Detection of infectious hypodermal and haematopoietic necrosis virus (IHHNV) in farmed Australian Penaeus monodon by PCR analysis and DNA sequencing

Infectious hypodermal and haematopoietic necrosis virus (IHHNV) of shrimp has recently been classified as Penaeus stylirostris brevidensovirus (PstDNV) in the family Parvoviridae. Genetic variants have been reported in the Black Tiger shrimp Penaeus monodon over its natural range from East Africa to Australasia. Previous reports from Australia have suggested that a distinct, non-infectious type of IHHNV that is inserted into the shrimp host genome is the only type of IHHNV that occurs there. Here we describe an infectious type of IHHNV identified from farmed P. monodon in Australia in April 2008 by PCR amplification from two regions of the IHHNV genome, one reported to be discriminatory for the infectious type of IHHNV and the other (from IHHNV ORF1/2) not described in the non-infectious, inserted type. In addition, we used overlapping PCR primers to amplify all of the ORFs of the IHHNV genome (approximately 3.6 kb) from the Australian samples, except for the hairpin loop ends (GQ475529). Comparison of the maximum possible portion of this sequence with 8 GenBank records of IHHNV isolates reported from Asia (2814 bases relative to positions 588 to 3413 of GenBank AF273215) revealed 94–95% identity in nucleic acid sequence and 96 to 97% identity in amino acid sequence. These results were in agreement with an official report by the World Organization for Animal Health in July 2008 for the presence of infectious IHHNV in Australia.