Abstract :
Recently, a new member of the Bluetongue virus (BTV) serogroup named Toggenburg
Orbivirus (TOV) in goats from Switzerland has been described. The epidemiology and host
range of TOV are currently unknown. Since TOV causes cross-reactions in laboratory tests
used for BTV diagnosis, this study was carried out in order to determine the spatial and temporal
spread of TOV. Therefore, serum samples from a national survey in goats, collected
during winter and spring 2008 in Switzerland, were serologically examined. Additionally,
cattle and sheep from holdings with seropositive goats were tested for the presence of viral
RNA and antibodies against BTV and TOV. All goat samples analysed within routine diagnostics
at the Institute of Virology and Immunoprophylaxis from 2008 to 2009 were also
tested for the presence of TOV. Finally, goat sera collected 1998 in the Canton of Ticino (TI)
were analysed.
Although the TOV index cases had been identified in flocks north of the Alps, no additional
TOV-positive herds were found by serological testing in this region. In contrast, south of the
Alps, i.e. in the Canton of Ticino (TI), an apparent seroprevalence of 49% in goats was found
at animal and 60% at herd level. In the eastern and western part of the Swiss Alps 15.2% and
10% of tested goats were serologically positive, respectively. A within-herd prevalence of
up to 100% was found in some of the positive flocks. The positive flocks in TI were mainly
found in three of the five districts, but seropositive animals were identified in each district.
Certain selected seropositive flocks were investigated virologically. By RT-qPCR andgenome
sequencing, the presence of TOV could be confirmed in all investigated seropositive flocks.
By testing the goats within routine diagnostics, TOV genome was detected in one goat
showing BT-like clinical symptoms from the central Alps and in three healthy animals
imported from Germany.
Although 3.8% of the sheep from flocks with TOV-positive goats or in contact with
these animals showed a positive antibody reaction, TOV-specific RNA was not found
in any of the tested sheep and also not in cattle from flocks with TOV-positive goats.
