Partial cloning of the genome of infectious hypodermal and haematopoietic necrosis virus, an unusual parvovirus pathogenic for penaeid shrimps; diagnosis of the disease using a specific probe

The infectious hypodermal and haematopoietic necrosis virus (IHHNV), pathogenic for penacid shrimp, is an icosahedral unenveloped particle, 22 nm in diameter, with an ssDNA linear genome, and proposed to be a member of the Parvoviridae. A large majority of minus-strand DNA is incorporated into the capsids compared to the plus-strand. A small amount of reannealed plus- and minus-strands (dsDNA) obtained after nucleic acid extraction was blunt-ended and cloned into the system pUC18/Escherichia coli strain DH5α. Selected clones were studied and characterized using restriction enzymes. One of them, BQ31, was used to construct different sized probes labelled with digoxigenin-11-dUTP. These probes failed to hybridize with DNA of some insect parvoviruses and with DNA of a parvo-like virus of shrimp. They reacted strongly with dilutions of homogenized IHHNV-infected shrimp tissues and, conversely, did not react with uninfected shrimp tissues. They hybridized in situ, in sections of infected animals, labelling strongly the target cells and particularly the nuclear Cowdry type A inclusion body, which is the most diagnostic characteristic of this disease.