Experimental infection of brown trout (Salmo trutta), zebrafi sh (Danio rerio), and swan mussel (Anodonta cygnea) with infectious pancreatic necrosis virus (IPVN)

Abstract

Aim. Although more than 80 fi sh species and some invertebrate aquatic organisms are known to be susceptible to in- fectious pancreatic necrosis virus (IPNV) and aquatic birnaviruses, relatively little is known about its ability to infect brown trout (Salmo trutta), zebrafi sh (Danio rerio), and a mollusk, swan mussel (Anodonta cygnea). Therefore, the aim was to study in more detail the effects of IPNV on the said organisms. The information on the virulence of birnaviruses for aquatic organisms is important for better understanding of their transmission and for the identifi cation of suscep- tible or transient (symptomless) hosts. Methods. Cell culture method, using RTG-2 cells, was used for in vitro culti- vation of IPNV as well as virus titer assessment. The supernatants from infected RTG-2 cells were used for artifi cial inoculation to obtain experimental infection of the fi sh and mollusk. Fish and mollusk behaviour and mortality were monitored daily. The infectious titer of the virus in experimental animals was assessed by cell culture assay and reverse transcription PCR (RT-PCR). Results. This paper presents the results of IPNV experimental infection of brown trout (Salmo trutta), zebrafi sh (Danio rerio), and an aquatic invertebrate mollusk - swan mussel (Anodonta cygnea). The mortality of brown trout and zebrafi sh was 76.6 and 40 % respectively. Swan mussel was apparently resistant to the virus, but it apparently accumulated and maintained substantial levels (up to 10 -10 ID 50 /ml -1 ) of the virus for the dura- tion of the experiment (35 days). The highest infectious titer was found in brown trout (10 6 ID 50 /ml -1 ). In zebrafi sh and swan mussels, it was up to 10 4.5 ID 50 /ml -1 and 10 2 ID 50 /ml -1 respectively. Conclusions. At the end of the experiments the IPNV titers were higher than the initial viral doses in brown trout and zebrafi sh, indicating virus reproduction. In diseasesd fi sh the blackening, whirling and anorexia were observed. It was shown that swan mussel accumulates and maintains virus for at least 35 days under experimental conditions and that it may act as symptomless vector of IPNV