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Epizootic ulcerative syndrome is one of the most serious infections noticed in the finfish of Asia-Pacific during the last three decades. Different viral agents and a consistent fungus were isolated from the EUS infected fishes from various countries. Rhabdoviruses are by far the most isolated group of viruses followed by birnaviruses. One reovirus...
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... Among the various diseases, Epizootic Ulcerative Syndrome (EUS) is a disease affecting a wide range of wild and farmed freshwater and estuarine fish [13] which has spread across south-east Asia, India and later to Pakistan and Africa [14]. Pathological survey of skin ulcers revealed that the microbe associated is Aphanomyces [15]. ...
... John and George [14] reported that snakeheads were the most seriously affected species eventhough species like Puntius clarias, Indian major carps, Anabas, Mugil, Glossogobius, Spiny eel, Swamp eel and Gouramis were also affected. These results are in line with the observations noticed in the present study. ...
Fishes form an important source of cheap protein for people of many countries. The majority of the global production comes from freshwater aquaculture (58%) followed by marine (36%) and brackish water (6%). With an average increase in aquaculture production of 11% during the last decade, aquaculture has become the fastest growing sector of the world food economy However, fish diseases is now posing a great threat to achieve maximum production and has become a limiting factor to the success of aquaculture. Among the various diseases, Epizootic Ulcerative Syndrome (EUS) is a disease affecting a wide range of wild and farmed freshwater and estuarine fish which has spread across south-east Asia and India. From the fish survey, Food Fishes were collected from the Arasalar estuary, Puducherry State, India. The fish caught were identified and average 200 species of each fish were examined for EUS (Epizootic ulcerative syndrome) infection for the four seasons of the year (Pre-summer, Summer, Post-summer and Rainy season). The results of the number of fishes with EUS that could be identified in the different seasons are reported. Of the 75 fishes, that were examined, 12 were affected with EUS. This shows that 16% of the fishes were subjected to infection. Among Lizaparsia, 11 species were infected representing 14.6% of infection and among Mystus, seven fishes were infected forming 9.3% of infection. With regard to Oreochromis mossambicus, only four species were infected forming 5.3% of infection. With regard to Glossogobius giuris, nine species were infected thus 12% of infection. Nevertheless, during this period, the range of infection ranged from nil to 16%. During the pre-summer season, the percentage of infection again ranged from nil but to 12%. The maximum infection was noticed in Liza parsia (9 fishes) representing 12% infection, Puntius filamentosus (8 fishes) recording 10.6% followed by Glossogobius and Mystus (8%) and Oreochromis mossambicus (1.33%) infection respectively. During the summer and the post-summer season, none of the fishes that were investigated recorded any signs of EUS. Thus, an overall comparison reveals that the highest percentage of EUS was recorded in the rainy season followed by the pre-summer season and least in summer and post-summer season.
... Obviously, the intensive culture of snakehead has resulted in a severe impact on water quality that consequently caused an increase in the severity and frequency of fish diseases such as severe ulcerative disease (John & George, 2012;Kasornchandra et al., 1992), hemorrhagic disease, and internal white spot disease . The typical symptoms of "white spots disease" are severe multiple white nodules scattered throughout the spleen, liver, and kidney, which cause rapid morbidity and high mortality, reaching levels of approximately 45%, resulting in serious economic loss, which jeopardizes the development of snakehead aquaculture (Liu et al., 2019;. ...
Snakehead, Channa striata, has a long history of invasion and associated negative impacts on the biodiversity of native aquatic organisms in the Mekong Delta. However, internal white spot disease caused by Aeromonas schubertii has a massive effect on the production of snakehead fish but also can spread to wild populations and to consumers. The aim of the study was to investigate the prevalence of multi‐antibiotic resistance (MAR) of A. schubertii isolated from snakehead fish cultured in several Mekong Delta fish farms, as well as its potential to spread throughout the infection season. Based on morphological and biochemical tests, as well as phylogenetic analysis of three housekeeping genes (16S rRNA, gyrB, and rpoD), isolates recovered from white nodules were strongly identified as A. schubertii. The antibiotic susceptibility testing revealed that all of the isolates (n = 25) were phenotypically multidrug‐resistant, with resistance to erythromycin (84%), rifampicin (84%), flumequine (88%), amoxicillin (96%), ciprofloxacin (92%), and florfenicol (92%). The multiple antibiotic resistance indices ranged from 0.33 to 0.92, with A. schubertii isolate As28 being resistant against 11 out of the 12 tested antibiotics. In particular, 15 MAR phenotypes (MARPs) were found in 25 isolates with 8 isolates (32%) commonly displaying MAR phenotypes against patterns of Ery–Rif–Flq–Aml–Cip–Flo, and four isolates (16%) expressing patterns of Ery–Rif–Nov–Flq–Aml–Cip–Flo. A hierarchical clustering analysis of their antibiotic‐resistant bacteria may indicate cross‐invasion between ponds/fish farms and its ability to survive in aquatic environments for long periods (at least 3 months). Our results suggest that the diversity of MARPs bacteria in snakehead represents a potential hazard to modifying the composition of native aquatic organisms, especially to consumers. To successfully manage C. striata in the future, several eco‐friendly techniques should be used to restrict the spread of A. schubertii inside the invaded habitat of the Mekong Delta river.
... Fish rhabdoviruses generally show tissue tropism to kidney, spleen, and brain while liver, heart, and gill are also found to be the multiplication sites albeit with low titers [80]. Rhabdoviruses were isolated from infected snakeheads (Ophicephalus striatus) from various Southeast Asian countries such as Thailand, Myanmar (Burma), and Philippines in 1980s and also from other epizootic ulcerative syndrome (EUS)-infected fishes [81][82][83]. Striped snakehead skin ulcerative disease reported in striped snakehead in Burma and Thailand caused large, deep ulcerations of the skin on the head and body of fish [82,84]. Infected fish show signs of lethargy leading to mortality within 1 week [79]. ...
Aquaculture, being the fastest growing food production sector, has now become vital to the socioeconomic development of many countries. In India, aquaculture plays a significant role in food production, ensuring nutritional security, boosting agricultural exports, and generating job opportunities. The production of farmed fish has greatly expanded qualitatively and quantitatively in both freshwater and marine water regimes to fulfill the ever-growing demand. However, the occurrence of diseases is the main obstacle to sustainable aquaculture production, which has an impact on the socioeconomic status of fish farmers of the country. Viral diseases inflict irreparable damage to the aquaculture enterprise causing large-scale economic losses and ecological problems. Recently, there has been a spike in the incidence of new emerging viral diseases in diverse species of aquaculture species. Prophylactics by far being the only feasible method of viral disease control, the development of viral vaccines is highly imperative. A precise understanding of the disease pathology, etiological agent, and species susceptible to the specific diseases are highly essential in this perspective. The chapter highlights the emerging and reemerging viral diseases in the Indian aquaculture sector.
... Possible diseases diagnosis on the basis of clinical symptoms. As per clinical signs and farmer's interrogations, we observed mainly possible chances of Epizootic ulcerative syndrome (EUS), Dropsy, Tail and fin rot disease, Saprolegniasis and Cotton wool diseases in climbing perch (Kawai) on mostly RAS farms except on 2 RAS sites where no infectious symptoms reported due to optimum stocking density practices as per our analysis (Table 5) (Kumar et al., 2022;Sergaliyev et al., 2017;John & George 2012;Robert et al., 2003). rate of mortality due to (below 8000 fishes per 50000 litre tanks) optimum stocking densities (Table 5). ...
Recirculatory aquaculture system (RAS) provides appropriate water quality parameters and a pathogen free environment during the culture period because productive growth of fish depends on various factors like: water quality, pathogen free environment, stocking density and seed quality etc. Sometimes, disease outbreaks in RAS reveal the favourable conditions of pathogens which lead into a higher rate of mortality in this super intensive system where water exchange is limited. Pathogenic infection in RAS causes mass mortality once it comes out. In this concern, our surveillance is aimed to identify the climbing perch common symptomatic disease outbreaks in RAS of Haryana state. During 2021-2022 survey we examined randomly total 14 RAS of distinct districts in Haryana and on each site we collected 20-40 symptomatic infected pieces of Climbing Perch (Anabas testudineus). As per farmer interrogation we observed that dispersion of fish infection varies with stocking densities. RAS farmers with high stocking densities (10000-25000/50000 litre tanks) in our surveillance got various pathogenic infections in their stock as compare to optimum stocking density farms (3000-8000/50000 litre tanks) respectively. Tail and fin rot, red spot and white cotton like growth on body were the most common symptomatic infections in climbing perch under RAS systems of Haryana. This survey on distinct RAS farms of Haryana also highlighted the most common treatment measures that a farmer adopted to get rid from these mortal diseases.
... Possible diseases diagnosis on the basis of clinical symptoms. As per clinical signs and farmer's interrogations, we observed mainly possible chances of Epizootic ulcerative syndrome (EUS), Dropsy, Tail and fin rot disease, Saprolegniasis and Cotton wool diseases in climbing perch (Kawai) on mostly RAS farms except on 2 RAS sites where no infectious symptoms reported due to optimum stocking density practices as per our analysis (Table 5) (Kumar et al., 2022;Sergaliyev et al., 2017;John & George 2012;Robert et al., 2003). rate of mortality due to (below 8000 fishes per 50000 litre tanks) optimum stocking densities (Table 5). ...
Recirculatory aquaculture system (RAS) provides appropriate water quality parameters and a pathogen free environment during the culture period because productive growth of fish depends on various factors like: water quality, pathogen free environment, stocking density and seed quality etc. Sometimes, disease outbreaks in RAS reveal the favourable conditions of pathogens which lead into a higher rate of mortality in this super intensive system where water exchange is limited. Pathogenic infection in RAS causes mass mortality once it comes out. In this concern, our surveillance is aimed to identify the climbing perch common symptomatic disease outbreaks in RAS of Haryana state. During 2021-2022 survey we examined randomly total 14 RAS of distinct districts in Haryana and on each site we collected 20-40 symptomatic infected pieces of Climbing Perch (Anabas testudineus). As per farmer interrogation we observed that dispersion of fish infection varies with stocking densities. RAS farmers with high stocking densities (10000-25000/50000 litre tanks) in our surveillance got various pathogenic infections in their stock as compare to optimum stocking density farms (3000-8000/50000 litre tanks) respectively. Tail and fin rot, red spot and white cotton like growth on body were the most common symptomatic infections in climbing perch under RAS systems of Haryana. This survey on distinct RAS farms of Haryana also highlighted the most common treatment measures that a farmer adopted to get rid from these mortal diseases.
... Các loài Vibrio chính gây bệnh lở loét ở cá trên thế giới bao gồm V. harveyi, V. parahaemolyticus, V. alginolyticus, V. anguillarum, V. vulnificus [1]. Căn bệnh này liên quan đến hơn 100 loài cá [7]. Chúng gây bệnh bằng cách sản sinh ra các độc tố hay nội độc tố với lượng lớn. ...
In this study, we have successfully cloned and expressed the trh gene encoding for a thermostable
direct hemolysin-related hemolysin of Vibrio parahaemolyticus, which caused ulcer disease in snapper
(Sciaenops ocellatus) raising in coastal areas of Thua Thien-Hue province. The full-length of trh gene
was 462 bp (including start codon ATG and termination codon TGA). Similarity level of this gene
sequence was 100% compared to the trh gene sequence published on the GenBank (accession
number KP836471.1). The trh gene created an entire polypeptide sequence consisting of 154 amino
acids and its similarity level was 100% compared to the polypeptide chain published on the GenBank
(accession number ALZ44850). The result of analyzing SDS electrophoresis showed that 6xHis-TRH
fusion protein had a molecular weight of approximately 21 kDa (including 3.7 kDa of 6xHis fusion tail).
... Tolerance to high stocking densities, rapid growth rate and the ability to withstand wider water quality fluctuations make murrels one of the potential candidate species for freshwater aquaculture. Although the fish is comparatively resistant to infectious diseases, occasional mortalities do occur due to fungal, bacterial and viral aetiological agents (Puttinaowarat et al., 2002;John and George, 2012). ...
... Rhabdoviruses were isolated from infected snakeheads from Thailand, Myanmar (Burma) and Philippines in 1980s and later from separate instances of epizootic ulcerative syndrome (EUS) (Frerichs et al., 1986;Ahne et al., 1988;John and George, 2012). Complete genome sequence of one of the rhabdoviruses isolated and characterised from snakehead, snakehead rhabdovirus (SHRV) (Wattanavijarn et al., 1986;Kasornchandra et al., 1992), is currently available (GenBank Accession no. ...
... Though the primary aetiological role has not been fully established in fishes suffering from severe surface ulcerations in Southeast Asia, rhabdoviruses are the main group of viral agents that were isolated from these fishes (John and George, 2012). In the present investigation of the fish mortality associated with skin lesions, extensive deep ulcerations similar to those observed in EUS were not noticed. ...
A novel viral agent was isolated from striped snakehead (Channa striata Bloch, 1793) suffering from mortality with dermal ulcerations and haemorrhagic areas in South India. The virus growth was well supported in striped snakehead (SSN-1) and sea bass caudal peduncle (SBCP2a) cell lines at 27 °C while EPC cells were refractory to the virus. Transmission electron microscopy of the infected cells revealed bullet shaped virions with the size ranging from 150 to190 nm length and 46 to 60 nm width. RT-PCR targeting block III fragment of the rhabdovirus L polymerase gene amplified an expected genomic portion of 483 bp. Phylogenetic analysis indicated 91% homology to the equivalent region of the reported snakehead rhabdovirus L polymerase. Experimental infection studies using cell culture grown virus induced 100% morality in juvenile snakehead in five days. Fish showed listlessness, neural pathology and lethargy before dying. Clinical signs included haemorrhages at the fin bases, exophthalmia, darkening of the skin, vascular congestion around the eyes and reddish iris and surface ulcers. The virus caused extensive necrosis of kidney, spleen and liver. The clinical pathology along with the morphology and phylogenetic homogeneity indicates that the virus belongs to the genus Novirhabdovirus under the family Rhabdoviridae. The present study forms the first report of isolation of a fish rhabdovirus in India.
... Since its first report from Japan, the disease was more recently observed in several southern African countries (Iberahim, Trusch and van West 2018). Although pathogenic viruses, bacteria, fungi and protozoan and metazoan parasites are routinely co-isolated from EUS-affected fishes, there is no evidence that these other pathogens causally contribute to the disease (John and George 2012;Kamilya, Dibyendu and Baruah 2014). Nor are we aware of any more recent evidence that Pfiesteria piscicida or Pseudopfiesteria shumwayae play any role in the pathogenesis of this infectious disease, as claimed in the past. ...
In the 1990's the estuarine dinoflagellate Pfiesteria piscicida came under intense scientific scrutiny and garnered widespread media and public attention, as it was blamed for causing dramatic finfish kills and human health effects in coastal North Carolina and Chesapeake Bay. Universities, marine science institutions and state agencies in the region focused on environmental and human health, quickly turned their attention to research on, and monitoring of, this organism and its' perceived adverse health impacts. Federal and state funding quickly became available to support these efforts and resulted in rapid scientific advances, but also troubling controversies regarding interpretation of data. Researchers soon realized that morphologically similar dinoflagellates, now known as Pfiesteria-like dinoflagellates (PLDs), were initially counted as Pfiesteria cells, often co-occurred at fish kill events, and that this resulted in early Pfiesteria cell counts at fish kills likely being significantly inflated. Further, although P. piscicida might be observed in a water sample collected from a fish kill event, it was often found at low abundance or was absent. Other PLDs, most notably Karlodinium veneficum, were subsequently found at high abundance in samples from several mortality events in Maryland waters of Chesapeake Bay. Additionally, the complex multi-stage life cycle of P. piscicida, initially reported to involve several amoebae and chrysophyte-like cyst stages, came under intense * Corresponding Author's Email: kreece@vims.edu. Kimberly S. Reece, R. Wayne Litaker, Allen R. Place et al. 304 scrutiny. The life cycle was ultimately shown to be simpler; lacking amoebae and chysophyte-like cyst stages and typical of other dinoflagellate species. However, the longest-standing and most troubling controversy surrounded the possible production of a toxin by P. piscicida and Pseudopfiesteria shumwayae, and the role that toxin played in adverse human health effects and as a cause of finfish mortalities and ulcerous lesions often observed on fish during kill events. The causes of the fish kill events in North Carolina estuaries during the late 1990's have never been identified, however, the deeply penetrating ulcers in menhaden, Brevoortia tyrannus, at the time attributed to Pfiesteria toxin, are now known to be caused by a highly pathogenic water mold called Aphanomyces invadans. Pfiesteria has been clearly shown capable of killing fish in a captive environment from which the fish cannot escape, however, the mechanism of pathogenicity has been shown not to be due to toxin but to the micropredatory feeding activity (myzocytosis), which at abnormally high cell concentrations results in disruption and loss of the fish epidermis and ultimately, loss of osmoregulatory ability and death. To date, the full structure of a Pfiesteria toxin remains unresolved and no adverse human health impacts from contact with coastal waters where Pfiesteria occurs have been confirmed, despite an extensive multistate study conducted by the Centers for Disease Control and Prevention. It also has been demonstrated that Pfiesteria has a simple dinoflagellate life cycle lacking amoeboid or chrysophyte stages and does not cause fish lesions or kill fish by means of a toxin. The history of the events, controversies, research and current status surrounding the Pfiesteria story will be reviewed in this chapter.
... In the aquatic environment, fish are in constant interaction with a wide range of pathogenic and nonpathogenic environmental microorganisms (Subramanian et al., 2007). Many diseases are being reported to cause mortality in snakeheads and epizootic ulcerative syndrome (EUS) is one of the most devastating diseases reported till date (John and George, 2012). Among snakeheads, the effect of EUS is more in C. striata compared to other species of the genus Channa (Frerichs et al., 1989). ...
Co-infections in fish by the wide array of pathogens have been little researched, although such infections are commonly noticed in nature. A murrel farm recorded 100% mortality in adults of Channa striata within 3-4 days of infection during winter. The clinical signs included cloudy eyes, excess mucus secretion, haemorrhages on the body, lethargy and anorexia before mortality. Heavy infection with Ichthyophthirius multifiliis on the body surface and Zschokkella auratis, a new myxosporean to this country, in the brain tissue were detected by wet mount microscopy and 18s rDNA sequencing, respectively. Histological sections of the brain also demonstrated the presence of myxosporean cyst. Examination of eye fluid and eye tissue revealed the presence of bacterium Acinetobacter baumannii and blood samples containing Aeromonas sobria and Klebsiella pneumoniae were detected species-specific PCRs for 16s rDNA followed by sequencing. Interestingly, samples collected from infected fishes also revealed multiple parasitic pathogens viz., Epistylis sp., Trichodina sp., Argulus siamensis and Ergasilus sp. Thus, it was delineated that prolonged low water temperature might be playing one of the influential roles in creating stress in fish, thus making the fish susceptible to complicated or mixed bacterial and parasitic infections.
... The disease was first identified in Japan in 1971 and similar conditions were identified in 1972 in South East Queensland (Australia). Later, these outbreaks had spread widely across the North America and Asia-Pacific region; and caused substantial economic loss to the aquaculture industries in various countries including Thailand, China, Vietnam, Lao PDR, Malaysia, Myanmar, Cambodia, Sri Lanka, Bangladesh, India, Philippines, Hong Kong, Nepal, Bhutan, Singapore and Pakistan John and George 2012). ...
Aphanomyces invadans, an oomycyte fungus most frequently recognized as a causative agent of epizootic ulcerative syndrome (EUS) is a seasonal epidemic pathogen of great importance in wild and farmed fish in both freshwater and estuarine environments. EUS is a complex infectious etiology which leads to necrosis ulcerative lesions and granulomatous response in fishes. It is a cause of death of approximately 92 species that has been recorded in wild as well as in commercial culture systems worldwide. Several environmental and biological factors are responsible for the growth and establishment of A. invadans, which further attracts secondary pathogens to enter the lesions thus, increasing the severity of the infection. Methods for the proper identification of A. invadans, includes PCR detection and microscopy. However, the pathogenicity of the A. invadans is still unknown. In order to discover new effective treatment to fight the disease, a better understanding of the infection process is necessary. The studies on fungal infection in fishes indicate the immune response pattern in fish against A. invadans that serves as an important key for the development of targeted therapeutics and vaccines to prevent the disease and to maintain EUS free aquaculture systems. The immune mechanisms that respond to stimulation, interaction between the immune system of host species and A. invadans, different factors of A. invadans and its pathogenicity as well as various approaches of treatment has been discussed in this review.
