Background and aims
Infectious agents have long been recognised as important factors influencing genetic variation associated with resistance and susceptibility to diseases. Cetacean morbillivirus (CeMV) is a highly contagious and deadly virus that is increasing in both geographic distribution and incidences. The largest mortality event in the Southern Hemisphere occurred in South Australia in 2013. It lasted approximately seven months and killed at least 41 southern Australian bottlenose dolphins (Tursiops sp.), predominately from the population in Gulf St Vincent. Here we aimed to identify candidate genes that may confer resistance or susceptibility to CeMV.
We conducted a genome-wide association study by generating double-digest restriction site-associated DNA (ddRAD) data for case (non-survivors) and control (putative survivors) bottlenose dolphins of this population. This included identifying single nucleotide polymorphisms (SNPs) with divergent allele frequencies between case and control, and then annotating the associated candidate genes.
The dataset consisted of 262,892,901 filtered-sequence reads, from which 35,493 high quality SNPs were obtained. Association analyses found significant differentiation in allele frequencies amongst case and control dolphins at five SNPs. Annotation of these SNPs and associated flanking sequences resulted in two candidate genes (MAPK8, Mitogen-Activated Protein Kinase 8 and INADL, InaD-like protein annotation), which may be associated with stress response and CeMV immune response.
We identified two candidate genes that have strong evidence for association with resistance and susceptibility to CeMV. Biomarkers for these genes can now be developed to assess genetic variation in other cetacean populations affected by CeMV.