The remarkable growth of shrimp farming production in the last four decades required, among others, the intensification of the culture systems. However, this also motivated the emergence of serious infectious diseases such as white spot syndrome virus (WSSV). Since its appearance in 1992, WSSV provokes yearly high economic losses worldwide. To date, there are no sound solutions for this problem in shrimp pond culture.
It is widely accepted that WSSV infects shrimp mainly by oral route. This work aimed to develop a feed additive capable of controlling shrimp mortality due to WSSV infection, by inactivating the virus in the gut of shrimp before it can infect the animal.
Five products proprietary to Proviron (Belgium) were tested. First, the antiviral activity of these experimental products towards WSSV was tested in vitro, at a concentration of 0.5% (Figure 1). The 2 products inducing the highest antiviral activity were selected. Second, an in vitro dose-response was done for the selected products (Figure 2). The product inducing the strongest WSSV inactivation and respective effective concentration range, were selected. In a third trial, diets were supplemented with the selected product at concentrations of 0.2% and 0.4%. Groups of P. vannamei shrimp were fed with the experimental diets for 1 week. Based on the results a concentration of 0.4% was chosen for further animal trials.
The in vitro results clearly demonstrated that Product 1 and 3 have a strong antiviral activity towards WSSV in vitro, being Product 1 (ProvifeedTMNoSpot) the strongest. The in vivo validation trial demonstrated that this product also presents an antiviral activity when fed to shrimp, shown by the reduction of WSSV-provoked mortality in the treatment groups with 25% after feeding ProvifeedTMNoSpot for 4 weeks. On top of the reduced mortality it was shown that the incorporation of the feed ingredient in shrimp feed resulted in a significant increase in daily weight gain and a significant reduction in feed conversion ratio.