Cinnamaldehyde, a major component of Cinnamomum cassia Presl ethanol extract, has the potential to unlock the outbreak of WSSV.

The white spot syndrome virus (WSSV) is rapid onset and high mortality, which has caused a devastating blow to shrimp culture around the world. However, there are no effective measures to prevent and control the WSSV. Thus, it is urgent to find a safe and efficient measures to prevent the outbreak of WSSV. Here, the anti-WSSV activities of 20 Chinese herbal medicine ethanol extracts were evaluated in Litopenaeus vannamei. Among these, the ethanol extract of cinnamon (Cinnamomum cassia Presl) had the highest inhibition rate of 91% on WSSV genome replication. Surprisingly, cinnamaldehyde, the main component of cinnamon extract, has a simple structure and could reduce the copy level of viral genome in shrimp, with the strongest inhibitory effect of 93% at 72 h, and more than 40% of diseased shrimp survived. Further experiments showed that cinnamon extracts and cinnamaldehyde could prolong the cumulative survival time of WSSV-infected larvae, and continuous treatment with cinnamaldehyde could maintain the replication of WSSV genome at a low level. In addition, cinnamon extracts and cinnamaldehyde could significantly inhibit the horizontal transmission of virions at 72 h by 71% and 42%, respectively. Obviously, this further reduces the risk of WSSV outbreak. Similarly, cinnamaldehyde pre-incubated shrimp and virions could improve the tolerance of shrimp to WSSV and reduce the infectivity of virions. Taken together, cinnamon extract and cinnamaldehyde could inhibit WSSV genome replication and reduce mortality rate of WSSV-infected shrimp. The results provided a scientific basis for the use of cinnamon extract and cinnamaldehyde to unlock the outbreak of WSSV, and were worthy of further study and consideration. • Cinnamon ethanol extract and cinnamaldehyde exhibited anti-WSSV activity. • Cinnamaldehyde could reduce the infectivity of WSSV virions and has therapeutic effect on WSSV-infected shrimp. • The structure of cinnamaldehyde is simple and could block the horizontal transmission of WSSV. [ABSTRACT FROM AUTHOR]