The pathogenicity of bacteria associated with transport-stressed Chanos chanos fingerlings

Two isolates of Aeromonas hydrophila biovar hydrophila and two isolates of Pseudomonas-like bacteria cultured from milkfish, Chanos chanos, fingerlings stocked in Laguna Lake(Philippines) pens after transport were tested for virulence against healthy milkfish fingerlings. Various combination of bacterial and different routes of inoculation (intraperitoneal injection, bath treatment of scaled fish and bath treatment of unscaled fish) were tested. Results show that bacterial entry in the pathogenesis of the test bacteria to challenged fish is more effective in fishes with scales removed than in uninjured fish or though intraperitoneal injection. The minimum lethal dose of A. hydrophila to scaled fish appeared less than 105 cells/ml of water medium. For Pseudomons-like isolates, the minimum lethal dose was at the level 105 cells/ml of water medium. Fish mortalities significantly increased on day 2 in all bacteria but A. hydrophila was significantly more virulent than the Pseudomonas-like inocula. When A. hydrophilawas injected intraperitoneally into undamaged fish, the maximum dose of 107cells per 2-g fish was needed to cause significant moralities. In general, virulence of the isolates was directly proportional to dose as well as to the length of exposure. A cute signs of bacterial infected scaled milkfish. Lethargic fish displayed spastic and unbalanced swimming movement before death. The virulence of the bacteria as evaluated in this study should lead to further investigation on the role of extracellular factors in bacterial pathogenesis to milkfish fingerling

Studies on the causative organism of Sarotherodon niloticus (Linnaeus) fry mortalities - 2. Identification and characterization of the physiological properties of Pseudomonas fluorescens

SEAFDEC Contribution No. 148.Identification and examination of the physiological characteristics of Pseudomonas sp. isolated from fry of Sarotherodon niloticus (L.) was conducted. Based on morphological and biochemical tests, the bacterium was identified to be a strain closest to Pseudomonas fluorescens. In vitro physiological growth patterns at varying temperatures, NaCl concentrations, and pH were observed for a maximum of eleven days incubation while growth of the test bacterium into various water media were observed for a maximum of 148 days. Bacterial growth occurred between 10° to 41°C with optimum growth at 25° to 30°C. The bacterium tolerated NaCl concentrations of 0 to 50 ppt. Optimum growth, however, was obtained from 0 to 15 ppt. It was found that growth was possible only at pH 5.0 to 9.7. Optimum growth occurred at pH ranging from 5.7 to 8.4. Inoculation of the test bacterium into different freshwater media obtained from various sources resulted in growth and rapid multiplication. Viability was maintained throughout the 148 day incubation period. Growth in the brackishwater medium was observed only until 50 days. No growth was observed in the seawater medium

Disease investigation of transported Chanos chanos stocked in Laguna Lake, Philippines

Milkfish,Chanos chanos fingerlings transported by boat (petuya) for seven to eight hours were observed for stress-inducing factors during transport, daily for 10 days after stocking in pens in Laguna Lake, Philippines. Handling, hauling, and crowding of fish contributed to stressful conditions. Likewise, the transport procedure of the clising the water entry hole at the bottom of the boat to block water exchange was associated with decreased dissolved oxygen and increase tubidity, with respective values of 2.4 mg/l and 79 Formalin Turbidity Units when water change was possible. In addition , marked and abrupy fluctuations in salinity from 15 to 30 ppt then 0 ppt within 1 to 3 hr were observed during transport. Although moralities during transport were minimal, subseqeunt deaths after stocking in pens mounted to not less than 2.4%. Reddish snout, scale loss and hemorrhagic areas along the lateral body surface wwere observed. Bacterial counts of water increased significantly during trasnport when water exchange was stopped. Kidney and skin/muscle specimens yielded significantly higher bacterial counts on days 2, 3, 5 and 8 poststocking predominated by Aeromonas hydrophila biovar hydrophila and two species of gram-negative bacilli phenotypically resembling Pseudomonas sp

Histopathology of the chronic soft-shell syndrome in the tiger prawn Penaeus monodon

SEAFDEC Contribution No. 219.One of the disease problems that affect the production of tiger prawn Penaeus monodon Fabricius in brackish-water ponds is the chronic soft-shell syndrome, a condition in which the prawn shell is persistently soft for several weeks. To determine the extent of damage in affected prawns, the histopathology of this syndrome was studied using light microscopy, transmission and scanning electron microscopy, and histochemical determination of calcium. Light microscopic studies of the exoskeleton of soft and normal hard-shelled prawns showed several distinct layers: an outer epicuticle, a thick exocuticle and a thinner endocuticle overlying the epidermis. The cuticular laters of the soft shell oftern had a rough or wrinkled surface and were usually disrupted and separated from the epidermis while those of the hard shell were generally intact and attached to the epidermis. The exocuticle and endocuticle of the hard shell were considerably thicker than those of the soft shell. Ultrastructural observations revealed the presence of a very thin membranous later under the endocuticle. Tegumental ducts and pore canals traversed the 4 cuticular layers and were distinctly observed as pore openings on the epicuticle surface. The epicuticle had a bilaminar and non-lamellate structure. The exocuticle had more widely-spaced lamellae consisting of fibers arranged in a more compact pattern than in the endocuticle. Histochemical determination of calcium was done in exoskeleton and hepatopancreas of soft- and hard-shelled prawns. The hepatopancreas of soft-shelled prawn stained more intensely for calcium than that of the hard-shelled one. There was no great difference in calcium content of hard and soft shell, although the former stained slightly more intensely. Histopathological changes in the hepatopancreas of soft-shelled prawns were also observed

Studies on the chronic soft-shell syndrome in the tiger prawn, Penaeus monodon Fabricius, from brackishwater ponds

SEAFDEC Contribution No. 182.Prawn culture is becoming more widespread in the Philippines. In recent years, prawn production in brackishwater ponds has been adversely affected by a chronic soft-shell syndrome. A field survey of prawn ponds in the island of Panay showed that occurrence of soft-shelled prawns could be predicted with 98% accuracy under poor soil and water conditions in the ponds. Some management practices were also highly correlated with the soft-shell syndrome. Soft- and hard-shelled prawns collected during the survey were analyzed for calcium and phosphorus levels. In soft-shelled prawns, calcium and phosphorus levels were significantly higher in the hepatopancreas, and phosphorus was significantly lower in the exoskeleton than in hardshelled prawns. Chitinoclastic bacteria, Vibrio and Aeromonas, were isolated from soft-shelled prawns but experimental infection with these species to induce soft-shelling gave largely negative results. Laboratory experiments using an organostannous pesticide revealed that a 96-h exposure to at least 0.0154 ppm of the pesticide could result in soft-shelling of 47-60% of the prawns. Soft-shelled prawns were fed various quantities of frozen mussel meat for 4 weeks to find out if soft-shelling could be reversed by dietary manipulation. Successful reversal of soft-shelling, general improvement of shell quality, and best growth and survival rates were observed in prawns fed a 14% mussel meat diet

Diseases of penaeid shrimps in the Philippines

The manual provides information on the diseases that affect the 3 major species of shrimps culture in the Philippines: Penaeus monodon, P. merguiensis and P. indicus. It includes the common name of the disease, causative agent, species affected, stages affected, gross signs, effects on the host and methods of prevention and treatment.1st Ed