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    • Book chapter

      Bacterial loads in hatcheries and virulence of Vibrio spp. to larvae of the tiger shrimp Penaeus monodon 

      JL Torres - In T Bagarinao (Ed.), Research Output of the Fisheries Sector Program, 2007 - Bureau of Agricultural Research, Department of Agriculture
      Shrimp hatcheries are high-density systems and are prone to diseases. A small-scale and a large-scale hatchery for the tiger shrimp Penaeus monodon in Iloilo, Philippines were monitored over two months for water quality and shrimp survival. Water quality (water temperature, pH, salinity, dissolved oxygen, and specific gravity) was not significantly different between the two hatcheries. However, the small hatchery seemed to favor survival of eggs to early postlarval stages, whereas the large hatchery favored the survival of late postlarvae. The normal microflora and bacterial loads of tiger shrimp eggs, larvae, postlarvae, and rearing water were determined to identify the dominant bacteria and potential pathogens. Shrimp eggs harbored the lowest heterotrophic bacterial counts. The counts increased from the nauplii to the mysis stages, decreased during the mysis stage, and then gradually increased in the older larvae. Bacterial loads in the rearing water reflected those in raw sea water and reservoir-aged sea water. Vibrio, Pseudomonas, and Aeromonas were not detected in eggs but were found in postlarvae. Ubiquitous in sea water, these bacteria increased with the build-up of organic matter. The bacterial load in the water adversely affected larval survival. Forty bacterial strains were isolated from tiger shrimp eggs, larvae, postlarvae, from the feeds, and from the rearing water. These were tested for biochemical characteristics and segregated into eight groups or genera. Six genera were found in the mysis and five genera in the postlarvae. The Vibrio species were dominant. Only Escherichia spp. were present in feeds, whereas five genera were present in the rearing water. Only Vibrio and Pseudomonas were present in both larvae and water. Moraxella, Aeromonas, and Klebsiella were found in larvae but not in rearing water. Micrococcus and coryneforms were found only in rearing water. Four Vibrio isolates were tested for virulence against shrimp postlarvae at inoculation densities of 102 and 107 cfu/ml. The four Vibrio species caused mortality of postlarvae, and more at the higher inoculation density. The most virulent was Vibrio anguillarum—30% of postlarvae died after 24 h exposure to a bacterial density of 102 cfu/ml, and all larvae died after 48 h at 107 cfu/ml. Shrimp hatcheries must have protocols for hygiene and sanitation and for disease prevention and control.
    • Conference paper

      Bacterial studies of epizootic ulcerative syndrome (EUS) outbreak in the Philippines 

      ER Cruz-Lacierda & JL Torres - In RJ Roberts, B Campbell & IH MacRae (Eds.), ODA Regional Seminar on Epizootic Ulcerative Syndrome, 25-27 January 1994, Bangkok, Thailand, 1994 - Aquatic Animal Health Research Institute
      Epizootic ulcerative syndrome (EUS) is a disease of wild and cultured freshwater fishes in Asia and IndoPacific (Roberts et al., 1986; Lilley et al., 1992). In the Philippines, the first confirmed EUS outbreak is reported in Laguna de Bay in December 1985 to February 1986 (Llobrera and Gacutan, 1987). Since then, EUS has been observed annually in the lake during the coldest months of the year - December to February or March. The disease has spread throughout Luzon, affecting wild and cultured fishes in lakes, ponds, paddy fields, and rice fish systems (Bondad-Reantaso et al., 1992). In September to December 1990, EUS was recorded among brackishwater and marine fishes from a lagoon in northern Luzon (Reantaso, 1991).

      Although EUS is recognized as a regional problem, no definite primary causative agent has been established. Virus, fungi, bacteria, and parasites have been isolated in EUS-positive fishes, but none has been implicated as the primary pathogen (Roberts et al., 1993a & 1993b). Among the bacteria associated with EUS, Aeromonas hydrophila is consistently isolated in affected fishes from the Philippines (Llobrera and Gacutan, 1987; Torres et al., 1990; Lio-Po et al., 1992). This paper reviews the work done on the bacterial aspects of EUS in the Philippines.