Genetic diversity in the yellow head nidovirus complex

Area of Science:

• Aquaculture Virology
• Shrimp Pathology
• Molecular Phylogenetics

Background:

• Yellow head virus (YHV) causes significant disease outbreaks in Penaeus monodon shrimp.
• Previous studies have indicated genetic diversity within YHV, but comprehensive regional analysis was lacking.

Purpose of the Study:

• To genetically characterize yellow head-related viruses in Penaeus monodon from the Indo-Pacific.
• To investigate the relationship between viral genotypes and disease presentation or host health status.

Main Methods:

• Phylogenetic analysis of amplified ORF1b gene segments from shrimp samples.
• Sequence comparison of structural protein genes (ORF2, ORF3), intergenic regions (IGRs), and 3'-UTRs.
• Identification and analysis of conserved motifs and structural features within viral genomes.

Main Results:

• At least six distinct genetic lineages (genotypes) of yellow head-related viruses were identified.
• Genotype 1 (YHV) was exclusively found in diseased shrimp, while other genotypes, including genotype 2 (GAV), were detected in both diseased and healthy shrimp across various locations.
• Conserved motifs in transcription regulating sequences (TRSs) and compensatory substitutions in 3'-UTR hairpin-loop structures were identified across genotypes.

Conclusions:

• The genetic diversity of yellow head-related viruses has implications for disease diagnosis and management in Penaeus monodon aquaculture.
• The findings suggest that some YHV genotypes may have reduced pathogenicity or exist as asymptomatic infections in shrimp.
• Structural features in the 3'-UTR likely play crucial roles in viral replication and are conserved despite genetic divergence.