Modelo de infecção experimental e efeito da temperatura na patogenicidade do ISKNV em juvenis de tilápia do Nilo (Oreochromis niloticus)

The rapid growth of world aquaculture production has significantly contributed to nutritional development and food security around the world. However, many of the features of aquaculture that present opportunities for increased production also represent risk factors for the emergence and spread of diseases. The Infectious Spleen and Kidney Necrosis Virus - ISKNV is a virus with global distribution that causes serious economic losses to the aquaculture industry. ISKNV has been associated with outbreaks of high mortality in several marine and freshwater fish species. Since 2015, Nile tilapia (Oreochromis niloticus) farms, in different parts of the world were affected by outbreaks with high mortality rates that were later confirmed as caused by ISKNV. In Brazil, the first report of infection by the virus occurred in 2020, evidencing the high risk of spreading the disease as a threat to the development of the Brazilian aquaculture. Recent studies in several species of fish and peneid shrimp proved effect of water temperature in the pathogenesis of other virus species. In spite the importance of tilapia and the disease, the effect of water temperature on ISKNV virulence has never been scientifically addressed. Thus, an experimental infection model, based on the inoculation of viral homogenates, was developed to reproduce the disease under experimental conditions. Afterwards, fish groups maintained under different water temperatures (26, 28, 30, 32, and 34°C) were challenged to address its effect on the virus virulence. The results showed a significant reduction in the mortality in groups kept at higher temperatures. In conclusion, disease was successfully reproduced under lab conditions and high temperature reduced the ISKNV virulence in Nile tilapia juveniles, being the hyperthermia a possible way to control the disease at field.