Rate (ROI) and severity (SOI) of infection of white spot disease in cultured and captured Penaeidshrimps in the Persian Gulf using histopathology and polymerase chain reaction

Abstract

White Spot Disease (WSD) is well known as a widespread viral disease in shrimps from 1992. Many studies focused on morphological, histopathological and epidemiological characteristic and pathogenecity of the disease but less on the determination of the severity of WSD using the histopathological features in target tissues. A generalized scheme for assigning a numerical qualitative value to severity grade of infection considering to histopathology and counting the inclusion bodies in different level of infection and different microscopic fielding immersion lens was accomplished before. This study was conducted in order to estimate the rate of infection (ROI) and the severity of infection (SOI) of WSD in native shrimps inthePersian Gulf.About 90 live specimens of affected cultured Penaeusindicuswere collected from Abadan region, south Iran and 150 specimens of native shrimps were captured from the Persian Gulf.Histopathological changes were observed by light microscope in target organs such as: gills, cuticular epidermis, heart, hemolymph, fore stomach and hepatopancreas. ROI and SOI were estimated respectively by standard formulas and grading between 0-4 based on the percentage of white spot syndrome virus WSSV positive cells in selected fields of microscope. The results were confirmed by conducting nested PCR method. The SOI of P. styliferawasestimated in grade fourand its ROI was about 85% as the most susceptible species.Histopathologic infection of Metapenaeusaffinisshrimp by WSD was observed also during this study