BACKGROUND : Several European countries suffered important economic losses during the past decade due to the
emergence of bluetongue and Schmallenberg viruses. Both are viruses of veterinary importance and are spread
by Culicoides spp. This triggered many European countries to start Culicoides population monitoring. Recently a
one year monitoring study at 16 sites in Belgium revealed that important variation existed in Culicoides abundance and
species diversity between collection sites. In order to analyze whether this variation is consistent over years, a detailed
analysis of monitoring data collected at seven locations in Belgium between 2007 and 2011 was performed in this study.
At all locations, biting midges were collected with OVI black light traps set-up in close proximity to livestock.
RESULTS : In total, 42 different Culicoides species were morphologically identified. Species of the subgenus Avaritia
represented 83% of all collected midges. Nevertheless, important differences in species composition were found
between sites. Furthermore, statistical differences between sites were found for the total and maximum annual
abundance, showing that a consistent higher or lower number of Culicoides could be collected depending on the
selected collection site. Yearly, up to 16 and 30-fold differences in total and maximum annual abundances between sites,
respectively, were found. Also the month in whichmost Culicoides were collected varied greatly between years, both at
local (from May to October) and country level [May (2008), June (2010), July (2009), August (2011), October (2007)]. Finally,
the average vector-free period over all sites and years was 173 days and could roughly be defined between November
and the end of April. Interestingly, important yearly variations of up to two months in the duration of the vector-free
period were found between the studied collection sites. In contrast to the abundance parameters, no specific sites
could however be identified where monitoring consistently showed shorter or longer vector-free periods.
CONCLUSIONS : In conclusion, our results show that the selection of collection sites for Culicoides monitoring, even in a
small country such as Belgium, strongly influences abundance parameters and that yearly variation in seasonality occurs.
This emphasizes that care should be taken when using such parameters in risk assessments for transmission of Culicoidesborne
diseases and that more clear and strict guidelines for Culicoides monitoring should be considered when monitoring
data are used for legislative purposes.
Additional file 1: Table S1. Location, sampling period, local ecological
factors in the immediate vicinity of the collection site and eco-region with
its characteristic ecological aspects for all 7 collection sites.
Additional file 2: Table S2. Species diversity and relative abundance (%)
of Culicoides collected with OVI traps from 2007 to 2011 at 7 sites in Belgium).