Risk factors associated with white spot syndrome virus outbreaks in marine shrimp farms in Rayong Province, Thailand

Abstract

The purpose of this study was to determine risk factors for white spot disease (WSD) in Rayong, Thailand. A study was conducted from October 2014 to March 2015 to identify potential farm-level risk factors using a validated questionnaire. We completed 1 questionnaire for each farm; a total of 38 questionnaires from the case farms and 127 questionnaires from the control farms were collected. The results showed that the presence of WSD in previous crops and the use of seawater were risk factors (p < 0.01), indicating that the environment plays an important role in WSD outbreaks in Rayong. Good management practices for pond preparation and other mitigation steps should be part of a control measure program for WSD in this region.KEY WORDS: Shrimp ⋅ Epidemiology ⋅ Risk factors ⋅ White spot syndrome virus 124: 193-199, 2017 temperature and pH affected the shrimp and influenced WSD infection. Corsin et al. (2003) indicated that, in Karnataka, India, potential risk factors for WSSV included improper salinity in transportation bags, improper post-larvae (PL) length, and late stocking date. However, very little information is available about risk factors at the pond or farm level. Corsin et al. (2001) reported that the location of a pond close to the sea was a risk factor in Vietnam. In the Philippines, an important risk factor was feeding live mollusks to the shrimp (Tendencia et al. 2011). Recently, in Thailand, Piamsomboon et al. (2015) indicated that risk factors included the sourcing of water from communal canals, the use of year-round cultures, and an owner operating multiple farm sites. Resale or republication not permitted without written consent of the publisherDis Aquat OrgThe purpose of the present study was to identify farm-level risk factors for WSD in Rayong, Thailand. Results of this study will be used to improve or establish measures that can be used to prevent or control WSD in this area. This will reduce the economic losses of farmers in Rayong. In addition, conclusions from this study may also in struct disease evaluation and control in other geographical areas, both in side and outside Thailand. MATERIALS AND METHODS Target population and study frameworkAll active marine shrimp farms in Rayong were examined in this study. We selected this area because marine shrimp culture is predominant. Most of the farms in this area are located in 2 districts: the Mueang Rayoung District and the Klaeng District (Fig. 1). A study was conducted from October 2014 to March 2015 to identify potential among-farm (farmlevel) risk factors using a validated questionnaire. At the initiation stage of this study, the laboratory results from passive surveillance by the Department of Fisheries (DoF) of Thailand were used to categorize shrimp farms as either cases or controls. To qualify as a suspected farm for WSD, a farmer had to have called in a report to the local DoF and had to have brought at least 15 suspected shrimp to the laboratory. The following clinical signs were used to define the suspected cases and ide...

A longitudinal study of risk factors associated with white spot disease occurrence in marine shrimp farming in Rayong, Thailand

“…Generally, farmers need to add water during cultivation; hence, they use water directly from natural reservoirs or reservoir ponds, increasing the risk of WSD occurrence through untreated water. This result is consistent with our previous study, indicating that water added without treatment during ponding is a major risk factor ( Yaemkasem et al, 2017 ). In contrast, a closed recirculation system can reduce the risk of WSD more than an ordinary closed system; however, the operation of this system is more expensive.…”

“…In the structured interview schedule, questions included those on farm information, farm practices, farm biosecurity, and possible risk factors associated with WSD ( Supplement 2 ). All questions were designed based on literature reviews ( Piamsomboon, Inchaisri & Wongtavatchai, 2015 ; Yaemkasem et al, 2017 ). In detail, the questions adopted from Piamsomboon, Inchaisri & Wongtavatchai (2015) were those related to farm area, culture area, number of pondings, water reserve area, source of farming water, owner of multiple farms, adjacent farms, water management, and application of fertilizer.…”

“…In detail, the questions adopted from Piamsomboon, Inchaisri & Wongtavatchai (2015) were those related to farm area, culture area, number of pondings, water reserve area, source of farming water, owner of multiple farms, adjacent farms, water management, and application of fertilizer. Questions derived from Yaemkasem et al (2017) included those on biosecurity measures, farm characteristics, stocking density, feeding management, geographical factors, pond preparation, and water management. Finally, questions based on our own experiences in the study area included those on modernizing the water management system, the ponding system, factors related to weather and environment, source of PL, vector control, disease status, and laboratory confirmation of WSD.…”

“…Possible risk factors have been reported in several studies, including: wastewater from a contaminated processing plant ( Reddy, Jeyasekaran & Shakila, 2013 ), pond location near a sea ( Corsin et al, 2001 ), feeding infected carriers, sharing of the water source with infected farms, high stocking density of shrimp ( Tendencia, Bosma & Verreth, 2011 ), appearance of previously infected crops and seawater use ( Yaemkasem et al, 2017 ), owners who own multiple farms ( Piamsomboon, Inchaisri & Wongtavatchai, 2015 ), low atmospheric temperature and high daily atmospheric temperature ( Piamsomboon, Inchaisri & Wongtavatchai, 2016 ), presence of weed on the farm site and inappropriate concentration of ammonia and oxygen ( Talukder et al, 2021 ), and insecure post-larvae (PL) provider ( Worranut et al, 2018 ). However, only a few studies have applied analytical techniques to understand factors that may vary over time.…”

The impact of farm practices and wild carriers on white spot disease in marine shrimp in Rayong Province, Thailand

“…However, filtering the water before filling up culture ponds will prevent the entry of species that could be disease carriers [ 10 ]. Researchers have reported that in Thailand, sourcing water from communal canals, culturing shrimp year-round, a single owner operating more than one farm, the presence of WSD in previous crops, and the use of seawater were associated with WSD [ 11 , 12 ]. Studies in Rayong Province, Thailand, between October 2015 and September 2018 reported significant disease clustering in ponds near the sea [ 13 ].…”