title: Experimental studies on comparison of the vector competence of four Italian Culex pipiens populations for West Nile virus.
abstract: BACKGROUND
  West Nile virus (WNV) is a vector-borne disease responsible for causing epidemics in many areas of the world. The virus is maintained in nature by an enzootic bird-mosquito-bird cycle and occasionally transmitted to other hosts, such as equines and humans. Culex species, in particular the ubiquitous species Culex pipiens is thought to play a major vector role both in enzootic and epizootic maintenance and transmission of WNV. Introduced in Europe in recent years, since 2008 WNV has been stably circulating mainly in the Northeastern regions of Italy, although sporadic equine and/or human cases, as well as WNV infected Cx. pipiens pools, have been recorded in other Italian areas. The scope of our study was to evaluate the potential competence of some Italian populations of Cx. pipiens to transmit WNV and to assess their ability for vertical transmission of the virus. For this purpose four Italian populations, from different areas, were experimentally infected.
  
  
  METHODS
  After the infectious blood meal, fed females were monitored for 32 days to determine the length of viral extrinsic incubation period. WNV titre of infected mosquitoes was evaluated both by quantitative Real Time PCR and viral titration by Plaque Forming Units/ml (PFU/mL) in VERO cells. Potential Infection, Dissemination, Transmission rates (IR, DR, TR) were assessed by detection of the virus in body, legs plus wings and saliva of the fed females, respectively.
  
  
  RESULTS
  All tested populations were susceptible to the WNV infection. The viral presence in legs and wings demonstrated the ability of WNV to disseminate in the mosquitoes. Viral RNA was detected in the saliva of tested populations. No significant differences in TR values were observed among the four studied populations. The offspring of the Cx. pipiens infected females were WNV negative.
  
  
  CONCLUSIONS
  Our study addressed an important issue in the knowledge on the complex WNV-vector relationships in Italy, indicating that all Italian Cx. pipiens populations tested exhibited vector competence for WNV. Further studies should be performed in order to better clarify the role of other factors (vector density, climatic conditions, reservoir presence etc.) in order to predict where and when WNV outbreaks could occur.
authors.affiliation: Unit of Viral diseases and attenuated vaccine, Department of Infectious, Parasitic and Immune-Mediated Diseases Istituto Superiore di Sanità, Rome, Italy. claudia.fortuna@iss.it.
authors.forename: Claudia
authors.initials: C
authors.lastname: Fortuna
authors.affiliation: Unit of Viral diseases and attenuated vaccine, Department of Infectious, Parasitic and Immune-Mediated Diseases Istituto Superiore di Sanità, Rome, Italy. mariaelena.remoli@iss.it.
authors.forename: Maria Elena
authors.initials: ME
authors.lastname: Remoli
authors.affiliation: Unit of Vector-borne Diseases and International Health, Department of Infectious, Parasitic and Immune-Mediated Diseases Istituto Superiore di Sanità, Rome, Italy. marco.diluca@iss.it.
authors.forename: Marco
authors.initials: M
authors.lastname: Di Luca
authors.affiliation: Unit of Vector-borne Diseases and International Health, Department of Infectious, Parasitic and Immune-Mediated Diseases Istituto Superiore di Sanità, Rome, Italy. francesco.severini@iss.it.
authors.forename: Francesco
authors.initials: F
authors.lastname: Severini
authors.affiliation: Unit of Vector-borne Diseases and International Health, Department of Infectious, Parasitic and Immune-Mediated Diseases Istituto Superiore di Sanità, Rome, Italy. luciano.toma@iss.it.
authors.forename: Luciano
authors.initials: L
authors.lastname: Toma
authors.affiliation: Unit of Viral diseases and attenuated vaccine, Department of Infectious, Parasitic and Immune-Mediated Diseases Istituto Superiore di Sanità, Rome, Italy. eleonora.benedetti@iss.it.
authors.forename: Eleonora
authors.initials: E
authors.lastname: Benedetti
authors.affiliation: Unit of Viral diseases and attenuated vaccine, Department of Infectious, Parasitic and Immune-Mediated Diseases Istituto Superiore di Sanità, Rome, Italy. paola.bucci@iss.it.
authors.forename: Paola
authors.initials: P
authors.lastname: Bucci
authors.affiliation: Istituto Zooprofilattico Sperimentale delle Venezie, Legnaro, PD, Italy. fmontarsi@izsvenezie.it.
authors.forename: Fabrizio
authors.initials: F
authors.lastname: Montarsi
authors.affiliation: National Centre for Epidemiology, Surveillance and Health Promotion, Unit of Statistics Istituto Superiore di Sanità, Rome, Italy. giada.minelli@iss.it.
authors.forename: Giada
authors.initials: G
authors.lastname: Minelli
authors.affiliation: Unit of Vector-borne Diseases and International Health, Department of Infectious, Parasitic and Immune-Mediated Diseases Istituto Superiore di Sanità, Rome, Italy. dainela.boccolini@iss.it.
authors.forename: Daniela
authors.initials: D
authors.lastname: Boccolini
authors.affiliation: Unit of Vector-borne Diseases and International Health, Department of Infectious, Parasitic and Immune-Mediated Diseases Istituto Superiore di Sanità, Rome, Italy. roberto.romi@iss.it.
authors.forename: Roberto
authors.initials: R
authors.lastname: Romi
authors.affiliation: Unit of Viral diseases and attenuated vaccine, Department of Infectious, Parasitic and Immune-Mediated Diseases Istituto Superiore di Sanità, Rome, Italy. mariagrazia.ciufolini@iss.it.
authors.forename: Maria Grazia
authors.initials: MG
authors.lastname: Ciufolini
mesh_terms: D000818:Animals; D003465:Culex / Q000821:virology*; D005260:Female; D007303:Insect Vectors / Q000821:virology*; D007558:Italy; D060888:Real-Time Polymerase Chain Reaction; D019562:Viral Load; D010948:Viral Plaque Assay; D014902:West Nile virus / Q000254:growth & development / Q000302:isolation & purification*