Abstract

Background:
Koi herpesvirus (KHV; Cyprinid herpesvirus-3) is one of the most devastating viral pathogens affecting the aquaculture of common carp (Cyprinus carpio), causing substantial economic losses worldwide. Although horizontal transmission has been well documented, broodstock reproductive materials’ contribution to parentassociated transmission remains incompletely understood. Integrated hatchery management strategies combining biosecurity, egg disinfection, spawning management, and molecular surveillance have been insufficiently evaluated under field conditions.

Aim:
This study aimed to evaluate the application of integrated hatchery biosecurity, optimized Sanosil® egg disinfection, selective spawning management, and nested polymerase chain reaction (PCR) monitoring during common carp seed production under commercial hatchery conditions.

Methods:
A field-based observational study was conducted in a commercial hatchery in Bogor, Indonesia, from October to December 2023. We screened for KHV in broodstock, reproductive materials, larvae, environmental samples, and hatchery-associated organisms using nested PCR targeting the thymidine kinase (TK) gene. Egg disinfection was evaluated using Sanosil® at concentrations of 0, 5, 10, 20, and 40 ppm. Spawning performance, hatchability, and molecular monitoring after hatching were assessed throughout a single production cycle.

Results:
One pooled sperm sample from an asymptomatic male broodstock tested positive for KHV deoxyribonucleic acid (DNA), whereas eggs, female broodstock, environmental samples, and most reproductive materials were negative for KHV DNA. At 40 ppm, Sanosil® produced the highest observed hatchability while minimizing visible microbial contamination. Artificial stripping with proper egg handling achieved up to 90% hatchability and generated PCR-negative larvae, whereas 2 stripping funnels with poor hatchability yielded PCR-positive larvae. Fry remained PCR-negative before vaccination, before booster vaccination, and after booster vaccination, with no clinical signs of KHV disease.

Conclusion:
Integrated hatchery management combining molecular screening, strict biosecurity, optimized egg disinfection, selective spawning, and routine PCR monitoring was associated with the production of PCR-negative common carp fry under field conditions. However, the limited sample size, single production cycle, and absence of confirmatory molecular analyses indicate that these findings should be regarded as preliminary and require validation through larger controlled studies.

Key words: Biosecurity; Common carp; Hatchery management; Koi herpesvirus; Nested PCR.