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Virulence Variation of White Spot Syndrome Virus in Pacific White Shrimp Litopenaeus vannamei
Author(s) -
Laramore S. E.,
Scarpa J.,
Laramore C. R.,
Lin J.
Publication year - 2009
Publication title -
journal of aquatic animal health
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.507
H-Index - 52
eISSN - 1548-8667
pISSN - 0899-7659
DOI - 10.1577/h08-012.1
Subject(s) - litopenaeus , shrimp , white spot syndrome , biology , white (mutation) , virulence , virus , penaeidae , fishery , zoology , virology , decapoda , genetics , crustacean , gene
The virulence of seven geographic isolates of white spot syndrome virus (WSSV; genus Whispovirus ; China (strain CH1995), Nicaragua (strain N2000), Honduras (strain H2000), Ecuador (strains E‐L1999 and E‐LT2002), and Mexico (strains M‐M2001 and M‐LP2001)) was compared using a series of challenge experiments, each lasting 10 d. For each isolate, four quantified dilutions (10 −6 , 10 −7 , 10 −8 , and 10 −9 ) of a viral inoculum were prepared from WSSV‐infected shrimp tissue. Each viral inoculum was injected into 10 specific pathogen‐free juvenile Pacific white shrimp Litopenaeus vannamei (0.25–1.50 g); controls received injections of marine crustacean physiological saline (3.2%). The minimum dose of viral inoculum that killed 50% of injected shrimp (LD50) was calculated for dilution, tissue concentration, and viral DNA amount. The CH1995 and M‐M2001 isolates were the least virulent, with LD50 values of 10 −6 to 10 −7 of viral inoculum. The isolates could be grouped into three virulence clusters (CH1995 and M‐M2001; N2000 and E‐LT2002; and H2000, E‐L1999, and M‐LP2001). Virulence clusters were not altered by LD50 values based on viral DNA concentration, although a slight shifting of order in regards to virulence was seen among the three most virulent isolates (E‐L1999, H2000, and M‐LP2001). Overall, results indicate that there is a measurable virulence difference among WSSV isolates, which may correspond to geographical region.