Infectious hypodermal and hematopoietic necrosis virus (IHHNV) is a serious pathogen, which for the last 24 years has been responsible for negatively affecting the growth and survival of some species of cultured penaeid shrimp. The Pacific white shrimp Litopenaeus vannamei is particularly affected by IHHNV as the virus can cause poor growth and physical deformities in infected populations. There are no known treatments for shrimp affected with IHHNV and management tools for preventing this disease are limited to the exclusion of the virus from cultured shrimp populations. Previous studies have determined that warm-water culture conditions inhibit the replication rate of two other important shrimp viruses, White spot syndrome virus (WSSV) and Taura syndrome virus (TSV) in L. vannamei. The purpose of this study was to compare the effect of water temperature on the replication rate of IHHNV in shrimp held in warm water (32.8 ± 1.0 °C), compared to the replication rate of IHHNV in shrimp held in cool water (24.4 ± 0.5 °C). A total of 72 specific pathogen-free (SPF) L. vannamei were used for this study. They were divided into four groups, namely 1) saline-injected shrimp held in warm water (31.1 ± 1.0 °C), 2) saline-injected shrimp held in cool water (26.3 ± 0.6 °C), 3) IHHNV-injected shrimp held in warm water (32.8 ± 1.0 °C), and 4) IHHNV-injected shrimp held in cool water (24.4 ± 0.5 °C). The concentration of IHHNV in shrimp collected from day 1 through day 17 post-exposure was measured with real time polymerase chain reaction (PCR) using the TaqMan® technique. The results from samples collected on days 6, 12, and 17 post-exposure showed a statistically significant difference (p < 0.05) between the viral load of the IHHNV-injected shrimp held in warm water versus the IHHNV-injected shrimp held in cool water. The IHHNV-injected shrimp held in the warm-water conditions averaged 1.44 × 103, 1.77 × 103, and 1.20 × 105 virus copies/50 ng of shrimp tissue DNA on days 6, 12, and 17, respectively. The IHHNV-injected shrimp in the cool-water conditions averaged 2.25 × 105, 1.8 × 106, and 4.6 × 106 virus /50 ng DNA on days 6, 12, and 17, respectively. These results clearly indicate that under these conditions water temperature had a profound effect on the replication rate of IHHNV in L. vannamei. The results support the findings of the previous studies and further point to the potential application of elevated environmental temperature as a management strategy for certain viral diseases within the shrimp farming industry.
ASJC Scopus subject areas
- Aquatic Science