Testing of UK Populations of Culex pipiens L. for Schmallenberg Virus Vector Competence and Their Colonization.
BACKGROUND
Schmallenberg virus (SBV), an arboviral pathogen of ruminants, emerged in northern Europe during 2011 and has subsequently spread across a vast geographic area. While Culicoides biting midges (Diptera: Ceratopogonidae) have been identified as a biological transmission agent of SBV, the role of mosquitoes (Diptera: Culicidae) as potential vectors has not been defined beyond small-scale field collections in affected areas. Culex pipiens L. are one of the most widespread mosquitoes in northern Europe; they are present on farms across the region and have previously been implicated as vectors of several other arboviruses. We assessed the ability of three colony lines of Cx. pipiens, originating from geographically diverse field populations, to become fully infected by SBV using semi-quantitative real-time RT-PCR (sqPCR).


RESULTS
Two colony lines of Cx. pipiens were created in the UK ('Brookwood' and 'Caldbeck') from field collections of larvae and pupae and characterised using genetic markers. A third strain of Cx. pipiens from CVI Wageningen, The Netherlands, was also screened during experiments. Intrathoracic inoculation of the Brookwood line resulted in infections after 14 days that were characterised by high levels of RNA throughout individuals, but which demonstrated indirect evidence of salivary gland barriers. Feeding of 322 individuals across the three colony lines on a membrane based infection system resulted in no evidence of full dissemination of SBV, although infections did occur in a small proportion of Cx. pipiens from each line.


CONCLUSIONS
This study established two novel lines of Cx. pipiens mosquitoes of UK origin in the laboratory and subsequently tested their competence for SBV. Schmallenberg virus replication and dissemination was restricted, demonstrating that Cx. pipiens is unlikely to be an epidemiologically important vector of the virus in northern Europe.
Vector-borne Viral Diseases Programme, The Pirbright Institute, Pirbright, Surrey, United Kingdom.
Robyn
R
Manley
Vector-borne Viral Diseases Programme, The Pirbright Institute, Pirbright, Surrey, United Kingdom.
Lara E
LE
Harrup
Vector-borne Viral Diseases Programme, The Pirbright Institute, Pirbright, Surrey, United Kingdom.
Eva
E
Veronesi
Vector-borne Viral Diseases Programme, The Pirbright Institute, Pirbright, Surrey, United Kingdom.
Francesca
F
Stubbins
Vector-borne Viral Diseases Programme, The Pirbright Institute, Pirbright, Surrey, United Kingdom.
Jo
J
Stoner
Vector-borne Viral Diseases Programme, The Pirbright Institute, Pirbright, Surrey, United Kingdom.
Simon
S
Gubbins
Vector-borne Viral Diseases Programme, The Pirbright Institute, Pirbright, Surrey, United Kingdom.
Anthony
A
Wilson
Vector-borne Viral Diseases Programme, The Pirbright Institute, Pirbright, Surrey, United Kingdom.
Carrie
C
Batten
Laboratory of Entomology, Wageningen University and Research (WUR), Wageningen, The Netherlands.
Constantianus J M
CJ
Koenraadt
Vector-borne Viral Diseases Programme, The Pirbright Institute, Pirbright, Surrey, United Kingdom.
Mark
M
Henstock
Vector-borne Viral Diseases Programme, The Pirbright Institute, Pirbright, Surrey, United Kingdom.
James
J
Barber
Vector-borne Viral Diseases Programme, The Pirbright Institute, Pirbright, Surrey, United Kingdom.
Simon
S
Carpenter
D000818:Animals; D002044:Bunyaviridae Infections / Q000635:transmission / Q000662:veterinary* / Q000821:virology; D003465:Culex / Q000235:genetics / Q000821:virology*; D004247:DNA / Q000235:genetics / Q000302:isolation & purification; D007303:Insect Vectors / Q000235:genetics / Q000821:virology*; D008297:Male; D016851:Orthobunyavirus / Q000235:genetics / Q000302:isolation & purification*; D012367:RNA, Viral / Q000235:genetics / Q000302:isolation & purification; D060888:Real-Time Polymerase Chain Reaction; D012418:Ruminants / Q000821:virology*; D006113:United Kingdom
D012367:RNA, Viral; D004247:DNA