Identification of Tilapia Lake Virus in Egypt in Nile tilapia affected by 'summer mortality' syndrome

Abstract

Egyptian fish farms have faced unexplained mortality of tilapia during the summer months in recent years. Epidemiological surveys indicated that 37% of fish farms were affected in 2015 with an average mortality rate of 9.2% and a potential economic impact of around US$ 100 million. Despite a number of researchers and organizations investigating potential causes results so far have been inconclusive. Meanwhile recent reports emerged of the presence of a new orthomyxovirus, Tilapia Lake Virus (TiLV) in Israel, which shares a border and migrating avifauna with Egypt. Tissue samples from seven farms affected by ‘summer mortality’ were tested at the University of Stirling for TiLV. Samples from three of seven farms tested positive using PCR; the first time that TiLV has been identified in Egypt. Sequence analysis yielded a TiLV sequence with 93% homology to the published TiLV sequence described from Israel. More research is required to determine if TiLV is linked to ‘summer mortality’.