Epidemiological assessment and Motif Fingerprint-based Genomic Characterization of Tilapia Lake Virus (TiLV) infection and co-infections in Colombia

Tilapia Lake Virus (TiLV) infection is one of the most challenging diseases of tilapia (Oreochromis sp.) production systems globally. Limited studies on the epidemiology of TiLV have been evaluated. In this study, we assessed the TiLV infection status in Colombia Departments by RT-PCR amplification of a pool of tissues (liver, spleen, eye, and brain) collected from units of five to ten tilapias per lot/pond. From June 2016 to March 2018, epidemiological assessments of TiLV infection reported positive cases of TiLV from 109 out of 463 submitted samples (23%) representing 25 TiLV positive farms, 28 districts, and 13 departments. The spatial distribution suggests a widespread TiLV reporting in Colombia including 21 TiLV positive municipalities out of 29 sampled. Segment 6 of Colombian TiLV had 98 to 100% homology to Ecuador, Israel and Peru. Almost all cases of TiLV (103/109: 94.4%) correlated to mortality in all life stages of tilapia. However, no clinical signs but positive for TiLV were found in six alevin cases (6.1%) from three Epidemiological Units (EU). Among the 109 cases, 44 cases (49.5%) had concomitant TiLV infection with other bacterial and/or parasitic diseases, highlighting the complex interactions between the virus and other pathogens. There was no correlation between the rainy/dry season or environmental temperature with the presentation of TiLV infection. This study is the first comprehensive epidemiological study of TiLV status in South America.