White spot syndrome virus (WSSV) in cultured Penaeus monodon in the Philippines

The prevalence and geographic distribution of white spot syndrome virus (WS SV) infection among cultured penaeid shrimp in the Philippines was determin ed from January to May, 1999, using PCR (polymerase chain reaction) protoco l and Western blot assays. A total of 71 samples consisting of 18 post-larv ae (PL) and 53 juvenile/adult shrimp samples (56 to 150 days-of-culture, DO G) were screened for WSSV. Of the 71 samples tested, 51 (72%) were found po sitive for WSSV by PCR: 61% (31/51) after 1-step PCR and 39% (20/51) after a-step, non-nested PCR. Of the PL and juvenile/adult shrimp samples tested, 50 and 79% were positive for WSSV, respectively. By Western blot, only 6 o f the 51 (12%) PCR-positive samples tested positive for WSSV. Of the 20 sam ples negative for WSSV by PCR, all tested negative for WSSV by Western blot assay. This is the first report of the occurrence of WSSV in the Philippin es.