White spot syndrome virus (WSSV) is a significant pathogen impacting crustaceans globally, posing a threat to aquaculture industries. In the United States, WSSV has been documented in Louisiana crayfish farms since 2007. In 2022, Procambarus clarkii housed in laboratory raceways at the E.W. Shell Fisheries Center in Auburn, Alabama, exhibited lethargy and mortality patterns consistent with WSSV. qPCR assays later confirmed the presence of WSSV, indicating the first documented case of this disease in Alabama.
From 2022 to 2023, crayfish surveys conducted across two watersheds revealed that WSSV was both widespread and seasonal, affecting P. clarkii and other crayfish species. The highest WSSV detections occurred when water temperatures ranged between 18 and 30 ℃. Given that pathogens often become more virulent under stress, we hypothesized that laboratory stressors could activate WSSV in otherwise healthy carriers. To test this, crayfish suspected of carrying WSSV but testing negative were subjected to PIT-tagging, a stressful procedure, while a control group was left untagged. Both groups experienced 100% survival over 12 weeks, with only two borderline positive WSSV detections in the control group at the end of the study.
This study demonstrates that WSSV is now endemic in parts of Alabama, affecting multiple crayfish species during warmer months. However, our results suggest neither warm temperatures nor laboratory-induced stress reliably trigger virulence or detectable WSSV levels at the study site. Further research is necessary to identify the specific conditions under which WSSV becomes pathogenic, leading to high mortality rates in crayfish populations.