Prospecção de fatores de risco associados a mortalidade de camarões marinhos Litopenaeus vannamei (BOONE, 1931) cultivados em viveiros sob a influência do vírus da síndrome da Mancha Branca (WSSV).

Abstract

ABSTRACT Litopenaeus vannamei shrimp farming is an important source of food and income in the northeast Brazilian countryside. However, the activity involves high risks, especially because of the impacts caused by diseases, such as White spot syndrome (WSS). WSS is the one which causes high losses to the Brazilian shrimp farming sector. This disease impacts the industry of the country since 2016. The infectious agent is a double stranded DNA virus capable of infecting a wide range of hosts and to cause massive mortalities. Thus, the present work aims to identify and to characterize the risk factors associated with the mortalities in L. vannamei culture systems located in the western littoral of the state of Ceará. First, it was sought to characterize the occurrence of WSS outbreaks in the study region through presumptive analysis, histopathological analysis, qPCR and water quality analysis, in order to assess the effects of the disease on mortality rates. Later, a questionnaire covering 32 risk factors associated with shrimp farming was applied to 29 farms from the region to prospect risk factors. The surveyed farms were characterized by low technological level, adopting strategies of coexistence with the WSSV, stocking huge earthen ponds with low shrimp density. Micro producers were 59% of the farmers, followed by 14% of small producers, 21% of medium sized producers and only 7% large scale producers. The qPCR analysis detected the presence of the virus in all 10 monitored farms. The shrimps presented a low infection severity index in the histopathological analysis and a good sanitary state in the presumptive analysis. The correlation and regression analysis showed that the mortality rates in the farms were not affected by the sanitary parameters evaluated. The study points that mortality in the culture system seems to be affected by other factors besides WSS. The risk factor analysis model developed pointed to three risk factors associated with the mortality rates: (1) the use of settling ponds; (2) the average level of the ponds during shrimp stocking; (3) the macroscopic aspect of the cultured shrimp.