Detection and Characterization of Circulating Strains of ISKNV (Infectious Spleen and Kidney Necrosis Virus) in the State of São Paulo

• Grant number: 23/17337-0
• Support Opportunities: Scholarships in Brazil - Master
• Start date: June 01, 2024
• End date: June 15, 2025
• Field of knowledge: Agronomical Sciences - Fishery Resources and Fishery Engineering - Aquaculture
• Principal Investigator: Cláudia Maris Ferreira Mostério
• Grantee: Guilherme Nunes Ferrez
• Host Institution: Instituto de Pesca. Agência Paulista de Tecnologia dos Agronegócios (APTA). Secretaria de Agricultura e Abastecimento (São Paulo - Estado). São Paulo , SP, Brazil
• Associated scholarship(s): 24/13226-1 - Total genome sequencing of the Infectious Spleen and Kidney Necrosis Virus (ISKNV) obtained from tilapia (Oreochromis niloticus) farmed in the state of São Paulo/Brazil, BE.EP.MS

Abstract

The occurrence of emerging diseases in aquaculture is a matter of concern for both academia and the production sector. Among these diseases we can highlight the infectious spleen and kidney necrosis virus (ISKNV). It is not a zoonosis and is not a compulsorily notifiable disease, but it potentially causes major losses in farming and can infect marine and freshwater fish. This pathology is characterized by splenic necrosis and the presence of hypertrophic cells, which can be found mainly in the intestinal mucosa, renal and hepatic parenchyma. Its main clinical signs are: anorexia, lethargy, rapid opercular movement; change in body color, exophthalmos and abdominal distension; some forms of diagnosis include histopathological or molecular examinations. The aim of this work is to track the occurrence of ISKNV in four hydrographic regions in the state of São Paulo and to sequence the total genome of the circulating strains found. To date, fingerlings have been randomly sampled from the population of four tilapia farms in three different hydrographic regions in the state of São Paulo (n=567). The animals were insensitized using eugenol followed by medullary sectioning, after which necropsy was performed and the target organs (spleen and kidney) were removed. Organ pools were made from three animals and total DNA was extracted from the samples followed by conventional PCR amplifying a 777 bp fragment of the MCP (Major Capsid Protein) gene. Primers corresponding to ²-actin will be used for endogenous quality control of the DNA extractions, indicating the viability of the genetic material present in the samples. The positive ISKNV samples will be sequenced using the Sanger method to compare the fragment obtained with the reference sequences deposited in the Genbank database. Subsequently, all the remaining positive samples will be sequenced and similarity analyses will be carried out to assess polymorphic regions. Samples will also be sent for total sequencing of the viral genome, which will be carried out at Washington State University, Pullman, US. The results obtained will help advance knowledge of the occurrence of ISKNV in the state of São Paulo.