Pathogenesis of acute and chronic diseases caused by cyprinid herpesvirus‐3

Abstract

The pathogenesis of cyprinid herpesvirus-3 (CyHV-3) was studied using different lineages of carp/koi. After exposure to the virus, infected cells were first found in the skin by histopathology and by in situ hybridization. The epidermis of the skin was most severely damaged and often sloughed off in the fish sampled on days 5 through 8, and the fish that were highly sensitive to the virus died within 8 or 10 days after infection. Serum osmolality of the infected fish, particularly just before death, was significantly lower, suggesting that the osmotic shock consequent on the damage to the skin was the direct cause of the acute deaths. On the other hand, clinical and histopathological observations indicate that the carp of a less sensitive lineage most probably died of viral encephalitis around 3 weeks after infection. For these fish, the largest number of infected cells was found in the central nervous system (CNS) sampled on day 12. A substantial amount of viral genome was found in the CNS of carp surviving more than 1 year after the infection. Thus, the CNS is probably a major target for CyHV-3, and the virus can persistently infect the CNS, presumably establishing latency.

Cyprinid Herpesvirus 3

“…In the skin, the lesions can appear as soon as 2 dpi and worsen with time ( Fig. 6b; Miwa et al, 2014). The cells exhibiting degeneration and necrosis show various stages of nuclear degeneration (e.g., pale coloration, karyorrhexis, pyknosis), frequently associated with characteristic intranuclear inclusion bodies (Fig.…”

“…The number of goblet cells is reduced by 50% in infected fish, and furthermore, they appear mostly slim and slender, suggesting that mucus has been released and not replenished . At later stages, erosion of skin epidermis is frequently observed Miwa et al, 2014). A recent report revealed that the damages caused to the skin of the body and fins were the most pronounced lesions (Miwa et al, 2014).…”

“…At later stages, erosion of skin epidermis is frequently observed Miwa et al, 2014). A recent report revealed that the damages caused to the skin of the body and fins were the most pronounced lesions (Miwa et al, 2014).…”

“…It is accompanied by blood vessel congestion and degeneration of the tubular epithelium in many nephrons (Pikarsky et al, 2004). Intranuclear inclusion bodies are mainly found in hematopoietic cells (Miwa et al, 2014;Miyazaki et al, 2008). In the spleen, the main susceptible cells are the splenocytes.…”

“…This grading system classifies the lesions according to three criteria, i.e., (i) hyperplasia of epithelial cells, (ii) presence and extent of degeneration and necrosis, and (iii) presence and abundance of intranuclear inclusion bodies. As the number of presumed infected cells does not always correlate with the severity of the lesions, the combination of these criteria is necessary to obtain a reliable histopathological grading system (Boutier et al, 2015;Miwa et al, 2014).…”