#Experimental #studies of #susceptibility of #Italian #Aedes albopictus to #Zika virus (@eurosurveillanc, abstract)

[Source: Eurosurveillance, full page: (LINK). Edited.]

Eurosurveillance, Volume 21, Issue 18, 05 May 2016 / Rapid communication

Experimental studies of susceptibility of Italian Aedes albopictus to Zika virus

Di Luca, Severini, Toma, Boccolini, Romi, Remoli, Sabbatucci, Rizzo, Venturi, Rezza, and Fortuna: Experimental studies of susceptibility of Italian Aedes albopictus to Zika virus

Author affiliations: 1. Unit of Vector-borne Diseases and International Health, Department of Infectious, Parasitic and Immune-Mediated Diseases, Istituto Superiore di Sanità, Rome, Italy; 2. These authors contributed equally; 3. National Reference Laboratory for Arboviruses, Department of Infectious, Parasitic and Immune-Mediated Diseases, Istituto Superiore di Sanità, Rome, Italy; 4. European Programme for Public Health Microbiology Training (EUPHEM), Department of Infectious, Parasitic and Immune-Mediated Diseases, Istituto Superiore di Sanità, Rome, Italy; 5. National Center for Epidemiology and Health Promotion, Istituto Superiore di Sanità, Rome, Italy

Correspondence: Claudia Fortuna ( claudia.fortuna@iss.it)

Citation style for this article: Di Luca M, Severini F, Toma L, Boccolini D, Romi R, Remoli ME, Sabbatucci M, Rizzo C, Venturi G, Rezza G, Fortuna C. Experimental studies of susceptibility of Italian Aedes albopictus to Zika virus. Euro Surveill. 2016;21(18):pii=30223. DOI: http://dx.doi.org/10.2807/1560-7917.ES.2016.21.18.30223

Received:22 April 2016; Accepted:04 May 2016

 

Abstract

We report a study on vector competence of an Italian population of Aedes albopictus for Zika virus (ZIKV). Ae. albopictus was susceptible to ZIKV infection (infection rate: 10%), and the virus could disseminate and was secreted in the mosquito’s saliva (dissemination rate: 29%; transmission rate: 29%) after an extrinsic incubation period of 11 days. The observed vector competence was lower than that of an Ae. aegypti colony tested in parallel.

Zika virus (ZIKV) is an emerging mosquito-borne virus (Flaviviridae family) isolated from different Aedes species in the past. In the recent outbreaks that occurred in Latin America, Aedes aegypti is believed to be the main vector. The isolation of ZIKV from this mosquito species in Malaysia [1], and early experimental studies [2,3] appear to confirm this hypothesis. Recent vector competence studies have also shown that the American Ae. albopictus exhibits similar transmission potential as the American Ae. aegypti [4].

Ae. albopictus is widespread in Mediterranean countries, in particular in Italy where it caused an outbreak of Chikungunya virus (CHIKV) (Togaviridae family, Alphavirus genus) in 2007 [5]. To assess the risk of ZIKV transmission, we evaluated the vector competence of an Italian Ae. albopictus population for the virus. Potential vertical (transovarial) transmission of ZIKV was also evaluated.

Experimental infection by membrane feeding technique

Oral infection was performed in a BSL-3 laboratory using a ZIKV strain of the Asian genotype (kindly provided by Dr Isabelle Leparc-Goffart of the French National Reference Centre for Arboviruses in Marseille​) isolated from a patient returning from French Polynesia in 2013 [6]. Ten-day-old mosquito females from an Italian Ae. albopictus population (collected in Scalea town, Calabria region, in the late summer of 2015) and from a long-established colony of Ae. aegypti (collected in Reynosa, Mexico, in 1998) were allowed to feed for 1 hour through a membrane feeding apparatus. The virus was diluted in rabbit blood (final virus concentration: 6.46 log10 plaque-forming units (PFU)/mL) and maintained at 37 °C by a warm water circulation system. After the blood meal, fully engorged females were transferred to cages and maintained on a 10% sucrose solution in a climatic chamber (26 ± 1 °C; 70% relative humidity; 14 h:10 h light/dark cycle) for 21 days. Ten mosquitoes from either species were individually processed at 0, 3, 4, 7, 11, 14, 18 and 21 days post infection (dpi). To evaluate viral infection, dissemination and transmission, body (head, thorax and abdomen), legs plus wings, and saliva were analysed, as previously described [7]. ZIKV titre was evaluated by quantitative reverse transcription PCR (qRT-PCR). Specific primers ZIKV 1086 and ZIKV 1162c were used, with 5-FAM as the reporter dye for the probe (ZIKV 1107-FAM) [8]. Crossing point values were compared with a standard curve obtained from 10-fold serial dilutions of virus stock of known concentration [810].

Mosquito bodies were analysed in order to evaluate the infection rate (IR), calculated as the number of ZIKV-positive bodies with respect to the total number of fed females. Legs plus wings were tested to assess the dissemination rate (DR), calculated as the number of the specimens with ZIKV-positive legs plus wings among the number of specimens with ZIKV-positive bodies. The saliva of the potentially infected females was processed to assess the transmission rate (TR), defined as the number of mosquitoes with ZIKV-positive saliva among the number of specimens with ZIKV-positive bodies [7]. The potential vector competence was expressed as population transmission rate (PTR), calculated as the number of specimens with ZIKV-positive saliva with respect to the total number of fed mosquitoes [9,11].

Vector competence analysis

Mean viral titres and IR, DR, and TR values are shown in Figures 1 and 2.

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All of the Ae. aegypti and Ae. albopictus bodies analysed immediately after the infectious blood meal (day 0) showed positive results, with mean viral titres of 3.85 ± 0.44 log10 PFU/mL and 3.57 ± 0.28 log10 PFU/mL, respectively, confirming the ingestion of infectious viral particles. The viral titres detected in the bodies increased gradually in both mosquito colonies, reaching 5.18 ± 0.16 log10 PFU/mL in Ae. aegypti and 4.88 ± 0.21 log10 PFU/mL in Ae. albopictus at 18 and 14 dpi (Figure 1A). As expected, differences in IR values between the two species were observed (Figure 2A). In particular, Ae. albopictus showed lower IR values than Ae. aegypti at all collection times. Whereas an IR of 40% was already detected at 3 dpi for Ae. aegypti, infected Ae. albopictus specimens were observed starting from 7 dpi, with an IR value of 20%. Cumulative IR values were 43% for Ae. aegypti and 10% for Ae. albopictus (Table).

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Disseminated infection was observed in Ae. aegypti starting from 3 dpi, with a mean viral titre of 2.74 ± 0.06 log10 PFU/mL (DR 50%), while in Ae. albopictus, the presence of the virus in legs and wings was detected from 11 dpi, with a lower viral titre (1.62 log10 PFU/mL) and an equal value of DR (50%) (Figures 1B and 2B). Starting from 4 dpi, the saliva of Ae. aegypti showed ZIKV particles (titre of 1.99 log10 PFU/mL and TR of 17%) and remained positive throughout all collection times. In particular, the viral titres increased reaching the highest levels after 11 dpi (2.64 ± 0.50 log10 PFU/mL). In contrast, virus was detected in the saliva of Ae. albopictus at 11 and 14 dpi, with TR values of 50% at both collection points, showing a longer extrinsic incubation period (EIP). Cumulative DR and TR values were 73% and 60% for Ae. aegypti and 29% and 29% for Ae. albopictus. Finally, PTR values were 26% for Ae. aegypti and 3% for Ae. albopictus (Table).

After the infectious blood meal, 40 to 50 engorged mosquitoes from each species were kept separate in different cages, under the same laboratory conditions as the ones analysed above, and were allowed to lay eggs (first gonotrophic cycle). Two weeks after the infectious blood meal, a second uninfected blood meal was provided to obtain a second gonotrophic cycle. Pools of 15 to 30 specimens (males and females) from the first and second gonotrophic cycles of both species were processed by qRT-PCR and were negative for ZIKV.

Discussion

Little is known on ZIKV despite its significant epidemic potential [12]. The introduction and dissemination of this previously neglected flavivirus in Latin America, raised concern in temperate climate countries with established Ae. albopictus populations [3]. In light of the spread of this mosquito species in Italy, proven vector in the 2007 outbreak of CHIK [5], it is particularly important to evaluate its vector competence for ZIKV and to assess the potential risk transmission in Italy as well as in other Mediterranean countries. Our study shows that the Italian Ae. albopictus population is susceptible to ZIKV, allowing viral replication and dissemination also in the salivary glands. The short persistence of the virus in the mosquito’s saliva, the PTR value of 3% and the long EIP indicate a low transmission efficiency compared with that of Ae. aegypti. In addition, it should be noted that despite the use of a long-established mosquito colony, not representative of a wild population, the vector competence of Ae. aegypti for ZIKV was significant in our experiment. A recent modelling study [13] that was based on parameters of susceptibility to infection of the Ae. albopictus derived from mosquito populations from the United States and Singapore [4,14], also estimated a low risk of sustained autochthonous transmission of ZIKV in northern Italy. Our results are similar to the above results on American Ae. albopictus and substantially confirm the low epidemic potential of ZIKV in Italy. However, the epidemic potential and the capacity to cause long chains of transmission depends on a series of factors such as the abundance of the mosquito population, the density of the human population, feeding host preferences, biting rates and environmental conditions. High mosquito density, day-biting activity, opportunistic feeding behaviour and climatic and environmental adaptability can affect the efficiency of Ae. albopictus as a vector, favouring its primary role in epidemics, also in the presence of a limited vector competence [15].

Our results also have important public health implications for preparedness. In fact, the extended EIP, which is consistent with the results of studies using American Ae. albopictus mosquitoes [4], would allow the implementation of mosquito control measures that are likely to be more efficient than those implemented in areas infested by the tropical mosquito Ae. aegypti. Moreover, our analysis of offspring of both species from the first and second gonotrophic cycle showed no evidence of transovarial transmission of ZIKV; this finding adds knowledge on the bionomics of this vector and may aid the optimisation of vector control management. Finally, ZIKV appears to be less well adapted to the Italian Ae. albopictus than the A226V variant of CHIKV (data not shown), which caused more than 250 cases in Italy after a single introduction from Kerala, India [5,16].

In conclusion, this experimentally infected Italian Ae. albopictus population appeared to be a competent vector for ZIKV, albeit less efficient than the primary vector Ae. aegypti. However, we should not forget the risk posed by CHIKV and dengue virus that remains high in southern European countries, where small outbreaks and clusters of autochthonous cases have been already documented [17,18].

Acknowledgements

We would like to acknowledge Dr Raniero Guerra (MoH) for fruitful discussion.

Conflict of interest

None declared.

Authors’ contributions

DLM, SF, TL, BD, RME, SM, VG and FC performed the experiments; DLM, SF, TL, BD, VG and FC analysed the data; DLM, SF, TL, BD, VG, RR, RC, RG and FC wrote the manuscript.

References

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  7. Fortuna C, Remoli ME, Di Luca M, Severini F, Toma L, Benedetti E,  et al.  Experimental studies on comparison of the vector competence of four Italian Culex pipiens populations for West Nile virus. Parasit Vectors. 2015;8(1):463. DOI: 10.1186/s13071-015-1067-z PMID: 26383834

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  10. Lanciotti RS, Kerst AJ, Nasci RS, Godsey MS, Mitchell CJ, Savage HM,  et al.  Rapid detection of west nile virus from human clinical specimens, field-collected mosquitoes, and avian samples by a TaqMan reverse transcriptase-PCR assay. J Clin Microbiol. 2000;38(11):4066-71.PMID: 11060069

  11. Richards SL, Anderson SL, Lord CC, Smartt CT, Tabachnick WJ. Relationships between infection, dissemination, and transmission of West Nile virus RNA in Culex pipiens quinquefasciatus (Diptera: Culicidae).J Med Entomol. 2012;49(1):132-42. DOI: 10.1603/ME10280 PMID: 22308781

  12. Powers AM. Overview of emerging arboviruses.Future Virol. 2009;4(4):391-401. DOI: 10.2217/fvl.09.19

  13. Guzzetta G, Poletti P, Montarsi F, Baldacchino F, Capelli G, Rizzoli A,  et al.  Assessing the potential risk of Zika virus epidemics in temperate areas with established Aedes albopictus populations. Euro Surveill. 2016;21(15):30199. DOI: 10.2807/1560-7917.ES.2016.21.15.30199 PMID: 27104366

  14. Wong PS, Li MZ, Chong CS, Ng LC, Tan CH. Aedes (Stegomyia) albopictus (Skuse): a potential vector of Zika virus in Singapore.PLoS Negl Trop Dis. 2013;7(8):e2348. DOI: 10.1371/journal.pntd.0002348 PMID: 23936579

  15. Bonizzoni M, Gasperi G, Chen X, James AA. The invasive mosquito species Aedes albopictus: current knowledge and future perspectives.Trends Parasitol. 2013;29(9):460-8. DOI: 10.1016/j.pt.2013.07.003 PMID: 23916878

  16. Talbalaghi A, Moutailler S, Vazeille M, Failloux AB. Are Aedes albopictus or other mosquito species from northern Italy competent to sustain new arboviral outbreaks?Med Vet Entomol. 2010;24(1):83-7. DOI: 10.1111/j.1365-2915.2009.00853.x PMID: 20377735

  17. Grandadam M, Caro V, Plumet S, Thiberge JM, Souarès Y, Failloux AB,  et al.  Chikungunya virus, southeastern France. Emerg Infect Dis. 2011;17(5):910-3. DOI: 10.3201/eid1705.101873 PMID: 21529410

  18. Marchand E, Prat C, Jeannin C, Lafont E, Bergmann T, Flusin O,  et al.  Autochthonous case of dengue in France, October 2013. Euro Surveill. 2013;18(50):20661. DOI: 10.2807/1560-7917.ES2013.18.50.20661 PMID: 24342514

Keywords: Research; Abstracts; Aedes Albopictus; Italy; Zika Virus.

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#Spread of the Invasive #Mosquitoes #Aedes aegypti and Aedes albopictus in the #BlackSea Region Increases Risk of #Chikungunya, #Dengue, and #Zika #Outbreaks in #Europe (PLoS Negl Trop Dis., extract)

[Source: PLoS Neglected Tropical Diseases, full page: (LINK). Extract.]

OPEN ACCESS / VIEWPOINTS

Spread of the Invasive Mosquitoes Aedes aegypti and Aedes albopictus in the Black Sea Region Increases Risk of Chikungunya, Dengue, and Zika Outbreaks in Europe

Muhammet M. Akiner, Berna Demirci, Giorgi Babuadze, Vincent Robert, Francis Schaffner

Published: April 26, 2016 / http://dx.doi.org/10.1371/journal.pntd.0004664

Citation: Akiner MM, Demirci B, Babuadze G, Robert V, Schaffner F (2016) Spread of the Invasive Mosquitoes Aedes aegypti and Aedes albopictus in the Black Sea Region Increases Risk of Chikungunya, Dengue, and Zika Outbreaks in Europe. PLoS Negl Trop Dis 10(4): e0004664. doi:10.1371/journal.pntd.0004664

Editor: Roberto Barrera, Centers for Disease Control and Prevention, Puerto Rico, UNITED STATES

Published: April 26, 2016

Copyright: © 2016 Akiner et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Funding: This work was carried out under the VectorNet framework contract OC/EFSA/AHAW/2013/02-FWC1 funded by the European Food Safety Authority (EFSA) and the European Centre for Disease prevention and Control (ECDC). The funders contributed to the study design, but had no role in data collection and analysis, decision to publish, or preparation of the manuscript.

Competing interests: I have read the journal’s policy and the authors of this manuscript have the following competing interests: Francis Schaffner is employed by the private company Avia-GIS, performing consultancy about vector surveillance and control, and producing software to support vector surveillance and mapping.

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The yellow fever and dengue mosquito Aedes aegypti previously flourished around the Mediterranean and Black Sea for decades until the 1950s, and was responsible of large outbreaks of both yellow fever and dengue [1]. The first well-described large dengue outbreak in Greece in 1927–28 caused more than 1 million cases (90% of the population in Athens) with 1000–1500 fatalities. The disappearance of Ae. aegypti from the European continent in Mediterranean, Black Sea, and Macaronesian biogeographical regions [2] is not well understood and its return in these regions raises concerns about a possible resurgence of the pathogens that can be transmitted by this vector species. Besides, the tiger mosquito Aedes albopictus is extending its distribution range worldwide, and it has already invaded large parts of the Mediterranean [1].

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Keywords: Research; Abstracts; Zika Virus; Chikungunya Fever; Dengue Fever; European Region; Aedes Aegypti, Aedes Albopictus.

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Assessing the potential #risk of #Zika #virus #epidemics in temperate areas with established #Aedes albopictus populations (@eurosurveillanc, edited)

[Source: Eurosurveillance, full page: (LINK). Edited.]

Eurosurveillance, Volume 21, Issue 15, 14 April 2016 / Rapid communication

Assessing the potential risk of Zika virus epidemics in temperate areas with established Aedes albopictus populations

G Guzzetta 1 , P Poletti 1 2 , F Montarsi 3 , F Baldacchino 4 , G Capelli 3 , A Rizzoli 4 , R Rosà 4 , S Merler 1

Author affiliations: 1. Fondazione Bruno Kessler, Trento, Italy; 2. Dondena Centre for Research on Social Dynamics and Public Policy, Bocconi University, Milan, Italy; 3. Istituto Zooprofilattico Sperimentale delle Venezie, Padova, Italy; 4. Department of Biodiversity and Molecular Ecology, Research and Innovation Centre, Fondazione Edmund Mach, San Michele all’Adige (Trento), Italy

Correspondence: Stefano Merler (merler@fbk.eu)

Citation style for this article: Guzzetta G, Poletti P, Montarsi F, Baldacchino F, Capelli G, Rizzoli A, Rosà R, Merler S. Assessing the potential risk of Zika virus epidemics in temperate areas with established Aedes albopictus populations. Euro Surveill. 2016;21(15):pii=30199. DOI: http://dx.doi.org/10.2807/1560-7917.ES.2016.21.15.30199

Received:25 March 2016; Accepted:14 April 2016

 

Abstract

Based on 2015 abundance of Aedes albopictus in nine northern Italian municipalities with temperate continental/oceanic climate, we estimated the basic reproductive number R0 for Zika virus (ZIKV) to be systematically below the epidemic threshold in most scenarios. Results were sensitive to the value of the probability of mosquito infection after biting a viraemic host. Therefore, further studies are required to improve models and predictions, namely evaluating vector competence and potential non-vector transmissions.

In 2015, the largest recorded epidemic of Zika virus (ZIKV) started in Brazil and has since then expanded progressively to most countries in Central and South America [1]. We provide estimates of the basic reproduction number (R0) of ZIKV in northern Italy, based on estimates of the mosquito abundance from entomological surveillance data.

 

Entomological surveillance in northern Italy

Aedes albopictus mosquitoes were collected using 54 Biogents Sentinel traps (Biogents AG, Regensburg, Germany, hereafter abbreviated as BG) baited with BG lures and CO2 from dry ice, running for 24 hours and placed by entomologists at selected locations in nine municipalities (Figure 1) at altitudes ranging from 74 m a.s.l. to 650 m a.s.l and geographical coordinates between 10°49’04.9”E and 12°12’54.2”E longitude and 45°53’26.9”N and 46°09’59.4”N latitude. Temperatures at trap locations were obtained from land surface temperature satellite data with a resolution of 250 m [2] (Figure 2).

 

Mosquito population dynamics

We developed a population model representing the developmental cycle of mosquitoes by means of temperature-dependent parameters (Figure 3) and fitted it to capture data in order to estimate the density of female adult mosquitoes per hectare over time at each municipality. For two towns (Belluno and Feltre), human landing captures were carried out (seven and five sessions, respectively) where BG traps were positioned. Two experts performed the catches, rotating between the two sites, acting as human baits and collectors. The mosquitoes were collected by a handheld aspirator during the three hours preceding sunset. Human landing data were used for independent validation of the local mosquito abundance predicted by the model.

The four main stages of the Aedes albopictus life cycle (eggs, larvae, pupae and adults) are modelled. Biological parameters encoding mortalities, developmental rates and the length of the gonotrophic cycle depend on the average daily temperature recorded at the site of capture, according to equations provided in [6] and based on experimental data [20]. The site-specific density-dependent factors and the capture rate (common to all sites) are free model parameters estimated by fitting model outputs to experimental capture data.

Given the model-predicted daily number of mosquitoes NV and the number of bites per mosquito per day k, the following relation should hold:

k NV = HLR T,

where HLR is the hourly human landing rate estimated from data and T is the average duration of biting activity during a day (set to 12 hours, based on several studies on daily landing patterns, e.g. [3]).

Figure 4 shows a comparison between observed trapping captures and corresponding model estimates over time for all nine sites considered. Values of the coefficient of determination R2, ranged between 0.47 and 0.87, depending on the site (average across sites: 0.71). Model-predicted hourly HLR (i.e. k × NV / T) were in good agreement with the observed HLR during 2015 (Figure 5; R2 = 0.57), thereby validating the use of model-predicted mosquito densities.

Model predictions shown as average and 95% confidence intervals over 10,000 stochastic simulations.

 

Basic reproduction number of Zika virus

We assumed that the only route of transmission for ZIKV is via mosquito bites. R0 can be calculated from densities of human and mosquito populations and several epidemiological parameters according to the following Formula [4]:

R0 = k2 pV pH g (lV / (mv (lV + mV)) (V/H)

Symbols, interpretations, values and literature references are reported in the Table.

When R0 < 1 (epidemic threshold), the probability of observing sustained transmission of ZIKV after importation of a case is negligible. When R0 > 1, the outbreak probability is given by the following Formula [5]:

p 0 = 1 − (RVH + 1) / (RVH (RHV + 1))

where RVH = k pV g (lV / (lV + mV)) (V/H)

and RHV = k (pH / mV).

Using baseline parameter values (Table), the expected value of R0 stayed far below the epidemic threshold of 1 at all sites and times in our simulations (Figure 6A), resulting in a low risk of autochthonous transmission of ZIKV.

We re-computed the values of R0 under a range of worst-case scenarios for parameter values and model assumptions. In all scenarios, all epidemiological parameters but one were fixed at their baseline values and sensitivity was assessed against variations of the selected parameter. Firstly, we set the mosquito biting rate (k) to the largest estimate for the 2007 Italian chikungunya virus outbreak (k = 0.16 days−1 [6]). In this scenario, the peak value of R0 never exceeded 0.8. Secondly, we assumed daily temperatures in the upcoming mosquito season to be 2 °C higher than those recorded in 2015 (an extreme scenario in climatological terms) under baseline parameter values. This resulted in an increase of the peak mosquito abundance of 17% to 95%, depending on the town; however, even in this case, R0 remained far from the epidemic threshold (peak values below 0.4 at all sites). Thirdly, R0 remained below 1 even when considering 100% human susceptibility to infection given a bite from an infected mosquito (pH) [7,8].

Finally, we considered the variability of R0 with respect to the probability of a mosquito being infected upon biting of a viraemic human host, pV. The very low baseline value (6.7%) was suggested by a recent experimental study [7], but previous work had estimated a value of 100% [8]. Resulting predictions were very sensitive to the value of this parameter. When we used the value provided by the latter study (pV = 100%), the peak value of R0 exceeded the epidemic threshold in seven of nine towns, with values as high as 3.8 in the highly mosquito-infested towns of Feltre and Riva del Garda (Figure 6B). In Strigno and Belluno, R0 remained systematically below the epidemic threshold because of the low ratio of mosquitoes per human (V/H in equations above). In all other towns, the minimum value of pV required to have R0 above 1 ranged from 25% to 50%.

We call epidemic season the time of the year when the local mosquito abundance is sufficiently high for R0 to exceed the epidemic threshold. According to model estimates, the epidemic season in the worst-case scenario of pV = 100% was predicted to last between two and three months in the seven towns at higher risk (Figure 6C). In this scenario, for every ZIKV case imported within the epidemic season, the average probability of observing an outbreak of local transmission ranged from 18% in Tenno to 39% in Feltre and Riva del Garda (Figure 6D).

 

Discussion

Although ZIKV infection in humans is generally asymptomatic or very mild, there is growing evidence of association with Guillain–Barré’ syndrome [9] and congenital neuronal defects in newborns [10,11]. The flow of international travellers to and from Latin America raises potential concerns for the occurrence of outbreaks also in Europe during the summer months when the mosquito activity is higher [12]. The Latin-American epidemic is likely to be driven by Ae. aegypti, a mosquito species that is currently present in Europe only in Madeira (Portugal) and around the Black Sea [13]. However, in many European countries Ae. albopictus is now endemic [13]. This species has been demonstrated to transmit ZIKV both in the laboratory [7,8] and in the wild [14], although its estimated transmission efficiency is much lower than measured for Ae. aegypti [7]. Based on data-driven estimates of the abundance of Ae. albopictus mosquitoes in nine municipalities of northern Italy, we expect a low risk of autochthonous mosquito-borne transmission of ZIKV. In addition, it must be considered that there is not yet sufficient evidence of the real vector competence of Ae. albopictus in the wild for the circulating strain. Indeed, there have not been any documented ZIKV outbreaks in Europe in the last decades, despite the repeated introductions of the virus by viraemic travellers. Our findings may be applicable to other areas of Europe with temperate climate [15] and with established Ae. albopictus populations [13], such as eastern France, central Europe and the Balkan states. Our predictions do not apply to Mediterranean areas where the risk may be substantially higher because climate conditions for Ae. albopictus are more favourable.

The most important source of variability in our results was the value for the mosquitoes’ susceptibility to infection. Two studies on vector competence provide tentative estimates: one where Ae. albopictus mosquitoes from a humid subtropical climate (Central Florida, United States) were infected with the Asian ZIKV genotype involved in the large South American outbreak [7], and one using Ae. albopictus from a tropical rainforest climate (Singapore) infected with an Ugandan ZIKV genotype [8]. We chose the first study as a baseline, because the viral strain used in the experimental setting was more relevant for the ongoing epidemic, and the second study to set the worst-case scenario (pV = 100%).

Additional sources of uncertainty come from sexual transmission of ZIKV [16]; much higher viral loads have been found in semen than in blood [17]; however, the relative contribution of non-vector transmission is currently not quantified. To improve models and predictions, further studies are required that evaluate the vector competence and capacity of European populations of Ae. albopictus for the circulating strain of ZIKV and the potentially related contributions of non-vector transmission.

 

Acknowledgements

We thank for mosquito collection Daniele Arnoldi, Francesca Bussola, Charlotte Lapère, Sara Carlin, Graziana Da Rold, Marco Dal Pont, Nicola Ferro Milone, Luca Tripepi. We thank Markus Metz and Markus Neteler for providing us with LST temperature data. This work was funded by the Autonomous Province of Trento (Italy), Research funds for Grandi Progetti, Project LExEM (Laboratory of excellence for epidemiology and modelling, http://www.lexem.eu).

Conflict of interest: None declared.

Authors’ contributions: GG, PP, AR, RR, GC and SM conceived of the study. FM and FB supervised field work. GG and PP performed the analysis. All authors contributed to interpret results. GG drafted the first version of the manuscript. All authors read and approved the final version of the manuscript.

 

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Keywords: Research; Abstracts; Zika Virus; Aedes Albopictus; Italy.

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#Zika #virus #outbreak in the #Americas: Is #Aedes albopictus an overlooked culprit? (BioRxIV, abstract)

[Source: BioRxIV, full page: (LINK). Abstract, edited.]

New Results

Zika virus outbreak in the Americas: Is Aedes albopictus an overlooked culprit?

Azeem Mehmood Butt, Izza Nasrullah, Raheel Qamar, Yigang Tong

doi: http://dx.doi.org/10.1101/044594

This article is a preprint and has not been peer-reviewed.

 

Abstract

Codon usage patterns of viruses reflect a series of evolutionary changes that enable viruses to shape their survival rates and fitness toward the external environment and, most importantly, their hosts. In the present study, we employed multiple codon usage analysis indices to determine genotype specific codon usage patterns of Zika virus (ZIKV) strains from the current outbreak and those reported previously. Several genotype specific and common codon usage traits were noted in ZIKV coding sequences, indicative of independent evolutionary origins from a common ancestor. The overall influence of natural selection was found to be more profound than that of mutation pressure and acting on specific set of viral genes belonging to ZIKV strains of Asian genotype from the recent outbreak. Furthermore, an interplay of codon adaptation and deoptimization have been observed in ZIKV genomes. The collective findings of codon analysis in association with the geographical data of Aedes populations in the Americas suggests that ZIKV have evolved a dynamic set of codon usage patterns in order to maintain a successful replication and transmission chain within multiple hosts and vectors.

Copyright: The copyright holder for this preprint is the author/funder. It is made available under a CC-BY-NC-ND 4.0 International license.

Keywords: Research; Abstracts; Zika Virus; Aedes Albopictus.

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#Global #risk of #Zika #virus depends critically on #vector #status of #Aedes albopictus (The Lancet Infect Dis., summary)

[Source: The Lancet Infectious Diseases, full page: (LINK). Summary.]

Correspondence

Global risk of Zika virus depends critically on vector status of Aedes albopictus

Lauren M Gardner, Nan Chen, Sahotra Sarkar

Published Online: 17 March 2016 / Publication stage: In Press Corrected Proof / DOI: http://dx.doi.org/10.1016/S1473-3099(16)00176-6

© 2016 Elsevier Ltd. All rights reserved.

 

Summary

Constância F J Ayres recently pointed out that Zika virus has been collected from several mosquito species including those from the genera, Anopheles, Culex, and Mansonia besides Aedes. Moreover, at least ten Aedes species are known to harbour Zika virus. However, the presence of the virus does not automatically make the species an efficient vector for the disease. It is, therefore, unfortunate that a recent risk map published in The Lancet considers Aedes aegypti and Aedes albopictus together. On the same basis, WHO has predicted that the virus will establish itself in all countries in the Americas except Canada and Chile.

(…)

Keywords: Research; Abstracts; Zika Virus; Aedes Albopictus.

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#Diagnostic #challenges to be considered regarding #Zika #virus in the context of the presence of the vector #Aedes albopictus in #Europe (@eurosurveillanc, extract)

[Source: Eurosurveillance, full page: (LINK). Extract.]

Eurosurveillance, Volume 21, Issue 10, 10 March 2016  / Letter

Letter to the editor: diagnostic challenges to be considered regarding Zika virus in the context of the presence of the vector Aedes albopictus in Europe [      ]

R Vorou 1

Author affiliations: 1. Unit for Strategic Development and Policy, Hellenic Center for Diseases Control and Prevention, Athens, Greece

Correspondence: Rengina Vorou ( vorou@keelpno.gr)

Citation style for this article: Vorou R. Letter to the editor: diagnostic challenges to be considered regarding Zika virus in the context of the presence of the vector Aedes albopictus in Europe. Euro Surveill. 2016;21(10):pii=30161. DOI: http://dx.doi.org/10.2807/1560-7917.ES.2016.21.10.30161

Received:04 March 2016; Accepted:10 March 2016

______

To the editor: The recent rapid communication by G. Venturi et al. [1] is very useful as it highlights infection by Zika virus, a flavivirus, as a differential diagnosis for patients presenting with a maculopapular rash accompanied with fever upon return to Europe from south-east Asia, the Pacific area islands, and Central and South America.

(…)

Keywords: Research; Abstracts; Zika Virus; Aedes Albopictus.

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Differential #Susceptibilities of #Aedes aegypti and Aedes albopictus from the #Americas to #Zika #Virus (PLoS Negl Trop Dis., abstract)

[Source: PLoS Neglected Tropical Diseases, full page: (LINK). Abstract, edited.]

Open Access / Peer-reviewed / Research Article

Differential Susceptibilities of Aedes aegypti and Aedes albopictus from the Americas to Zika Virus [      ]

Thais Chouin-Carneiro,  Anubis Vega-Rua,  Marie Vazeille,  André Yebakima,  Romain Girod,  Daniella Goindin,  Myrielle Dupont-Rouzeyrol,  … Ricardo Lourenço-de-Oliveira,  Anna-Bella Failloux

Published: March 3, 2016 / DOI: 10.1371/journal.pntd.0004543

 

Abstract

Background

Since the major outbreak in 2007 in the Yap Island, Zika virus (ZIKV) causing dengue-like syndromes has affected multiple islands of the South Pacific region. In May 2015, the virus was detected in Brazil and then spread through South and Central America. In December 2015, ZIKV was detected in French Guiana and Martinique. The aim of the study was to evaluate the vector competence of the mosquito spp. Aedes aegypti and Aedes albopictus from the Caribbean (Martinique, Guadeloupe), North America (southern United States), South America (Brazil, French Guiana) for the currently circulating Asian genotype of ZIKV isolated from a patient in April 2014 in New Caledonia.

Methodology/Principal Findings

Mosquitoes were orally exposed to an Asian genotype of ZIKV (NC-2014-5132). Upon exposure, engorged mosquitoes were maintained at 28°±1°C, a 16h:8h light:dark cycle and 80% humidity. 25–30 mosquitoes were processed at 4, 7 and 14 days post-infection (dpi). Mosquito bodies (thorax and abdomen), heads and saliva were analyzed to measure infection, dissemination and transmission, respectively. High infection but lower disseminated infection and transmission rates were observed for both Ae. aegypti and Ae. albopictus. Ae. aegypti populations from Guadeloupe and French Guiana exhibited a higher dissemination of ZIKV than the other Ae. aegypti populations examined. Transmission of ZIKV was observed in both mosquito species at 14 dpi but at a low level.

Conclusions/Significance

This study suggests that although susceptible to infection, Ae. aegypti and Ae. albopictus were unexpectedly low competent vectors for ZIKV. This may suggest that other factors such as the large naïve population for ZIKV and the high densities of human-biting mosquitoes contribute to the rapid spread of ZIKV during the current outbreak.

 

Author Summary

Zika virus (ZIKV) is an emerging mosquito-borne arbovirus causing dengue-like symptoms. This virus was commonly detected in Africa and Asia. Since its emergence in Yap Island in Micronesia in 2007, ZIKV reemerged in the South Pacific region in 2013 and ultimately reached the American continent in 2015. The human biting mosquito Aedes aegypti and the less anthropophilic Aedes albopictus have been incriminated as vectors of ZIKV. Our study showed that American populations of Ae. aegypti and Ae. albopictus were able to become infected and disseminate ZIKV within the mosquito general cavity at early days (4, 7) post-infection (dpi). Nevertheless, transmission was unexpectedly low and only detected at 14 dpi. Our findings will help in designing more adapted vector control strategies and limiting the impact of a new emerging threat on human health in the Americas as did the chikungunya in 2014.

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Citation: Chouin-Carneiro T, Vega-Rua A, Vazeille M, Yebakima A, Girod R, Goindin D, et al. (2016) Differential Susceptibilities of Aedes aegypti and Aedes albopictus from the Americas to Zika Virus. PLoS Negl Trop Dis 10(3): e0004543. doi:10.1371/journal.pntd.0004543

Editor: Michael J. Turell, United States Army Medical Research Institute of Infectious Diseases, UNITED STATES

Received: January 8, 2016; Accepted: February 24, 2016; Published: March 3, 2016

Copyright: © 2016 Chouin-Carneiro et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Data Availability: All relevant data are within the paper.

Funding: This study was funded by the Institut Pasteur, the French Government’s Investissement d’Avenir program, Laboratoire d’Excellence “Integrative Biology of Emerging Infectious Diseases” (grant n°ANR-10-LABX-62-IBEID). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Competing interests: The authors have declared that no competing interests exist.

Keywords: Research; Abstracts; Zika Virus; Aedes Aegypti; Aedes Albopictus.

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