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Ictalurid herpesvirus 1 (IcHV1) is the most significant viral agent in U.S. catfish aquaculture. Little is known regarding the genetic stability and antigenic variability of IcHV1. Herein, the genetic and antigenic diversity of IcHV1 field isolates was assessed by restriction fragment length polymorphism (RFLP) analysis and serum neutralization assays. RFLP analysis identified two distinct genotypes (IcHV1A and IcHV1B), both discrete from blue catfish alloherpesvirus (BCAHV). Neutralization assays with anti‐IcHV1 monoclonal antibody Mab‐95 indicate shared antigenic determinants for IcHV1A and IcHV1B that are absent from BCAHV, which Mab‐95 did not neutralize. Virulence assessments with representative isolates demonstrate significant differences between isolates within RFLP groups and pooled RFLP group data suggest IcHV1B (pooled survival [mean ± SE]: 58.3% ± 2.6) may be more virulent than IcHV1A (survival: 68.6% ± 2.4). Rechallenges with representative IcHV1A and IcHV1B isolates indicate a cross‐protective effect, with fish surviving initial exposure to IcHV1A or IcHV1B showing robust protection when subsequently re‐exposed to IcHV1A or IcHV1B. This work demonstrated significant differences in virulence between case isolates, identifying two discrete IcHV1 lineages, distinct from BCAHV, with similar virulence in channel and channel × blue catfish hybrids and a cross‐protective effect in catfish surviving exposure to either lineage. [ABSTRACT FROM AUTHOR]

The channel catfish virus (CCV) can cause lethal hemorrhagic infection in juvenile channel catfish, thereby resulting in a huge economic loss to the fish industry. The genome of the CCV has been fully sequenced, and its prevalence is well documented. However, less is known about the molecular mechanisms and pathogenesis of the CCV. Herein, the channel catfish ovary cells (CCO) were infected with CCV and their transcriptomic sketches were analyzed using an RNA sequencing technique. In total, 72,686,438 clean reads were obtained from 73,231,128 sequence reads, which were further grouped into 747,168 contigs. These contigs were assembled into 49,119 unigenes, of which 20,912 and 18,333 unigenes were found in Nr and SwissProt databases and matched 15,911 and 14,625 distinctive proteins, respectively. From these, 3641 differentially expressed genes (DEGs), comprising 260 up-regulated and 3381 down-regulated genes, were found compared with the control (non-infected) cells. For verification, 16 DEGs were analyzed using qRT-PCR. The analysis of the DEGs and their related cellular signaling pathways revealed a substantial number of DEGs that were involved in the apoptosis pathway induced by CCV infection. The apoptosis pathways were further elucidated using standard apoptosis assays. The results showed that CCV could induce extrinsic apoptosis pathway (instead of a mitochondrial intrinsic apoptosis pathway) in CCO cells. This study helps our understanding of the pathogenesis of CCV and contributes to the prevention of CCV infection in channel catfish. [ABSTRACT FROM AUTHOR]

The article discusses the detection of channel catfish virus (CCV) associated with mortality of cultured channel catfish in Mexico. The good quality of channel catfish' flesh and flavor has resulted the increase catfish consumption and growing fish farming industry. However, the detection of Herpesvirus ictaluri CCV was first isolated in the U.S. in 1960 that led the high mortality rates with significant economic losses of catfish industry. The histophathological examination has revealed multifocal necrotic areas and hemorrhage in the internal organs with viral infection.The CCV's infection is the most severe of the fish herpesvirus which proliferation was caused by stressful environmental conditions such as high temperature, low water quality, low oxygen level and poor feeding.

A quantitative bioassay employing immersion exposure was developed for the infection of channel catfish Ictalurus punctatus with the protozoan parasite Ichthyophthirius multifiliis, commonly referred to as ich. This bioassay as well as waterborne challenge of channel catfish with channel catfish virus (CCV) was used to investigate the effect of confinement stress on the sensitivity of the fish to exposure of these pathogens. Infestation by ich was shown to be proportional to the density of infective theronts in the exposure tank and low-water crowding stress was shown to increase susceptibility of catfish to infection. Mortality from CCV was related to the virus exposure dose; however, low-water crowding stress did not affect mortality. Increased susceptibility, due to crowding stress of naı¨ve channel catfish to I. multifiliis but not to CCV, suggests a difference in the defence mechanisms. Stress-induced increased susceptibility to I. multifiliis may be due to a suppression of an innate protection mechanism. The lack of effect of stress on CCV mortality may be due to protection afforded by an inducible system which was not affected by the stressor, or the lethal effects of the virus were too fast for the stress to change susceptibility in fish exposed to CCV for the first time. [Copyright &y& Elsevier]