The Pathogenicity of Vibrio anguillarum and White Spot Syndrome Virus against Litopenaeus vannamei under Different Temperature Conditions

Key words: 
• temperature /
• Vibrio anguillarum /
• white spot syndrome virus /
• Litopenaeus vannamei

Abstract: Litopenaeus vannamei were infected separately or co-infected with Vibrio anguillarum and white spot syndrome virus（ WSSV） at different concentrations under three different temperature conditions（ 19 ± 1,25 ±1,31 ± 1 ℃）. The infected L. vannamei were sampled at the 0,6 12,24,48,72,96 hrs after infection to observe and record their infection rate and mortality and determine their WSSV load. The cumulative mortality and WSSV load of L. vannamei infected were found lower than 11. 1% and 1. 2 × 10³ copies / g,respectively during the experiment at the temperature of（ 19 ± 1） ℃. At the temperature of（ 25 ± 1） ℃ the cumulative mortality of L. vannamei was significantly different between the single infection of WSSV and the co-infection of WSSV and V. anguillarum at 48 h-96 h（ P ＜ 0. 05）,and between the co-infection groups（ P ＜ 0. 05）,with the maximum mortality of the co-infection group at the concentration of 2. 3 × 10⁶cfu·m L^-1 being 77. 8%. At the temperature of（ 31 ± 1） ℃,the cumulative mortality of L. vannamei in each infection group began to increase at 48 h,and the virus replication and the cumulative mortality of L. vannamei was significantly higher in the co-infection group than in the WSSV infection group. Therefore,V. anguillarum and WSSV had a low pathogenicity at the lower temperature. As the temperature increased,the pathogenicity of Vibrio anguillarum and WSSV in coinfection increased with the temperature. That means temperature could significantly affect the pathogenicity of V. anguillarum and WSSV.