Susceptibility of Atlantic halibut Hippoglossus hippoglossus to infectious pancreatic necrosis virus

Abstract

lnfectious pancreatic necrosis virus (IPNV), serotype NI, isolated from Atlantic halibut Hippoglossus hippoglossus, was used to bath-challenge (2 X l o 5 0 TCIDso ml-' for 1 h) Atlantic halibut fry of different sizes at 12 and 15°C in 3 trials. In all trials, the fry challenged at 15°C experienced significantly higher cumulative mortality compared to the unchallenged fry. The smallest fry (mean weight 0.1 g) also experienced significantly higher mortality compared to the controls when infected at 12"C, whilst the medium-sized fry (mean weight 1.0 g) did not display any mortality when infected at this temperature. The largest fry (mean weight 3.5 g) were only challenged at 15'C, resulting in 30 % cumulative mortality All fry infected at 15°C and the small fry infected at 12OC remained IPNV positive during the entire experimental period. In contrast, the medium-sized fry infected at 12 "C seemed to be able to clear the infection after 3 wk. Moribund and diseased fry showed clinical signs such as distended stomach and uncoordinated swimming. Patholog~cal findings included necrosis of the liver, kidney and intestine, but the pancreatic t~ssue was unaffected. lmmunohistochemistry revealed strong positive reactions to IPNV in the livers of challenged individuals.

Pathology associated with an aquareovirus in captive juvenile Atlantic halibut Hippoglossus hippoglossus and an experimental treatment strategy for a concurrent bacterial infection

“…A similar virus was detected in Atlantic salmon, but the histo-pathologic lesions were different and mainly associated with a cardiomyopathy (Grotmol et al 1997a). Infectious pancreatic necrosis virus (IPNV) is a common pathogen of Atlantic salmon (Wolf 1988), and this virus has also been associated with mortalities of Atlantic halibut in Norway (Mortensen et al 1990, Biering et al 1994, Biering & Bergh 1996 and juvenile Atlantic halibut in Scotland (Rodger & Frerichs 1997). The histopathological lesions associated with IPNV infections of Atlantic halibut larvae varied distinctly from those of Atlantic salmon fry.…”

“…The histopathological lesions associated with IPNV infections of Atlantic halibut larvae varied distinctly from those of Atlantic salmon fry. The most characteristic lesion was focal liver necrosis in halibut (Biering et al 1994) and no pancreatic lesions that typify IPNV infection of salmonids were seen (Ferguson 1989). Pancreatic acinar cell necrosis was described in halibut 'fry' infected with IPNV (Rodger & Frerichs 1997).…”

Diseases, prophylaxis and treatment of the Atlantic halibut Hippoglossus hippoglossus: a review

“…Thus, since the early 1990s, the amount of experience and knowledge of diseases of viral, bacterial or parasitical etiology of the Atlantic halibut has grown significantly. The evidence for the importance of diseases that affect the early life stages, such as infections by birnaviruses (Biering et al 1994), nodaviruses (Grotmol et al 1995(Grotmol et al , 1997, or various opportunistic bacteria (Bergh et al 1992b) has now been demonstrated by different challenge experiments (Table 1).The parasite fauna of wild Atlantic halibut have not been widely studied, for which reason our knowledge of potential harmful parasites in farmed fish is limited. Studies of parasites on wild halibut have mainly concentrated on describing metazoan parasites, particularly helminths (e.g.…”

“…Furthermore, isolates from salmonids have been found to establish an infection in halibut (Biering 1997b), so that transfer of virus between salmon and halibut cannot be excluded. There is reason to believe that IPNV is widespread in Norwegian halibut stocks (Biering 1997b), captive as well as wild.On the basis of challenge experiments with halibut fry (Biering et al 1994) and yolk-sac larvae (Biering & Bergh 1996) it has been concluded that the virus is the cause of the disease. Temperature influenced mortality, as fry challenged at 15°C had significantly higher mortality than fry challenged at 12°C (Biering et al 1994).…”

“…Fry with a mean size of 3.5 g suffered relatively low, but significant, mortality when infected at 15°C. Larger fish are probably not severely affected by IPNV infections, but they respond to challenge with a strong humoral immune response (Biering 1997a).The most characteristic clinical signs of disease in challenged fish are a distended stomach, uncoordinated swimming and trailing, and white faecal casts (Biering et al 1994). The symptoms were most prominent in small fry, but were also observed in larger individuals.…”