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Infection in Nile tilapia Farms with Emphasis on its Effect on Growth Performance.
Pseudomonas aeruginosa is a G-ve bacterium causing diseases threat the animals, poultry and fish resources. Extracts of plants or their by-products contain some exclusive compounds that can be effective as chemotherapists and vaccines. The yucca has been suggested suitable for water quality management in aquaculture systems.
In Egypt, fish production comprises 20% of the white animal protein production, 17% of which is derived from aquaculture and the common cultured fish is Tilapia nilotica (Oreochromis niloticus) which have attained a great economic importance.
Pseudomonades are considered one of the most important fish pathogens which are responsible for ulcer like diseases including ulcerative syndrome. The disease is characterized by petechial hemorrhage, darkness of the skin, detached scales, abdominal ascites and exophthalmia. Moreover, Pseudomonas can cause a problem for human consumers too, generally caused by only one species (most frequently Ps. aeruginosa), cause healthcare associated illnesses.
“Pseudomonas aeruginosa is a gram-negative rod shape bacterium belonging to the family Pseudomonadaceae. This species is highly adaptable opportunistic pathogen, capable of surviving in a variety of environment, including aquaculture environment.”
Several plant extracts are reported to stimulate appetite and promote weight gain when they are administered to cultured fish. The yucca has been suggested suitable for water quality management in aquaculture systems. The effect of feeding diets containing yucca extract or probiotic on growth performance, nitrogen utilization, digestibility, blood parameters, ceacal microbial activity were studied and the results showed that the yucca extract reduced blood and ceacal urea and ammonia concentrations by using these additives.
The aim of the present study was to investigate the prevalence of Pseudomonas aeruginosa in some Nile tilapia at Kafre EL-Sheikh governorate, and also evaluate the effect of dietary supplementation of yucca extract on growth performance and diseases resistance of Nile tilapia challenged with Pseudomonas aeruginosa.
Material and Methods
Fish samples. A total of 150, apparently healthy, Nile tilapia were obtained from a private fish farm in Kafre EL-Sheikh Governorate and transported a live to Animal Health. Fish were acclimated for 2 weeks during the acclimation period fish fed on the basal diet only.
Isolation and identification of Pseudomonas aeruginosa from fish samples. Specimens from gills, liver, kidneys, brain and spleen of examined fish were taken under aseptic conditions and inoculated in trypticase soya broth. The growing colonies were purified in pure form and identification of all isolates was done by cultural, morphological and biochemical characters.
Molecular identification of Pseudomonas aeruginosa and detection of some virulence genes. DNA extraction from 10 isolates biochemically identified as Pseudomonas aeruginosa was performed using the QIAamp DNA Mini kit The sample was then washed and centrifuged following the manufacturer’s recommendations.
PCR amplification. For PCR, primers were utilized in a 25 μl reaction containing 12.5 μl of EmeraldAmp Max CR Master Mix. The products of PCR were separated by electrophoresis on 1.5% agarose gel. For gel analysis, 20 μl of the PCR products were loaded in each gel slot. The gel was photographed by a gel documentation system (Alpha Innotech, Biometra) and the data was analyzed through computer software.
Experimental design and feeding diets. 150 fish were divided to five groups (30 fishes per group) were fed the prepared pelleted experimental diet for two months according to the experimental design.
All fish in each group were weighted at the beginning (Wi) and biweekly for a continuous 8 weeks. Feed intake was readjusted according to the average body weight each period. Weight gain (WG), gain percent (G%), relative growth rate (RGR), Feed conversion ratio (FCR), feed efficiency (FE), protein efficiency ratio (PER) and Metabolizable Energy were calculated.
Sample collection and analysis of kidney and liver functions. At the end of the feeding trial before the challenge, all the fish in each aquarium were counted and weighed. For the blood collection, five fish per aquarium were randomly selected and euthanized. Blood samples were obtained from the caudal vein of the fish.
Preparation of the bacterial strain for experimental challenge. The selected virulent bacterial isolate was sub-cultured in tryptic soya broth at 37°C for 24 hrs.
Bacterial pellets were then taken after centrifugation of the broth solution. Bacterial pellets were then suspended in sterile physiological buffer saline (PBS) solution.
Experimental challenge. After the end of the experiment (after 8 weeks), fish in all groups were challenged intraperitoneal (IP) with one of the virulent Pseudomonas aeruginosa strain that previously isolated from Oreochromis niloticus. Dead and survivor fish were subjected to clinical and bacteriological examination.
Bacteriological investigation. For bacterial re-isolation samples from gills, liver, kidneys, brain and spleen of fishes were collected from 10 fishes. Then a loopful of the broth was streaked onto nutrient agar and Pseudomonas agar medium with supplement (cetrimide) then incubated at 37°C for 24 – 48 hr.
Statistical analysis. Statistical analysis was made using Analysis of Variance (ANOVA) one-way analysis of variance for study the effect of different treatment groups on the different studied variables studied that includes (growth performance parameters, hematological and biochemical) variables using (SAS, 2004).
Results and Discussion
Our results showed that fishes infected with Pseudomonas aeruginosa showed hemorrhages all over the fish body especially at the base of fins, tail and fins rot; detachment of scales, darkness in skin, skin ulceration, exophthalmia and abdominal distention. Post mortem, these fishes showed abdominal dropsy with reddish ascetic exudates; enlarged and congested liver and spleen.
Pseudomonas aeruginosa was isolated from diseased Oreochromis niloticus in which 10 positive samples out of 70 tested ones with a percent of 14.28. All the isolates of Pseudomonas aeruginosa produced blue green colonies on nutrient agar due to production of pyoverdin and pyocynin pigments. Also they produced green colonies on Pseudomonas agar supplemented with Cetrimide.
The biochemical tests indicated that Pseudomonas aeruginosa positive to citrate utilization test, positive to catalase test, oxidase and citrate test, positive to motility test while negative to indole test, methyl red, vogaus proskauer, indole production, urease and H2S production on triple sugar iron (TSI).
PCR used in diagnosis of bacterial fish diseases, isolated from cultured fish, it is a very fast and accurate method. These results were agreement with Abd El Tawab et al. (2016) who detected PCR could be used for detection of Pseudomonas aeruginosa virulence genes.
Polymerase chain reaction (PCR) can be used for detection of virulence genes of Pseudomonas aeruginosa giving positive results for outer membrane lipoprotein gene (oprL) at 504 bp.
Growth performance
The Yucca schidigera extract 0.1% group significantly increased final body weight by about 13.56% more than control groups (groups 1 and 2) moreover, increased significantly the total gain, gain percent and relative growth rate by about 39.66%, 38.92% and 29.36% respectively.
Also supplementation of the Yucca schidigera extract in the Nile tilapia diet by about 0.1% improved FCR, FE and PER by about 16.95%, 21.65% and 18.5% respectively throughout whole experimental period while increasing Yucca schidigera extract in tilapia fish diet by level 0.14 and 0.2% had no significant effect on the previous mentioned parameters when compared with control and 0.1% yucca groups.
“The results of current study indicated an improved growth performance (final weight, total gain, gain % and relative growth rate) for Nile Tilapia when fed diet supplemented with 0.1% Yucca schidigera extract.”
Supplementation of basal diet with a Yucca schidigera extract 0.1% significantly increased feed intake, relative growth rate (RGR), protein efficiency ratio PER) and improved feed conversion ratio (FCR) compared with O. niloticus fed the basal diet. This means a decrease in the amount of feed necessary for animal growth which could result in a reduction in the production cost.
Effect of dietary supplementation of yucca extract on kidney and liver functions
Addition of YMS0.1% has not any adverse effect on kidney and liver health. However, most of the herbal substances are poorly absorbed, and they produce some effects in animals such as diarrhea. If used in higher doses, they are able to harm intestine and even destruction of red blood cells resulting from hemolysis could occur. Thus, high levels of yucca meal can be detrimental to fish health.
The re-isolation and survival rate after experimental challenge
The re-isolation rate of Pseudomonas aeruginosa from 10 survival fishes after challenge decreased in groups fed on yucca extract than the control group. Also in our study, after challenge with Pseudomonas aeruginosa all treated groups showed a reduced mortality and morbidity rate compared to the control group and the best survival was observed in group fed on 0.1% yucca extract.
Conclusion
Based on the results obtained, it can concluded that yucca extract in the diet can be used as a cost- effective, safe and biocompatible feed additive for supplementation in Nile tilapia diets to improve growth performance and enhance disease resistance in cultured fish. The optimum inclusion level of yucca extract on juvenile Nile tilapia diets was found to be 0.1% in the diet in which this concentration give the best growth performance and disease resistance.
This is a summarized version developed by the editorial team of Aquaculture Magazine based on the review article titled “YUCCA PLANT AS TREATMENT FOR PSEUDOMONAS AERUGINOSA INFECTION IN NILE TILAPIA FARMS WITH EMPHASIS ON ITS EFFECT ON GROWTH PERFORMANCE” developed by: EL-KEREDY M.S. ABEER – Regional Kafrelsheikh Animal Health Research Institute, AND NEHAL A.A. NAENA – Regional Kafrelsheikh Animal Health Research Institute. The original article was published on JULY 2020, through ALEXANDRIA JOURNAL OF VETERINARY SCIENCES under the use of a creative commons open access license. The full version can be accessed freely online through this link: DOI:10.5455/ajvs.113537
More information: www.yucca.com.mx
