Fitness and virulence of different strains of white spot syndrome virus

Pradeep, Balakrishnan; Karunasagar, Iddya

doi:10.1111/j.1365-2761.2009.01053.x

Cited by 31 publications

(29 citation statements)

References 29 publications

(51 reference statements)

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“…As the sensitivity of our assay varies depending on the VNTR locus and RU variants present, the actual frequency of mixed-genotype infections may be higher than our estimates. Others have reported evidence for the occurrence of mixed-genotype infections in the field (Hoa et al, 2005;Pradeep et al, 2008a), and mixedgenotype infections have been studied in laboratory settings (Marks et al, 2005;Pradeep et al, 2009). The work presented here provides the first confirmation -by cloning and sequence analysis -that mixed-genotype WSSV infections occur in the field.…”

supporting

confidence: 66%

Mixed-genotype white spot syndrome virus infections of shrimp are inversely correlated with disease outbreaks in ponds

Hoa

Zwart

Phượng

et al. 2010

Journal of General Virology

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Outbreaks of white spot syndrome virus (WSSV) in shrimp culture and the relationship between the virus and virulence are not well understood. Here, we provide evidence showing that WSSV mixed-genotype infections correlate with lower outbreak incidence and that disease outbreaks correlate with single-genotype infections. We tested 573 shrimp samples from 81 shrimp ponds in the Mekong delta with outbreak or non-outbreak status. The variable number tandem repeat (VNTR) loci of WSSV were used as molecular markers for the characterization of single-and mixed-genotype infections. The overall prevalence of mixed-genotype WSSV infections was 25.7 %. Non-outbreak ponds had a significantly higher frequency of mixed-genotype infections than outbreak ponds for all VNTR loci, both at the individual shrimp as well as at the pond level. The genetic composition of WSSV populations appears to correlate with the health status of shrimp culture in ponds. The causal relationship between genotypic diversity and disease outbreaks can now be experimentally approached.

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supporting

confidence: 66%

Mixed-genotype white spot syndrome virus infections of shrimp are inversely correlated with disease outbreaks in ponds

Hoa

Zwart

Phượng

et al. 2010

Journal of General Virology

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“…The 10 970 bp Indel-II deletion was correlated most strongly with disease, followed by the 8539 bp Indel-II deletion, although this deletion type was also detected commonly in healthy PL and juveniles sampled when ponds were stocked. Such correlations concur with previous evidence of specific WSSV genotypes associating with disease (Hoa et al 2005, Musthaq et al 2006) and with WSSV strains with shorter genomes being more virulent (Marks et al 2005, Pradeep et al 2009, Zwart et al 2010). However, why WSSV strains with longer Indel-II deletions seem to cause or result from disease remains to be elucidated.…”

Section: Discussionsupporting

confidence: 91%

Indel-II region deletion sizes in the white spot syndrome virus genome correlate with shrimp disease outbreaks in southern Vietnam

Tuyet¹,

Zwart²,

Phượng³

et al. 2012

Dis. Aquat. Org.

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Sequence comparisons of the genomes of white spot syndrome virus (WSSV) strains have identified regions containing variable-length insertions/deletions (i.e. indels). Indel-I and Indel-II, positioned between open reading frames (ORFs) 14/15 and 23/24, respectively, are the largest and the most variable. Here we examined the nature of these 2 indel regions in 313 WSSVinfected Penaeus monodon shrimp collected between 2006 and 2009 from 76 aquaculture ponds in the Mekong Delta region of Vietnam. In the Indel-I region, 2 WSSV genotypes with deletions of either 5950 or 6031 bp in length compared with that of a reference strain from Thailand (WSSV-TH-96-II) were detected. In the Indel-II region, 4 WSSV genotypes with deletions of 8539, 10 970, 11 049 or 11 866 bp in length compared with that of a reference strain from Taiwan (WSSV-TW) were detected, and the 8539 and 10 970 bp genotypes predominated. Indel-II variants with longer deletions were found to correlate statistically with WSSV-diseased shrimp originating from more intensive farming systems. Like Indel-I lengths, Indel-II lengths also varied based on the Mekong Delta province from which farmed shrimp were collected.KEY WORDS: White spot syndrome virus · Disease status · Farming system · Epidemiology · ORF 14/15 · ORF 23/24Resale or republication not permitted without written consent of the publisher Dis Aquat Org 99: [153][154][155][156][157][158][159][160][161][162] 2012 highly (> 99.5%) conserved (Nadala & Loh 1998, Marks et al. 2004.The 2 major genomic indels are located between open reading frames (ORFs) 14/15 (Indel-I) and 23/24 (Indel-II) of the sequenced Thai strain WSSV-TH-96-I (van Hulten et al. 2001, Marks et al. 2004. Compared with another sequenced Thai strain (WSSV-TH-96-II), WSSV-TH-96-I has a 5.3 kb deletion in Indel-I (Marks et al. 2005) and differs from a strain from Taiwan (WSSV-TW) by possessing a 13.2 kb deletion in Indel-II (Marks et al. 2004). Sequence analyses of these 2 indel regions in other Asian WSSV strains have identified intermediatelength deletions (Dieu et al. 2004, Zwart et al. 2010. For example, WSSV strains from China contain shorter Indel-II deletions (1168 to 5928 bp) compared with WSSV-TW, while strains from Vietnam contain a medium-length Indel-II deletion (~8539 bp) not yet found in strains examined from other geographic regions (Dieu et al. 2004; see also Yang et al. 2001, Lan et al. 2002, Tan & Shi 2011.Indel-I and Indel-II regions are now being used as molecular markers to study WSSV epidemiology (Dieu et al. 2004, Zwart et al. 2010, and Indel-II is proving to be particularly useful for examining the spatiotemporal spread of WSSV at regional (Dieu et al. 2010) and intercontinental levels (Zwart et al. 2010). Data on Indel-II support a hypothesis that all WSSV strains affecting farmed shrimp have a recent common ancestor. This virus presumably circulated in China or Taiwan before spreading to shrimp farms in Vietnam, from there to Thailand (Dieu et al. 2004) and from there to India (Pradeep et al. 2008a)...

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“…In a previous study, we showed that two variable regions with large deletions (ORF23/24 and ORF14/ 15) and three VNTR loci (ORF75, ORF94 and ORF125) could be used as molecular markers for epidemiological studies (Dieu et al, 2004 Pradeep et al, 2008aPradeep et al, , b, 2009Tan et al, 2009), but a statistically supported model was not derived. Moreover, the degree of between-isolate variation for these loci appears to be very different.…”

Section: Discussionmentioning

confidence: 95%

“…A number of subsequent studies on WSSV epidemiology have used the regions with genomic deletions (Musthaq et al, 2006;Waikhom et al, 2006;Pradeep et al, 2008b) or one or more VNTR loci (Hoa et al, 2005;Kiatpathomchai et al, 2005;Kang & Lu, 2007;Pradeep et al, 2008a;Tan et al, 2009), or both (Dieu et al, 2004;Marks et al, 2005;Pradeep et al, 2009), as genetic markers to characterize WSSV variants. VNTRs appear to be more variable than the deletions (Dieu et al, 2004).…”

Section: Introductionmentioning

confidence: 99%

Evaluation of white spot syndrome virus variable DNA loci as molecular markers of virus spread at intermediate spatiotemporal scales

Dieu

Marks

Zwart

et al. 2010

Journal of General Virology

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Variable genomic loci have been employed in a number of molecular epidemiology studies of white spot syndrome virus (WSSV), but it is unknown which loci are suitable molecular markers for determining WSSV spread on different spatiotemporal scales. Although previous work suggests that multiple introductions of WSSV occurred in central Vietnam, it is largely uncertain how WSSV was introduced and subsequently spread. Here, we evaluate five variable WSSV DNA loci as markers of virus spread on an intermediate (i.e. regional) scale, and develop a detailed and statistically supported model for the spread of WSSV. The genotypes of 17 WSSV isolates from along the coast of Vietnam -nine of which were newly characterized in this study -were analysed to obtain sufficient samples on an intermediate scale and to allow statistical analysis. Only the ORF23/24 variable region is an appropriate marker on this scale, as geographically proximate isolates show similar deletion sizes. The ORF14/15 variable region and variablenumber tandem repeat (VNTR) loci are not useful as markers on this scale. ORF14/15 may be suitable for studying larger spatiotemporal scales, whereas VNTR loci are probably suitable for smaller scales. For ORF23/24, there is a clear pattern in the spatial distribution of WSSV: the smallest genomic deletions are found in central Vietnam, and larger deletions are found in the south and the north. WSSV genomic deletions tend to increase over time with virus spread in cultured shrimp, and our data are therefore congruent with the hypothesis that WSSV was introduced in central Vietnam and then radiated out.

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Fitness and virulence of different strains of white spot syndrome virus

Cited by 31 publications

References 29 publications

Mixed-genotype white spot syndrome virus infections of shrimp are inversely correlated with disease outbreaks in ponds

Mixed-genotype white spot syndrome virus infections of shrimp are inversely correlated with disease outbreaks in ponds

Indel-II region deletion sizes in the white spot syndrome virus genome correlate with shrimp disease outbreaks in southern Vietnam

Evaluation of white spot syndrome virus variable DNA loci as molecular markers of virus spread at intermediate spatiotemporal scales

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