Global distribution of white spot syndrome virus genotypes determined using a novel genotyping assay.

White spot disease, caused by infection with white spot syndrome virus (WSSV), is a serious panzootic affecting prawn aquaculture. The disease has spread rapidly around the prawn-culturing regions of the world through a number of previously identified mechanisms. The ability to distinguish and trace strains of WSSV is of great benefit to identify, and then limit, the translocation routes of the disease. Here, we describe a novel genotyping method using 34 short tandem repeat regions of the viral genome concurrently. This technique is highly sensitive to strain differences when compared to previous methods. The efficacy of the described method is demonstrated by testing WSSV isolates from around the globe, showing regional genotypic differences. The differences in the genotypes were used to create a global minimum spanning network, and in most cases the observed relationships were substantiated with verification of transboundary movement. This novel panel of STR markers will provide a valuable epidemiological tool for white spot disease. We have applied this to an outbreak of the disease in Queensland, Australia, that occurred in 2016. While the results indicate that the source of this outbreak currently remains cryptic, the analyses have provided valuable insights with which to further study the origins of the strains involved.

Effect of dietary supplementation with zinc enriched yeast (Saccharomyces cerevisiae) on immunity of rainbow trout (Oncorhynchus mykiss).

Zinc (Zn) is an essential trace element in all living organisms, and the first eukaryotic Zn uptake transporter was discovered in the yeast, Saccharomyces cerevisiae. Zinc-enriched yeast is a currently available Zn supplement. The purpose of the investigation was to compare and evaluate the effect of Zn enriched yeast in rainbow trout. The fish (mean body weight 10 ± 0.5 g) were fed a commercial diet supplemented with 0 (control), 1 × 10(6), 1 × 10(7) and 1 × 10(8) CFU/g of Zn-enriched yeast for 60-days. Results showed that significant increase in serum lysozyme activity, complement activity and total immunoglobulin were seen in all treatment groups during feeding trial when compared to the control group. On the basis of our findings, Zn-enriched improved rainbow trout growth, some immune parameters and disease resistance.