Molecular Survey for Flaviviruses in Wild Cetaceans from Brazil

Flaviviruses (genus Orthoflavivirus, family Flaviviridae) are positive-sense RNA viruses able to infect a wide range of hosts and are associated with disease in humans, domestic animals and wildlife; thus, they are considered a major global health concern. The sylvatic cycle is potentially linked with human outbreaks; therefore, it is essential to monitor and understand flavivirus infections in wildlife. Little is known about flaviviruses in cetaceans. To fill part of this knowledge gap, we surveyed for the presence of flavivirus RNA in tissues (brain, spleen, lung, kidney, lymph node, liver, and adrenal gland) and serum samples of 151 cetaceans of 22 species that were found stranded, bycaught, or live captured in scientific expeditions in Brazil in two different biomes (marine and Amazon basin). Total RNA was extracted from 589 samples (523 tissues and 66 sera) using commercial kits; subsequently, a broad-range real-time PCR targeting the Orthoflavivirus genus was performed. All individuals were negative for flavivirus RNA (95% confidence interval, 0-1.96%). These results potentially indicate that the known flaviviruses, if present, have limited circulation in wild cetaceans, likely accidental hosts. Future studies are warranted to understand the epidemiology of flaviviruses within the genus Orthoflavivirus in cetaceans.