Tissue Tropism of White Spot Syndrome Virus in Artificially Infected Shrimp Collected From South East Coastal Part of Bangladesh

Abstract

White spot is a common symptom that frequently reported from a variety of culturing farms and ghers in Bangladesh specially in Khulna region which is caused by a DNA virus of White spot syndrome virus (WSSV). This virus causes a serious economic losses of shrimp Penaeus monodon and the incidence of the disease is severe. In this study, polymerase chain reaction (PCR) was used to determine the pattern of WSSV virus multiplication in tissues of shrimp and in addition the entrance of virus route as well. Viral solution was isolated from moribund WSSV infected shrimp using PBS solution and injected in 3rd and 4th segment of pleon. Every time 3 samples were collected randomly from tanks after each 3,6,12 and 24 hour post inoculation (hpi). Two different pairs of primers yielding amplicons ranging from 298 and 941 bp were used. The results revealed that none of the sample showed positive result at one step PCR test using 941 bp. The samples were then subjected to 2 step PCR using 1ul of first step amplified product as a DNA template and the results of PCR analysis showed that all the tissue or organ of gill, hemolymph, abdominal muscle, pleopods, and the tail muscle investigated. WSSV in the injected shrimp was particularly prevalent in the gills(60%), followed in order of decreasing prevalence by hemolymph(57%),abdominal muscle(50%), pleopods(46%), and the tail muscle(23%).Since no mortality occurred during experimental period the virus in shrimp was considered in the carrier state. This suggests that disease outbreaks do not occur if shrimp defense mechanisms manage to contain low intensity viral infections under low-stress culture conditions. Conversely, outbreaks may occur under stressful conditions.