West Nile Virus Surveillance Research Articles

Contrasted Epidemiological Patterns of West Nile Virus Lineages 1 and 2 Infections in France from 2015 to 2019.

Since 2015, annual West Nile virus (WNV) outbreaks of varying intensities have been reported in France. Recent intensification of enzootic WNV circulation was observed in the South of France with most horse cases detected in 2015 (n = 49), 2018 (n = 13), and 2019 (n = 13). A WNV lineage 1 strain was isolated from a horse suffering from West Nile neuro-invasive disease (WNND) during the 2015 episode in the Camargue area. A breaking point in WNV epidemiology was achieved in 2018, when WNV lineage 2 emerged in Southeastern areas. This virus most probably originated from WNV spread from Northern Italy and caused WNND in humans and the death of diurnal raptors. WNV lineage 2 emergence was associated with the most important human WNV epidemics identified so far in France (n = 26, including seven WNND cases and two infections in blood and organ donors). Two other major findings were the detection of WNV in areas with no or limited history of WNV circulation (Alpes-Maritimes in 2018, Corsica in 2018–2019, and Var in 2019) and distinct spatial distribution of human and horse WNV cases. These new data reinforce the necessity to enhance French WNV surveillance to better anticipate future WNV epidemics and epizootics and to improve the safety of blood and organ donations.

Thermal thresholds heighten sensitivity of West Nile virus transmission to changing temperatures in coastal California.

Temperature is widely known to influence the spatio-temporal dynamics of vector-borne disease transmission, particularly as temperatures vary across critical thermal thresholds. When temperature conditions exhibit such 'transcritical variation', abrupt spatial or temporal discontinuities may result, generating sharp geographical or seasonal boundaries in transmission. Here, we develop a spatio-temporal machine learning algorithm to examine the implications of transcritical variation for West Nile virus (WNV) transmission in the Los Angeles metropolitan area (LA). Analysing a large vector and WNV surveillance dataset spanning 2006-2016, we found that mean temperatures in the previous month strongly predicted the probability of WNV presence in pools of Culex quinquefasciatus mosquitoes, forming distinctive inhibitory (10.0-21.0°C) and favourable (22.7-30.2°C) mean temperature ranges that bound a narrow 1.7°C transitional zone (21-22.7°C). Temperatures during the most intense months of WNV transmission (August/September) were more strongly associated with infection probability in Cx. quinquefasciatus pools in coastal LA, where temperature variation more frequently traversed the narrow transitional temperature range compared to warmer inland locations. This contributed to a pronounced expansion in the geographical distribution of human cases near the coast during warmer-than-average periods. Our findings suggest that transcritical variation may influence the sensitivity of transmission to climate warming, and that especially vulnerable locations may occur where present climatic fluctuations traverse critical temperature thresholds.

Serological survey for Saint Louis encephalitis virus and West Nile virus in domestic mammals in Córdoba, Argentina: are our pets potential sentinels?

We evaluated the seroprevalence of Saint Louis encephalitis virus (SLEV) and West Nile virus (WNV) in dogs and cats in Córdoba, Argentina. Monotypic and heterotypic serological patterns were differentiated by means of a neutralization test. The SLEV seroprevalence in dogs was 14.6% (44/302; 100% monotypic). Two out of 94 (2.1%, 100% monotypic) cats were positive for WNV only. Four dogs (1.3%) exhibited neutralizing antibody titers against SLEV and WNV. During the study, three dogs seroconverted to SLEV. Our study demonstrates that pets were useful for detecting viral activity and could be considered as sentinels in the local surveillance of SLEV and WNV.

Bird Species Involved in West Nile Virus Epidemiological Cycle in Southern Québec.

Despite many studies on West Nile Virus (WNV) in the US, including the reservoir role of bird species and the summer shifts of the Culex mosquito, feeding from birds to mammals, there have been few equivalent studies in the neighboring regions of Canada where WNV is endemic. Here, a priority list of bird species likely involved in WNV transmission in the greater Montréal area is constructed by combining three sources of data: (i) from WNV surveillance in wild birds (2002–2015); (ii) blood meal analysis of Culex pipiens–restuans (CPR), the primary enzootic vectors of WNV in the region, collected from surveillance in 2008 and 2014; (iii) literature review on the sero-prevalence/host competence of resident birds. Each of these data sources yielded 18, 23 and 53 species, and overall, 67 different bird species were identified as potential WNV amplifiers/reservoirs. Of those identified from CPR blood meals, Common starlings, American robins, Song sparrows and House sparrows ranked the highest and blood meal analysis demonstrated a seasonal shift in feed preference from birds to mammals by CPR. Our study indicates that there are broad similarities in the ecology of WNV between our region and the northeastern US, although the relative importance of bird species varies somewhat between regions.

West Nile virus in Europe: after action reviews of preparedness and response to the 2018 transmission season in Italy, Slovenia, Serbia and Greece

BackgroundAfter Action Reviews (AAR) with a One Health perspective were performed in Slovenia, Italy, Serbia and Greece following a severe West Nile virus (WNV) transmission season in 2018. A protocol combining traditional techniques and organizational process analysis was developed and then implemented in each country.ResultsIn 2018, response to the unusually intense transmission season of WNV in Slovenia, Italy, Serbia and Greece took place through routine response mechanisms. None of the four countries declared a national or subnational emergency. We found a very strong consensus on the strengths identified in responding to this event. All countries indicated the availability of One Health Plans for surveillance and response; very high laboratory diagnostic capacity in the human, veterinary and entomology sectors and strong inter-sectoral collaboration with strong commitment of engaged institutions as critical in the management of the event. Finally, countries implementing One Health surveillance for WNV (in terms of early warning and early activation of prevention measures) consistently reported a positive impact on their activities, in particular when combining mosquito and bird surveillance with surveillance of cases in humans and equids. Recurring priority areas for improvement included: increasing knowledge on vector-control measures, ensuring the sustainability of vector monitoring and surveillance, and improving capacity to manage media pressure.ConclusionsThe AARs presented here demonstrate the benefit of cross-sectoral and cross-disciplinary approaches to preparedness for West Nile virus outbreaks in Europe. In the coming years, priorities include fostering and strengthening arrangements that: enable coordinated One Health surveillance and response during WNV transmission seasons; ensure adequate laboratory capacities; strengthen risk communication; and fund longer-term research to address the knowledge gaps identified in this study.

Epidemiological surveillance of West Nile virus in the world and Brazil

West Nile virus (WNV) is a neurovirulent mosquito-borne Flavivirus that is maintained in nature by a zoonotic transmissioncycle between avian hosts and ornithophilic mosquito vectors, mostly from the Culex genus. Until the 1990s, WNV wasconsidered to be an old-world arbovirus, but in 1999, WNV emerged in the United States (US) and spread rapidly, becoming amajor threat to public health. WNV adapted to the transmission cycle involving American mosquitoes and birds and reachedCentral and South America in subsequent years. In 2003, the National West Nile Fever Surveillance System was created in Brazilbased on serological screening of animals and sentinel vectors, as recommended by the Pan American Health Organization(PAHO) and the World Health Organization (WHO). Since 2008, serological evidence of WNV infection in Brazilian horseshas been reported, and the circulation of WNV has been monitored through the regular serological screening of sentinel horsesand reporting of encephalomyelitis cases. Horses are highly susceptible to WNV infection, and outbreaks of neurologicaldisease among horses often precede human cases. In this regard, equine surveillance has been essential in providing earlywarning to public and animal health authorities in several countries, including Brazil. This demonstrates the need for animaland public health intervention programs to allocate resources to make veterinarians aware of the role they can play in thehuman surveillance processes by monitoring horses. This review discusses the importance of equine surveillance and the gapthat veterinarians can fill on the front line in human surveillance, in Brazil and worldwide, in the context of “One Health”

A 15 Year Evaluation of West Nile Virus in Wisconsin: Effects on Wildlife and Human Health.

West Nile virus (WNV) is the most important and widespread mosquito-borne virus in the United States (U.S.). WNV has the ability to spread rapidly and effectively, infecting more than 320 bird and mammalian species. An examination of environmental conditions and the health of keystone species may help predict the susceptibility of various habitats to WNV and reveal key risk factors, annual trends, and vulnerable regions. Since 2002, WNV outbreaks in Wisconsin varied by species, place, and time, significantly affected by unique climatic, environmental, and geographical factors. During a 15 year period, WNV was detected in 71 of 72 counties, resulting in 239 human and 1397 wildlife cases. Controlling for population and sampling efforts in Wisconsin, rates of WNV are highest in the western and northwestern rural regions of the state. WNV incidence rates were highest in counties with low human population densities, predominantly wetland, and at elevations greater than 1000 feet. Resources for surveillance, prevention, and detection of WNV were lowest in rural counties, likely resulting in underestimation of cases. Overall, increasing mean temperature and decreasing precipitation showed positive influence on WNV transmission in Wisconsin. This study incorporates the first statewide assessment of WNV in Wisconsin.

West Nile or Usutu Virus? A Three-Year Follow-Up of Humoral and Cellular Response in a Group of Asymptomatic Blood Donors.

West Nile virus (WNV) and Usutu virus (USUV) are two related arboviruses (genus Flavivirus, family Flaviviridae), with birds as a reservoir and mosquitoes as transmitting vectors. In recent years, WNV epidemiology changed in many European countries with increased frequency of outbreaks posing the issue of virus transmission risks by blood transfusion. USUV emerged for the first time in birds of the Tuscany region (Italy) in 1996 and in 2001 in Austria. While WNV is responsible for both mild and neuroinvasive diseases, USUV infection is usually asymptomatic and neuroinvasive symptoms are rare. Since WNV and USUV co-circulate, the surveillance of WNV allows also the detection of USUV. Due to the great similarity in amino-acid sequence of major surface proteins of the two viruses, a high cross-reactivity can lead to misinterpretation of serological results. Here, we report the results obtained from 54 asymptomatic blood donors during a three-year follow-up showing an unexpected high positivity (46.3%) for USUV. The major obstacle encountered in the differential diagnosis between these two viruses was the high cross-reactivity found in neutralizing antibodies (NT Abs) and, in some cases, a long follow-up was mandatory for a correct diagnosis. Moreover, two new ELISpot assays were developed for a more rapid and specific differential diagnosis, especially in those cases in which NT Abs were not determinant. Using a combination of Enzyme-linked immunospot (ELISpot), molecular, and serological tests, we could identify 25 true positive WNV and 25 true positive USUV blood donors. Our data highlight the importance of raising awareness for increasing USUV infections in endemic countries involved in blood transfusion and organ donation.

The Influence of Sociodemographic Factors on the Engagement of Citizens in the Detection of Dead Corvids During the Emergence of West Nile Virus in Ontario, Canada.

West Nile virus (WNv) was introduced into North America in 1999, and by 2002 was identified in most regions of Ontario, Canada. Surveillance of WNv included testing of corvids found dead and reported by citizens across Ontario, which at the time was a novel citizen science application for disease surveillance. While this surveillance program was successful for timely identification of WNv as it emerged and spread across the province, it is important to consider the influence of non-disease factors on surveillance data collected by the public. The objective of this study was to examine associations between rates of citizen phone reports of dead corvids and sociodemographic factors within the geographic areas where the reports were obtained. The data were grouped by forward sortation area (FSA), a geographical area based upon postal codes, which was linked with census data. Associations between the weekly rate of citizen reports and FSA-level sociodemographic factors were measured using multilevel negative binomial models. There were 12,295 phone call reports of dead corvids made by citizens in 83.3% of Ontario FSAs. Factors associated with the weekly rate of phone reports included the proportion of high-rise housing, the proportion of households with children, the proportion of seniors in the population, the proportion of citizens with no knowledge of either official language and the latitude of the FSA. There were higher rates of citizen phone reports in FSAs with <80% high-rise housing and greater proportions of households with children. A positive and negative association in the rate of calls with the proportion of seniors and latitude of the FSA, respectively, were moderated by the proportion of the population with knowledge of official language(s). Understanding the sociodemographic characteristics associated with citizen reporting rates of sentinels for disease surveillance can be used to inform advanced cluster detection methods such as applying the spatial scan test with normal distribution on residuals from a regression model to reduce confounding. In citizen-derived data collected for disease surveillance, this type of approach can be helpful to improve the interpretation of cluster detection results beyond what is expected.

Error associated with estimates of Minimum Infection Rate for Endemic West Nile Virus in areas of low mosquito trap density

West Nile Virus (WNV) is a mosquito-borne infection that can cause serious illness in humans. Surveillance for WNV primarily focuses on a measure of infection prevalence in the Culex spp. mosquitos, its primary vectors, known as the Minimum Infection Rate (MIR). The calculation of MIR for a given area considers the number of mosquitos tested, but not the relative effort to collect mosquitos, leading to a potential underestimation of the uncertainty around the estimate. We performed Value of Information analysis on simulated data sets including a range of mosquito trap densities in two well-studied counties in Illinois between 2005 and 2016 to determine the relative error introduced into MIR associated with changing the density of mosquito traps. We found that low trap density increases the potential for error in MIR estimation, and that it does so synergistically with low true MIR values. We propose that these results could be used to better estimate uncertainty in WNV risk.

Clinical and virological findings in patients with Usutu virus infection, northern Italy, 2018.

BackgroundUsutu virus (USUV) is a mosquito-borne flavivirus, which shares its transmission cycle with the phylogenetically related West Nile virus (WNV). USUV circulates in several European countries and its activity has increased over the last 5 years.AimTo describe human cases of USUV infection identified by surveillance for WNV and USUV infection in the Veneto Region of northern Italy in 2018.MethodsFrom 1 June to 30 November 2018, all cases of suspected autochthonous arbovirus infection and blood donors who had a reactive WNV nucleic acid test were investigated for both WNV and USUV infection by in-house molecular methods. Anti-WNV and anti-USUV IgM and IgG antibodies were detected by ELISA and in-house immunofluorescence assay, respectively; positive serum samples were further tested by WNV and USUV neutralisation assays run in parallel.ResultsEight cases of USUV infection (one with neuroinvasive disease, six with fever and one viraemic blood donor who developed arthralgia and myalgia) and 427 cases of WNV infection were identified. A remarkable finding of this study was the persistence of USUV RNA in the blood and urine of three patients during follow-up. USUV genome sequences from two patients shared over 99% nt identity with USUV sequences detected in mosquito pools from the same area and clustered within lineage Europe 2.ConclusionsClinical presentation and laboratory findings in patients with USUV infection were similar to those found in patients with WNV infection. Cross-reactivity of serology and molecular tests challenged the differential diagnosis.

Characterization of Three Novel Viruses from the Families Nyamiviridae, Orthomyxoviridae, and Peribunyaviridae, Isolated from Dead Birds Collected during West Nile Virus Surveillance in Harris County, Texas.

This report describes and characterizes three novel RNA viruses isolated from dead birds collected during West Nile virus surveillance in Harris County, TX, USA (the Houston metropolitan area). The novel viruses are identified as members of the families Nyamaviridae, Orthomyxoviridae, and Peribunyaviridae and have been designated as San Jacinto virus, Mason Creek virus, and Buffalo Bayou virus, respectively. Their potential public health and/or veterinary importance are still unknown.

Prospects of leveraging an existing mosquito-borne disease surveillance system to monitor other emerging mosquito-borne diseases: a systematic review of West Nile Virus surveillance in Canada (2000–2016)

The objective of this paper was to characterize the role of the current West Nile Virus (WNV) surveillance in supporting the identification of and public health preparedness for other emerging mosquito-borne diseases in Canada. We systematically reviewed publicly accessible WNV surveillance records published within the federal, provincial (n = 10), territorial (n = 3), and regional health authorities (n = 95) between 2000 and 2016. We describe the strategic approaches and activities to WNV surveillance from 124 websites, four public health databases, and three custom Google search engines. WNV surveillance in Canada can address emerging mosquito-borne diseases. However, surveillance practices are likely to underestimate the true risks. Prioritizing and strengthening WNV surveillance by all levels of the Canadian Government through timely surveillance measures, consistent and representative data for accurate prediction of trends and risks are recommended.

Usefulness of Eurasian Magpies (Pica pica) for West Nile virus Surveillance in Non-Endemic and Endemic Situations.

In September 2017, passive surveillance allowed the detection of West Nile virus (WNV) lineage 2 for the first time in northern Spain in a northern goshawk (Accipiter gentilis). However, a cross sectional study carried out in Eurasian magpies (Pica pica) in a nearby area evidenced that WNV had been circulating two months earlier. Therefore, active surveillance in Eurasian magpies proved its effectiveness for the early detection of WNV in a non-endemic area. Further surveys in 2018 and the beginning of 2019 using young magpies (i.e., born after 2017) showed the repeated circulation of WNV in the same region in the following transmission season. Therefore, active surveillance in Eurasian magpies as well proved to be useful for the detection of WNV circulation in areas that may be considered as endemic. In this manuscript we present the results of those studies and discuss reasons that make the Eurasian magpies an ideal species for the surveillance of WNV, both in endemic and non-endemic areas.

Integrated West Nile Virus Surveillance in Harris County, Texas, 2003 to 2018

ObjectiveThis abstract aims to: 1) describe human WNV infections in Harris County excluding the City of Houston, Texas, 2003 to 2018; 2) explore geographical distributions of WNV positive mosquito pools in relation to human cases; 3) provide a brief overview of the county’s rigorous multidisciplinary WNV surveillance and control in mosquitoes and humans.IntroductionWest Nile virus (WNV) is the leading cause of autochthonous arboviral disease in the United States1. The virus is primarily spread to people through the bite of infected Culex species of mosquitos. WNV was first identified in Harris County, Texas, in 20022. Since then, the mosquito-borne virus has become endemic in the region, with surges in 2012 and 2014. Although majority of individuals infected are asymptomatic, WNV induced neuroinvasive infections often result in hospitalizations and adverse outcomes3-7, thus may pose a significant concern in public health and healthcare. The Harris County Public Health (HCPH) Surveillance and Epidemiology Unit (SEU) conducts surveillance of WNV in humans, in collaboration with Mosquito and Vector Control Division (MVCD) that monitors the virus in mosquito populations and birds. Mosquito abatement activities are implemented in areas where positive mosquitoes and human cases are identified. In this integrated model, clusters of WNV positive mosquito pools in relation with human cases provide comprehensive surveillance data to guide targeted efforts of mosquito control, disease prevention, and community education.MethodsSurveillance data of human WNV cases and WNV tested mosquito pools 2003 to 2018 in Harris County excluding the City of Houston were used for the analysis. Human cases included were confirmed and probable cases. Frequencies, percentages, age-adjusted annual average rates were used to describe the data. Geographical locations of WNV positive mosquito pools and human cases were mapped and analyzed using ESRI ArcGIS to determine the spatial relationship between the positive mosquito pools and human cases. Space-Time analysis was performed on 16 years of human disease data using Scan statistics in SatScan™ to test the effect of time and identify significant geographical clusters of WNV cases over time, which revealed a statistically significant cluster in 2012 to 2014 in northwest of Harris County. Subsequently, human cases and WNV positive mosquito pools of 2012 to 2014 were selected for hotspot analysis to verify the results from Satscan analysis and visualize the geographical cluster. Human cases were aggregated into census tracts and analyzed by optimized hotspot method; the positive mosquito pools were geocoded using their intersection locations and analyzed by ESRI Getis-Ord Gi hotspot method.ResultsFrom 2003 to 2018, a total of 295 confirmed and probable human WNV cases were identified, including 217 neuroinvasive and 78 fever cases. The median age of patients was 58 years old; 64.8% were male. The onset of majority of the cases (80.7%) concentrated in July to September. Among case-patients, 72.9% were hospitalized, and 3.4% died. The annual average age-adjusted incidence rate of WNV was 0.7 per 100,000 during 2003 to 2018. However, the rate was 1.8 and 2.7 per 100,000 in 2012 and 2014, respectively. Over 68% of the cases clustered in west and northwest of the county.The annual WNV positive mosquito pools ranged from 0.2% to 10.2% amongst the years. The number of WNV positive mosquito pools in 2014 was more than 4 times higher than the average number during those years, the highest record in the County.Hot spots of human cases and the positive mosquito pools were both identified in northwest Harris County. There was a significant geographical overlap between human cases and the positive mosquito pools.The space-time analysis for the 16 years detected a significant high-risk cluster in 2012 to 2014 in northwest Harris County. Findings from optimized hotspot analysis on human cases are consistent with the results from SatScan analysis. Statistically significant hot spots of positive mosquito pools identified by Getis-Ord Gi hotspot analysis displayed highly overlay with the statistically significant cluster of human cases detected by Satscan space-time analysis.ConclusionsWNV infection is underestimated. Studies suggest that every one case identified represent five infections 8-9. Therefore, the actual number of cases is likely substantially higher. Clinicians should be alerted in WNV season and consider testing and reporting as early as possible, especially in neuroinvasive patients. The public should be encouraged to utilize personal protection, particularly during peak seasons. This analysis shows that GIS mapping and optimized hotspot analysis of WNV human cases in relation to positive mosquito pools can provide statistical evidences of areas most affected, thus inform targeted mosquito control, prevention and education strategies in people living in areas with high virus activitie

One Health approach for West Nile virus surveillance in the European Union: relevance of equine data for blood safety.

West Nile virus (WNV) infection is notifiable in humans and equids in the European Union (EU). An area where a human case is detected is considered affected until the end of the mosquito transmission season (week 48) and blood safety measures have to be implemented. We used human and equine case notifications between 2013 and 2017 to define the WNV distribution in the EU and to investigate the relevance of using equine cases as a complementary trigger for blood safety measures. Adding areas with equine cases to the definition of an affected area would have a major impact on blood safety measures. Adding areas with equine cases where human cases have been reported in the past would increase the timeliness of blood safety measures with only a limited impact. Although the occurrence of human and/or equine cases confirms virus circulation in the EU, no evidence was found that occurrence of equine cases leads to human cases and vice versa. We conclude that information about equine data should contribute to raising awareness among public health experts and trigger enhanced surveillance. Further studies are required before extending the definition of affected areas to areas with human and/or equine cases.

Implementation of the One Health approach to fight arbovirus infections in the Mediterranean and Black Sea Region: Assessing integrated surveillance in Serbia, Tunisia and Georgia.

BackgroundIn the Mediterranean and Black Sea Region, arbovirus infections are emerging infectious diseases. Their surveillance can benefit from one health inter‐sectoral collaboration; however, no standardized methodology exists to study One Health surveillance.MethodsWe designed a situation analysis study to document how integration of laboratory/clinical human, animal and entomological surveillance of arboviruses was being implemented in the Region. We applied a framework designed to assess three levels of integration: policy/institutional, data collection/data analysis and dissemination. We tested the use of Business Process Modelling Notation (BPMN) to graphically present evidence of inter‐sectoral integration.ResultsSerbia, Tunisia and Georgia participated in the study. West Nile Virus surveillance was analysed in Serbia and Tunisia, Crimea‐Congo Haemorrhagic Fever surveillance in Georgia. Our framework enabled a standardized analysis of One Health surveillance integration, and BPMN was easily understandable and conducive to detailed discussions among different actors/institutions. In all countries, we observed integration across sectors and levels except in data collection and data analysis. Data collection was interoperable only in Georgia without integrated analysis. In all countries, surveillance was mainly oriented towards outbreak response, triggered by an index human case.DiscussionThe three surveillance systems we observed prove that integrated surveillance can be operationalized with a diverse spectrum of options. However, in all countries, the integrated use of data for early warning and inter‐sectoral priority setting is pioneeristic. We also noted that early warning before human case occurrence is recurrently not operationally prioritized.

“One Health” approach in West Nile disease surveillance: the northwestern Italian experience

Purpose: West Nile Disease (WND) is a zoonotic infection with a complicated transmission cycle, involving pathogen, human and animal hosts, vectors and ecosystem. Public Health Authorities are encouraging interaction between multiple disciplines to implement a comprehensive surveillance system. The aim of this work is to present the “One Health approach” enforced in Northern Italy, focusing on Piemonte, Liguria and Valle d’Aosta Regions (Northwestern Italy). Methods & Materials: Since 2015, Veterinary and Human Public Health Authorities of some Northern Italian Regions enforced an integrated Surveillance Plan aiming to early detect the West Nile Virus (WNV) spread during the transmission season and to activate control measures to reduce the risk of human transmission. The working group established throughout the whole Po river valley a standardized protocol of human, entomologic and veterinary surveillance activities. This allowed to connect the surveillance of human clinical cases with entomological surveillance and veterinary monitoring, giving an accurate assessment of the epidemiological situation, and implementing extensive control measures in case of outbreak. In order to apply the guidelines, in Piemonte, Liguria and Valle d’Aosta Regions an information network was activated between Veterinary Services and local Human Health Authority. Results: The first local WNV detection (animals, vectors or humans) in a Province during the transmission season was identified as trigger criteria to activate the information flows between Public Health Authorities. Immediately WNV Nucleic Acid Amplification Test (NAT) screening of all blood donations was introduced in affected areas and blood donors having been for at least one night in the affected Provinces were deferred from donations for 28 days. The integrated surveillance system allowed to detect WNV circulation in Piemonte Region in vectors, animal and human hosts. To date, more than 80.000 blood bags were screened, and no one tested positive. Conclusion: The described multidisciplinary approach allows to early detect WNV appearance during the transmission season. The network has been demonstrated a key point to timely implement control measures against the spread of the infection and the risk of human transmission. This approach was adopted at National level in 2016 where the Ministry of Health published the National integrated WNV Surveillance Plan, actually unique in Europe.

Evaluating the impact of Aedes japonicus invasion on the mosquito community in the Greater Golden Horseshoe region (Ontario, Canada).

BackgroundAedes japonicus was first documented in Ontario, Canada, in 2001. The objective of this study was to determine the effect of Ae. japonicus establishment on the abundance of other mosquitoes in the Greater Golden Horseshoe (GGH) region of Ontario.MethodsAdult mosquito data from the Ontario West Nile virus surveillance program were used. Descriptive analyses, linear trends and distribution maps of average trap count per month for six mosquito species of interest were produced. Multivariable negative binomial regression models were constructed to 1) test whether the invasion of Ae. japonicus affected the abundance of other mosquitoes by comparing the time period before Ae. japonicus was identified in an area (pre-detection), to after it was first identified (detection), and subsequently (establishment), and 2) identify the variables that explain the abundance of the various mosquito species.ResultsThe monthly seasonal average (May–October) of Ae. japonicus per trap night increased from 2002 to 2016, peaking in September, when the average of most other mosquitoes decrease. There were increased numbers of Ae. triseriatus/hendersoni (Odds Ratio (OR): 1.40, 95% Confidence Interval (CI): 1.02–1.94) and decreased numbers of Coquillettidia perturbans (OR: 0.43, 95% CI: 0.26–0.73) in the detection period, compared to the pre-detection period. Additionally, there was a decrease in Cx. pipiens/restuans (OR: 0.87, 95% CI: 0.76–0.99) and Cq. perturbans (OR: 0.68, 95% CI: 0.49–0.94) in the establishment period, compared to the pre-detection period. None of the most parsimonious explanatory models included the period of the establishment of Ae. japonicus.ConclusionsThere is no evidence that the introduction of Ae. japonicus significantly reduced populations of Ae. triseriatus/hendersoni, Cx. pipiens/restuans or An. punctipennis in the GGH. While further research is needed to understand the impact of the Ae. japonicus invasion on other mosquito species, our work indicates that, on a regional scale, little impact has been noted.

Resource-Effective Serosurveillance for the Detection of West Nile Virus in Switzerland Using Abattoir Samples of Free-Range Laying Hens

West Nile virus (WNV) is an important zoonotic pathogen maintained in a natural transmission cycle between mosquitoes and birds as reservoir hosts. In dead-end hosts, such as humans, infection may result in fatal neurologic disease translating into disease and death-related suffering and increased health care costs. In humans, WNV may also be transmitted through blood transfusions and organ transplants. WNV is not present in Switzerland yet, but competent vector species (especially Culex pipiens and Aedes japonicus) are prevalent and an introduction of the virus, likely through wild birds, is expected at any time. Therefore, it is important for Switzerland to be prepared and establish a surveillance system for WNV to initiate increased prevention activities, such as the screening of blood and organ donations and public education activities in case virus circulation is detected. The long-term goal of these surveillance measures would be a reduced infection rate in humans resulting in less suffering and reduced health care costs. To provide the basis for a pragmatic and resource-effective WNV surveillance program, this study used aliquots of serum samples of free-range laying hens taken at the abattoir and collected in the frame of the ongoing Swiss Avian Influenza and Newcastle Disease monitoring program for a 2-year period. All 961 aliquots were analyzed using a commercial competitive WNV enzyme-linked immunosorbent assay (ELISA). The study allowed to set up sampling and laboratory routines as a basis for future WNV surveillance activities. At this stage there is no evidence for circulation of WNV in Switzerland.