The relation between farming practices, ecosystem, and white spot in syndrome virus (WSSV) disease outbreaks in penaeus monodon farms in the Philippines

The white spot syndrome virus (WSSV) affecting shrimp aquaculture in most producing countries has caused huge economic losses resulting in bankruptcy to both large and small farmers. Studies done on WSSV epidemiology were mostly tank-based and on species other than Penaeus monodon. There is a need to investigate WSSV epidemiology in P. monodon in on-farm situations, thus including both risk and protective factors. This thesis aimed to generate knowledge that can improve prevention against WSSV in shrimp culture through better farm husbandry by studying the epidemiology of WSSV in on-farm situations. To achieve this goal data from cross-sectional and case studies were analysed to identify on-farm WSSV risk and protective factors, and longitudinal studies were done to assess factors affecting water quality and causing WSSV infection to result in an outbreak. The thesis identified the following WSSV risk factors related to the physico-chemical parameters of the water: low and fluctuating temperature, low and fluctuating salinity, and pH fluctuation. The risk of high temperature and high salinity for an outbreak of WSV disease may be related to fluctuations in these two parameters. Risk factors related to farm husbandry techniques were feeding with molluscs, sludge removal and its deposition on the dike, sharing water source with other farms and having the same receiving and intake water. Identified WSSV protective factors were high mangrove to pond area ratio, feeding with natural food or phytoplankton, and higher percentage of beneficial bacteria like the yellow colonies that grow on thiosulphate citrate bilesalt sucrose agar, a Vibrio selective medium. Results of the longitudinal studies demonstrated that WSSV infection may not result in outbreaks in greenwater pond and in ponds with mangroves in the receiving environment. Our results did not provide explanations why the WSSV infection did not result in an outbreak in farms with mangroves in the receiving environment. In greenwater ponds, this was attributed to the better water and soil quality, higher plankton count, and higher heterotrophic bacterial count.</p

Identification of Stressors that Affect White Spot Syndrome Virus (WSSV) Infection and Outbreak in Pond Cultured Penaeus monodon

White spot syndrome virus (WSSV) has been a big problem to the worldwide shrimp industry. Exposure to stressors related to physicochemical water parameters affect WSSV infection but not all WSSV infections result in outbreaks. This paper describes a detailed monitoring of important physicochemical water parameters on a farm with 11 ponds that had WSSV infection. The virus was detected in shrimp exposed to two or more simultaneous stress factors (temperature, pH, water level) or multiple stressors for a number of days. Exposure to more than three stressors resulted in an outbreak of the disease within 3-6 days. Outbreaks were experienced in ponds with a temperature of 26-27°C, a pH lower than 8.0, pH fluctuation of 1.0, and a water depth of less than 1 m. Shrimp stocked in eight of the ponds were successfully harvested after 128-173 days of culture

White spot syndrome virus (WSSV) risk factors associated with farming practices in polyculture and monoculture P. monodon farms in the Philippines

White spot sydrome virus (WSSV) is one of the most important viral disease of shrimp. Several studies to control the disease have been done. Tank experiments identified WSSV risk factors related to the physico chemical properties of the water. A few studies reported pond level WSSV risk factors. This study identifies the risk factors associated with essentially two different farming systems: polyculture and semi-intensive monoculture of Penaeus monodon. Data were gathered from a total of 174 shrimp farmers in eight provinces of the Philippines using a structured questionnaire. Forty-seven variables related to pond history and site description, period of culture, pond preparation techniques, water management, culture methods, feed and other inputs, and biosecurity measures were investigated. In the analysis for combined monoculture and polyculture farms, feeding live molluscs was identified as important WSSV risk factors. In addition to feeding live molluscs, sharing of water source with other farms, having the same receiving and water source, larger pond size, and higher stocking density were identified as important WSSV risk factors in monoculture farms. Climate, i.e. stocking during the cold months and sludge removal and its deposition on the dikes were identified as WSSV risk factors in polyculture farms. Protective factors, listed in decreasing significance, were feeding with planktons and high mangrove to pond area ratio, both observed in the dataset with both monoculture and polyculture farms, while only the latter was observed in the dataset for monoculture farms only. No protective factor was observed in the dataset for polyculture farms. This study confirmed the negative effect of sharing water source with other farms and identified several new factors influencing WSSV infection such as feeding live molluscs increases the risk, while feeding with planktons and high mangrove to pond area ratio reduce the risk

WSSV risk factors related to water physico-chemical properties and microflora in semi-intensive P .monodon culture ponds in the Philippines

Whitespot syndrome virus, WSSV, is the most important among the shrimp diseases. One of the suggested WSSV risk factors is the occurrence of stress since stressors could compromise the shrimp defence system thus increasing the risk of WSSV infection. Stressors are usually related to the physico-chemical properties of both water and pond bottom. This paper investigates the effect of some biotic and abiotic components of the pond ecosystem on WSSV infection and outbreak. Water physico-chemical properties and microflora of 91 production cycles of 8 semi-intensive shrimp farms were analyzed to determine WSSV risk factors, using factor analysis and logistic regression. Fluctuations of temperature and pH are important risk factors that will result to an infection but not necessarily to an outbreak. Exposure to high salinity and high temperature are important factors for an infection to result to an outbreak. The risk of an infection is reduced when the water temperature is high, salinity fluctuations are small, and percentage of yellow Vibrio colonies is greater than the green ones. Further studies are needed to clarify the effects of water depth, water transparency, and various bacterial counts; these factors could be individual or interactive

ASSESSMENT OF SATELLITE PRECIPITATION PRODUCTS IN THE PHILIPPINE ARCHIPELAGO

Precipitation is the most important weather parameter in the Philippines. Made up of more than 7100 islands, the Philippine archipelago is an agricultural country that depends on rain-fed crops. Located in the western rim of the North West Pacific Ocean, this tropical island country is very vulnerable to tropical cyclones that lead to severe flooding events. Recently, satellite-based precipitation estimates have improved significantly and can serve as alternatives to ground-based observations. These data can be used to fill data gaps not only for climatic studies, but can also be utilized for disaster risk reduction and management activities. This study characterized the statistical errors of daily precipitation from four satellite-based rainfall products from (1) the Tropical Rainfall Measuring Mission (TRMM), (2) the CPC Morphing technique (CMORPH) of NOAA and (3) the Global Satellite Mapping of Precipitation (GSMAP) and (4) Precipitation Estimation from Remotely Sensed information using Artificial Neural Networks (PERSIANN). Precipitation data were compared to 52 synoptic weather stations located all over the Philippines. Results show GSMAP to have over all lower bias and CMORPH with lowest Mean Absolute Error (MAE) and Root Mean Square Error (RMSE). In addition, a dichotomous rainfall test reveals GSMAP and CMORPH have low Proportion Correct (PC) for convective and stratiform rainclouds, respectively. TRMM consistently showed high PC for almost all raincloud types. Moreover, all four satellite precipitation showed high Correct Negatives (CN) values for the north-western part of the country during the North-East monsoon and spring monsoonal transition periods

Resistência a antimicrobianos de bactérias oriundas de ambiente de criação e filés de tilápias do nilo (Oreochromis niloticus) Antibacterial resistance in bacteria from fish pond and Nile tilapia fillets (Oreochromis niloticus)

A resistência de bactérias a antimicrobianos foi determinada em uma piscicultura de tilápias (Oreochromis niloticus) em tanques de terra, sem utilização de antibióticos para profilaxia ou controle de doenças. Foi selecionado um tanque, capturados peixes e coletadas amostras de conteúdo intestinal e superfície dos peixes, água de abastecimento e do tanque, ração, filés de tilápias frescos e congelados. Colônias representativas foram selecionadas e analisadas pelos testes de Gram, catalase, oxidase e oxidaçãofermentação. Foram selecionadas 89 amostras e submetidas a antibiograma, utilizando vários antimicrobianos. A maioria das bactérias pertenceu às famílias Enterobacteriaceae e Vibrionaceae. Tanto no ambiente de criação como nos filés de tilápias observou-se que os isolados bacterianos apresentaramse resistentes principalmente a ampicilina e eritromicina. O índice de múltipla resistência a antimicrobianos (MAR) foi calculado, sendo que do total de 89 isolados analisados 74 (83%), apresentaram MAR ³ 0,2, ou seja apresentaram-se resistentes a dois ou mais antimicrobianos. As freqüências de índice MAR foram altas e maiores na ração.<br>This study was conducted in a freshwater tilapia farm that has not used any antibiotic. It was selected one pond, caught 15 fishes and collected samples of intestinal content and mucus surface, water influent and pond water, ration, fresh tilapia fillets and frozen fillets.. Phenotypical characteristics, Gram stain, oxidase production, oxidative-fermentative utilization of glucose (O-F) were determined of representative colony. Were selected 89 strains and submitted for antimicrobial sensitivy test using several antibiotics. The major identified bacterial families were belonged Enterobacteriaceae and Vibrionaceae. The most isolates showed resistance to ampicilin and eritromicin. From the 89 isolates evaluated 74 (83%) showed a multiple antibiotic resistance index (MAR) ³ 0.2, that mean resistance to two or more antibiotics. The MAR índice frequency were higher and bigger in the rations