present survey provided another example
of the effect of climate change on an
infectious disease in a marine organism.
A dramatic decline of WSD prevalence
from 2012 to 2014 was observed
in the present study. An emergence of
the early mortality syndrome (EMS),
now known as acute hepatopancreatic
necrosis disease (AHPND), has attacked
shrimp culture in this area since late
2011. EMS/AHPND was present in most
of the samples analyzed, and this may
have masked the decrease in WSD pre -
valence as it was calculated based on
the ratio of WSSV PCR-positive samples
to total number of samples analyzed. In
addition to the sudden prevalence of
EMS/AHPND that caused mass mortality
in early stocking post-larvae, shrimp
farmers in this area decreased their
operations. Shrimp cultured areas and
production yield of Chanthaburi pro -
vince de creased by over 40% in 2014
compared with 2011 (Department of
Fisheries 2014). This also explains the
marked deviation of the predicted values
in the multivariate NBR model,
while the predicted values during 2009
to 2011 corresponded to observed values.
Despite the deviated prevalence,
the number of WSD cases re mained the
same, and the influence of climate factors
was still apparent in the area. The
emergence of a new disease may affect
the prevalence of endemic WSD; however, this study’s
findings suggest that WSD is still a major constraint
in this shrimp farming community, especially when
temperatures are low and fluctuate.
The results of the present study suggest that the
occurrence of WSD in shrimp culture communities in
Chanthaburi province, Thailand, is more prevalent
during October to February. The occurrence of WSD
is significantly related to low atmospheric temperature
and a high degree of daily temperature variation.
In contrast to reports in Mexico and the Philippines,
this study found that the effect of rain was
not an important influence of WSD occurrence in
this area. Because WSD prevalence evidently differs
among geographical locations and culture systems,
investigations of disease prevalence should be im -
plemented specifically to accommodate dissimilarities
in shrimp culture conditions. Although our re -
sults present a correlation between climate and WSD