Molecular characterization of strains of decapod penstyldensovirus 1 (PstDV1) isolated in farmed Litopenaeus vannamei from Venezuela

PstDV1 has caused losses to the shrimp farming industry that resulted in millions of dollars worldwide. In Venezuela, it was not until 1985 when it was reported as being introduced in farmed Litopenaeus vannamei and since then its presence has been confirmed in those populations. The analysis of variability in the nucleotide sequence can be a very powerful tool for epidemiological and evolutionary understanding. Due to the importance of the aquaculture of L. vannamei in Venezuela, and the effect that this disease could have on the industry, we set to characterize the strains of PstDV1 present in three different regions of Venezuela. Samples of L. vannamei were collected from farms in the states of Nueva Esparta, Zulia and Falcon, finding prevalences from 7 to 15%. PstDV1 positive PCR samples were used to amplify two fragments (1974 and 1244 bp) which contain the complete sequence of the 3 coding regions, except for 63 bp. The presence of macroscopic clinical signs of infection was not detected in any of the studied shrimp. The combined sequence of two fragments was 2816 bp in size, covering 88.8% of the coding regions of the three ORFs, and 69.1% of the total genome. The sequences from Zulia and Nueva Esparta showed no difference, while the sequence from Falcon showed a 99.6% homology to the other two. When the sequences were compared to the one reported from Hawaii, 14 nucleotide substitutions were identified. The phylogenetic analysis carried out using previously published sequences from all over the world showed the formation of 5 groups: the biggest containing samples from Asia, Hawaii and the Americas, showing low sequence divergence; the second represented only by an infectious sample from Australia; the third containing samples from Asia; the fourth group represented only by a sample from East Africa (Tanzania) showing the highest sequence divergence and the last group was represented by a sample from Australia and the endogenous sequence obtained from Penaeus monodon sampled in Madagascar and the Indo-Pacific region. The present study shows the first PstDV1 sequences in introduced L. vannamei shrimp farmed in Venezuela.