Molecular characterization of aeromonas hydrophila isolated from pangasius hypophthalmus (sauvage, 1878) in Pahang river, Malaysia

Pahang, Malaysia are very famous of its Pangasius spp (Patin) aquaculture activity. Pangasius spp. has excellent potential for inland aquaculture system with its fast growing ability and good market value in European markets (Singh and Lakra, 2012).Pangasius spp. is one of the largest and most important inland fisheries in the world which mainly contribute as a food source. The production of Pangasius spp. in Malaysia showed tenfold increased from 1,625.21 tonnes in 2000 to 10,891.51 tonnes in 2011. However, Pangasius culture has been reported to face disease problem causing almost 30% mortalities especially in Sungai Pahang and Sungai Kuantan due to multiple infections of bacteria and virus. The reported bacterial disease was Motile Aeromonas Septicemia (MAS) while virus is channel catfish virus (CCV). Thus, the aim of this study is to understand Aeromonas hydrophila that had cause MAS infection in Pangasius hypophthalmus at Pahang River. Bacteria were collected from liver, kidney and spleen of Pangasius hypophthalmus cultured in Pahang River Malaysia. Isolated bacteria were cultured onto Brain Heart Infusion (BHI) Agar and identified using Gram staining, biochemical tests and API systems. Aeromonas spp. isolates were then subjected to conventional Polymerase Chain Reaction (PCR) using 16s rRNA gene and ITS gene. The amplified genes were sent for DNA sequencing and the results were tested with BLASTn to search for any sequence similarity with other bacteria in the Genebank. Construction of phylogenetic tree was carried out using MEGA 6 software. From the DNA sequencing method, isolates obtained were confirmed as Aeromonas hydrophila. Neighbor-joining method of phylogenetic tree constructed also reveals that the genetic variation of the isolates is similar with Aeromonas hydrophila from China and India. Thus, this information will facilitate to trigger a better prevention and treatment against MAS

A review of betanodavirus vaccination as preventive strategy to viral nervous necrosis (VNN) disease in grouper

Viral disease outbreak is the most serious issue as it may cause severe losses to farmers as well as to economy in the marine industry worldwide. Among fish viral diseases, betanodavirus is a significant pathogen that causes viral nervous necrosis (VNN) and can result in mass mortalities to fish culture especially at larval stages. In Malaysia, betanodavirus had been isolated from groupers, seabass, red snappers, and golden pomfret. Recently, inconsistent seed supply is observed due to viral infection at larval stages which limits the growth of fish culture. Therefore, seeds of grouper are often imported from neighboring countries such as Indonesia by farmers. Strict importation regulations should be practiced as the importation of fish seeds may become a possible source of the virus entering the country. It is a challenge to track farmers who are affected by the disease in order to segregate or eliminate the VNN carrier spawners. This scenario had resulted in incomplete destruction of diseased fish population and leads to re-occurrence of the disease at the early stage of grouper. This situation warrants immediate attention to develop promising prevention strategies such as a new vaccine which is very important and could work effectively with better farm management approaches. This article discusses the occurrence of viral nervous necrosis (VNN) disease in Malaysia and reviews possible preventive measures via vaccination to combat the disease

Determination of LD50 for Streptococcus agalactiae and Staphylococcus aureus infections in tilapia

One hundred and sixty fingerlings and 80 adult tilapias were experimentally infected with Streptococcus agalactiae and Stapylococcus aureus to determine their LDso. Four concentrations of Streptococcus agalactiae (109, 108,107, 106 CFU/mL) were used in this experimental infection. These tilapias were divided into 4 groups of 40 fingerlings and 20 adults per group. Groups 1, 2, 3 and 4 of the fingerlings were exposed to 109, 10,107, 106 CFU/mL of S. agalactiae by immersion in 2 L inoculum solution for 20 min. Similarly, the adult groups were exposed to the same concentrations of S. agalactiae but by intraperitoneal injection at the rate of 1 mL of the inoculum per gram. Similar procedures were repeated using exposure to Staphylococcus aureus alone or a combination of S. agalactiae and S. aureus. All test groups were observed for signs of infections. On Day 7 post-infection (pi), all fish that were still alive were humanely killed. The LDso of the adult tilapia that were exposed to S. agalactiae, S. aureus or mixed infection was 2.3884 x 107,2.8151 X 108 , and 4.2409 x io', respectively. For the fingerling groups, the LDso for S. agalactiae, S. aureus, and mixed infection was 2.9242 x 1020,2.8665 x 1017 , and 4.9748 x IO!', respectively. Experimental infection in adults could be established within 12 h post-injection to 6.3 x 109 CFU per mL and 9.7 x 109 CFU per mL of S. agalactiae and S. aureus, respectively. For fingerlings, infection could be established within 72 h following bath immersion to 6.3 x 109 CFU per mL and 9.7 x 109 CFU per mL of S. agalactiae and S. aureus, respectively

Edwardsiella ictaluri: pathogenicity and LD50 in Pangasius nasutus

This study focuses on pathogenicity and LD50 of Pangasius nasutus against Edwardsiella ictaluri. Pangasius nasutus or ‘patin buah’ is a native freshwater species of peninsular Malaysia and can be found in Pahang River. The market price for this species is high as it tastes better compared to other catfish. Edwardsiella ictaluri is a pathogenic bacteria and the causative agent that cause enteric septicemia of catfish (ESC) in the Pangasius species. However, the prevention measures against Edwardsiella ictaluri are still unknown for Pangasius nasutus due to the lack of research and study. Therefore, the objective of this study is to identify Edwardsiella ictaluri isolated from Pangasius nasutus cultured in Pahang River using polymerase chain reaction (PCR) and to determine the pathogenicity and LD50 of Pangasius nasutus against Edwardsiella ictaluri through injection method. There are four different concentrations of Edwardsiella ictaluri (1×1020 , 1×109 , 1×108 , 1×107 ) that were injected intraperitoneally including normal saline water as control to a total of 50 Pangasius nasutus. Observation of clinical signs and mortality were carried out for 30 days and LD50 was determined. The earliest clinical sign was observed at concentration of 1×1010 cfu/ml at 2 hours postinfection of Edwardsiella ictaluri where pale liver and congested kidney can be observed after dissection. Other clinical signs observed are inflammation on tail and fin, hemorrhagic fin, hemorrhagic upper mandible, discoloration, and inflammation on the lower part of body. The first mortality of Pangasius nasutus was at concentration 1×1010 cfu/ml at 2 hours of post infection. The highest cumulative mortality was recorded at concentration 1×1010 cfu/ml with 100% of mortality rate. From the result, the value of LD50 of Edwardsiella ictaluri calculated was 1×106 cfu/ml. From this study, it can be concluded that Edwardsiella ictaluri does affect the survivability Pangasius nasutus in Malaysia

The significance of multiple bacterial infections in lutjanus sp. in Malaysian marine cage culture system

The epizootiology of disease problems in Lutjanus erythropterus (Crimson snapper) was conducted in Pulau Langkawi Kedah, the northern state of Peninsular Malaysia, for a period of eight months until harvest due to reported continuous mortality of about 30% after two months introduction, incurring high economic loss. Infected fish was morbid, discoloured with haemorrhagic ulcers in dorsal areas and severe necrosis of caudal region. Monthly sampling revealed multiple Vibrio infections with variable prevalence rate during grow-out stage as shown in Fig.1. Necropsy revealed abnormal liver, with cases of severe whitish nodules in kidney and spleen. The caudal peduncle area was soft and fluffy to touch, releasing yellowish exudates when cut. Histopathological diagnosis of the kidney, spleen and muscle using Grocott and Modified Ziehl Nelsen staining revealed red, long, thin and filamentous organisms in the granulomatous lesions suggestive of nocardiosis shown in Fig. 2. Further sampling of the Lutjanus sp that were above 250g(5thmonth), showed exopthalmus with watery brain, in which case Streptococcus iniae was isolated for three consecutive months. Vibriosis was prevalent throughout the culture period with concurrent infection of V. vulnificus and V. alginolyticus during the later period nearing harvesting. The study has shown that multiple bacterial infections are prevalent throughout culture period infecting at different level and stages of fish growth causing continuous mortality. High economic loss is expected with the recorded pattern of disease infections and thus knowing the source of fish with better treatment regime for effective control is needed for sustainable healthy production. Fig.1. Multiple Vibrio sp. infection in Lutjanus erythropterus (Crimson Snapper) Fig.2. Nocardia spp. Infection in Lutjanus erythropterus (Crimson Snapper

Outbreak of polycystic liver in red hybrid tilapia, Oreochromis niloticus (L.) x Oreochromis mossambicus (Peters)

Polycystic lesions have been reported in many different fish species. This paper reports for the first time a case of polycystic lesions in the liver of tilapia. A group of 700 tilapia juveniles of approximately 50 g was obtained from a hatchery in Negeri Sembilan, Malaysia. When they were between 130 and 250 g, they started to show distended abdomen but appetite remained normal. Post-mortem examination on 30 randomly selected tilapia revealed numerous large masses containing jelly-like material in the peritoneal cavity of 33% of the fish. Histopathology revealed typical cystic lesion of liver tissue. This is the first report in hybrid tilapia and is presumed to be the result of a genetic anomaly

Current status and advances of fish vaccines in Malaysia

Fish diseases have a significant negative influence on the Malaysian aquaculture industry. Since the 1980s, the sector has grown in size, which has resulted in a rise in the prevalence of infectious outbreaks affecting both freshwater and marine cultured fish species. Demand for commercially available fish vaccinations is predicted to increase as infectious disease outbreaks continue to occur. In Malaysia, aquaculture vaccine research and development (R&D) are still in its infancy, with most efforts concentrating on producing vaccines against bacterial infections, most notably streptococcosis, vibriosis, andmotile Aeromonas septicemia. Despite several attempts, no homegrown vaccine has been effectively introduced into the manufacturing pipeline to date. At the moment, only three imported aquatic vaccines have received full permission, a far cry from the 314 and 60 vaccines licensed in the poultry and porcine industries, respectively. This review will describe recent findings regarding the development of aquaculture vaccines for certain fish species and diseases in Malaysia. In our opinion, R&D on fish vaccines is critical to the aquaculture industry’s viability