KMT1 gene. This case underscores the potential for significant economic losses due to hemorrhagic septicemia in camels and highlights the need for early detection and treatment to mitigate its impact. The initial attempt at implementing a vaccination program effectively controlled the potential further outbreak. This study emphasizes the importance of continuous surveillance and preventive measures in managing hemorrhagic septicemia in livestock., Competing Interests: Conflict of interests: The authors declare no conflicts of interest.

Diseases represent a serious setback in cultured fish by directly affecting production and causing serious economic losses. Early detection and precise identification of pathogens by polymerase chain reaction (PCR) can help in the selection of preventive and early treatment measures and reduce the losses. In this study, a multiplex PCR assay was demonstrated for simultaneous detection of Edwardsiella tarda and Aeromonas hydrophila. The primer pairs of the major fimbrial subunit (etfA) gene from type I fimbrial gene cluster of E. tarda (415 bp) and cytotoxic enterotoxin (act) gene of A. hydrophila (232 bp) were selected as targets. The multiplex PCR using the target genes simultaneously detected E. tarda and A. hydrophila in different organs (muscle, spleen, liver, and head kidney) of challenged Pangasius pangasius. This method was also capable of simultaneously detecting E. tarda and A. hydrophila in naturally infected catfish, thus indicating mixed bacterial infection in 37.50 % of the diseased population. The results suggested the usefulness of etfA and act genes for the rapid detection of mixed A. hydrophila and E. tarda infection in diseased catfish, irrespective of species. The multiplex PCR method can be useful in commercial aquaculture for performing routine disease diagnosis and detection of these bacterial pathogens. [ABSTRACT FROM AUTHOR]

Aeromonas hydrophila is a bacterium associated with many diseases and disorders such as fin rot, skin ulcers and lethal hemorrhagic septicemia in fish. It bears several virulence factors including type III secretion system (T3SS), aerolysin, cytolytic enterotoxin and enzymes (e.g., hemolysins, lipase) that seem to play an important role in its pathogenesis. Detection of virulence markers by polymerase chain reaction (PCR) is a key procedure in defining the pathogenic ability of pathogenic bacteria and preparing a vaccine for its treatment. In this sense, this study was aimed to determine the frequency of virulence genes in isolates obtained from infected cultured carps in Khuzestan province. Out of 200 moribund carps with septicemic symptoms, 125 isolates were belonged to the motile aeromonads and 59 isolates were identified as A. hydrophila by biochemical methods. Finally, using PCR analysis, 31 isolates were identified as A. hydrophila. Five virulence genes were detected in these isolates including hemolysin, aerolysin, cytolytic enterotoxin and T3SS (aopB and ascV) by specific primers. Results showed that 23 (74.19%), 18 (58.06%), 16 (51.61%), 13 (41.63%) and 10 (32.25%) isolates possessed cytolytic enterotoxin, hemolysin, aerolysin, and T3SS genes, respectively. The results of the present study showed that among 31 isolates, only five isolates had all of dominant virulence genes. Thirteen other isolates had genotypes including hlyA+, aerA+, and act+. The remaining isolates had at least one virulence gene. This study showed that determination of the virulence genes by PCR can be a reliable method to identify a potential pathogenic Aeromonad strain. [ABSTRACT FROM AUTHOR]

Pasteurella multocida causes hemorrhagic septicemia (HS), an acute, often fatal, septicaemic disease in ruminants. It is commonly observed in the world's tropical regions, especially in Asian and African countries. In the present study, eleven blackbucks (Antilope cervicapra) were diagnosed positive for hemorrhagic septicemia by using Leishman stain of blood smear showing bipolar organisms. The blackbucks were treated with bolus sulphadimidine @ 5 gm, powder uniselit @ 5 gm and liquid ostovet @ 25 mL per animal/day for seven days and after that bolus sulphadimidine @ 2.5 gm was given for the next three days. Following treatment eight blackbucks recovered and became normal. A post-mortem examination was performed on three blackbucks one died on first day and two blackbucks on the third day, which confirmed the changes typical of HS in lungs, liver and kidneys. [ABSTRACT FROM AUTHOR]

Hemorrhagic septicemia (HS) caused by Pasteurella multocida B:2 and E:2 is among the fatal bacterial diseases in cattle and buffaloes that are economically valuable in Asian and African countries. The current work aims to study the prevalence of HS among buffaloes, cattle, sheep, and goats in 41 countries in 2005–2019. The data analysis revealed that 74.4% of the total infection rate in the world was distributed among cattle, followed by buffaloes (13.1%). The mortality of HS among cattle and buffaloes increased in 2017–2019 compared to the period between 2014 and 2016. The best measure to control the disease is through vaccination programs. Current commercial vaccines, including live-attenuated vaccines and inactivated vaccines, have some shortcomings and undesirable effects. Virus-like particles (VLPs) have more potential as a vaccine platform due to their unique properties to enhance immune response and the ability to use them as a platform for foreign antigens against infectious diseases. VLPs-based vaccines are among the new-generation subunit vaccine approaches that have been licensed for the human and veterinary fields. However, most studies are still in the late stages of vaccine evaluation.

The global ornamental fish trade carries important risk factors for spreading pathogens between different countries and regions, not only for ornamental fish but also for cultured fish and even other animal species. In the current study, we reported the capacity of Aeromonas veronii and A. hydrophila isolated from ornamental fish to experimentally infect the reared Amazonian fish Colossoma macropomum. For this, those bacteria were identified, and a primary characterization was performed. Fish were inoculated with 0.1 mL of increasing concentrations of A. hydrophila or A. veronii (C1 = 1 × 102; C2 = 1.8 × 104; C3 = 2.1 × 106; C4 = 2.4 × 108 bacterial cells per mL) in the coelomic cavity. In the control group, fish received the same volume of sterile saline solution (0.9 %). Fish presented petechiae, skin suffusions, and mortality rates up to 100 % according to the inoculum concentration. Histopathologically, fish presented necrosis with karyolysis, loss of the cytoplasmic delimitation of cells of the renal tubules and hepatocytes, hemorrhage, cellular edema, and the presence of bacterial cells. The LD 50–96h of A. veronii on C. macropomum was estimated at 2.4 × 106 CFU mL−1 and of A. hydrophila at 1.408 × 105 CFU mL−1. The results demonstrated that it is possible that Aeromonas species isolated from ornamental fish affect C. macropomum, causing similar clinical signs and lesions. This shows the importance of promoting risk control measures worldwide regarding the trade of ornamental fish. • Aeromonas species from ornamental fish can infect Colossoma macropomum, the most produced Amazonian fish species. • The mortality rate can reach up to 100 % when C. macropomum is experimentally infected with A. hydrophila or A. veronii. • Ornamental fish trade is a major risk factor for disease transmission in aquaculture. [ABSTRACT FROM AUTHOR]

Aeromonas hydrophila is a freshwater, facultatively anaerobic, chemo-organoheterotrophic bacterium that distressed fishes with gastroenteritis, septicemia and causes a disease known as Motile Aeromonas Septicemia (MAS), which affects the aquatic environment. Haemolysin, aerolysin, cytosine, gelatinase, enterotoxin and antimicrobial peptides have been identified as virulence factors in A. hydrophila . Medicinal herbs/plants and their uses are the instant, easily available, cost-effective, efficient and eco-friendly approach for socio-economic, sustainable development of modern aquaculture practice. Phytotherapy either through a dip or by incorporation into the diets is an alternative approach to synthetic pharmaceuticals to diminish the pathogenicity of aquatic environmental pathogens. Due to the presence of remarkable phytoconstituents like flavonoids, alkaloids, pigments, terpenoids, steroids and essential oils, the medicinal plant exhibits anti-microbial, appetite-stimulating, anti-stress, growth-promoting and immunostimulatory activities. Aqua-industry preferred phytotherapy-based techniques/compounds to develop resistance against a variety of aquatic pathogens in culturable fishes because they are inexpensive and environment-friendly. As a result, this review elaborates on the diverse applications of phytotherapy as a promising tool for disease management in aquaculture and a major step toward organic aquaculture., Competing Interests: The authors declare no conflict of interest., (© 2023 The Authors.)

The present study was conducted to assess the protective efficacy of a trivalent oral vaccine containing chitosan-PLGA encapsulated inactivated viral haemorrhagic septicemia virus (VHSV), Streptococcus parauberis serotype I and Miamiensis avidus antigens, followed by its oral (incorporated in feed) administration to olive flounder (Paralichthys olivaceus) fingerlings for a period of 15-consecutive days. After 35 days of initial vaccination, three separate challenge studies were conducted at the optimal temperature of the targeted pathogens using an intraperitoneal injection route. RPS analysis revealed moderate protection in the immunized group against all the three pathogens viz., VHSV (53.30% RPS), S. parauberis serotype-I (33.30% RPS), and M. avidus (66.75% RPS), as compared to the respective non-vaccinated challenge (NVC) control group. In addition, the immunized fish demonstrated significantly (p < 0.05) higher specific antibody titres in serum and significant (p < 0.05) upregulation in the transcript levels of immune genes of Igs (IgM, IgT, pIgR), TLRs (TLR 2, TLR 7), cytokines (IL-1β, IL-8) and complement pathway (C3) in the mucosal and systemic tissues than those of NVC control fish, suggesting orchestration of pathogen-specific host immune responses thereby favouring its combativeness against the three pathogens. The expression dynamics of IFN-γ, Mx, caspase 3 genes post VHSV challenge; IFN-γ, TLR 2, caspase 1 genes post S. parauberis serotype I challenge and CD-8α, IL-10, TNF-α genes post M. avidus challenge further substantiates the efficacy of the vaccine in stimulating antiviral, antibacterial and antiparasitic immune responses in the host resulting in their better survival. The findings from the present study reflect that the formulated trivalent oral vaccine incorporating VHSV, S. parauberis serotype I and M. avidus antigens can be a promising prophylactic strategy to prevent the associated disease outbreaks in olive flounder., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Viral diseases of fish cause significant economic losses in the aquaculture industry. Viral haemorrhagic septicemia virus (VHSV) is one of the most important viral diseases that affects more than 80 fish species. Detection of the disease, especially in the field, is critical to managing disease prevention and control programmes. Recombinase polymerase amplification (RPA) is an isothermal method with a very short amplification period and a single incubation temperature ranging from 37 to 42°C, which is a good alternative to the polymerase chain reaction (PCR). This study aimed to develop an RPA assay as sensitive as a real-time RT-PCR to detect VHSV. For this purpose, primers and probes are designed for the same targeted region of gG of VHSV. The ssRNA standards were prepared to find the detection limits of the assay. Detection limits were found ten-fold differences between real-time RT-PCR and real-time RT-RPA. While the detection limit of the RT-PCR was found as 95.5 viral RNA molecules/reaction in 95% probit value, the detection limit of RT-RPA was found as 943.75 viral RNA molecules/reaction in 95% probit value using ssRNA standards. These results show that RPA is a suitable test for VHSV Ie detection., (© 2022 John Wiley & Sons Ltd.)

Hemorrhagic septicemia (HS) caused by Pasteurella multocida B:2 and E:2 is among the fatal bacterial diseases in cattle and buffaloes that are economically valuable in Asian and African countries. The current work aims to study the prevalence of HS among buffaloes, cattle, sheep, and goats in 41 countries in 2005–2019. The data analysis revealed that 74.4% of the total infection rate in the world was distributed among cattle, followed by buffaloes (13.1%). The mortality of HS among cattle and buffaloes increased in 2017–2019 compared to the period between 2014 and 2016. The best measure to control the disease is through vaccination programs. Current commercial vaccines, including live-attenuated vaccines and inactivated vaccines, have some shortcomings and undesirable effects. Virus-like particles (VLPs) have more potential as a vaccine platform due to their unique properties to enhance immune response and the ability to use them as a platform for foreign antigens against infectious diseases. VLPs-based vaccines are among the new-generation subunit vaccine approaches that have been licensed for the human and veterinary fields. However, most studies are still in the late stages of vaccine evaluation. [ABSTRACT FROM AUTHOR]

The profitability of the olive flounder (Paralichthys olivaceus) aquaculture industry in Korea depends on high production and maintenance of flesh quality, as consumers prefer to eat raw flounders from aquaria and relish the raw muscles as 'sashimi'. For sustaining high production, easy-to-deliver and efficient vaccination strategies against serious pathogens, such as viral hemorrhagic septicemia virus (VHSV), is very important as it cause considerable losses to the industry. Whereas, a safe and non-invasive vaccine formulation that is free from unacceptable side-effects and does not devalue the fish is needed to maintain flesh quality. We previously developed a squalene-aluminium hydroxide (Sq + Al) adjuvanted VHSV vaccine that conferred moderate to high protection in flounder, without causing any side effects when administered through the intraperitoneal (IP) injection route. However, farmers often demand intramuscular (IM) injection vaccines as they are relatively easy to administer in small fishes. Therefore, we administered the developed vaccine via IP and IM routes and investigated the safety and persistency of the vaccine at the injection site. In addition, we conducted a comparative analysis of vaccine efficacy and serum antibody response. The clinical and histological observation of the IM and IP groups showed that our vaccine remained persistence at the injection sites for 10-17 weeks post vaccination (wpv), without causing any adverse effects to the fish. The relative percentage of survival were 100% and 71.4% for the IP group and 88.9% and 92.3% for the IM group at 3 and 17 wpv, respectively. Thus, considering the persistency period (24 wpv) and both short and long-term efficacy of our vaccine, the present study offers an option to flounder farmers in selecting either IM or IP delivery strategy according to their cultured fish size and harvesting schedule - IM vaccination for small-sized fish and IP vaccination for table-sized fish., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier Ltd. All rights reserved.)