Investigation on white spot syndrome virus (WSSV) in Penaeus monodon brood, nauplii, post larvae and cultured shrimp in Cox’s Bazar, Bangladesh by using nested PCR techniques

Investigations were carried out between April 2014 to June 2016 for detecting white spot syndrome virus (WSV) in tiger shrimp, Penaeus monodon broods, nauplii, post larvae and cultured shrimp by using nested PCR techniques. The presence viral DNA was observed in shrimp culture farms in Cox’s Bazar. Of 558 grow out shrimp samples tested, 239 (42.83%) were found to be positive for WSSV by PCR assay. Of 91 post larvae collected in adjacent river and canal, 41 (45.05%) were infected with WSSV and 70 juvenile shrimps collected, 45 (64%) of the samples were positive for WSSV infection. Selected shrimp hatcheries in the region also showed continual occurrence of WSSV infection and 149 nauplii were tested, 39(26.17%) were positive for WSSV by PCR assay. In hatcheries, 248 nos. P. monodon broods collected, 125(50.40%) were found positive for WSSB. The average WSSV infection in brood shrimps were increased as 32%, 34% and 69% for the years 2014, 2015 and 2016, respectively. P. monodon broods collected from the deep sea zone, WSSV prevalence was 57% in summer (May), falling to 0% during winter month (November). Many of the brooders and juveniles did not exhibit any external symptoms of WSSV infection, however, following PCR amplification with WSSV detection primers clear products were revealed, indicating the presence of latent infection. Thus, effective prevention and control measures are urgently needed to control the spread of the WSSV disease in the shrimp industry. Diagnostic PCR can be applied to screen for carrier brood stock and shrimp larvae used for shrimp culture