Analysis of repeated compound units in ORF94 of white spot syndrome virus isolated from Litopenaeus vannamei from outbreak and non-outbreak shrimp farms in Sonora, Mexico
White spot syndrome virus (WSSV) is the viral pathogen with the most negative impact on shrimp farming. In Sonora, Litopenaeus vannamei culture has decreased 50% during 2010-2012 due to WSSV outbreaks. The ORF94 has proven to be most useful for the analysis of WSSV variability. Several studies have suggested a correlation between its Repeat Units (RUs) and WSSV virulence as follows: the fewer RUs (<9) the higher mortality rate. In order to support this, we analyzed shrimps from eight farm periods and identified the WSSV-variety present in each one. In outbreaks, the presence of <8 RUs with a dominance of 3 RUs was notable in the last four years. Although it is still not clear how host-virus interactions and pond's environment affect the transition of the infection just from the presence of the virus in shrimps to an outbreak, these results are a step forward in understanding the pond status and ways of predicting the likelihood of a WSSV infection becoming an outbreak.