EFFICACY OF Azadirachta indica LEAF EXTRACT ON THE INFECTIVE LIFE-STAGE OF Acusicola sp. (Copepoda: Ergasilidae) FROM RABBITFISH (Siganus guttatus)

Truong Thi Hoa*⁽¹⁾, Tran Nam Ha⁽¹⁾

⁽¹⁾ University of Agriculture and Forestry, Hue University,

No 102 Phung Hung Street, Hue City, Viet Nam

* Corresponding author: truongthihoa@huaf.edu.vn

The ergasilid copepods Acusicola sp. were sampled from Rabbitfish (Siganus guttatus) cultured in Thua Thien Hue province, Vietnam and described based on morphological and molecular evidence. The effect of Azadirachta indica leaf extract on the infective life-stage of Acusicola sp. was assessed in vitro. Acusicola sp. were exposed for 24 hr to different concentrations of A. indica leaf extract and then observed until 30 hr in non-A. indica leaf extract media. A. indica leaf extract with concentrations of 10, 50, 100, and 500 ppm were obtained through dilutions with filtered and sterilized seawater. Negative control group (No A. indica leaf extract added) was maintained the same way as treated groups. Each experimental group was tested in triplicate. The results showed that A. indica leaf extract was able to kill Acusicola sp. at 500 ppm and there were statistically significant higher mortalities at 500 ppm at 24 hr (p< 0.05) compared to lower concentrations. Mortality increased further and significantly after transfer to clean seawater at 30 hr (p<0.05) compared to lower concentrations. When using A. indica leaf extract at 50 ppm and 10 ppm concentrations, mortality did not increase significantly (p<0.05) after transfer to clean seawater at 30 hr (p<0.05). In addition, mortalities increased even after removing the extract suggesting a residual and prolonged effect on the survival of the parasite. Our results indicated that the infective life-stage of Acusicola sp. from Rabbitfish is sensitive to A. indica leaf extract and may be used to control or prevent the infestation of Acusicola sp.

Keywords: Acusicola sp., Azadirachta indica, Neem leaf extract, Rabbitfish

A MIXTURE SUPPLY OF Psidium guajava L. AND Azadirachta indica EXTRACT STRONGLY ENHANCE THE IMMUNE RESPONSES, ANTIOXIDANT,
AS WELL AS DISEASE RESISTANCE IN RED TILAPIA (Oreochromis sp.) COMPARE TO SINGLE DIETS

Nhu Q. Truong^1*, Hang T. B. Bui², Hang T. T Nguyen², Mai T. Nguyen³, Quynh D. Nguyen², Ha T. K. Nguyen², Hoa T . T Tran², Thu N. M Vu¹, Bich N. Tran¹, Patrick Kestemont⁴, Phuong T. Nguyen²

¹ College of Agriculture, Cantho University, Cantho City, Vietnam

² College of Aquaculture and Fisheries, Cantho University, Cantho City, Vietnam

³ Faculty of Fisheries, Vietnam National University of Agriculture, Hanoi, Viet Nam

⁴ Research Unit in Environmental and Evolutionary Biology (URBE), Institute of Life, Earth and Environment, University of Namur, Namur, Belgium

*Corresponding author: tqnhu@ctu.edu.vn

The study was conducted to compare the effect of a single supply or mixture of ethanol plant extract-based diets on the immune responses, antioxidant activities, and disease resistance of red tilapia (Oreochromis sp.). Fish were fed diets containing guava (Psidium guajava-0.3%), neem tree (Azadirachta indica-0.3%), and their mixture (v:v) at 0.1%:0.5%, 0.2%:0.1%, 0.4%:0.2%, and 0.8%:0.4% in 6 weeks. The immune and antioxidant parameters were examined at W3, W6 post-feeding, and after the challenge test. The challenge test with Streptococcus agalactiae was done at W6. The results showed that extract-based diets significantly improved total white blood cells (WBC), respiratory burst, lysozyme, and complement, peroxidase, and catalase activities in the dose and time-dependent manners. Specifically, dietary supplementation with all mixture groups, except the group of 0.1%:0.5% simultaneously increased  WBC,  respiratory burst, lysozyme, complement, and catalase activities after 6 week-feeding. Similarly, diets supplemented with combined extracts could significantly decrease the mortality of red tilapia following bacterial infection compared to control and single supply. The extract-based diets, with single Pg and Pa extracts, and to a lesser extent to combined extracts could significantly improve the immune responses, antioxidants as well as disease resistance again pathogen.

EFFECT OF SALINITY LEVELS ON BIOMASS QUALITY OF ARTEMIA FRANCISCANA CULTURED IN VINH CHAU SALTPANS

Duong Thi My Han^1*, Nguyen Thi Hong Van¹ and Nguyen Van Hoa¹

¹: College of Aquaculture and Fishery, Cantho University

^*Corresponding author: dtmhan@ctu.edu.vn

This study was done by collecting the Artemia biomass that was cultured in Vinh Chau saltpans at different salinities, from 40-80‰ and then was analyzed to assess the proximate composition as well as the fatty acid profiles; aiming to determine the effect of cultured salinities on these constituents and as consequense giving notice to both Artemia culturists and consumers. The results showed that only protein was affected by salinity, ranging from 50-55% (P<0.05), while other components had no significant difference. Collected biomass at salinity of 50, 60 and 70‰ contained higher protein content than 40, 80‰ and 60s (stable salininity at 60‰; P>0.05). The highest total fatty acid (TFA) was recorded 40‰ (78.4 mg/g); The lowest was at 80‰ (59.8 mg/g) which was 5-31% lower than when cultured at other salinities. the PUFA content was highest at 50‰, followed by 60s, 80‰ and low at 60‰ and 70‰. Most of fatty acids, fatty acid classes and essential fatty acids were not significantly affected by salinity levels, indicating that they were probably influenced by the combined effected from many field culture conditions as well as the pond management.

Keyword: Artemia biomass, salinity, proximate composition, fatty acid profiles

EFFECTS OF INITIAL STOCKING DENSITIES ON POPULATION DEVELOPMENT AND BIOMASS YIELD OF ARTEMIA FRANCISCANA CULTURING IN VINH CHAU SALTPANS

 Le Van Thong^1*, Nguyen Thi Hong Van¹ and Nguyen Van Hoa¹

¹: College of Aquaculture and Fishery, Cantho University

Email: vanthong@ctu.edu.vn

The study was conducted in saltpans with four treatments corresponding to four initial densities of 100, 150, 200 and 250 nauplii/L  to evaluate the effect of stocking densities on Artemia performance, their population development, reproduction as well as biomass yield. This experimment was carried out in 500m² earthern ponds at Vinh Chau saltpans during 6 weeks.The results showed that stocking densities significantly affected to the length of Artemia. After 14 days, Artemia were stocked at 250nauplii/L giving smallest length and statistically significant differed (p<0.05) with the remained treatments. The results also indicated that population composition was effected by stocking densities, especially the Nauplii, Preadult and female (p<0.05) . In addition, the fecundity was not differently among treatments (p>0.05) ranged from 71-90 embryos/female/brood. Biomass yield was revealed to be related to initial stocking densities (p<0.05; r²>0.8), highest yield was observed at 150-200nauplii/L (613-669kg/ha/6 weeks) while lower yields were in 100 nauplii/L(458kg) and 250 nauplii/L(443kg).

Keywords: Artemia, stocking densities, population composition, biomass yield.

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PRESENCE OF ANISAKIS (NEMATODA) ON SARDINE (SARDINELLA SPP.) AND SCAD (DECAPTERUS SPP.) AT THE NORTHERN COAST OF REMBANG REGENCY CENTRAL JAVA

Lutfi Septiana D, Rizka Fauziana S, Alusia Melanita RU, Murwantoko, Eko Setyobudi*

Fisheries Department Faculty of Agriculture Universitas Gadjah Mada

Jl. Flora Gedung A-4 Bulaksumur Yogyakarta 55281

^*Corresponding author: setyobudi_dja@ugm.ac.id

This study aims to determine the prevalence, mean intensity, and target organs of Anisakis larvae infection on Sardinella spp. and Decapterus spp. from the Northern Coast of Rembang, Central Java. A total of 444 fish samples, consisting of 303 sardines and 141 scads were collected from Tasik Agung Fishing Port Rembang. Fish samples were measured for body length and weight, then dissected for Anisakis larvae examination, that is, in the abdominal cavity, digestive tract, internal organs, and muscles. The Anisakis collected were identified molecularly using the PCR-RFLP method and direct sequencing. The result showed that sardines and scad from the northern coast of Rembang Regency were susceptible to infection with Anisakis, with different levels of infection. Bali sardine (S. lemuru) was infected with a very low prevalence and mean intensity (P= 1.97%, MI= 1.5 larvae/ind.), while scad had a very high prevalence and mean intensity, i.e. prevalence of 100% with mean intensity of 12.63 larvae/ind. for Indian scad (D. russelli) and prevalence of 96% with a mean intensity of 14.33 larvae/ind. shortfin scad (D. macrosoma). Anisakis larvae were mostly found in the abdominal cavity with a percentage of 83.33% (S. lemuru), 99.03% (D. russelli), and 94.26% (D. macrosoma), and were not found in muscle. Molecular identification showed that Anisakis was found in Sardinella lemuru and Decapterus spp. was Anisakis typica.

Keywords: infection, mean intensity, pelagic, prevalence, Java Sea, zoonosis

EVALUATION OF FUNGAL INFECTION ON THE ASIAN SWAMP EEL (MONOPTERUS ALBUS) CULTURED

Khang B.N. Huynh^1,*Quyen N.T. Ha¹ and Thy M.T. Dang¹

1Institute of Aquaculture and Fisheries, Can Tho University, Campus II, 3/2 Street, Ninh Kieu District, Can Tho City, Viet Nam

*Corresponding author: khangm0620004@gstudent.ctu.edu.vn

The Asian swamp eel (Monopterus albus) is not only an economically important freshwater species in aquacultural production, but also has a high nutritional level in Mekong Delta. The objectives of this study were to determine the fungal infected on Asian swamp eel at the hatchery. A total of 250 eggs and 181 samples from fry to fingerling were collected at Can Tho, Hau Giang, and Tra Vinh. The clinical signs were secretion of swimming lethargy, feeding reduction, mucus mass, red spots and white spots on the body. The results showed that the prevalence of fungal infection was highest in fry (88.2%),   lowest   in   fingerlings   (9.3%),    and    eggs    (80.8%).   The   fungi    were    identified   as Achlya sp., Achlya     bisexualis, Achlya     klebsiana, Protoachlya      paradoxa, Aspergilus sp.,   and Fusarium sp. The infection rate in eggs of Achlya sp. and Protoachlya paradoxa was 53.2% and 27.6%, respectively. The infection rate of Achlya bisexualis (67.5%) was higher than that of Achlya klebsiana (20%) in the fry. The fingerling was infected Achlya sp. (7.5%) and Fusarium sp. (1.3%). The results also indicated that Achlya sp. was identified with a high infection rate in eggs and fingerlings.

Keywords: Achlya, Fusarium, Monopterus albus, Swamp eel,

ISOLATION AND SELECTION OF BACILLUS AND LACTIC ACID BACTERIA WITH THE CAPABILITY TO INHIBIT HEMORRHAGIC BACTERIA IN ASIAN SWAMP EEL (Monopterus albus Zuiew, 1793) IN THE MEKONG DELTA OF VIETNAM

Dung T. Tu^1,*, Loi V. T. Nguyen², Thanh S. Nguyen³, Thanh V. Nguyen⁴, Trung B. Nguyen¹, Khoi M. Le¹

1College of Aquaculture & Fisheries, Can Tho University, Can Tho City, Viet Nam

2Graduate student of ¹Biotechnology Course 27, Biotechnology Research and Development Institute, Can Tho University, Can Tho City, Viet Nam

3Advanced Program in Aquaculture Course 44, College of Aquaculture and Fisheries, Can Tho University, Can Tho City, Viet Nam

4Biotechnology Research and Development Institute, Can Tho University, Can Tho City, Viet Nam

*Corresponding author: ttdung@ctu.edu.vn

This study aimed to select strains of Bacillus spp. and lactic acid bacteria strains that might fight against Aeromonas veronii CT07 causing hemorrhagic disease in Asian swamp eel. A total of 30 Bacillus spp. strains and 20 lactic acid bacteria strains were isolated from healthy eels cultured in tanks in An Giang, Can Tho, and Hau Giang in Vietnam. The results of the bacterial screening showed that both 2 groups including 6 Bacillus spp. strains and 20 lactic acid bacterial strains were resistant to A. veronii CT07 by drip technique. Wherein, the Bacillus B13 and lactic acid L1 bacterial strains demonstrated the largest inhibition zone. A comparison of the antimicrobial properties of bacteriocins from Bacillus strains and lactic acid bacteria revealed that 20 different lactic acid bacteria strains were unable to inhibit A. veronii CT07, whereas 1/30 of the Bacillus strains were resistant to A. veronii CT07. Moreover, the partial sequencing of the 16S rRNA gene confirmed that the Bacillus B13 and lactic acid L1 bacterial strains were Bacillus amyloliquefaciens and Lactobacillus plantarum, respectively. In conclusion, these two bacterial strains have the potential to be used as probiotics in disease control in intensive Asian swamp eel farms.

Keywords: Asian swamp eel, Aeromonas veronii, Bacillus spp., lactic acid bacteria.

EFFECTS OF DIETARY ORAL VACCINE SUPPLEMENTARY FREQUENCY AND THE ABILITY TO ENHANCE THE EFFECTIVE VACCINE BY Β-GLUCAN AND VITAMIN C IN PREVENTING DISEASE CAUSED BY EDWARSIELLA ICTALURI ON STRIPED CATFISH (PANGASIANODON HYPOPHTHALMUS) IN THE MEKONG DELTA OF VIET NAM

Khoi M. Le^1*, Trung B. Nguyen¹, Hieu T. Huynh², Dung T. Tu¹

¹College of Aquaculture & Fisheries, Can Tho University, Can Tho City, Vietnam

² Aquatic Pathology Course 44, College of Aquaculture and Fisheries, Can Tho University, Can Tho City, Vietnam

^*Corresponding author: lmkhoi@ctu.edu.vn

This study was conducted to evaluate the effects of feeding frequency using an oral vaccine and the potential of β-glucan and vitamin C to enhance the vaccine efficacy in preventing disease caused by Edwarsiella ictaluri in striped catfish (Pangasianodon hypophthalmus) in the Mekong Delta of Vietnam. Experiment 1 was randomly arranged with 6 treatments, including control with no vaccinations applied to the feed and five treatments with vaccines added to the feed at different feeding frequencies. Growth performance and specific antibody levels in experimental fish were measured at the beginning and on day 21 of the experiment. After three weeks, the experimental fish were challenged with E. ictaluri to assess the vaccine’s relative percentage survival (RPS). The results revealed that the vaccination fed continuously for 9 days had the greatest RPS value (42±7.07%), whereas the growth performance of feeding vaccine treatment groups was lower than in the control, the difference was not statistically significant. Experiment 2 was performed to investigate the potential of utilizing β-glucan and vitamin C to boost vaccination protection with 8 treatments, including a vaccine- and stimulant-free control treatment, 2 treatments with stimulant and without the vaccine, and 5 treatments using vaccine continuously for 9 days in combination with different concentrations of immunostimulants. The results showed that the vaccination supplemented with 2% β-glucan might not only improve the RPS value (52.4±0%) and the antibody level (6.25±1.77) but also reduce the negative effects of oral vaccines. In conclusion, the results of this study revealed that β-glucan might be used as an adjuvant to an oral vaccination in striped catfish.

Keywords: Edwarsiella ictaluri, immunostimulant, oral vaccine, striped catfish.

IDENTIFICATION AND CHARACTERIZATION OF BACILLUS SPECIES WITH THE POTENTIAL PROBIOTIC ACTIVITY AGAINST PIRAB^VP-BEARING VIBRIO PARAHAEMOLYTICUS CAUSING ACUTE HEPATOPANCREATIC NECROSIS DISEASE IN MARINE SHRIMP

 Cuong T. Le^1*, Cam Hong Van², Thu Thi Anh Nguyen²

¹Institute of Aquaculture, Nha Trang University, Nha Trang, Vietnam

²Institute for Biotechnology and Environment, Nha Trang University, Nha Trang, Vietnam

^*Corresponding author: cuonglt@ntu.edu.vn

Vibrio parahaemolyticus, carrying the binary PirA^VP and PirB^VP toxin genes is the causative agent of acute hepatopancreatic necrosis disease (AHPND) in marine shrimp that has caused significant economic loss for worldwide shrimp industry. Using beneficial microbes as an alternative to antibiotics is one of the most effective and environmentally friendly methods in controlling the outbreak of AHPND in shrimp production systems. In the present study, 33 Bacillus isolates obtained from 20 gut samples of grown-out shrimps and 20 mangrove sediment samples were screened for their probiotic properties against pirAB^Vp-bearing V. parahaemolyticus strains isolated from farmed shrimps infected with AHPND. Of the investigated isolates, nine showed clear antagonistic activity and extracellular enzyme production such as amylase, protease, lipase, cellulase. No hemolytic activity was detected in two of these isolates, Bacillus CCT-Ba9 and CCT-Ba42 indicating their safety as good probiotic candidates. Biochemical and 16S rRNA sequencing analysis identified them as B. pumilus and B. subtilis, respectively. Both species could grow within a pH range from 4.0 to 8.0 and salinity from 0 to 50‰. Our results demonstrated that Bacillus CCT-Ba9 and CCT-Ba42 are promising probiotic strains and may have applications to prevent/control the outbreak of AHPND in shrimp aquaculture.

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Keywords: Vibrio parahaemolyticus, Acute Hepatopancreatic Necrosis Disease, AHPND, Bacillus, Shrimp, Disease

EFFECT OF DIETARY VITAMIN E ON GROWTH, BODY COMPOSITION AND NONSPECIFIC IMMUNITY OF SNUBNOSE POMPANO TRACHINOTUS BLOCHII (LACEPÈDE, 1801)

Hanh T. Pham*, Khang T. Nguyen, Hich V. Tran, Hoang M. Le

Institute of Aquaculture, Nha Trang University, No 2 Nguyen Dinh Chieu Street, Nha Trang City, Viet Nam

^*Corresponding author: hanhpt@ntu.edu.vn

A 10-week feeding trial was conducted to determine the optimal dietary vitamin E requirements for snubnose pompano (Trachinotus blochii) juveniles. The experiment consisted of 6 dietary treatments supplemented with 6 levels of vitamin E (0 (control), 100, 200, 400, 800 and 1.600 mg/kg diet). Fish (body weight = 5,3 ± 0,15g) were randomly contributed into these treatments with three replicates (200L composite tanks) each. The results showed that vitamin E supplementation affected on growth parameters (length gain, weight gain, specific growth rate (in length and weight)), hepatic steatosis index (HSI), whole body protein, lipids contents, red blood cells, white blood cells, hematocrit (Hct) and serum lysozyme content. The growth performance, HSI, biochemical composition, hematological and immune indexes of fish improved gradually and maximised when the vitamin E supplementation leveled from 100 and 200 mg/kg up  to 400 mg/kg (P < 0.05). However, there was no significant difference in these parameters when dietary vitamin E was higher (800 và 1.600 mg/kg). Survival rate, visceral index (VSI), ash and moisture contents of fish did not affected by neither the presence nor levels of vitamin E. We suggest that, vitamin E is essential and its supplemantation of 400 mg/ kg is optimal for growth, biochemistry and immune response in snubnose pompano at juvenile stage.

Keywords: snubnose pompano, Trachinotus blochii, vitamin E, growth, body composition, nonspecific immunity

ISOLATION, IDENTIFICATION, AND POTENTIAL PROBIOTIC CHARACTERIZATION OF LACTIC ACID BACTERIA ISOLATED FROM INTESTINAL TRACTS OF MARINE FISH

Rohaya Salah, Supinya Thapthong, Saweit Chaimongkol, Pochanart Kanjan* Department of Agricultural and Fishery Science, Faculty of Science and Technology, Prince

of Songkla University, Pattani 94000, Thailand

 *Corresponding author: pochanart.k@psu.ac.th

This study involved isolation of lactic acid bacteria (LAB) from intestinal tracts of marine fish and characterization of their physiological and probiotic properties based  on antibacterial activity against pathogenic bacteria, salt tolerance, and antibiotic susceptibility. A total of 38 presumptive LAB colonies that appeared as Gram-positive and catalase- negative were collected. Only 5 isolates designated LAB 1, LAB 3, LAB 11, LAB 29 and LAB 37 exhibited an excellent inhibitory zone diameter against aquatic pathogenic bacteria when evaluated by agar spot test. Lactic acid bacterial isolates with antibacterial activity showed strong salt tolerance which survival rates more than 90% and presented no significant concerns with regards to antibiotic resistance. Among these, isolate LAB 29 showing the highest antibacterial activity against all pathogenic bacteria was identified as Lactobacillus plantarum based on 16S rRNA sequence analysis. This research suggests that selected LAB could be used as a food/feed supplement to reduce pathogenic bacteria in food or aquatic animal.

Keywords: Lactic acid bacteria; marine fish; pathogenic bacteria; probiotic

PHARMACOKINETICS OF CEFOTAXIME AND HEPATOPANCREAS HISTOLOGY IN WHITE-LEG SHRIMP (Litopenaeus vannamei)

Huynh Thi Kim Duyen^1*, Marie-Louise Scippo², Caroline Douny², Siska Croubels³, Mathias Devreese³, Dang Thi Hoang Oanh¹, Nguyen Quoc Thinh¹, Nguyen Ngoc Vui¹, Tran Minh Phu¹

¹Department of Seafood Science and Technology, College of Aquaculture and Fisheries, Can Tho University, VietNam

²Department of Food Sciences, Faculty of Veterinary Medicine, University of Liège, Belgium

³Department of Pharmacology, Toxicology and Biochemistry, Faculty of Veterinary Medicine, Ghent University, Belgium

*Corresponding author: htkduyen@ctu.edu.vn

The study was conducted to determine pharmacokinetic of cefotaxime and the effects of cefotaxime on shrimp hepatopancreas. The content of the research included (i) cefotaxime distribution in shrimp hepatopancreas and plasma and their pharmacokinetic data when feeding at a concentration of 25 mg/kg shrimp, sampling was done at 0.5, 1, 2, 4, 8, 12, 24 hours after feeding medicated feed, (ii) determination of minimum inhibition concentration and antibiogram of cefotaxime on Vibrio parahaemolyticus isolates by dilution method and plating, (iii) the impact of cefotaxime on shrimp hepatopancreas will be determined through histology. The results showed that selected Vibrio parahaemolyticus strains were susceptible to cefotaxime through the low MIC values and large inhibition diameter, 28-32 mm. The calculation on the liver of T > MIC (Minimum Inhibitory Concentration) revealed a potential therapeutic effect on acute hepatopancreatic necrosis disease a common disease in shrimp if the dosing interval is 4.6 hours. A higher administered dose of cefotaxime to shrimp should be trialed to achieve the desired cefotaxime concentration in plasma as MIC. Results from histology analysis revealed that cefotaxime did not affect shrimp hepatopancreas even feeding twice a day for three consecutive days.

Keywords: cefotaxime, hepatopancreas, pharmacokinetics/pharmacodynamics, white-leg shrimp