Relative risk assessment: Influence of cannibalism on white spot syndrome virus transmission in whiteleg shrimp (Penaeus vannamei) under different conditions

White spot syndrome virus (WSSV) has emerged as a significant viral pathogen in shrimp aquaculture since it was first identified in 1992. Similar to most crustacean pathogens, cannibalism is the most crucial mechanism for the horizontal transmission of WSSV. While several studies have reported the impact of cannibalism on WSSV transmission, a comprehensive investigation that reflects varying conditions has not yet been conducted. Herein, we investigated the impact of cannibalism on WSSV transmission in whiteleg shrimp (Penaeus vannamei) from the perspective of a relative risk assessment. In Experiment 1, cannibalistic behaviors of healthy whiteleg shrimp were monitored at three different stocking densities. The number of cannibalism incidents increased threefold at higher densities, whereas the odds ratios were not significantly different. In Experiment 2, WSSV infection and mortality were observed in shrimp administered high-severity (G2-G3) tissues (1 to 20% biomass inoculum), whereas shrimp administered low-severity (G0-G1) tissues were not infected with WSSV, regardless of the amount of inoculum. However, shrimp administered high-severity (G2-G3) tissue showed a 3.47-fold increase in hazard as biomass increased from 1 to 20%. Experiment 3 compared feeding challenge tests at 30 degrees C and 25 degrees C. When shrimp were administered 10% biomass of high-severity (G2-G3) tissue, the hazard ratio increased 3.88-fold at 25 degrees C compared with 30 degrees C. This study found a direct correlation between WSSV severity grade, prevalence, water temperature, and transmission through the cannibalism route. These findings provide insights into WSSV transmission via cannibalism and clarify that proper carcass removal measures can directly aid in inhibiting white spot disease progression.