In Iran, the aquaculture industry is critically impacted by viral outbreaks, particularly the Koi herpesvirus (KHV), which has led to significant mortality in common carp populations. Recent studies have identified at least three genotypes of Cyprinid herpesvirus 3 (CyHV-3), with one new genotype being recorded, highlighting a worrying diversification within the virus in the region.
The backdrop of this research begins with the significant role that fisheries and aquaculture play in global food security, with the common carp accounting for a considerable portion of the world's aquaculture production. In Iran alone, carp production forms about 25-30% of the warm-water fish yield, emphasizing the economic importance of these species. However, despite this, lax sanitation and disease control measures challenge the industry's growth.
Between January 2020 and February 2023, researchers collected samples from 342 carp farms across three provinces: Khuzestan, Mazandaran, and Gilan. The results revealed a striking 85 farms were infected with KHV, showcasing a significant public health and economic concern as the mortality rates spanned from 40% to 100%. The study primarily focused on the koi carp, a popular ornamental variant, and demonstrated how viral infections can devastate fish populations.
Researchers categorized the virus types*using genetic sequencing methods, identifying two known Asian genotypes (A1 and A2) and auctioning for new variants. The testing included duplex PCR analysis that uncovered additional strains marked as J (I++ II +), an intermediate variant (I++ II -), and a novel genotype (I++ II -), showcasing the genetic complexity of CyHV-3 in West Asia.
The method for sample collection emphasized quality, involving tissue samples from kidneys and gills to assess the presence of KHV. The standard water quality parameters were maintained at pH levels between 7.5 and 8, suggesting that containment measures need to be reinforced to prevent the spread of the virus further. Areas with increasing infection rates signified trends that seemed higher during specific seasons, notably spring and fall when temperatures ranged between 22 to 25 °C.
Phylogenetic analyses further revealed the dynamic nature of CyHV-3, showing that Iranian KHV isolates formed distinct clusters indicative of significant evolutionary divergence. This study is pivotal as it is the first to document the additional intermediate strain of CyHV-3 in the region, stressing the continual need for monitoring and understanding emerging viral strains.
Significantly, the health risks presented by KHV highlight not just a biological threat but also affect economic stability, urging stakeholders to deploy robust biosecurity protocols. Iranian healthcare authorities must stay vigilant to prevent future outbreaks facilitated by live fish trade amid increased animal movements in Asia.
This research underscores the critical necessity for more sensitive diagnostic techniques to promptly identify KHV infections in fish farms. As the ornamental fish trade continues to expand, so does the urgent requirement to understand the geographical distribution and biological behavior of such pathogens to mitigate their impact effectively. To conclude, continuous surveillance and strategic interventions are imperative to safeguard Iran's aquaculture sector and help maintain its essential contributions to food security.
