Ranavirus detection by PCR in cultured tadpoles (Rana catesbeiana Shaw, 1802) from South America

Diseases in farmed tadpoles (Rana catesbeiana) are a common event, being an economically important threat for Uruguayan and Brazilian farms. Based on clinical signs and epizootiology, pathogens belonging to the Family Iridoviridae were suspected as the possible etiology. Although these viruses have already been widely incriminated affecting aquatic organisms including frogs, their presence in Brazil and Uruguay was never mentioned so far. The objective of this work was to detect the presence of ranaviral agents in affected tadpoles using Polymerase Chain Reaction (PCR) technique as a primary approach to the study of the disease. Primers were designed based on highly conserved iridoviral sequences. Major Capsid Protein (MCP) and Immediate Early Protein (IE) genes were the selected targets. A positive PCR result was obtained for both genes when sick tadpoles from Brazil and Uruguay were analyzed. To confirm the amplification of an Iridoviridae, PCR products were purified and sequenced. Amplified products showed high degree of homology with several members of the Iridoviridae, mostly with those belonging to the genus Ranavirus. Obtained sequences were registered in the GenBank with accession nos. AY585203, AY585204 and AY744387. This report indicates that Ranavirus should be considered into the aquatic organism disease etiologies throughout this geographical region.