White spot disease risk factors associated with shrimp farming practices and geographical location in Chanthaburi province, Thailand

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

Background and Aim

White spot disease (WSD) is a highly lethal and contagious viral disease in marine shrimp caused by the white spot syndrome virus (WSSV). White spot disease impacts the worldwide crustacean aquaculture sector, including Thailand. This study aimed to investigate the effect of farm management practices and wild carriers on WSD occurrence in grow-out marine shrimp farms in Rayong Province, Thailand.

Materials and Methods

A longitudinal study was conducted using a structured questionnaire from June 2018 to June 2020. A total of 186 questionnaires for 186 ponds were collected from 15 shrimp farms. Univariate and multivariable analyses using generalized estimating equations were used to determine the risk factors associated with WSD. In addition, possible carrier samples (wild shrimp and wild crabs) were collected inside and outside farms to test for the presence of WSSV.

Results

Direct discharge of treated wastewater into farm ponds was statistically significant in the final model (p < 0.01), with an odd ratio (OR) factor of 0.097 (95% confidence interval [CI] of OR = 0.007-0.242). Pooled sampling for WSSV in wild shrimp and crabs showed that 48 out of 936 (5.13%) samples tested positive for WSD using nested polymerase chain reaction. The samples from banana shrimp, jinga shrimp, banded snapping shrimp, dwarf prawn, whiteleg shrimp, green tidal crabs, and mangrove crabs tested positive.

Conclusion

Based on the findings of this study, we infer that the environment plays an important role in the spread of this disease. The results of this study will provide insights into the effective planning of disease control.

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

Background

A longitudinal study was conducted to analyze farm characteristics, farm practices, and biosecurity measures that influenced the occurrence of white spot disease (WSD) in shrimp farming in Rayong, Thailand.

Methods

Data were collected using a structured interview schedule administered between October 2017 and September 2019. A generalized estimating equations (GEE) model was used to identify risk factors. From the 270 responses, 86 possible risk factors were analyzed using univariate and multivariate analysis.

Results

We found that 17 possible risk factors were statistically significant with an alpha level of 1% and associated with WSD status. In the final model, multivariate analysis found that two independent variables were statistically significant. First, the absence of inclement weather during ponding was a statistically significant factor associated with WSD occurrence and it prevented WSD occurrence as the odds ratio (OR) was <1 (OR = 0.196, P = 1.3 × 10^-5). Second, the separation of ponds into three specific types (cultured, water treatment, and pond for water reservoir) was significantly associated with WSD occurrence. Likewise, the presence of this ponding system was a protective factor against WSD (OR = 0.0828, P = 0.001).

Conclusions

The results of this study offer a reference for farmers and relevant authorities when addressing WSD occurrence in shrimp farming. In addition, our results can help relevant authorities in controlling WSD in other endemic areas.

Spatial and temporal patterns of white spot disease in Rayong Province, Thailand, from october 2015 to september 2018

This study aimed to analyze the spatial and temporal patterns of white spot disease (WSD) in shrimp farms in Rayong Province, Thailand, between October 2015 and September 2018. The longitudinal data of all active shrimp farms were collected and categorized into two groups: cases and non-cases. A space-time permutation scan, epidemic curve, and time-series analysis were used to evaluate the spatiotemporal patterns. We assessed a total of 1126 ponds across 176 farms in two districts (Klaeng and Mueang Rayong) and identified three significant (P < 0.05) clusters of WSD cases. The biggest cluster encompassed 21 geographical coordinates. This cluster had a radius of 1.14 km and occurred between January 31, 2017, and February 28, 2017. The epidemic curve showed that the biggest outbreak peaked from December 2017 to February 2018. In the time-series analysis, the highest probability of actual WSD cases was at the beginning of each calendar year, consistent with the prominent high probability recorded in WSD forecasts. Our analysis presents the interaction between hotspot areas and time period. These results should help the relevant authorities implement appropriate surveillance programs and control measures to limit the occurrence and transmission of WSD.

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

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.