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Dibyendu Kamilya - One of the best experts on this subject based on the ideXlab platform.
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Epizootic Ulcerative Syndrome (EUS) in bata, Labeo bata (Hamilton 1822) from Tripura, India
Indian Journal of Fisheries, 2014Co-Authors: Arunjyoti Baruah, Dibyendu Kamilya, Ratan K. SahaAbstract:The occurrence of Epizootic Ulcerative Syndrome (EUS) in bata ( Labeo bata ) and the infectivity and role of Aphanomyces invadans in the aetiology of Ulcerative condition were investigated in the present study. Live fish ( L.bata ) samples with ulcerations were collected from a local fish farm in Tripura and were acclimatised in laboratory tanks with proper management. Case histories, clinical and gross signs of the sampled fishes were recorded. Histopathological study of muscle and liver tissue from the ulcerated fish showed the presence of oomycete hyphae and granulomas. Oomycete isolation was done from the affected muscles and was identified as Aphanomyces invadans based on colony morphology, growth and microscopic morphology. The results suggest that the Ulcerative condition in bata was due to EUS associated with A. invadans .
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Epizootic Ulcerative Syndrome (EUS) in fish: history and current status of understanding
Reviews in Fish Biology and Fisheries, 2014Co-Authors: Dibyendu Kamilya, Arunjyoti BaruahAbstract:Epizootic Ulcerative Syndrome (EUS) is one of the most important diseases affecting more than 100 species of wild and cultured finfish. EUS was first reported in farmed ayu ( Plecoglossus altivelis ) from Japan in 1971 and has since then spread across different countries of four continents including Asia, Australia, North America and Africa. The spread of the disease, especially in Asia–Pacific region and Africa has led to substantial damage to the fish resources and livelihood of the fish farmers. No reports are available confirming the outbreak of the disease from Europe and South America. The latest outbreak of EUS has been reported from Canada in a new susceptible species brown bullhead, Ameiurus nebulosus . It seems that the disease has potential to spread further, owing to the Epizootic nature of the disease and broad susceptible host range. Considering the global importance of this disease, this review provides the current status of understanding about the etiology, process of diseases development, species affected, diagnostic methods as well as control and preventive measures, in light of the historical developments in those areas.
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inter species transmission of the Epizootic Ulcerative Syndrome eus pathogen aphanomyces invadans and associated physiological responses
Israeli Journal of Aquaculture-bamidgeh, 2012Co-Authors: Arunjyoti Baruah, Ratan K. Saha, Dibyendu KamilyaAbstract:The Epizootic Ulcerative Syndrome (EUS) pathogen was transmitted to catla (Catla catla) using two experimental infection models: intramuscular injection and cohabitation. Oomycetes, recovered from naturally infected ulcerated bata (Labeo bata), were identified as Aphanomyces invadans based on morphology and histopathology. Lesions typical of EUS were reproduced in the catla using an intramuscular injection of 1×10 5 zoospores/ml autoclaved water from a EUS-affected pond. Lesions were first visible six days after injection; all lesions were swollen and Ulcerative 10 days after injection. In the cohabitation experiment with EUS-affected bata, apparently healthy catla exhibited lesions eight days after infection. Histopathology of the muscle and liver from experimentally-infected catla showed the presence of hyphae and granuloma. Twelve days after infection, immunological parameters (superoxide anion and nitric oxide production, leukocyte proliferation, lysozyme activity) of experimentally-infected catla were significantly higher (p 0.05). Biochemical parameters (total serum protein, serum glutamate pyruvate transaminase, serum glutamate oxaloacetate transaminase, and serum alkaline phosphatase were significantly higher (p<0.05) in intramuscularly-injected catla than in apparently healthy fish, however, in catla infected by cohabitation, only total serum protein significantly differed from the control (p<0.05).
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Immune responses and protection in catla (Catla catla) vaccinated against Epizootic Ulcerative Syndrome
Fish & Shellfish Immunology, 2011Co-Authors: Dipangka Saikia, Dibyendu KamilyaAbstract:Abstract Three different antigenic preparations from the Epizootic Ulcerative Syndrome (EUS) pathogen Aphanomyces invadans were evaluated as vaccine candidate in catla (Catla catla). Anti-catla enzyme immunoconjugate was prepared after isolating catla immunoglobulin and raising hyperimmune sera against it, in rabbit. Three antigens namely, fungal extract (FE), fungal extract mixed with Freund’s incomplete adjuvant (FIA) in a 1:1 (v/v) ratio (FE + A) and extra cellular product (ECP) were prepared and three groups of catla were vaccinated intramuscularly with all these antigens (200 μg/fish). Different cellular and humoral immune responses were measured for the entire vaccinated and control group on 0th, 5th, 15th and 25th day post vaccination. Thirty days after the vaccination, the fish were challenged with an A. invadans zoospore dose of 1 × 105 ml−1 and mortality and relative percent of survival (RPS) were recorded. Study of cellular immunological parameters including antigen-specific leukocyte proliferation, antigen-specific nitric oxide production and superoxide anion production showed significantly higher (p 0.05). Increased immune responses and protection have important implications with regard to the control of EUS by vaccination.
Supranee Chinabut - One of the best experts on this subject based on the ideXlab platform.
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effect of macrophages and serum of fish susceptible or resistant to Epizootic Ulcerative Syndrome eus on the eus pathogen aphanomyces invadans
Fish & Shellfish Immunology, 2001Co-Authors: David J C Miles, Somkiat Kanchanakhan, J H Lilley, Kim D Thompson, Supranee Chinabut, Alexandra AdamsAbstract:Epizootic Ulcerative Syndrome (EUS) is one of the most destructive diseases of fresh and brackish water farmed and wild fish in the Asia–Pacific region. The in vitro germination and growth of the propagules of the EUS pathogen, Aphanomyces invadans (=A. piscicida), were assessed in the presence of the head–kidney macrophages, serum, and serum heated to inactivate complement proteins, of three EUS-susceptible and one resistant fish species. The susceptible species were: striped snakehead (Channa striata), giant gourami (Osphronemus gouramy) and silver barb [Barbodes (=Puntius) gonionotus], and the resistant species was Nile tilapia (Oreochromis niloticus). Fish of all species were acclimatised to either low temperature (20° C±1·6) at which EUS is known to occur, or to high temperature (32° C±5·0) at which EUS does not occur, except for giant gouramis which were only studied at low temperature. The respiratory burst of the macrophages was assessed in the presence of A. invadans or the stimulant phorbol myristate acetate (PMA), and compared to that of controls. Anti- A. invadans antibody concentrations were assessed in all species except silver barbs. All assays were carried out at the same temperature, regardless of the temperature that the fish were kept at. Macrophages of all species other than snakeheads inhibited fungal germination at both temperatures, though only silver barb and gourami macrophages could inhibit germling growth. PMA increased the respiratory burst in nearly all cases. The respiratory burst in the presence ofA. invadans was consistently lower than that of controls, though the difference was only significant in the case of snakeheads. The respiratory burst of all macrophage treatments was higher at a low temperature. Except in the case of PMA-stimulated macrophages, regressions between respiratory burst and inhibitory action were only found in susceptible species, suggesting that the respiratory burst is important in those species, but is unable to prevent the proliferation of A. invadans. Serum inhibited fungal germination in all cases other than low temperature tilapia, indicating that the EUS resistance of tilapia is not due to the serum. Inhibition of germling growth by serum only occurred in silver barbs and gourami. Heated serum did not inhibit germination in any case except that of high temperature snakehead, and in fact stimulated germination in the case of tilapia. Heating serum did not affect the growth inhibiting activity of silver barbs and gouramis, but it stimulated growth in some groups. At high temperatures snakeheads had high anti- A. invadans antibody concentrations, which may explain the inhibitory activity of their heated serum. A role for complement and antibodies in defence against A. invadans in susceptible species is suggested.
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Epizootic Ulcerative Syndrome information up to 1997
Fish Pathology, 1998Co-Authors: Supranee ChinabutAbstract:Epizootic Ulcerative Syndrome or EUS has been endemic in many countries in Asia and the Indo Pacific region since 1980. It has affected a wide range of fish species. Infected fish reveal dermal Ulcerative lesions throughout the body. The outbreaks occur at certain times of the year, normally after flooding followed by cool weather. Typical clinical signs of the early stages of this disease are the petechial haemorrhagic lesions on the skin which later develop into deep Ulcerative lesions throughout the body. Mycotic granulomas spread throughout the lesions and also into some of the internal organs. These histopathological observations are key characteristics in the identification and confirmation of outbreaks of EUS. The epidemiology of this disease is still uncertain, however, a similar disease called mycotic granulomatosis was reported in Japan in 1971. In the following year red spot disease was reported in estuarine fish from Queensland, Australia. Since then the disease has spread to almost all countries in Southeast Asia and the Indian subcontinent. Recently (1996) an EUS outbreak in Pakistan has been reported. It seems clear from the epidemiological information, and research carried out, that EUS is infectious in nature. Parasites, bacteria and viruses found in diseased fish are considered to be the secondary agents. Aphanomyces invadans, a pathogenic water borne fungus, most likely plays an important role in these disease outbreaks.
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histopathology of snakehead channa striatus bloch experimentally infected with the specific aphanomyces fungus associated with Epizootic Ulcerative Syndrome eus at different temperatures
Journal of Fish Diseases, 1995Co-Authors: Supranee Chinabut, R J Roberts, G R Willoughby, M PearsonAbstract:Snakeheads, Channa striatus (Bloch), were inoculated with a spore suspension of the specific pathogenic Aphanomyces, isolated from fish affected by Epizootic Ulcerative Syndrome (EUS), in South East Asia. Fish were held at three different temperatures: 19, 26 and 31 °C. Histological changes induced by the infection are described. In the early stages of the disease, degenerative changes were observed in all samples, but inflammatory infiltrate was much more marked in fish kept at 26 and 31 °C. By 8 days post-injection, extensive mycotic granulomatosis was observed in the samples kept at 26 and 31 °C. The fish kept at 19 °C developed a severe invasive myonecrosis with limited macrophage response. From 14 to 28 days post-injection, healing became well established at 26 and 31 °C and surviving fish kept at these temperatures recovered completely by 28 days. The lesion was still progressing at 21 days post-injection in fish kept at 19 °C, and all such fish succumbed by this time. Thus, mortalities in the fish kept at 19 °C were considerably higher than in the groups of fish kept at 26 and 31 °C. The findings help to explain why mortalities from EUS occur when water temperatures are low.
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mycotic aspects of Epizootic Ulcerative Syndrome eus of asian fishes
Journal of Fish Diseases, 1993Co-Authors: R J Roberts, L G Willoughby, Supranee ChinabutAbstract:A survey of fish affected with Epizootic Ulcerative Syndrome taken from outbreaks in countries throughout South and South-East Asia showed that a morphologically typical fungus was consistently present within lesions. Although the majority of the fungal mycelium was dead in most lesions it proved possible to isolate a very delicate and culturally demanding Aphanomyces from such lesions in a few cases. It also proved relatively easy to isolate other members of the Saprolegniaceae including Aphanomyces from the surface of lesions, but these were considered saprophytes derived from background spore burdens in the water. Sporangium morphology of the putatively pathogenic isolates of Aphanomyces was different from that of saprophytic Aphanomyces strains and they also had a lower thermal tolerance. When a mycelium from these strains was placed below the dermis of healthy fish, it caused an inflammatory response and proceeded to migrate down into the tissues of the fish, inducing severe myonecrosis with chronic epithelial reaction. The saprophytic isolates induced a local host response followed by healing of the induced lesion, and destruction or expulsion of the mycelium. It is considered that the specific slow-growing, thermo-labile Aphanomyces is the pathogenic fungus which causes so much tissue damage in this disease, although it may not be a primary pathogen in its own right.
G. N. Frerichs - One of the best experts on this subject based on the ideXlab platform.
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Characteristics of a new reovirus isolated from Epizootic Ulcerative Syndrome infected snakehead fish.
Diseases of aquatic organisms, 2001Co-Authors: K. Riji John, M. Rosalind George, Randolph H. Richards, G. N. FrerichsAbstract:Epizootic Ulcerative Syndrome (EUS) has been infecting a wide range of fishes in the South and Southeast Asia for the last 2 decades. One reovirus-like agent (snakehead reovirus, SKRV), isolated from an EUS-infected snakehead fish and investigated in the present study, is the only reovirus so far isolated from an EUS-infected fish. SKRV was characterised by the presence of a double-stranded RNA genome with icosahedral symmetry and double capsid. The virus had an aver- age size of 71 nm, a buoyant density of 1.36 g ml -1 in CsCl and lacked a lipid-containing envelope. Apart from the above, the presence of a segmented genome and structural proteins falling into 3 spe- cific size classes confirmed that the virus belongs to the family Reoviridae. SKRV differed from aquareoviruses by the lack of a cytopathic effect (CPE) with syncitium formation and in the segmen- tation pattern of RNA genome. The resistance to pH (3.0 to 9.0) and heat treatment and inability to multiply in mammalian cell lines and haemagglutinate human 'O' red blood cells (RBCs) differenti- ated SKRV from the rest of the similar genera in the family Reoviridae. Serological comparison indi- cated the antigenic distinctness of the isolate from selected American and European aquareoviruses. SKRV grew well in SSN-1 and SSN-3 cells at 25 to 30°C but not in the most common Aquareovirus susceptible coldwater fish cell line— CHSE-214.
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Viruses associated with the Epizootic Ulcerative Syndrome (EUS) of fish in South-East Asia.
Veterinary research, 1995Co-Authors: G. N. FrerichsAbstract:A number of birnaviruses, rhabdoviruses and a reovirus have been isolated from occasional fish affected with the Epizootic Ulcerative Syndrome (EUS) in the past decade. The heterogeneous nature of these isolates, together with a low and inconsistent level of recovery from diseases specimens, suggests that these viruses may only represent adventitious infections unrelated to outbreaks of EUS. Furthermore, experimental induction of the condition by direct exposure to cell culture isolated viruses has not been achieved. The significance, if any, of C-type retroviruses identified in cell cultures derived from EUS-susceptible fish species is not known.
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Comparison of rhabdoviruses associated with Epizootic Ulcerative Syndrome (EUS) with respect to their structural proteins, cytopathology and serology
Journal of Fish Diseases, 1994Co-Authors: J H Lilley, G. N. FrerichsAbstract:. Seven rhabdoviruses isolated from fish suffering from Epizootic Ulcerative Syndrome (EUS) were compared in terms of their morphology, cytopathogenicity, antigenic relatedness and structural polypeptide composition. All strains exhibited a bullet-shaped morphology, but the T9204 isolate was found to be longer and more variable in length than the other strains. Sixteen fish cell lines investigated showed some variation in susceptibility to each isolate, but the cytopathic changes induced by T9204 in SSN-2, RSN, GCP, ONP, FHM, AS and MUL lines were significantly different from the other isolates. Polyclonal antisera raised against the BPV, 20E and SL11 strains neutralized six isolates (BPV, 02, 19, 20E, A4 and SL11), but not T9204. Conversely, anti-T9204 serum only neutralized homologous virus. Polyacrylamide gel electrophoresis demonstrated that BPV, 02, 19, 20E, A4 and SL11 had virtually identical protein profiles, whereas T9204 differed both in the number of protein bands and in their migration pattern. Western blots of these gels identified the proteins specific to T9204 that reacted with anti-T9204 serum. Therefore, the isolates represent two distinct species of fish rhabdoviruses, but as yet, no causal relationship with EUS, or any other disease condition, has been established.
Alexandra Adams - One of the best experts on this subject based on the ideXlab platform.
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effect of macrophages and serum of fish susceptible or resistant to Epizootic Ulcerative Syndrome eus on the eus pathogen aphanomyces invadans
Fish & Shellfish Immunology, 2001Co-Authors: David J C Miles, Somkiat Kanchanakhan, J H Lilley, Kim D Thompson, Supranee Chinabut, Alexandra AdamsAbstract:Epizootic Ulcerative Syndrome (EUS) is one of the most destructive diseases of fresh and brackish water farmed and wild fish in the Asia–Pacific region. The in vitro germination and growth of the propagules of the EUS pathogen, Aphanomyces invadans (=A. piscicida), were assessed in the presence of the head–kidney macrophages, serum, and serum heated to inactivate complement proteins, of three EUS-susceptible and one resistant fish species. The susceptible species were: striped snakehead (Channa striata), giant gourami (Osphronemus gouramy) and silver barb [Barbodes (=Puntius) gonionotus], and the resistant species was Nile tilapia (Oreochromis niloticus). Fish of all species were acclimatised to either low temperature (20° C±1·6) at which EUS is known to occur, or to high temperature (32° C±5·0) at which EUS does not occur, except for giant gouramis which were only studied at low temperature. The respiratory burst of the macrophages was assessed in the presence of A. invadans or the stimulant phorbol myristate acetate (PMA), and compared to that of controls. Anti- A. invadans antibody concentrations were assessed in all species except silver barbs. All assays were carried out at the same temperature, regardless of the temperature that the fish were kept at. Macrophages of all species other than snakeheads inhibited fungal germination at both temperatures, though only silver barb and gourami macrophages could inhibit germling growth. PMA increased the respiratory burst in nearly all cases. The respiratory burst in the presence ofA. invadans was consistently lower than that of controls, though the difference was only significant in the case of snakeheads. The respiratory burst of all macrophage treatments was higher at a low temperature. Except in the case of PMA-stimulated macrophages, regressions between respiratory burst and inhibitory action were only found in susceptible species, suggesting that the respiratory burst is important in those species, but is unable to prevent the proliferation of A. invadans. Serum inhibited fungal germination in all cases other than low temperature tilapia, indicating that the EUS resistance of tilapia is not due to the serum. Inhibition of germling growth by serum only occurred in silver barbs and gourami. Heated serum did not inhibit germination in any case except that of high temperature snakehead, and in fact stimulated germination in the case of tilapia. Heating serum did not affect the growth inhibiting activity of silver barbs and gouramis, but it stimulated growth in some groups. At high temperatures snakeheads had high anti- A. invadans antibody concentrations, which may explain the inhibitory activity of their heated serum. A role for complement and antibodies in defence against A. invadans in susceptible species is suggested.
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Immunostimulation of striped snakehead Channa striata against Epizootic Ulcerative Syndrome
Aquaculture, 2001Co-Authors: David J C Miles, Somkiat Kanchanakhan, J H Lilley, Jaree Polchana, Kim D Thompson, Alexandra AdamsAbstract:Abstract Five immunostimulants were injected intraperitoneally into striped snakeheads (Channa striata). The inhibitory effects of the serum and macrophages collected from the treated fish on the germination and subsequent growth of Aphanomyces invadans (=piscicida), the causative agent of Epizootic Ulcerative Syndrome (EUS), were then assessed. Salar-bec, a vitamin premix, and Ergosan, an alginate, both stimulated the inhibitory effects of serum on the germination and subsequent growth of A. invadans cysts, and the inhibitory effect of macrophages on growth. Betamak C85, a yeast extract containing β glucans and mannans, and Lysoforte, a lysophospholipid biosurfactant, induced little or no improvement in the parameters measured. Oro glo layer dry, a xanthophyll preparation, was rejected because of high mortalities among injected fish. Salar-bec showed the greatest improvement in the inhibition of both germination and growth by serum, and of growth by macrophages. It was selected for a tank trial in which snakeheads were fed on pellets coated with 2 g kg−1 Salar-bec, then injected with A. invadans. Control fish were fed on uncoated feed. Although the incidence of infection was not affected, hyphae appeared later in treated fish and granulomata developed faster at the infection site, suggesting an enhanced ability to contain the infection. Relative percent survival of treated fish was 59.2% higher than the controls over the 40-day trial. Anti-A. invadans antibody concentration was higher in treated fish, which may also have contributed to the containment of the infection.
Karl D.a. Huchzermeyer - One of the best experts on this subject based on the ideXlab platform.
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First record of Epizootic Ulcerative Syndrome from the Upper Congo catchment: An outbreak in the Bangweulu swamps, Zambia
Journal of Fish Diseases, 2017Co-Authors: C F Huchzermeyer, Karl D.a. Huchzermeyer, B.m. Macey, P A Colly, B M Hang'ombe, Kevin W. Christison, M M SongeAbstract:We report on the first outbreak of Epizootic Ulcerative Syndrome (EUS) amongst wild fish populations in the Bangweulu swamps, an inland delta, in the north of Zambia during 2014. The area supports a large and diverse fish fauna related to, but distinct from, that of the Zambezi River system where EUS outbreaks have occurred since 2006. A sizeable artisanal fishery, based on extensive fish weirs, is sustained by the annual flooding of the swamps, and observations of the disease outbreak by fishermen were recorded. Signs typical of infection with Aphanomyces invadans were observed in a number of species. Clinical observations, histology and molecular diagnostic methods were used to confirm infection with A. invadans in two of the most commonly and severely affected species. Several features of the wetland may have contributed to the outbreak and the annual recurrence of the disease. Modes by which the disease may have been introduced into the swamps are discussed. The outbreak is of great significance as the Bangweulu swamps drain into the Congo River in neighbouring Democratic Republic of Congo, Africa's largest drainage system with an extensive and diverse fish fauna previously unaffected by EUS.
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Epizootic Ulcerative Syndrome: Exotic fish disease threatens Africa’s aquatic ecosystems
Journal of The South African Veterinary Association-tydskrif Van Die Suid-afrikaanse Veterinere Vereniging, 2012Co-Authors: Karl D.a. Huchzermeyer, Benjamin C.w. Van Der WaalAbstract:In late 2006 an unusual Ulcerative condition in wild fish was reported for the first time in Africa from the Chobe and upper Zambezi Rivers in Botswana and Namibia. Concern increased with subsistence fishermen reporting large numbers of ulcerated fish in their catches. In April 2007 the condition was confirmed as an outbreak of Epizootic Ulcerative Syndrome (EUS). The causative agent, Aphanomyces invadans , is a pathogenic water mould of fish that shows little host specificity. Ulcers follow infection of tissues by oomycete zoospores, resulting in a granulomatous inflammation associated with invading oomycete hyphae. Granulomatous tracts surrounding oomycete hyphae within the necrotic tissues characterise the diagnostic histological picture. The upper Zambezi floodplain at the confluence with the Chobe River spans the four countries of Botswana, Namibia, Zambia and Zimbabwe, making disease control a challenge. The floodplain ecosystem supports a high fish diversity of around 80 species, and is an important breeding and nursery ground. The annual cycle of flooding brings about changes in water quality that are thought to favour the infectivity of A. invadans , with diseased fish appearing soon after the plains become flooded. Since 2006 the disease has spread rapidly upstream along the upper Zambezi and its tributaries. By 2010 the disease was reported from the Okavango Delta in Botswana and in 2011 from the Western Cape Province of South Africa. EUS has the potential to disrupt floodplain ecosystems elsewhere in Africa where high fish diversity forms the basis of subsistence fisheries and local economies, and is a direct threat to freshwater fish culture.
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Epizootic Ulcerative Syndrome: exotic fish disease threatens Africa's aquatic ecosystems.
Journal of the South African Veterinary Association, 2012Co-Authors: Karl D.a. Huchzermeyer, Benjamin C.w. Van Der WaalAbstract:In late 2006 an unusual Ulcerative condition in wild fish was reported for the first time in Africa from the Chobe and upper Zambezi Rivers in Botswana and Namibia. Concern increased with subsistence fishermen reporting large numbers of ulcerated fish in their catches. In April 2007 the condition was confirmed as an outbreak of Epizootic Ulcerative Syndrome (EUS). The causative agent, Aphanomyces invadans, is a pathogenic water mould of fish that shows little host specificity. Ulcers follow infection of tissues by oomycete zoospores, resulting in a granulomatous inflammation associated with invading oomycete hyphae. Granulomatous tracts surrounding oomycete hyphae within the necrotic tissues characterise the diagnostic histological picture. The upper Zambezi floodplain at the confluence with the Chobe River spans the four countries of Botswana, Namibia, Zambia and Zimbabwe, making disease control a challenge. The floodplain ecosystem supports a high fish diversity of around 80 species, and is an important breeding and nursery ground. The annual cycle of flooding brings about changes in water quality that are thought to favour the infectivity of A. invadans, with diseased fish appearing soon after the plains become flooded. Since 2006 the disease has spread rapidly upstream along the upper Zambezi and its tributaries. By 2010 the disease was reported from the Okavango Delta in Botswana and in 2011 from the Western Cape Province of South Africa. EUS has the potential to disrupt floodplain ecosystems elsewhere in Africa where high fish diversity forms the basis of subsistence fisheries and local economies, and is a direct threat to freshwater fish culture.
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Epizootic Ulcerative Syndrome affecting fish in the Zambezi river system in southern Africa.
Veterinary Record, 2008Co-Authors: T. G. Andrew, Karl D.a. Huchzermeyer, B. C. Mbeha, S. M. NenguAbstract:In late 2006, diseased fish of a variety of species began to appear in the Chobe and upper Zambezi rivers in southern Africa. In April 2007, investigations showed that the levels of pesticides and heavy metals in the tissues of the fish were very low, discounting pollution as an underlying cause for the disease. However, histological evidence showed that the disease closely resembled the Epizootic Ulcerative Syndrome caused by the oomycete Aphanomyces invadans , a serious aquatic pathogen that has been isolated from freshwater and estuarine fish in Japan, south-east Asia, Australia and the usa since the 1970s, but not previously recorded in Africa.