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Case Study: Diagnosis of ‘Aeromonashydrophila’ Infection Offishes in Shatt
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Carassiuegibeloal-Arab Region, North of Iraq
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Majid A. A. Bannai
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Aquaculture and marine fisheries, marine science center, Basrah University, Iraq
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[email protected]
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Abstract In this case study diagnosis Aeromonashydrophila infected wild fish carpCarassiuegibelo, in Shut
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Al-Arab riversouth of Iraq,revealed that A. hydrophila infection, cause of the motile Aeromonas septicemia
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(MAS).The total number of fish showing clinical abnormalities from which Aeromonashydrophila was
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isolated and identified was 20 fish by using electrical fish net
. Samples were collected during summer
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season.
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Keywords Diagnosis; Aeromonashydrophila; Shatt Al-Arab river; Carassiuegibelo
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Introduction
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All populations of organisms, including, aquatic animals are limited partially or completely by diseases in their
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ecosystem (Real, 1996). Disease prevalence in the ecosystem is influenced by numerous environmental factors
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including infectious organisms and stressors (Nilskautsky et. al, 2000).
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Aeromonas hydrophila and other motile aeromonads are among the most common bacteria in freshwater
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habitats throughout the world, and these bacteria frequently cause disease among cultured and feral fishes.
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From descriptions of fish diseases in the early scientific literature, Otte (1963).
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Aeromonas hydrophila and other aeromonads are among the most common bacteria in freshwater habitats
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throughout the world. Genus Aeromonas includes prominantmicrobiota in freshwater reservoirs where they
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together with other microorganisms act as natural bio-filters and promote self purification of the water body.
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The course of the disease usually runs in an acute manner. Clinical conditions associated with systemic
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infection result in mortality within 24–48 hours. In more chronic types of clinical conditions, eroded fins occur
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as well as skin lesions and sluggish swimming (Roberts and Sommerville, 1982. The mortality was between
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10% and 70% among cultured fish.
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There are some potential risk factors associated with the main diseases of fish such as season and water
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temperature (Ortega et. al; 1995). Mortality among high thermal stressed fish was 80% due to Aeromonas.
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(Noga, 1996). In intensive fish culture, mortality due to A. hydrophila infection was highest in late spring and
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early summer (Faisal et al., 1989).
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Diseases caused by Aeromonas species or other microorganisms lead to considerable economic losses in
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aquaculture. McPhearson et al., (1991) and Smith et al., (1994) reported that the prevalence of antibiotic
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resistant bacteria is a worldwide problem in aquaculture. Aeromonas hydrophila causes disease in fish known
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as “Motile Aeromonas Septicemia” (MAS), “Hemorrhagic Septicemia,” “Ulcer Disease,” or “Red-Sore
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Disease.” The many synonyms of this disease relate to the lesions caused by this bacterium which include
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septicemia where the bacteria or bacterial toxins are present within numerous organs of the fish, and ulcers of
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the fish’s skin. A wide variety of opportunistic, pathogenic bacteria enter into the body of fish and cause
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diseases when fish are subjected to bad treatment (Anderson, 1995; Schmidt et al., 2000). Toranzo et al.
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(2005) suggested that fish pathogenic bacteria in infected fish forms are saprophytic.
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In natural situations, infections of fish with Aeromonas hydrophila are probably a minor problem. However,
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with intensive fish-fanning systems, whether these systems are outdoor ponds or indoor aquaria or tanks, other
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factors must be considered. The common occurrence of this disease relates to stress conditions or factors of the
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fish. Fish experts agree that fish are easily stressed when mishandled, overcrowded, transported under poor
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conditions, are on a poor level of nutrition, have poor water quality. Experimental demonstration shows that
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fish which are in poor environments due to unsatisfactory water quality such as high nitrite levels, low levels
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of dissolved oxygen (DO), or high levels of carbon dioxide (CO) are more susceptible to infection by
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Aeromonas hydrophila. Additionally, 2a seasonal incidence of a higher number of rep-tedfish deaths in the
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spring is associated with decreased water temperatures.
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Motile aeromonads cause diseases wherever bait fishes or warm water or ornamental fishes arepropagated. To
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a lesser extent, these bacteria also initiate disease in cold-water species. Although diseases associated with
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motile aeromonads are most severe among fish that are propagated under conditions of intensive culture, these
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bacteria may also affect feral fish and arecommon in the intestinal flora of apparently healthy fish (Trust et al.
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1974). The bacterium is ubiquitous and occurs in most fresh water environments. It can be found both in the
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water column and in the top centimeter of sediment (Hazen 1979). Motile aeromonads are adapted to
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environments that have a wide range of conductivity, turbidity, pH, salinity, and temperature (Hazen et al.
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1978). Temperature optimums may depend upon the particular strain under investigation, but generally range
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from 25oC to 35°C. Consequently, most epizootics amongwarm water fishes in the southeastern United States
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are generally reported in spring and early summer (Meyer 1970).
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1 Fish Collecting
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20 Wild populations specimens weighing 50-80 g and measuring 12-25 cm were collected alive from Shautt
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Al-Arab river, north of Iraq by using electrical fish net
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measured at the time of collection using a digital thermometer, Samples were immediately kept in containers
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supplied with aerated river water and transported to the laboratory, Dept. of Aquaculture and marine fisheries,
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marine science center University. Fish were subjected to clinical and post mortem examination according to
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Austin and Austin (1999). And the copy of clinical photo send to Dr Austin Brain for identification.
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2 Results
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Presumptive diagnosis of A. hydrophila may be based on the species of fish affected, the past disease status of
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those fish, and the presence of clinical signs of disease. However, bacteria mustbe isolated and identified
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biochemically to provide a definitive diagnosis.
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Clinical finding, the presented study revealed that A. hydrophila infection, the cause of the motile Aeromonas
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septicemia (MAS).The total number of fish showing clinical abnormalities from which Aeromonashydrophila
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was isolated and identified
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Some of the collected fish showed one or more from the following signs according to the stage of disease;
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darkness in the color of the skin, detachment of the scales, large irregular hemorrhages on the body surface,
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ulcers on the skin varied from shallow to deep necrotizing ulcers, fin erosions, inflamed vent, exophthalmia,
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abdominal distension with sero-hemorrhagic fluids exuded from the vent as shown in Figure 1.
during summer season . Water temperature was
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Figure 1 Fish infected with Aeromonas hydrophila. Registered under charity number SC000278 Heriot-Watt
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University is a Scottish charity UK.
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3 Discussion
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The percent of infection in the wild stock during summer .These results are in agreement with those of Eissa et
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al., (1994) and Company et al., (1999) who reported that, the majority of the infection occurred during the
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change of water temperature, spawning season, As a result, the increase in the production of corticosteroids
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increases the susceptibility of the fish to A. hydrophila infection. Osborne et al. (1989) found high densities of
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motile aeromonads within the environment during the mid summer when sedimentary chlorophyll and water
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temperature were highest. Meyer (1970) stated that most epizootics among warm water fishes in southeastern
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United States are generally reported in late spring and early summer as the water temperature ranged from 25
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℃-35℃.
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4 Recommended Treatment
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Oxytetracycline (Terramycin) has been the drug of choice for treating motile aeromonads epticemias in fishes.
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The drug is approved for use with pond fishes, channel catfish, and salmonids. It is administered in feed at a
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daily rate of 50 to 75 mg/kg of fish for 10 days. Fish must be withdrawn from treatment for 21 days before
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they are stocked or eaten. This treatment sometimes produces dramatic results when it is administered for even
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2 or 3 days, and is particularly effective when fish become infected after they have been handled, crowded, or
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held under stress for short periods of time (Meyer 1964; Meyer and Collar 1964).
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Acknowledgements
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I am grateful to DrBrian Austin B.Sc., Ph.D., D.Sc., F.H.E.A., F.R.S.A.Heriot-Watt University is a Scottish
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charity Uk ,for identification of species of bacteria and registered under charity number SC000278 Heriot-
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Watt University and also to MisAmalAlsheraa to help for collected fish .
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