Parasite detection in the ornamental fish trade using environmental DNA

Area of Science:

• Aquatic ecology
• Parasitology
• Molecular biology

Background:

• Effective border control requires robust biosecurity to prevent exotic pest and disease introductions.
• Environmental DNA (eDNA) offers a potential method for detecting pathogens and parasites in the live ornamental fish trade.

Purpose of the Study:

• To assess the utility of eDNA for detecting Dactylogyrus spp. in ornamental fish imports.
• To evaluate a predictive framework for eDNA detection and its application in biosecurity.

Main Methods:

• Water samples from ornamental fish consignments (target cyprinids and non-target non-cyprinids) imported from Southeast Asia to Australia were analyzed.
• Quantitative PCR (qPCR) assays and Sanger sequencing were employed to detect eDNA of five Dactylogyrus species.
• A four-step predictive framework was utilized to interpret qPCR results.

Main Results:

• Dactylogyrus spp. eDNA was detected in both target and non-target fish consignments.
• Positive eDNA detections in non-target consignments indicated potential source water contamination.
• The findings highlight limitations of eDNA screening at border control due to contamination risks.

Conclusions:

• Screening for parasite eDNA in ornamental fish should occur during pre-export quarantine to prevent false positives at border control.
• The developed predictive framework can aid in minimizing false positive and false negative eDNA detections for aquatic organisms.
• eDNA techniques require careful consideration of contamination sources for effective biosecurity applications.