DAO prepress abstract  -  DOI: https://doi.org/10.3354/dao03161

Viral haemorrhagic septicaemia virus (VHSV Id) infections are detected more consistently using syndromic vs. active surveillance

Pia Vennerström*, Elina Välimäki, Tapani Lyytikäinen, Maria Hautaniemi, Gabriele Vidgren, Perttu Koski, Anna-Maija Virtala

*Email: pia.vennerstrom@evira.fi

ABSTRACT: The eradication of viral haemorrhagic septicaemia (VHS) from Finnish brackish water rainbow trout (Oncorhynchus mykiss) farms located in the restriction zone in the Province of Åland, Baltic Sea, failed several times in the 2000s. The official surveillance programme was often unable to find VHSV-positive populations and led to the misbelief in the fish farming industry that eradication of the virus could be achieved. The ability of three other surveillance programmes to detect infected fish populations was compared with the official programme. One programme involved syndromic surveillance based on the observation of clinical disease signs by fish farmers, while two programmes comprised active surveillance similar to the official programme, but included increased sampling frequencies and two additional tests. The syndromic surveillance concentrated on sending in samples for analysis when any sign of a possible infectious disease at water temperatures below 15C was noticed. This programme clearly outperformed active surveillance. A real-time reverse transcriptase-polymerase chain reaction method proved to be at least as sensitive as virus isolation in cell culture in detecting acute VHSV infections. An ELISA method was used to test fish serum for antibodies against VHSV. The ELISA method may be a useful tool in VHSV eradication for screening populations during the follow-up period, before declaring an area free of infection.