White spot syndrome virus molecular epidemiology: relation with shrimp farming and disease outbreaks

H. Tran Thi Tuyet

Research output: Thesisinternal PhD, WU

Abstract

White spot syndrome virus (WSSV), the causative agent of white spot disease (WSD), has been responsible for most shrimp production losses around the world since the early 1990s. Previous research has focused mainly on the characterization of WSSV genomic variation to gain a better insight in the evolution and spread of the virus at the regional and global levels.Although WSSV genetic variation at small spatial scales has been described, the question is whether there is a correlation between this genomic variation and shrimp farming practices and disease outbreak at the local and farm level. Therefore, the present research has been carried out to describe in detail WSSV genetic variation over space and time and to estimate transmission routesof WSSV genotypes in ponds with different farming regimens. Different molecular markers, natural variation contained within the WSSV genome, were tested to quantify these relationships in semi-intensive, extensive and rice-shrimp farming systems within the Ca Mau and Bac Lieu provinces, both in the Mekong Delta, Vietnam. The outcomes of the research showed that (i) there are differences in genetic structure of WSSV populations in shrimp culture areas, with more variation found in variable number tandem repeat (VNTR) regions, short adjoining repeat sequences, than in genomic regions in which large deletions occur; (ii) a correlation betweenWSSV population structure, disease outbreak status and pond farming system was observed, providing evidence that the WSSV VNTR structure (in particular the number of repeat units in ORF94) statistically correlate with disease outbreaks and to a lesser extent to farming system; (iii) mixed-genotype WSSV infections of shrimp are correlated with fewer disease outbreaks in ponds; and (iv) it might be possible to use molecular markers (ORF94 and ORF125) to predict the outcome of WSSV infections in shrimp ponds in the future. For field applications, these findings provide important information for the development of specific management strategies to control WSD.

Original languageEnglish
QualificationDoctor of Philosophy
Awarding Institution
  • Wageningen University
Supervisors/Advisors
  • Vlak, Just, Promotor
  • de Jong, Mart, Promotor
  • Phuong, N.T., Co-promotor, External person
  • Zwart, Mark, Co-promotor
Award date27 Apr 2012
Place of PublicationS.l.
Print ISBNs9789461732125
Publication statusPublished - 2012

Keywords

  • molecular epidemiology
  • shrimp culture
  • shrimps
  • white spot syndrome virus
  • viral diseases

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