Detection of infectious white spot syndrome virus in red claw crayfish (Cherax quadricarinatus) and red swamp crayfish (Procambarus clarkii) imported into Korea

White spot syndrome virus (WSSV) is one of the most virulent viruses in crustaceans, causing severe economic losses to aquaculture industry. In this study, we tested for the presence of WSSV in the commodity crayfish imported to Korea and also examined the potential infectivity of WSSV in the commodity WSSV-positive crayfish. For the sampling, two species of crayfish, Cherax quadricarinatus (320 red claw crayfish in eight batches) imported from Indonesia and Procambarus clarkii (40 red swamp crayfish in two batches) imported from China, were obtained from fishery markets in Korea. Five representative samples per batch (N = 50) were screened for WSSV using PCR assay, and the virus was detected in five C. quadricarinatus samples and one P. clarkii sample. Among the WSSV-positive samples, the highest virus titer (the copies ranged between 4.93 × 10⁵ and 8.36 × 10⁶ copies/μL) was detected in the P. clarkii sample (20−012) by qPCR, and a comparatively low titer was observed in the C. quadricarinatus sample (20–008) (the copies ranged between 5.94 × 10¹ and 3.86 × 10⁵ copies/μL). Following the virus infectivity test, WSSV infection was confirmed after feeding WSSV-positive crayfish tissue (20–008, 3.46 × 10⁷ WSSV copies/μL) to Penaeus vannamei (Pacific white shrimp, N = 42) at 5% shrimp biomass. This is the first report of confirmed infectivity of WSSV from the commodity crayfish imported into Korea, suggesting that virus-infected frozen crayfish may present a potential source of viral disease in Korean shrimp aquaculture. Therefore, accurate and strict monitoring of crustacean viruses is required for imported crayfish from foreign countries into Korea.