Climate factors influence the occurrence of white spot disease in cultured penaeid shrimp in Chanthaburi province, Thailand

This study investigated the prevalence of white spot disease (WSD) in an intensive shrimp culture area located in Chanthaburi province, Thailand, during 2009-2014. Retrospective data of 1952 WSD cases obtained from government laboratories were analyzed to study the association between WSD occurrence and climate factors using negative binomial regression (NBR) models. Climate factors included daily atmospheric temperature, relative humidity, wind speed, total amount of rainfall and rain days during the disease notifications. The annual prevalence of WSD was significantly higher from 2009 to 2011 than from 2012 to 2014. Interestingly, the monthly WSD occurrence was unchanged between those time periods. A high number of WSD cases was found between October and February, while fewer cases were reported during March to June, and the lowest numbers were reported in May. The multivariate NBR model indicated significant associations between an increased number of WSD cases with decreased atmospheric temperature and increased variation in daily atmospheric temperature. A high incident rate ratio (IRR) of WSD was observed when average atmospheric temperature ranged between 24.5 and 27.2 degrees C (IRR: 2.53, 95% CI: 1.72-3.75) and there was increased variation in daily atmospheric temperature (IRR: 1.08, 95% CI: 0.99-1.20). The time series analysis concluded that low ambient atmospheric temperature and high daily atmospheric temperature variation were promoting factors for WSD occurrence.