TDK conference 2014

Several important human and animal pathogen viruses belong to the family of Flaviviridae, genus Flavivirus. Three of them have been detected in Hungary: the West Nile virus (WNV), the Tick-borne encephalitis virus (TBEV) and the Usutu virus (USUV). Since flaviviruses have common surface antigens, cross-reactions can be observed during certain serological diagnostic tests, making the exact identification of these viruses difficult.

In this study serum samples were collected in different regions of Hungary between 2011 and 2013. We have conducted serological comparative survey using enzyme-linked immunosorbent assay (ELISA), indirect immunofluorescence (IF), haemagglutination inhibition (HI) and virus neutralisation (VN) to find the most appropriate test for WNV sero-diagnosis. By competitive IgG WNV ELISA from 462 samples, 120 proved to be positive against WNV: 83 birds, 5 horses and 32 dogs. For further comparative investigations we have chosen 40 samples which were found positive WNV antibodies in ELISA (6 bird, 12 horse and 22 dog samples), and we have tested their reactivity to all three virus antigens with HI and IF assays, and to WNV and Usutu virus antigens with VN. Using IF assay, 10 samples were found positive, whereas 18 samples were proven positive using HI assay and 19 using VN.

The results of this comparative study indicate that although ELISA, IF and HI assays are faster and simpler methods than the VN, their specificity is rather low, therefore positive results must be validated by VN test.

We have found antibodies against flaviviruses in one third of the tested dog samples. Some of the samples showed at least fourfold higher titres against WNV than against TBEV and USUV; which indicate that these dogs were infected with WNV without any clinical signs. Therefore dogs may be used as indicators to survey the presence of WNV and to assess the risk of human exposure.