Detection of Cyprinid herpesvirus 2 in association with an Aeromonas sobria infection of Carassius carassius (L.), in Italy

Abstract

Sixteen specimens of female crucian carp, Carassius carassius (L.), during the breeding season, were investigated for post-mortem and full diagnostic examination during a mortality outbreak in a tributary stream of the Arno River in Tuscany in 2011. Necropsy highlighted the presence of a swollen anus and widespread haemorrhages in the body, fins, gills and eyes. Haemorrhages in internal organs and spleen granulomas were also observed. Bacteria isolated from the brain, kidney and spleen of affected fish were identified as A. sobria. Microscopic lesions observed in gills were characterized by necrosis of the secondary lamellae, congestion and multifocal lamellar fusion. The kidney showed necrosis, oedema, fibrin exudation and areas of haemorrhages, while in the spleen the main lesions were by multifocal necrosis of the lymphoid tissue. In the gills, transmission electron microscopy revealed herpesvirus-like particles, subsequently identified as Cyprinid herpesvirus-2 (CyHV-2) with a nested PCR protocol. Although it was not possible to attribute a pathogenic role to CyHV-2 in this mortality event, the identification of this herpesvirus in crucian carp increases the concern about its potential role in this species.

CyHV‐2 transmission in traded goldfish stocks in Germany—A case study

“…The PCR showed an extremely low Ct (Ct = 6), which confirmed a high virus load and supported the assumption that the fish died from HVHN (Table ). The A. sobria and S. putrefaciens infections were most likely secondary infections, how it was earlier shown in HVHN outbreaks in goldfish in India and Italy, where multidrug resistant Aeromonas hydrophila and A. sobria were isolated as well (Fichi et al., ; Sahoo et al., ).…”

“…The disease is a potential threat for food security, especially in China where more than 2.5 M metric tons of crucian carp and Prussian carp are produced (FAO, ). The virus seems to be widely distributed in the world, and it was detected in Japan (Jung & Miyazaki, ), USA (Goodwin, Sadler, Merry, & Marecaux, ), China (Luo et al., ), Australia (Stephens, Raidal, & Jones, ) and recently in several European countries including the UK (Jeffery et al., ), France (Boitard et al., ), Switzerland (Giovannini et al., ) and Italy (Fichi et al., ). More critical for attempts to limit the spreading of the disease is the observation that surviving individuals become chronic carriers of a most probably latent infection without displaying external clinical signs (Wang, Xu, & Lu, ).…”

New detection of Cyprinid herpesvirus 2 in mass mortality event of Carassius carassius (L.), in Italy

“…), and again in 2011, CyHV‐2 was detected in association with an Aeromonas sobria infection in a mass mortality of crucian carp, Carassius carassius L., in Italy – although it was not possible to confirm the role of CyHV‐2 as causative agent (Fichi et al . ).…”

Detection of cyprinid herpesvirus 2 in peripheral blood cells of silver crucian carp, Carassius auratus gibelio (Bloch), suggests its potential in viral diagnosis

“…; Fichi et al . ; Ito & Maeno ). Since 1995, CyHV‐2 has been generally recognized as the causative pathogen of herpesviral hematopoietic necrosis (HVHN) disease of goldfish, Carassius auratus (L.) (Jung & Miyazaki ; Goodwin, Merry & Sadler ).…”