In order to obtain an indication of the distribution of
susceptible fish and identify any pattern in the geographic
occurrence of SVC, coordinates were obtained from the
LFMD for all SVC case and susceptible sites in England and
Wales. The percentage of the total number sites recorded
as holding SVC susceptible species (as listed by the OIE)
lying within each river catchment (which can be deemed
epidemiologically distinct in terms of connection via water
courses) in England and Wales was mapped. A second map
was also produced showing the average number of days in
a year when lake water temperatures would be permissive
for SVC disease expression (i.e. 10–17 ◦C). This was estimated
using the methods and data described by Thrush and
Peeler (2012) and plotted according to the British National
Grid coordinate system (origin x, y = 200 k, 200 k) with the
English and Welsh river catchment layer overlaid. Each
known SVC case was plotted on this map, presented based
on the year of occurrence in order to allow temporal trends
and associations with temperature to be viewed. All maps
were produced using Arc-Map version 9.3 (ESRI Corp. Redlands,
CA, USA). The total number of confirmed SVC cases
per year was also compared to average annual UK rainfall
and air temperature (data available from the UK Meteorological
office)