Evidence of West Nile virus lineage 2 circulation in Northern Italy.

Istituto G. Caporale Teramo, Via Campo Boario, 64100 Teramo, Italy.
Veterinary Microbiology (Impact Factor: 3.13). 02/2012; 158(3-4):267-73. DOI: 10.1016/j.vetmic.2012.02.018
Source: PubMed

ABSTRACT A West Nile virus (WNV) strain belonging to lineage 2 was for the first time detected in two pools of Culex pipiens collected in the province of Udine and in tissues of a wild collared dove (Streptopelia decaocto) found dead in the province of Treviso, in North East of Italy. It was molecularly identified by group and WNV lineage specific RT-PCRs and characterized by partial sequencing of the NS3 and NS5 genes. When compared with the sequences of same fragments of NS3 and NS5 of the WNV lineage 2 strain isolated from birds of prey in Hungary (2004), the phylogenetic analysis of these sequences revealed 100% and 99% similarity, respectively. As the Hungarian strain, the NS3 selected sequence differed from the 2010 Greek isolate by one amino-acid located at 249 site which is the site involved in genetic modulation of WNV pathogenicity. The Italian and Hungarian strains have histidine rather than proline at this site. The presence of a lineage 2 strain in regions where the lineage 1 strain is still circulating, creates a new scenario with unpredictable consequences. In this situation comprehensive investigations on the occurrence, ecology, and epidemiology of these different WNV strains circulating in Italy become the highest priority.

  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Abstract West Nile virus (WNV) is a zoonotic pathogen which is maintained in an enzootic cycle between mosquitoes and birds; humans, equines, other mammals and some bird species are dead-end hosts. Lineage 1 WNV strains have predominated in Europe since the 1960's. However, in 2004 lineage 2 strains emerged in Hungary and Russia, respectively, spreading since then to a number of neighbouring countries (e.g., Austria, Greece, Italy, Serbia and Romania). Wild bird mortality is a hallmark of North American WNV outbreaks, a feature uncommon in Europe. This study aimed to compare the course of infection of lineage 1 (NY99) and lineage 2 (Austria/2008) WNV strains in the house sparrow, a bird species common in Europe and North America. House sparrows were inoculated with either NY99 or Austria/2008 WNV strains, or sham-inoculated, and clinical and analytic parameters (viraemia, viral load, antibodies) were examined until 14 days after inoculation. Although all inoculated sparrows became infected, no mortality or clinical signs were observed due to the infection. However, the magnitude and duration of viraemia were higher for NY99- than for Austria/2008- infected birds. The house sparrow proved to be a competent host for both strains, although the competence index calculated for NY99 was higher than for Austria/2008. Viral load in tissues and swabs was also higher in NY99-inoculated sparrows. In conclusion, the house sparrow is a convenient avian model for studying host competence of WNV strains. The observed differences between NY99 and Austria/2008 strains might have important epidemiological consequences for disease incidence and dispersal capacity.
    Veterinary Microbiology 01/2014; · 3.13 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The recent spread of West Nile Virus in temperate countries has raised concern. Predicting the likelihood of transmission is crucial to ascertain the threat to Public and Veterinary Health. However, accurate models of West Nile Virus (WNV) expansion in Europe may be hampered by limited understanding of the population dynamics of their primary mosquito vectors and their response to environmental changes. We used data collected in north-eastern Italy (2009-2011) to analyze the determinants of the population growth rate of the primary WNV vector Culex pipiens. A series of alternative growth models were fitted to longitudinal data on mosquito abundance to evaluate the strength of evidence for regulation by intrinsic density-dependent and/or extrinsic environmental factors. Model averaging-algorithms were then used to estimate the relative importance of intrinsic and extrinsic variables in describing the variations of per-capita growth rates. Results indicate a much greater contribution of density-dependence in regulating vector population growth rates than of any environmental factor on its own. Analysis of an average model of Cx. pipiens growth revealed that the most significant predictors of their population dynamics was the length of daylight, estimated population size and temperature conditions in the 15 day period prior to sampling. Other extrinsic variables (including measures of precipitation, number of rainy days, and humidity) had only a minor influence on Cx. pipiens growth rates. These results indicate the need to incorporate density dependence in combination with key environmental factors for robust prediction of Cx. pipiens population expansion and WNV transmission risk. We hypothesize that detailed analysis of the determinants of mosquito vector growth rate as conducted here can help identify when and where an increase in vector population size and associated WNV transmission risk should be expected.
    Parasites & Vectors 01/2014; 7(1):26. · 3.25 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: SUMMARY The steep increase in human West Nile virus (WNV) infections in 2011-2012 in north-eastern Italy prompted a refinement of the surveillance plan. Data from the 2010-2012 surveillance activities on mosquitoes, equines, and humans were analysed through Bernoulli space-time scan statistics, to detect the presence of recurrent WNV infection hotspots. Linear models were fit to detect the possible relationships between WNV occurrence in humans and its activity in mosquitoes. Clusters were detected for all of the hosts, defining a limited area on which to focus surveillance and promptly identify WNV reactivation. Positive relationships were identified between WNV in humans and in mosquitoes; although it was not possible to define precise spatial and temporal scales at which entomological surveillance could predict the increasing risk of human infections. This stresses the necessity to improve entomological surveillance by increasing both the density of trapping sites and the frequency of captures.
    Epidemiology and Infection 03/2014; · 2.87 Impact Factor


Available from
May 21, 2014