Received date: March 07, 2017; Accepted date: March 24, 2017; Published date: March 27, 2017
Citation: Al-Taee AMR, Khamees NR, Al-Shammari NAH (2017) Vibrio Species Isolated from Farmed Fish in Basra City in Iraq. J Aquac Res Development 8:472. doi:10.4172/2155-9546.1000472
Copyright: © 2017 Al-Taee AMR, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
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Aim: This study was carried out to investigate the occurrence of potentially pathogenic species of Vibrio in seven types of fish sampled from fish farms located in different districts in Basra governorate, Iraq.
Methods and Results: A total of 153 live fishes was collected from fish farms during the period January- May 2016. Bacteria were isolated using selective medium thiosulfate citrate bile sucrose salt agar. Presumptive Vibrio colonies were identiﬁed using the VITEK 2 system and selected biochemical tests. In the present study V. alginolyticus (24 of 60) was the predominant species, followed by V. cholerae (10 of 60), V. furnisii (10 of 60), V. diazotrophicus (7 of 60), V. gazogenes (5 of 60) and V. costicola (4 of 60). The signs of vibriosis appeared in three types of fish, including Cyprinus carpio, Coptodon zilli and Planiliza subviridius in spite of the using Oxytetracycline in most fish farms.
Conclusion: The results of the present study demonstrated the presence of pathogenic Vibrio species nearly in all fish farms. So the farm owners should be concerned about the presence of these pathogenic bacteria which also contributes to human health risk and should adopt best management practices for responsible aquaculture to ensure the quality of fish.
Vibrio spp; Vibriosis; Cyprinus carpio; Coptodon zilli; Planiliza subviridius
The world fish production has grown recently- as a consequence of the decline production in capture fishery- with food fish supply increasing at an average annual rate of 3.2 percent, above the growth of the world population to 1.6 percent. World per capita apparent fish consumption increased from an average of 9.9 kg in the 1960s to 19.2 kg in 2012. According to the latest available statistics collected globally by FAO, world aquaculture production attained another all-time high of 90.4 million tons in 2012, including 66.6 million tons of food fish and 23.8 million tons of aquatic algae .
But this worldwide growth of aquaculture is overwhelmed by catastrophic ﬁsh diseases and spoilage caused by pathogenic bacteria, which are introduced to the fish farm through natural or artificial food sources, treated inlet water or through vertical transmission from brood stock [2-4]. The most diseases are caused by Vibrio spp., which are considered the well-known cause of a significant problem for the development of a sector with strong economic losses worldwide because of its high morbidity and mortality rates (mortality ≥ 50%) [5-8]. The Centers for Disease Control and Prevention  estimates that vibriosis causes 80,000 illnesses each year in the United States. About 52,000 of these illnesses are estimated to be the result of eating contaminated food and about 80% of infections occur between May and October when water temperatures are warmer.
Several factors have been proposed to influence the survival, persistence and ability of vibrios to cause infection. These include water temperature, UV or sunlight and salinity . Many studies have been conducted on seasonal variation of pathogenic Vibrio species in natural environments [11-15].
However, there is a little information pertaining to vibriosis and the presence of Vibrio species in the fish farms especially in Iraq. Hence, this paper attempts to describe the presence of Vibrio spp in different types of fish.
Fish samples collection
A total of 153 live fish was collected from fish farms located in different districts in Basra governorate, Iraq (Figure 1), over a five month period (January- May 2016). The parameters of water have been measured. Fish Samples included common carp (Cyprinus carpio) (65), silver carp (Hypophthalmichthys molitrix) (15), sea bream (Acanthopagrus arabicus) (6), green mullet (Planiliza subviridus) (23), molly fish (Poecilia latipinna) (15), Bue tilapia (Oreochromis aureus) (15) and redbelly tilapia (Coptodon zilli) (14). Live fish samples were transported to the laboratory within a few hours, the measurements of the total length and body weight are recorded (Table 1).
|Fish Species||Total Length, cm Range (Mean)||Body Weight, gm Range (Mean)|
|Cyprinus carpio||16-49 (36.44)||13.0-2353.9 (890.4)|
|Hypophthalmichthys molitrix||32-54 (32.66)||65.0-1360 (653.3)|
|Acanthopagrus aerobics||15-29 (28.3)||13.0-123.8 (22.4)|
|Oreochromis aureus||12.3-14.2 (12.62)||10.0-62.0 (42)|
|Coptodon zilli||12-14 (12.23)||10.0-65.0 (40)|
|Planiliza subviridus||11.3-16.4 (14.23)||12.0-650 (42)|
|Poecilia latipinna||5.2-6.5 (4.21)||4.0-6.44 (3.88)|
Table 1: Physical measurements taken at the time of collection.
Bacterial isolation and identification
The fish were killed by physical destruction of the brain, in order to prepare the samples for bacterial isolation. Initially a swab was taken from skin, fins and eyes while 1 gm of the gills and intestine were incised aseptically using a sterile scalpel. These samples were homogenized in 9 ml of sterile normal saline solution using a sterilized glass homogenizer (Brand- Germany). One milliliter aliquots of the homogenate solutions were serially diluted (10-1 to 10-7). Aliquots of 0.1 ml of the serial dilutions were inoculated onto thiosulfate citrate bile sucrose salt agar (TCBS) (Hi media- India) in duplicate using the spread plate method and the plates were incubated at 30°C for 24-72 h.
The presumptive Vibrio colonies, yellow- greenish- blue, on TCBS agar were picked and subjected to bacterial identification using VITEK 2 system (Biomerieux- USA) and biochemical tests  such as: oxidase test, H2S production, urease, indole production, Voges- Proskauer, fermentation of: glucose, lactose, inositol, raffinose, mannitol, dextrose, adonitol, fructose, dolcitol, xylose, arabinose, trehalose, salicin, rahmnose, milibiose, galactose, sorbitol, sucrose, mannose and inuline.
Water quality parameters
The study was conducted during January- May, 2016 in which there is a fluctuation in water quality parameters in the aquaculture throughout the sampling sites (Table 2). The mean of temperature fluctuated from 24.5°C to 30.1°C. Meanwhile the mean of salinity was recorded to range from 1.23 to 6.22 ppt. The pH was relatively from 6.5 to 7.2.
|Station||Temp (°C) Range (Mean)||Salinity ppt Range (Mean)||PH Range (Mean)|
|Hartha||18.5-32.4°C (24.5)||1.32-4.00 (1.34)||7.9-8.2 (7.1)|
|Mashab||13.0-33.0°C (29.8)||0.50-1.80 (1.23)||6.9-7.7 (6.8)|
|Basra University||19.0-32.0°C (26.4)||1.60-4.50 (2.1)||7.3-7.9 (7.1)|
|Muhaijran||16.0-30.0°C (26.2)||1.80-3.70 (1.54)||7.5-8.4 (6.5)|
|Seeba||12.0-30.0°C (28.2)||3.20-12.60 (6.22)||7.1-8.4 (7.2)|
|Marbad||18.0-34.0°C (30.1)||4.10-5.30 (4.5)||7.0-7.4 (7.1)|
Table 2: The water parameters of studied stations.
The fish in a culture system always exposed to a variety of stressors which including high stocking density, handling, transportation and poor water quality . On the other hand, fish immunity is reduced during a stressful event which causes the fish to become susceptible to disease infection 
The growth of Vibrio in water is increased by high levels of organic matters, high salinity, high water temperature (25°C to 32°C) and pH (5-9). While the low salinity and high pH (>9.5) had shown to reduce the growth of this bacterium . These favorable conditions for Vibrio were also observed in the present study.
In the present study, three types of aquaculture systems have been studied, the net cage aquaculture in Hartha station, which lies in the north of Shatt Al-Arab River. The second type is the terrestrial pond, which takes water either from Shatt Al-Arab River (Basra University, Muhaijran and Seeba stations) or from artesian wells as Marbad station. The third is Mashab station (net cage), which represent as a part of Hor Al-Hammar marsh and either take water from Shatt Al-Arab River and general downstream. There is an obvious effect of the temperature and salinity on the infected fish, especially in Seeba and Marbad stations. The present study agreed with Le Roux et al.  who reported that, Vibrio abound in the warm (>15°C) and saline aquatic environments. Finlay and Falkow  observed that, the occurrence of high total Vibrio count in the biofilm at high temperature concurred with the occurrence of disease outbreaks. Albert and Ransangan  revealed that, the water temperature has shown to play an important role in enhancing the growth of Vibrio spp, causing fish to stress and inducing severe vibriosis outbreak. Kaspart and Tamplin  noticed that, the optimal temperatures of survival of V. vulnificus 4965 was between 13 and 22°C in 10-ppt (noninhibitory salinity) sterile seawater, while the temperature outside this range reduced the time of survival.
A total number of 153 fish were sampled during the study. Almost all the primary isolates from sampled organs (skin, round mouth, fin base, gill cover and intestine) showed green and yellow colonies on TCBS. From the samples of fish examined, the average rate of infection was 43.79%, including 15.03% of them as a bacterial infection and identified as Vibrio spp. Two methods were used for identification of Vibrio spp., the VITEK 2 system which detect only V. cholerae (10 isolates) with probability 98% and confidence, excellent identification, while the other isolates were failed to identify with it, so its identified depending upon their biochemical profiles (Table 3) as V. gazogenes (5), V. alginolyticus (24), V. costicola (4), V. furnisii (10) and V. diazotrophicus (7).
|Tests||V. gazogenes||V. alginolyticus||V. costicola||V. furnisii||V. diazotrophicus|
|Fermentation of Glucose||-||-||+||+||-|
+: Positive, -: Negative, ND: Not Determined
Table 3: Biochemical profile of Vibrio sp.
The results of the present study indicated that, the infected fish display skin discoloration, red patches around the base of the fins and mouth and necrotic intestine. These signs have appeared in three types of fish, including Cyprinus carpio, Coptodon zilli and Planiliza subviridius (Figure 2 and Table 4). The infected fish were sampled from all stations (except Basra university station).
|Fish spp||Total Exam. Fish||Total Infected Fish||Disease|
|Cyprinus carpio||65||47||Vibriosis, Spring Viraemia of carp Virus (SVCV), Fin rot, Dropsy, Bacterial gill disease|
|Hypophthalmichthys molitrix||15||2||Viral hemorrhagic septicemia|
|Acanthopagrus arabicus||6||2||Pox disease|
|Poecilia latipinna||15||5||Red mouth|
Table 4: The types of fish and their disease signs.
In the present study, although the managers of the farms stated that, they use Oxytetracycline (1%) in all stations. Oxytetracycline is widely used to treat bacterial infections in aquaculture farms, such as vibriosis and furunculosis [23,24]. In spite of that, many infected cases have been detected among fish, particularly common carp, and this is may be related to that, the an extensive use of antibiotics can cause the development of antibiotic-resistant pathogens which can infect both cultured animals as well as humans [25-27].
V. cholerae was the most species isolated from intestinal necrosis in common carp and the infections were distributed in all stations (except Basra University station), while other species of Vibrio were isolated from external infections.
In the present study V. alginolyticus (40%) was the predominant species, followed by V. cholerae (16.6), V. furnisii (16.6%), V. diazotrophicus (11.6), V. gazogenes (8.3%) and V. costicola (6.66%). The species of Vibrio were different between farms and this is may be related to the different source of larvae or different source of water. This agreed with Bhaskar et al. who reported the presence of V. alginolyticus as the most common, followed by V. cholerae, V. parahemolyticus, and V. vulnificus in P. monodon culture system. Sanjoy et al.  isolated five species of Vibrio from shrimp farm and found that, V. cholerae was the most common species.
Many researchers found that, the virulence level of Vibriois dependent on fish species, doses of infection, the time of exposure and age of host species and pathogenic factors of the bacterial strains [29-32].
The results of the present study demonstrated the presence of pathogenic Vibrio species as V. cholerae, V. gazogenes, V. alginolyticus, V. costicola, V. furnisii and V. diazotrophicus nearly in all fish farms. So the farm owners should be concerned about the presence of these pathogenic bacteria which also contributes to human health risk and should adopt best management practices for responsible aquaculture to ensure the quality of fish.
We thank the College of Agriculture and Marine Science Center, Iraq for assistance during working period. We would like to thank the managers of the fish farms who have made the sampling possible.