Propagation of koi herpesvirus using embryonated chicken eggs: a potential substitute method for fish vaccine production?

Koi herpesvirus disease (KHVD) is caused by a large DNA virus that commonly infects carp, Cyprinus carpio (koi and common carp). KHVD has spread rapidly across the globe and caused high mortality in all ages of common carp and koi. Until now, no effective treatment has been applied to prevent KHV infection impacting the mass production of koi and common carp . An environmentally friendly alternative strategy for controlling fish disease is vaccination. One of the challenges facing conventional viral vaccine production is the requirement for koi or common carp cell cultures, which must be frequently maintained with expensive materials required for virus propagation. This study aims to obtain KHV that has been propagated in embryonated chicken eggs (ECE) to formulate an affordable KHV vaccine for the aquaculture industry. This research consisted of three stages; the first stage was virus inoculation into various parts of eggs (allantoic fluid, chorioallantoic membrane, amniotic fluid, and egg yolk). The second stage was observing viral growth and collecting ECE fluid and membranes. The third stage involved quantitatively determining the viral genomic copy numbers using the quantitative Polymerase Chain Reaction (qPCR) assay. KHV propagation in various parts of ECE resulted in varying viral genomic copy numbers with a high DNA copy number reported in allantoic fluid on the third day after inoculation. Further work is required to monitor virus titer in later passages and optimize methodology for using ECE as the potential alternative to cultured cells as the medium for virus propagation. In the future the system could be developed to produce promising vaccine candidates with more affordable vaccine prices for the Indonesian fish farming industry.