Now showing items 1-6 of 6

    • 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.
    • Article

      Characterization of a virus obtained from snakeheads Ophicephalus striatus with epizootic ulcerative syndrome (EUS) in the Philippines 

      GD Lio-Po, GS Traxler, LJ Albright & EM Leaño - Diseases of Aquatic Organisms, 2000 - Inter Research
      This is the first report of the isolation and characterization of a fish virus from the Philippines. The virus was isolated using snakehead spleen cells (SHS) from severely lesioned epizootic ulcerative syndrome (EUS)-affected snakehead Ophicephalus striatus from Laguna de Bay, in January 1991. The virus induced cytopathic effects (CPE) in SHS cells yielding a titer of 3.02 x 106 TCID50 ml-1 at 25°C within 2 to 3 d. Other susceptible cell lines included bluegill fry (BF-2), catfish spleen (CFS) and channel catfish ovary (CCO) cells. Replication in chinook salmon embryo cells (CHSE-214) was minimal while Epithelioma papulosum cyprini cells (EPC) and rainbow trout gonad cells (RTG 2) were refractory. Temperatures of 15 to 25°C were optimum for virus replication but the virus did not replicate at 37°C. The virus can be stored at -10 and 8°C for 30 and 10 d, respectively, without significant loss of infectivity. Viral replication was logarithmic with a 2 h lag phase; viral assembly in the host cells occurred in 4 h and release of virus occurred 8 h after viral infection. A 1-log difference in TCID50 titer between the cell-free virus and the total virus was noted. Freezing and thawing the virus caused a half-log drop in titer. Viral exposure to chloroform or heating to 56°C for 30 min inactivated the virus. Exposure to pH 3 medium for 30 min resulted in a more than 100 fold loss of viral infectivity. The 5-iododeoxyuridine (IUdR) did not affect virus replication, indicating a RNA genome. Neutralization tests using the Philippine virus, the ulcerative disease rhabdovirus (UDRV) and the infectious hematopoietic necrosis virus (IHNV) polyvalent antisera showed slight cross-reaction between the Philippine virus antiserum and UDRV but established no serological relationship with SHRV and IHN virus. Transmission electron microscopy (TEM) of SHS cells infected with the virus showed virus particles with typical bullet morphology and an estimated size of 65 x 175 nm. The Philippine virus was therefore a rhabdovirus, but the present study did not establish its role in the epizootiology of EUS.
    • Article

      The effects of iron compounds on the virulence of Vibrio anguillarum in Japanese eels and ayu 

      T Nakai, T Kanno, ER Cruz & K Muroga - Fish Pathology, 1987 - Japanese Society of Fish Pathology
      When Japanese eels (Anguilla japonica) were injected intramuscularly (IM) with ferric ammonium citrate (FAC) at a sublethal dose of 10 µg/g and followed by IM-injection with various doses of Vibrio anguillarum, FAC injection enhanced greatly the virulence of the pathogen to eels, lowering the LD50 value from 107.9 to 104.2 CFU/100 g. Similar effects were obtained with ferrous sulfate and ferric chloride in eels. However, such a virulence-enhancing effect of FAC was scarcely observed in ayu (Plecoglossus altivelis), which has high susceptibility to the pathogen by nature. It was also found that addition of FAC (10 µg/ml) in fish sera accelerated the bacterial growth in vitro but the effect was much greater in eel serum than in ayu serum. The results of these in vivo and in vitro experiments demonstrated that the availability of free iron in host fish would have a significant influence on the pathogenesis of V. anguillarum infection.
    • Article

      Experiments on virulence dose and portals of entry for Aeromonas hydrophila in walking catfish 

      GD Lio-Po, LJ Albright & EM Leaño - Journal of Aquatic Animal Health, 1996 - American Fisheries Society
      Aeromonas hydrophila, isolated from chevron snakehead Ophicephalus (=Channa) striatus affected with epizootic ulcerative syndrome (EUS), was injected intramuscularly into healthy walking catfish Clarias batrachus at varying 10-fold serial dilutions from 108 to 0 colony-forming units (cfu) per fish. Only 106 or more cfu/mL induced dermomuscular lesions. Initial healing of lesions was observed by day 7 but complete healing was not apparent until day 16. Experiments were also conducted on possible portals of entry of A. hydrophila into walking catfish: Intramuscular (IM) injection, gastric gavage, fish food, and immersion of injured fish in rearing water inoculated with the test bacteria. Injuries were caused by skin or muscle cut, dermal scraping or incision, fish bite, and cohabitation of fish with golden snails Ampullarius sp. Only IM injection treatment induced dermomuscular pathology in the test catfish. This suggests that a localization of A. hydrophila to a level of 106 cfu/mL in the musculature must be established for dermal lesions to develop.
    • Article

      Occurrence, characterisation and detection of potential virulence determinants of emerging aquatic bacterial pathogens from the Philippines and Thailand 

      RP Maluping, CR Lavilla-Pitogo, A DePaola, JM Janda & K Krovacek - The New Microbiologica, 2004 - Luigi Ponzio e Figlio Editori
      Strains of Aeromonas spp., 'non-cholera vibrios' (NCVs) and Plesiomonas shigelloides isolated from aquatic environments, fish and human diarrhoeal cases in the Philippines and Thailand were characterised for potential virulence markers. Thus, the production of cytotoxin, cell-associated and cell-free haemolysin and their capacity to adhere to human intestinal (Henle 407) cells in vitro was investigated. In addition, the occurrence of tlh and tdh haemolysin genes and urease activity among V. parahaemolyticus strains was investigated. The results showed that strains recovered from clinical sources (human and fish) produced these virulence factors, whereas these are absent in environmental strains.
    • Book | Conference publication

      Transboundary fish diseases in Southeast Asia: Occurrence, surveillance, research and training 

      CR Lavilla-Pitogo & K Nagasawa (Eds.) - 2004 - Aquaculture Department, Southeast Asian Fisheries Development Center
      The meeting aims to share and collect the most current information on the occurrence of transboundary fish diseases and surveillance, quarantine, diagnosis, monitoring, research and training for aquatic animal diseases in the SEAFDEC member countries. In the meeting, three viruses, namely KHV, WSSV and TSV, were highlighted because of their high virulence and devastating impact to the region.