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Streptococcosis and aeromoniasis are the main obstacles to sustainable tilapia production. Vaccination offered an effective method to control microbial infections. Previously, a feed-based bivalent vaccine (FBBV) containing killed whole organisms of Streptococcus agalactiae and Aeromonas hydrophila mixed with 10% palm oil was successfully developed, which provided good protection against streptococcosis and aeromoniasis in Oreochromis sp. However, the mechanisms of immunities in vaccinated fish still need clarification. Here, the hindgut transcriptome of vaccinated and control fish was determined, as the gut displays higher affinity towards antigen uptake and nutrient absorption. The efficacy of FBBV to improve fish immunity was evaluated according to the expression of immune-related genes in the vaccinated fish hindgut throughout the 8-week experimental period using RT-qPCR. The vaccinated fish hindgut at week 6 was further subjected to transcriptomic analysis due to the high expression of immune-related genes and contained killed whole organisms. Results demonstrated the expression of immune-related genes was in correlation with the presence of killed whole organisms in the vaccinated fish hindgut. Transcriptomic analysis has allowed the prediction of robust immune-related pathways, including innate and adaptive immunological responses in vaccinated fish hindgut than control fish. Pathways related to the regulation of lipid metabolism and modulation of the immune system were also significantly enriched (p ≤.05). Overall, results offer a fundamental study on understanding the immunological response in Oreochromis sp. following vaccination with the FBBV pellet and support further application to prevent bacterial diseases in aquaculture.

Tilapia culture is an important source of income and nutrition to many rural families. Since 2000, the production of tilapia increased and reached domestic and global markets. Major farmed species is Nile tilapia (Oreochromis niloticus), in earthen ponds and cage cultures. Intensification contributed to global tilapia disease outbreaks, with bacterial infections causing mortalities and morbidities, threatening sustainable production. At tilapia farms, high nutrient concentrations, water temperature and fish densities enhance bacterial growth including virulent bacterial clones and potential zoonotic bacteria. Global warming favours this. This review respectively provides a comprehensive overview of the most common and emerging bacterial pathogens, diseases, clinical presentations and diagnostics of tilapia, including bacteria and diseases with zoonotic potential. First, common bacterial disease outbreaks, including streptococcosis, motile Aeromonas septicaemia, francisellosis, columnaris disease and vibriosis are described. Then, information on emerging bacterial infections of concern for tilapia, like edwardsiellosis through Edwardsiella ictaluri and E. tarda, as well as Aeromonas schubertii is provided. Reports of infectious bacterial tilapia disease outbreaks from other bacteria, including Lactococcus garvieae, Aerococcus viridans, Pseudomonas spp., Mycobacterium marinum and Chlamydia spp., and others are reviewed. Furthermore, bacteria with zoonotic potential, like Streptococcus agalactiae ST283, S. iniae, Aeromonas sp., E. tarda, Vibrio vulnificus pathovar (pv) piscis and M. marinum are included in the review, to provide the most current overview of the disease risks affecting production and post-harvest stages. Additionally, the status and risks of antimicrobial resistance in bacteria from tilapia and other cultured fish through imprudent use of antibiotics, and its future at a global level are provided.

Tilapia culture is an important source of income and nutrition to many rural families. Since 2000, the production of tilapia increased and reached domestic and global markets. Major farmed species is Nile tilapia (Oreochromis niloticus), in earthen ponds and cage cultures. Intensification contributed to global tilapia disease outbreaks, with bacterial infections causing mortalities and morbidities, threatening sustainable production. At tilapia farms, high nutrient concentrations, water temperature and fish densities enhance bacterial growth including virulent bacterial clones and potential zoonotic bacteria. Global warming favours this. This review respectively provides a comprehensive overview of the most common and emerging bacterial pathogens, diseases, clinical presentations and diagnostics of tilapia, including bacteria and diseases with zoonotic potential. First, common bacterial disease outbreaks, including streptococcosis, motile Aeromonas septicaemia, francisellosis, columnaris disease and vibriosis are described. Then, information on emerging bacterial infections of concern for tilapia, like edwardsiellosis through Edwardsiella ictaluri and E. tarda, as well as Aeromonas schubertii is provided. Reports of infectious bacterial tilapia disease outbreaks from other bacteria, including Lactococcus garvieae, Aerococcus viridans, Pseudomonas spp., Mycobacterium marinum and Chlamydia spp., and others are reviewed. Furthermore, bacteria with zoonotic potential, like Streptococcus agalactiae ST283, S. iniae, Aeromonas sp., E. tarda, Vibrio vulnificus pathovar (pv) piscis and M. marinum are included in the review, to provide the most current overview of the disease risks affecting production and post-harvest stages. Additionally, the status and risks of antimicrobial resistance in bacteria from tilapia and other cultured fish through imprudent use of antibiotics, and its future at a global level are provided.

This paper summarizes the use of museum of biological collection (MBC) in comparison of chemical contaminants between the past and the present specimens. It is inferred that MBC provides a unique and crucial insight into the spatio-temporal trend of environmental contamination by establishing a historical reference point.

Vibriosis is one of the most common threats to farmed grouper; thus, substantial efforts are underway to control the disease. This study presents an oral vaccination against multiple Vibrio spp. in a marine fish with double booster immunisation. The Vibrio harveyi strain VH1 vaccine candidate was selected from infected groupers Epinephelus sp. in a local farm and was formalin inactivated and combined with commercial feed at a 10% ratio (v/w). A laboratory vaccination trial was conducted for seventy days. The induction of IgM antibody responses in the serum of Asian seabass Lates calcarifer immunised with the oral Vibrio harveyi strain VH1 was significantly (p < 0.05) increased as early as week one post-primary vaccination. Subsequent administration of the first and second booster for 5 consecutive days, starting on days 14 and 42, respectively, improved the specific antibody level and reached a highly significant (p < 0.05) value at days 35 and 49 before slightly decreasing from day 56 onwards. Antibody titres of the control unvaccinated group remained relatively stable and low throughout the experimental period. At the end of the 70-day vaccination trial, 23 days post final boost, an intraperitoneal challenge with a field strain of Vibrio harveyi, V. alginolyticus, and V. parahaemolyticus was carried out. Our challenge study showed that oral Vibrio harveyi strain VH1 vaccine candidate could induce significant protection, with an RPS of 70–80% against different Vibrio species. Thereafter, a field trial was conducted in a mariculture farm to study the effect of field vaccination using the oral Vibrio harveyi strain VH1 vaccine candidate. A total of 3000 hybrid grouper juveniles were divided into two groups in triplicate. Fish of Group 1 were not vaccinated, while Group 2 were vaccinated with the feed-based vaccine. Vaccinations were carried out on days 0, 14, and 42 via feeding the fish with the vaccine at 4% body weight for 5 consecutive days. At the end of the stud

This case report describes a 49-year-old immunocompromised woman with tenosynovitis of the left middle finger caused by Group B Streptococcus (GBS). She claimed that a fishbone picked over her left middle finger. An orthopaedic surgeon operated for incision and drainage of pus discharge, wound debridement of the left middle finger and A1 and A2 pulley release. Treatment was initiated with parenteral cefepime three times per day given the growth of mixed Enterobacter species on the culture media and continued with oral cefuroxime twice daily upon discharge for one week. Unfortunately, during the orthopaedic clinic follow-up, the wound was unclean with a slough and skin necrotic patch. Therefore, Ray’s amputation of the left middle finger proceeded. This case contributes to further investigation of the GBS tenosynovitis due to the rise in GBS invasive infections and shows the importance of early diagnosing and initiating treatment with antibiotics that are effective against this pathogen.

Tropical rivers and wetlands are recognized as one of the greatest and most abundant ecosystems in terms of ecological and social benefits. However, climate change, damming, overfishing, water pollution, and the introduction of exotic species threaten these ecosystems, which puts about 65% of river flow and aquatic ecosystems under a moderate to high level of threat. This paper aims to assess the environmental flow of the Selangor River based on the hydrological index method using the Global Environmental Flow Calculator (GEFC) and Indicators of Hydrological Alterations (IHA) software. The daily flow data collected by the Department of Irrigation and Drainage (DID), Malaysia, over a 60-year period (1960–2020) was used in this study to assess the Selangor River flow alterations. As per the results, the river flow has had two distinct periods over the last 60 years. In the first period, the river flows without any alteration and has a natural flow with high flood pulses and low flow pulses. While in the second, or post-impact, period, the flow of the river has a steady condition throughout the year with very little fluctuations between the dry and wet seasons of the year. From the overall comparison of the pre- and post-impact periods, it can be concluded that the minimum flow in the dry seasons of the year has increased, while the maximum flow has decreased in the monsoon seasons during the post-impact period. As a result, the Flow Duration Curve (FDC) and Environmental Management Class (EMC) analysis of the river flow recommends that the Selangor River be managed under EMC “C” to provide sufficient water for both human use and ecosystem conservation, which would also help to avoid a water level drop in the reservoirs. However, further holistic studies are suggested for a detailed analysis of the effects of the dams on aquatic biodiversity and ecosystem services in the Selangor River Basin.

Southeast Asia (SEA) is a socio-economically and environmentally dynamic region of the world, with abundant renewable freshwater resources. At the same time, the population of the region is increasing and leading towards unsustainable water use and strict water management. The overall environmental flow status of Southeast Asian Rivers is assessed in this study, which is based on a critical review of the available literature of some important river basins of the study area. The results show that all riparian countries of the Mekong River are trying to utilize the hydropower potential of the river where more than 12,000 dams are constructed, which leads to significant alteration of hydrological regime in all tributaries of MRB. The two influential countries China and India are sharing the Brahmaputra River, where both countries are planning to construct dams. The 400 planned dams on this river will make the area the most concentrated region of the world in terms of big dam construction, while the low lying areas in India and Bangladesh are posing the threat of nutrient pollution due to excessive agricultural activities. The Citarum River in Indonesia is suffering from overburden of pollution, which makes the river heavily polluted while the Muda river in Malaysia is facing a lack of Integrated Water Resources Management (IWRM) and lack of stakeholders’ engagement. Moreover, many of river basins in rest of SEA countries i.e. Lao PDR, Cambodia, Viet Nam, Myanmar, Philippines, Brunei Darussalam, and East Timor are lacking attention to research and policy to this field, therefore, the status of Environmental Flow is ranked unsatisfactory in most river basins of SEA.

(1) Background: Zinc oxide nanoparticles (ZnO NPs) are widely applied in various human products. However, they can be extremely toxic for aquatic organisms, particularly fish. This research was conducted to determine the LC50 of ZnO NPs on the embryos of Javanese medaka (Oryzias javanicus) in ultra-pure, deionized, and dechlorinated tap water; (2) Methods: The experiments were conducted in a completely randomized design (CRD) with three replicates for six treatments for acute (0.100, 0.250, 0.500, 1.00, 5.00, and 10.00 mg/L) exposures for each type of water; (3) Results: The LC50 of ZnO NPs at 96 h was determined as 0.643 mg/L in ultra-pure water, 1.333 mg/L in deionized water, and 2.370 in dechlorinated tap water. In addition to concentration-dependent toxicity, we also observed time-dependent toxicity for ZnO NPs. In addition, the sizes of ZnO NPs increased immediately after dispersion and were 1079 nm, 3209 nm, and 3652 nm in ultra-pure, deionized, and dechlorinated tap water. The highest concentration of measured Zn2+ in exposure concentrations was found in ultra-pure water, followed by deionized and dechlorinated tap water suspensions. Furthermore, Javanese medaka showed high sensitivity to acute exposure of ZnO NPs in all types of water.

In aquaculture, commercial fish such as red hybrid tilapia are usually raised at high density to boost the production within a short period of time. This overcrowded environment, however, may cause stress to the cultured fish and increase susceptibility to infectious diseases. Antibiotics and chemotherapeutics are used by fish farmers to overcome these challenges, but this may increase the production cost. Studies have reported on the potential of mushroom polysaccharides that can act as immunostimulants to enhance the immune response and disease resistance in fish. In the current study, hot water extract (HWE) from mushroom stalk waste (MSW) was used to formulate fish feed and hence administered to red hybrid tilapia to observe the activation of immune system. Upon 30 days of feeding, the fish were challenged with pathogen-associated molecular patterns (PAMPs) such as lipopolysaccharides (LPS) and polyinosinic:polycytidylic acid (poly (I:C)) to mimic bacterial and viral infection, respectively. HWE supplementation promoted better feed utilisation in red hybrid tilapia although it did not increase the body weight gain and specific growth rate compared to the control diet. The innate immunological parameters such as phagocytic activity and respiratory burst activity were significantly higher in HWE-supplemented group than that of the control group following PAMPs challenges. HWE-supplemented diet also resulted in higher mRNA transcription of il1b and tnfa in midgut, spleen and head kidney at 1-day post PAMPs injection. Tlr3 exhibited the highest upregulation in the HWE fed fish injected with poly (I:C). At 3-days post PAMPs injection, both ighm and tcrb expression were upregulated significantly in the spleen and head kidney. Results showed that HWE supplementation enhances the immune responses of red hybrid tilapia and induced a higher serum bactericidal activity against S. agalactiae.

Background and aim: Aeromonas hydrophila is a major cause of bacterial infections affecting a wide range of warm water fishes worldwide. In Malaysia, A. hydrophila isolations from diseased fishes were previously reported; however, with limited information. The present study investigates the antibiotic susceptibility and pathogenicity of A. hydrophila isolated from farmed red hybrid tilapia (Oreochromis spp.) in Malaysia. Materials and methods: A. hydrophila was biochemically identified and subjected to antibiotic susceptibility tests. The isolate was then intraperitoneally injected into red hybrid tilapia, and the mortality, clinicopathological changes, and LD50 were determined up to 240 h post-infection (hpi). Results: The isolate demonstrated multiple antibiotic resistances (MAR) toward amikacin, ampicillin, cefotaxime, amoxicillin, trimethoprim-sulfamethoxazole, erythromycin, and streptomycin, with a MAR index of 0.5. The experimental infection of A. hydrophila at 105 CFU/mL in the red hybrid tilapia resulted in 100% mortality at 240 hpi. The LD50 was determined at 1.1×104 CFU/mL. Infected fish demonstrated occasional erratic swimming patterns, localized hemorrhages and depigmentation on the body and operculum areas, fin erosion, enlargement of the gall bladder, and hemorrhage in internal organs. Microscopic observation of infected fish revealed brain congestion, tubular necrosis, and glomerular shrinkage in the kidneys, necrosis of hepatocytes, and congestion of blood vessels in the liver. Conclusion: The high virulence of A. hydrophila to the red hybrid tilapia emphasizes the importance of active, on-going monitoring of its prevalence in Malaysian tilapia farming.

An unknown disease event in marine cage-cultured Asian seabass (Lates calcarifer) was observed in Malaysia in September 2019, which affected adult-sized fish and resulted in significant mortality. Affected fish showed gross signs resembling scale drop disease such as lethargy, darkened dorsal part of the body, easily detached scales, severe scale loss, reddening and hemorrhage at the ventral part of the body, and tendency to swim at the water surface. Histopathological examinations revealed abnormal changes in multiple internal organs including vacuolated cytoplasm hepatocytes, necrotic kidney tubules, atrophied glomeruli, blood congestion and hemorrhage in the spleen and brain, as well as penetration of lymphocytic inflammatory cells. Notably, basophilic hypertrophied cells and intracytoplasmic inclusion bodies were occasionally observed in the liver, indicating suspected viral aetiology. Transmission electron microscopy (TEM) revealed the presence of multiple viral particles in the cytoplasm of the infected cells. Subsequently, PCR and sequence analyses revealed that all affected fish were positive to scale drop disease virus (SDDV), which was absent from the clinically healthy fish. Phylogeny analysis based on complete ORF 060 L (encoding major capsid protein) revealed high similarity between the SDDV from Malaysia, Thailand and Singapore. This study provides first evidence of SDDV infection in cultured Asian seabass in Malaysia. We thus recommend that active surveillance should be prioritized for concentrated Asian seabass farming areas in Malaysia to prevent spread of the disease nation-wide.

A high death rate among red hybrid tilapias was observed in a farm in Selangor, Malaysia, in January 2020. The affected fish appeared lethargic, isolated from schooling group, showed loss of appetite, red and haemorrhagic skin, exophthalmia and enlarged gall bladders. Histopathological assessment revealed deformation of kidney tubules, and severe congestion with infiltrations of inflammatory cells in the brains and kidneys. Syncytial cells and intracytoplasmic inclusion bodies were occasionally observed in the liver and brain sections. Tilapia Lake Virus (TiLV), Aeromonas hydrophila and Streptococcus agalactiae were identified in the affected fish, either through isolation or through PCR and sequencing analysis. The phylogenetic tree analysis revealed that the TiLV strain in this study was closely related to the previously reported Malaysian strain that was isolated in 2019. On the other hand, A. hydrophila and S. agalactiae were closer to Algerian and Brazilian strains, respectively. The multiple antibiotic resistance index for A. hydrophila and S. agalactiae was 0.50 and 0.25, respectively. Co-infections of virus and bacteria in cultured tilapia is a new threat for the tilapia industry.

Booster biocides have been rapidly growing in use, mainly in the shipping industry and in agricultural activities. The use of booster biocides is known to cause adverse effects on marine ecosystems, such as by inhibiting the photosynthesis process in marine plants, and they have the potential to accumulate in marine organisms. In the present study, booster biocides of Irgarol 1051, diuron, 3,4-dichloroaniline (3,4-DCA) and chlorothalonil were measured in the major blood cockle (Tegillarca granosa) cultivation areas along the west coast of Peninsular Malaysia. The highest Irgarol 1051 mean was found in the blood cockle with a value of 98.92 ± 13.65 µg/kg in Kapar, Selangor, while the means of diuron and its metabolites and 3,4-DCA showed the highest values of 40.31 ± 7.61 and 41.42 ± 21.58 µg/kg in Kapar, Selangor and Sungai Ayam, Johor, respectively. Sungai Ayam, Johor also exhibited the highest amount of chlorothalonil of 29.76 ± 8.80 µg/kg. By referring to sediment quality guidelines, about 72% and more than 90% of sediment samples exceeded the environmental risk limits (ERLs) and maximum permissible concentration (MPC) for Irgarol 1051 and diuron, respectively. However, referring to the risk characterization ratio (RCR), none of the blood cockle samples exceeded 1, which means that there is no potential for adverse effects to occur. Thus, the contaminants in the marine ecosystem caused by booster biocides are highlighted as a serious issue, mainly in sediment.

This study aimed to determine the lethal concentration (LC50) of Terminalia catappa leaves extract on three cyprinid species; carp (Cyprinus carpio), goldfish (Carassius auratus) and tiger barb (Puntigrus tetrazona) through the acute toxicity test. The leaves of T. catappa were extracted with methanol and prepared in various immersion concentrations (40, 80, 100, 150, 200, 250, 300, and 350 mg/L). These extracts were immersed in the aquarium and left for 24 h before performing the acute toxicity test. The water quality was also analyzed before and after adding the extract immersions into the aquarium. The acute toxicity test conducted for 96 h with 10 fishes of each cyprinid species (4.0-6.0 cm length) in 30 L water capacity aquarium. The mortality of each cyprinid species was recorded at 24 h time interval and LC50 of the extracts throughout 96 hours was determined through the probit analysis application. Specifically, the LC50 of T. catappa leaves extract were 349.89, 338.65 and 318.48 mg/ exhibited for carp, goldfish and tiger barb, respectively. A high concentration range of any plant-based extract has the potential to become toxic to particular fishes. Thus, it is an effort from this study to identify the safety margin of T. catappa leaves extract before its therapeutic values can be further manipulated and elucidated in aquaculture research.

Skin abrasions often occur in farmed fish following handling by labourers, injury by farm facilities, cannibalism and ectoparasites. Vibrio spp. are opportunistic pathogens that can invade host fish through damaged tissues and cause outbreaks of vibriosis. This study describes the effect of skin abrasions on the infectivity of V. harveyi using Asian seabass Lates calcarifer (Bloch, 1790) fingerlings as a case example and compares bacterial load and fish survival following immersion challenge with different doses. In total, 315 fish (6.67 ± 1.8 g) were divided into 3 treatments: skin abrasion followed by immersion infection, immersion infection only and an uninfected, uninjured control. Fish in the infection treatments were divided into 3 subgroups and exposed in triplicate to a 7 d immersion challenge with 106, 107 and 108 CFU ml-1 of live V. harveyi. No mortalities were observed in the control and immersion infection groups. However, fish in the skin abrasion treatment group that were infected with 108 CFU ml-1 of live V. harveyi showed signs of progressing disease throughout the experiment, which resulted in mortalities. Significantly higher bacterial loads (p < 0.05) were recorded in the intestine, liver and gills of the fish in this group. Fish in the skin abrasion treatment that were exposed to 107 and 108 CFU ml-1 of V. harveyi showed 100% mortality by Days 5 and 4, respectively. These findings confirm that skin injuries increase the susceptibility of seabass fingerlings to V. harveyi infection.

Vibrio harveyi causes vibriosis in various commercial marine fish species. The infection leads to significant economic losses for aquaculture farms, and vaccination is an alternative approach for the prevention and control of fish diseases for aquaculture sustainability. This study describes the use of formalin-killed Vibrio harveyi (FKVh) strain Vh1 as a vaccine candidate to stimulate innate and adaptive immunities against vibriosis in a marine red hybrid tilapia model. Tilapia are fast growing; cheap; resistant to diseases; and tolerant to adverse environmental conditions of fresh water, brackish water, and marine water and because of these advantages, marine red hybrid tilapia is a suitable candidate as a model to study fish diseases and vaccinations against vibriosis. A total of 180 healthy red hybrid tilapias were gradually adapted to the marine environment before being divided into two groups, with 90 fish in each group and were kept in triplicate with 30 fish per tank. Group 1 was vaccinated intraperitoneally with 100 µL of FKVh on week 0, and a booster dose was similarly administered on week 2. Group 2 was similarly injected with PBS. Skin mucus, serum, and gut lavage were collected weekly for enzyme-linked immunosorbent assay (ELISA) and a lysozyme activity assay from a total of 30 fish of each group. On week 4, the remaining 60 fish of Groups 1 and 2 were challenged with 108 cfu/fish of live Vibrio harveyi. The clinical signs were monitored while the survival rate was recorded for 48 h post-challenge. Vaccination with FKVh resulted in a significantly (p < 0.05) higher rate of survival (87%) compared to the control (20%). The IgM antibody titer and lysozyme activities of Group 1 were significantly (p < 0.05) higher than the unvaccinated Groups 2 in most weeks throughout the experiment. Therefore, the intraperitoneal exposure of marine red hybrid tilapia to killed V. harveyi enhanced the resistance and antibody response of the fish against vibriosis.

Streptococcus agalactiae is one of the most important pathogens infecting tilapia worldwide. In this study, we determined the serotype, sequence type (ST), virulence gene profile and pathogenicity of S. agalactiae isolated from cultured fish. A collection of 256 S. agalactiae that were previously isolated from outbreaks of streptococcosis in red hybrid tilapia in Peninsular Malaysia were studied. The genotype and ST of the isolates were determined by molecular serotyping of the capsular polysaccharide (cps) gene clusters, and multi-locus sequence typing (MLST). The virulence gene profiles were constructed using m-PCR for 14 standard virulence genes with published primers. Two serotypes, with different associated STs, were identified in this study: serotypes Ia ST7 and III ST283. Serotype Ia ST7 lacks lmb, scpB, pavA, fbsB, cyl, bca, cspA and bac genes, which were present in serotype III ST283. The LD50–240h of S. agalactiae in red hybrid tilapia for serotypes Ia ST7 and III ST283 were 8.7 × 103 CFU/mL and 6.3 × 103 CFU/mL, respectively. The histopathological findings were consistent with meningitis, necrosis of hepatocytes, coagulative tubular necrosis and hypocellular of the spleen. Histopathological scores revealed significant differences (p < 0.05) between the two serotypes in all lesions in the brain, liver (except hepato-necrosis) and spleen, but not the kidney. This study revealed that S. agalactiae serotypes Ia ST7 and III ST283 currently exist in cultured tilapia in Malaysia. This molecular epidemiology study could be useful for the future development of cross protective vaccines against streptococcosis in the region.

This study assessed the fish community structures and influences of water quality on fish occurrences in Pahang and Tembeling rivers, Pahang. Fish samplings and water quality measurements were conducted in Kuala Mai, Pahang River and Ulu Tembeling, Tembeling River from 12 and eight different sampling points, from October 2007 to September 2008, and August 2006 to August 2007, respectively. The fish diversity, richness and evenness indices were determined, while the water quality parameters were compared for both rivers. Multivariate analyses were then used to explore the effects of water physicochemical parameters on the fish occurrences. A total of 2,391 individuals were collected from this study, comprising of 20 families and 65 species of fish. Using the gill nets, cast nets and fishing rods, a total of 55 fish species from 17 families were recorded in Kuala Mai, Pahang River, compared to 47 species from 15 families in Ulu Tembeling, Tembeling River. There were significant differences (p < 0.05) for fish diversity (H and 1-D), but not for fish evenness (e) and richness (D) between both rivers. The mean water temperature, ammonia nitrogen and total suspended solids were significantly different (p < 0.05) in both rivers. Apart from the influences of pH, alkalinity and phosphate in both rivers, the results showed that the temperature, dissolved oxygen and conductivity were the major influencers on the fish occurrences in Kuala Mai, Pahang River, while ammonia nitrogen and total suspended solids in Ulu Tembeling, Tembeling River. Fish conservation and stock management efforts are urgently needed due to the decreasing number of near-threatened, endangered and critically endangered fish species in both rivers.

This paper reports the identification of Streptococcus iniae from a large collection of isolates previously identified as Streptococcus sp., Lactococcus lactis subsp. lactis or Leuconostoc sp. A total of 204 bacterial isolates recovered either from the brain, eye, or kidney of red tilapias in previous disease outbreaks and disease monitoring in Malaysia from 2006 to 2008 were used. PCR identification revealed that 34 (16.7%) of the isolates were confirmed as S. iniae. Our records showed that S. iniae-infected fish exhibited lethargy, exophthalmia, and erratic swimming patterns. Pathological lesions including generalised congestion of the internal organs, splenic infarction with soft and oedematous brain. Histopathological examination revealed multifocal encephalitis as one of the major findings. However, 44% and 26.5% of the tilapias from which S. iniae was isolated did not manifest any clinical sign and pathological lesion, respectively. This study revealed that S. iniae was responsible for streptococcosis in cultured red tilapia in Malaysia since 2006.

An ideal model organism for neurotoxicology research should meet several characteristics, such as low cost and amenable for high throughput testing. Javanese medaka (JM) has been widely used in the ecotoxicological studies related to the marine and freshwater environment, but rarely utilized for biomedical research. Therefore, in this study, the applicability of using JM in the neurotoxicology research was assessed using biochemical comparison with an established model organism, the zebrafish. Identification of biochemical changes due to the neurotoxic effects of ethanol and endosulfan was assessed using Fourier Transform Infrared (FTIR) analysis. Treatment with ethanol affected the level of lipids, proteins, glycogens and nucleic acids in the brain of JM. Meanwhile, treatment with endosulfan showed alteration in the level of lipids and nucleic acids. For the zebrafish, exposure to ethanol affected the level of protein, fatty acid and amino acid, and exposure to endosulfan induced alteration in the fatty acids, amino acids, nucleic acids and protein in the brain of zebrafish. The sensitive response of the JM toward chemicals exposure proved that it was a valuable model for neurotoxicology research. More studies need to be conducted to further develop JM as an ideal model organism for neurotoxicology research.

In order to understand the life history of the Asian swamp eel, Monopterus javanensis found in paddy fields, the time of maturation of its gonads was studied by using the gonadal somatic index. The peak gonadal somatic index was first found during the ploughing and seedling seasons in 2011 and 2012. This was accompanied by the yellowish egg sac observation made in the eels during the ploughing and seedling seasons, which was indicative of the mid- and early maturation stages of the gonads. However, the decline in GSI from the growing until the harvesting seasons indicated the poor development of gonads since differentiating the sex of the eels was hard. This could be due to the heavy application of pesticides and fertilisers during the growing season as cadmium present as impurities in the fertilisers, which slowly accumulated in the gonads. The findings highlighted the availability of Asian swamp eels for local eel collectors as part of their income and the complexity of heavy metal bioaccumulation in their gonads for safe eel consumption. Overall, the habitat of the Asian swamp eels may induce the differences in the maturation timing for the species.