DETECTION OF WHITE SPOT SYNDROME VIRUS (WSSV) IN COMMERCIAL SHRIMP FEED BY PCR  

Bambang Hanggono*1, Yani Lestari N 1, Fatmawati1, Sumini1, Jee Eun Han2, Kathy FJ. Tang2
 
1Brackishwater Aquaculture Development Center Situbondo, Indonesia
2Aquaculture Pathology Laboratory University of Arizona Tucson, Arizona 85721
 USA

White spot syndrome virus (WSSV) is highly pathogenic to penaeid shrimp and has caused significant economic losses in the aquaculture industry around the world. During 2015, WSSV DNA was detected by 2 qPCR assays in several batches of commercial shrimp feed used by farmers in SE Asian countries. The 2 qPCRs targeted the ORF167 and ORF151 (encoding vp466) of Thailand WSSV genome. The presence of WSSV DNA was confirmed by a conventional PCR and direct sequencing a fragment (297-bp) of the ribonucleotide reductase small subunit (RR2) coding region. The nucleotide sequence was analyzed by the blast program, the result showed a 100% identity to those of several WSSV isolates (Table 1), confirming the presence of WSSV DNA. DNA extracton followed by a WSSV qPCR assay was used to determine the quantities of WSSV DNA present in the shrimp feed. The results showed WSSV was present in low quantities, ranging from 101 to 103 copies/mg feed. To determine if these WSSV PCR-positive feed are infectious, we performed bioassays feeding specific-pathogen-free shrimp with WSSV-positive feed for durations of 2-weeks to 1-month and then analyzed the indicator shrimp by PCR. The results showed that the shrimp were not infected from the ingesting the feed. It is likely that the WSSV virus is inactivated during the manufacturing processes. This suggests that authorities and producers need not be concerned with WSSV being spread through shrimp feed.