Monoclonal antibodies in fish and shellfish health management in India

The paper describes the superiority of monoclonal antibodies (MAb) over conventional polyclonal antisera. Studies undertaken indicate that Aeromonas hydrophila isolates are highly heterogenous and variation exists even between isolates from a farm, requiring a large number of MAbs for classification and use of information in vaccine development. However, some of the MAbs could be used for detection of homologous isolates in fish kidney by immunodot assay and evaluation and standardization of biofilm of A. hydrophila for oral vaccination in carps.

Investigation on bacterial flora of farmed freshwater prawn (Macrobrachium rosenbergii de Man) in Bangladesh

Total bacterial load in the haemolymph of freshwater prawn Macrobrachium rosenbergii varied from 6.2x10⁴ to 1.9x10⁷ CFU/ml whereas in the hepatopancreas, bacterial load varied from 1.9x10³ to 2.9x10⁵ CFU/g. The total bacterial load in the pond water varied from 2.6x10² to 4.1x10⁵ CFU/ml. The isolated bacterial genera in the haemolymph and the hepatopancreas of prawn were Streptococcus, Acinetobacter, Micrococcus, Aeromonas, Vibrio, Flavobacterium, Staphylococcus and Pseudomonas, whereas the detected bacterial genera in pond water were Micrococcus, Streptococcus, Vibrio, Flavobacterium, Staphylococcus, Pseudomonas and Aeromonas. Among the detected genera, Vibrio and Staphylococcus were found to be dominant genera in the haemolymph of the sampled prawn throughout the study period whereas Staphylococcus and Pseudomonas were dominant in pond water.

Study on the intestinal bacteria of Labeo rohita (Ham.)

The quantitative and qualitative aspects of intestinal bacteria of rohu fish (Labeo rohita) showed that total viable count of bacteria ranged from 9.9 x 106 to 1.4 x 107 CFU/g of intestine in different age groups of fish. The bacterial load was highest in the month of July and lowest in January. The genera of the isolates from intestine included Coryneform, Micrococcus, Flavobacterium, Cytophaga, Achromobacter, Aeromonas Enterobacteriaceae and Vibrio. Coryneform was the dominant group throughout the study period followed by Micrococcus and Enterobacteriaceae. Marked variations in the bacterial load and generic composition of intestinal bacteria were evident during the study period in different age groups of rohu fish.

Incidence of ulcer disease in African catfish (Clarias gariepinus Burchell) and trial for its chemotherapy

Young Clarias gariepinus cultured in an artificial tank were severely affected by an ulcer type of disease where 77% fish died within 5 weeks. From the lesions and kidney of affected fish Aeromonas, Pseudomonas, Flavobacterium, Micrococcus and Staphylococcus were isolated where Aeromonas was observed as the dominant bacteria. Among them, an A. hydrophila isolate AGK 34 was detected as a pathogen by the experimental challenge test. In order to find out a suitable remedial measure of the disease, four different chemotherapeutants were applied to the affected fish in 6 different ways under laboratory condition. Affected fish were recovered from the disease in different treatments. But the best result was obtained by a successive bath in 1-2% NaCl and subsequent oral treatment with commercial oxytetracycline at a dose of 75 mg/kg body weight of fish.

Bacterial flora associated with diseased fish and their antibiogram

Bacterial flora associated with tail rot/fin rot of Carassius auratus, Xiphophorus helleri and hemorrhagic ulcers of Clarias spp were studied. Sensitivity pattern of 33 isolates comprising Aeromonas spp, Pseudomonas spp and Gram-positive rods from diseased C. auratus, X. helleri and Clarias spp were screened against six broad-spectrum antibiotics viz. ciprofloxacin, chloramphenicol, co-trimoxazole, gentamycin, nitro-furantoin and oxytetracycline. Ciprofloxacin was the most effective in inhibiting bacteria at 0.05-0.10 µg/ml level. About 44% of Pseudomonas spp. was resistant to nitrofurantoin. Resistance to oxytetracycline was seen in 27% of Aeromonas spp Gram-positive rods were comparatively more resistant to antibiotics. The multiple antibiotic resistances were seen in 21% of the bacterial isolates of diseased fish.

Incidence of epizootic ulcerative syndrome (EUS) in freshwater fishes in the endemic area of Punjab, Pakistan

Incidence of Epizootic Ulcerative Syndrome (EUS) has been recorded for the first time in freshwater fishes in the endemic area of Punjab, Pakistan. Survey of private fish farms, hatchery and natural water bodies was conducted in a radius of 14 Km from around river Ravi near Lahore (Punjab Province) Pakistan. Out Of 1628 fishes belonging to 18 genera, 517 fishes of 10 genera were found affected with EUS. The incidence of EUS in culturable fishes was higher in Cirrhina mrigala (15.4%) moderate in Catla cat/a (13.3%) and lower in Labeo rohita (5.0%). Exotic fish, Chinese carp Ctenoparyngodon idella and Hypophthalmicthys molitrix were not affected with EUS. In non-culturable fishes the incidence of EUS was highest in Channa punctatus (72.8%) moderate in by C. straitus (65.45%) and comparatively lower Puntius ticto (43.7%). A slow growing temperature sensitive Saprolegnia spp. was isolated from all of EUS infected fish species. Aeromonas spp. and Pseudomonas spp. were isolated from the diseased fishes. Ectoparasites viz. Lernaea, Argulus and Triclwdina spp. were also isolated from the skin and gills of infected fish species. The disease was more severe in water having low alkalinity (70 mg/1), hardness (75 mg/1) and low temperature of 10-12 °C.

Incidence of ulcer type of disease in wild fishes of Bangladesh

Disease occurred in wild fish species investigated in different water bodies like canals, ditches, beel, haor, flood plain in 17 districts of Dhaka division. Haemorrhagic lesions were observed on the body surface of affected fishes. Incidence of the disease in the investigated water bodies ranged from 0 to 100%. In total 19 fish species were found to be affected and prevalence of infection ranged from 0.0 to 100.0%. Channa punctatus and Puntius ticto were severely affected in all locations. Percentage of infection in these fishes ranged from 0.0 to 100.0. The highest infection was observed in Netrokona, Kishoreganj, and Mymensingh districts. Bacterial genera isolated from the lesions of these affected fishes were Aeromonas, Pseudomonas, Flavobacterium, Micrococcus, and Staphylococcus. Among these isolates Aeromonas was the dominant. Abundance of Aeromonas in the lesions among the investigated bacteria ranged from 75 to 90%. Five identified Aero monas lrydrophila were examined for their pathogenicity and were able to infect the experimental fish, silver barb (Puntius gonionotus). The pathogen Aeromonas hydrophila was thus considered to have an association with the outbreak of ulcer type of disease in the investigated fish species.

Improved handling and preservation of freshwater giant prawn, Macrobrachium rosenbergii for producing safe and wholesome products

Studies were undertaken to evaluate the quality changes in freshwater giant prawn, Macrobrachium rosenbergii during various storage conditions of handling and preservation and producing safe and quality products. The samples kept in ice immediately after catch with head-on and head-less condition were found to be acceptable for 6 days and 7 days, respectively. Delaying of icing considerably shortened the shelf-life. The pH value increased from 6.36 to 8.0 after 10 days in ice. The initial average TVB-N value of sample increased from below 10 mg/100 g to 25 mg/100 g with the lapse of storage period. The Ca++ ATPase activity in presence of 0.1M KCl slightly decreased at the end of 10 days of ice storage. Immediately after harvest, initial aerobic plate count (APC) was 2.88x10^6 CFU/g which gradually increased to 1.12x10^8 CFU/g after 6 days in ice storage and showed early signs of spoilage. Initial bacterial genera in the prawn iced at 0 hours were comprised of Coryneform (22.21 %), Bacillus (7.40%), Micrococcus (11.11 %), Achromobacter (48.14%), Flavobacterium/Cytophaga (7.40%), Pseudomonas (3.70%) and Aeromonas (3.70%). During ice storage Coryneforms and Bacillus were always dominating along with less prominent ones - Micrococcus, Achromobacter and Flavobacterium. Studies were conducted on the stability of myofibrillar protein of M. rosenbergii under different storage and pH conditions. The influence of a wide range of pH on the remaining Ca++ ATPase activity of M. rosenbergii muscle myofibrils after storage at -20°C for 2 days, at 0°C for 2 days and at 35°C for 30 minutes demonstrated that ATPase activities were lower in acidic and alkaline pH regions and the activity remained relatively high. Mg++ ATPase activities both in presence and absence of Ca++ remained high at neutral pH compared to those of acidic and alkaline region. The solubility of myofibrillar protein decreased gradually both in acidic and alkaline pH regions. The study also examined the bacteriological quality of freshly harvested M. rosenbergii, pond sediment and pond water from four commercial freshwater prawn farms at Fulpur and Tarakanda upazilas in the district of Mymensingh. The study included aerobic plate count (APC), total coliform count, detection, isolation and identification of suspected public health hazard bacteria and their seasonal variation, salt tolerance test, antibiotic sensitivity test of the isolates and washing effect of chlorinated water on the bacterial load in the prawn samples. APC in sediment soil and water of the farm and gill and hepatopancreas of freshly harvested prawns varied considerably among the farms and between summer and winter season. The range of coliform count in water, gill and hepatopancreas ranged between 6 - 2.8x10^2 CFU/ml, 1.2x10^2 - 3.32x10^2 CFU/g and 1.43x10^2 - 3.89 x10^3 CFU/g, respectively. No coliform was detected in pond sediment sample. Suspected health hazard bacteria isolated and identified from pond sediment, water, gill and hepatopancreas included Streptococcus, Bacillus, Escherichia coli, Klebsialla, Salmonella, Staphylococcus, Pseudomonas and Aeromonas. Bacillus, Salmonella and Staphyloccus [sic], and were found to be highly salt tolerant and capable of growing at 10% NaCl. The antibiotic discs with different concentration of antibiotics were used for the sensitivity test. The organisms were found to be most sensitive against Tetracyclin and Gentamycin.

Study on regional differences in soil-water characteristics and their relevance to aquaculture productivity and fish disease

A total of 45 ponds used for fish polyculture were investigated in three zones of Bangladesh to identify the differences among the zones in respect to aqua-ecology, culture practices, fish productivity and health management. Four hundred and fifty fish from three zones were clinically examined by naked eye and histopathology. Out of total number of fish examined, 45 fish from Dhaka zones were examined for parasites and bacteria in addition to histopathology. Faded and haemorrhagic gill, skin, fin, scale loss and lesions were observed during fish examination. Aeromonas spp. Pseudomonas spp. and Streptococcus spp. were isolated respectively from 56%, 46% and 39% affected fish. Among the five water quality parameters analyzed, the highest average hardness and alkalinity respectively were recorded in Rajshahi (156 ppm and 142 ppm) followed by Dhaka (146 ppm and 132 ppm) and Chittagong (81 ppm and 90 ppm). The highest average pH was recorded in Mymensingh (7.52) followed by Rajshahi (7.13) and Chittagong (7.05). Water holding capacity of soil in Rajshahi zone was poor compared to other zones and farmers were found to be reluctant to fish farming.

Identification of causes of Thai pangas mortality in ponds and their control strategies

Mass mortality of Thai pangas (Pangasius hypophthalmus) is reported to be a big threat to monoculture of the species in Bangladesh. Twenty affected and twenty control Thai pangas ponds were investigated around Mymensingh district in order to identify the causes of pangas mortality. Sixty affected and sixty unaffected fish samples were examined and compared to find the fish-level variables associated with the disease. A range of haemorrhagic signs on snout, skin and fins were recorded during examination with naked eyes. Aeromonas spp. and Edwardsiella spp. were isolated from 87% and 80% of the affected fish, respectively. Even 4% of the seemingly healthy fish carried Aeromonas spp. on their skin. Among the four water quality parameters monitored, remarkably higher total ammonia (1.5 ppm) was found in water of the affected ponds compared to that of the unaffected ones (0.4 ppm). High ammonia in affected water caused by excessive organic decomposition and poor pond management might have reduced the immunity of fish, which predisposed them for bacterial invasion and consequent disease outbreak.

Health and disease status of Thai pangas, Pangasius hypophthalmus cultured in rural ponds of Mymensingh, Bangladesh

Thai pangas, Pangasius hypophthalmus is one of the important aquaculture species in Bangladesh. Over the last few years spectacular development has been taking place in Thai pangas farming in Mymensingh district. Due to availability of easy breeding and culture techniques as well as quick return, more and more people are converting their rice fields into pangas farms overnight. The present study was carried out to examine health and disease status of Thai pangas mainly through clinical, histopathological and bacteriological techniques. In addition, for collecting primary data on disease and health status of Thai pangas and the resultant socioeconomic impacts on rural households, questionnaire interview and participatory rural appraisal tools were used with selected farming households in three upazilas of Mymensingh district. The most prevalent diseases as reported by the farmers were red spot, followed by anal protrusion, tail and fin rot, pop eye, dropsy and gill rot. Other conditions like cotton wool type lesion, ulceration and white spot were reported but with lower incidence. Four isolates of Aeromonas hydrophila were recovered from kidney and lesion of diseased fish. Hemorrhage over the body especially near mouth and caudal region was noticed in the fishes associated with aeromonad infection. Internally, kidney, liver and spleen became swollen and enlarged. The isolates varied with their pathogenicity. All the four isolates were sensitive to Nitrofurantoin, Cotrimoxazole and Tetracycline but were resistant to Amoxycilline. An attempt was made to treat diseased fish with extracts from neem leaf, garlic and turmeric. Recovery of infection was monitored through mortality and histopathology. General histopathological changes of different organs were also studied. Extract from neem (Azadirachta indica) leaf gave better result. Telangiectasis, lamellar hypertrophy and hyperplasia hemorrhage, lamellar fusion, necrosis of lamellar epithelial cells, presence of parasites and their cysts were the major pathology of gills. Hemorrhagic lesion, pyknotic nuclei and melanomacrophage centers (MMC) were found in the liver of fish. Major pathologies in kidney of fish included presence of MMC, necrotic and ruptured kidney tubules, severe haemopoietic necrosis, and hemorrhage. The economic loss due to disease in Thai pangas farming was estimated from the difference between expected production and actual production. On an average, Thai pangas farmers of Mymensingh incur a loss of Tk. 23,104/ha/cycle due to fish disease (3.6% of expected total production). The loss, however, varied with location and size of farms, type of farmers and management practices. The study also highlighted fish health management related problems and recommended further work for the development of user-friendly farmer-oriented fish health management packages.

Microbiological evaluation and keeping quality of fishes reared in livestock sewage fed ponds without artificial feed

Livestock sewage has been utilized for fish culture. There is lack of information on microbiological evaluation and keeping quality of these fishes. This paper reveals the incidence, types of micro-organisms and keeping quality of fishes reared in livestock sewage fed ponds without artificial feed. These fishes revealed microbial incidence and keeping quality comparable to other fishes. Initial mesophilic and psychrophilic counts varied from 3.38 to 5.56 and 2.47 to 4.74. On an average, the counts reduced by about 40% after evisceration and washing. Whole as well as washed fishes had refrigerated (8 ± 1°C) life of not more than 4 days. The average psychrophilic and mesophilic counts of ice (0 to 1°C) stored whole fishes up to 10th day varied from 3.66 to 4.81, 4.61 to 5.24 and in eviscerated and washed fishes 2.17 to 3.69 and 2.78 to 4.41. Both remained acceptable till the 10th day. Qualitative study of surface slime and gills revealed presence of Aerobacter (Enterobacter), Aeromonas, Alcaligenes, Bacillus, Clostridia, E. coli, Klebsiella, Micrococci, Proteus and Pseudomonas.

Arylsulfatase - producing bacteria in marine sediments

A total of 313 strains of bacteria which hydrolysed tripotassium phenolphthalein disulfate (PDS) were isolated from the sediments of three biotopes, namely, Vellar estuary, backwater and mangrove during the period of investigation. They were identified to the generic level. The following genera were encountered, namely, Vibrio, Bacillus, Alcaligenes, Micrococcus, Pseudomonas, Cytophaga-Flavobacterium, Aeromonas, Corynebacterium and members of Enterobacteriaceae. Vibrio and Bacillus were found to be the dominant groups representing 29.26% and 41.80% respectively of the total isolates. Because of the importance of the Vibrio group in marine environment these isolates were further identified to the species level and it included V. parahaemolyticus, V. alginolyticus, V. consticola, V. anguillarum and V. fischeri. These observations suggest that different groups of arylsulfatase – producing bacteria probably occur in marine sediments.

Studies on lipolytic bacteria in stored fish Etroplus suratensis (Bloch)

The distribution of total hectrotrophic bacteria (THB) and lipolytic bacteria in various regions (body surface, gill, intestine and flesh) of fish Etroplus suratensis (Bloch) during storage at 28 ± 2°C and 4°C was studied. Pseudomonas dominated at reduced temperature whereas at 28 ± 2°C and in fresh condition Vibrio, Aeromonas, and Acinetobacter dominated. Lipolytic activity was elaborated by the members of various genera and their activity varied in different lipid compounds (tributyrin, tween 80, tween 60, tween 40 and tween 20). Tributyrin was utilized by majority of the isolates. All the selected isolates preferred a temperature of 35°C and pH 6.0 for their maximum growth. Aeromonas and Vibrio showed maximum growth at 0.5% NaCl concentration while 3% NaCl was found to be optimum for Pseudomonas.

Influence of a fish bacterium Lactobacillus sp. on the production of swordtail xiphophorus helleri (Heckel 1848)

The influence of a fish gut bacterium Lactobacillus sp on the production of swordtail Xiphophorus helleri was studied for a period of one year. The Lactobacillus sp P21 produced bacteriocin-like inhibitory substance and exhibited wide spectrum of action against Aeromonas hydrophila, Bacillus spp, Pseudomonas spp and Citrobacter freundi in vitro. The growth performance of X. helleri reared in the presence of Lactobacillus P21 at 106/ml rearing water was better than the control. The total plate counts, total MRS agar counts and the counts of motile aeromonads, presumptive pseudomonads, lactose fermenters and lactose non-fermenters in the gut of probiotic group were comparatively low than the control. On day 60 the count of Lactobacillus sp P21 was observed to be log 5.28/g in the gut of X. helleri indicating colonization of this bacterium in the gastrointestinal tract. The fecundity of X. helleri was in the range of 9-134. On average, it produced from 39.42±18.72 fry/female in control group to 53.00±23.57 fry/female in probiotic group. The increase in average fecundity in probiotic group over the control group was about 25%. There existed significant difference between probiotic group and control in respect of average fecundity/female (p<0.02), average number of fry survived /female (p<0.006) and average number of fry dead/female (p<0.029). The results of the present study demonstrated that the rearing of X. helleri in probiotic-enriched water have growth inducing ability and favourably influenced the reproductive performance in terms of high fecundity, high fry survival, reduced fry mortality and reduced fry deformity.