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Climate Change, Dengue and Aedes Mosquitoes: Past Trends and Future Scenarios
Umeå universitet, Medicinska fakulteten, Institutionen för folkhälsa och klinisk medicin, Epidemiologi och global hälsa.
2018 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
Abstract [en]

Background Climate change, global travel and trade have facilitated the spread of Aedes mosquitoes and have consequently enabled the diseases they transmit (dengue fever, Chikungunya, Zika and yellow fever) to emerge and re-emerge in uninfected areas. Large dengue outbreaks occurred in Athens in 1927 and in Portuguese island, Madeira in 2012, but there are almost no recent reports of Aedes aegypti, the principal vector, in Europe. A dengue outbreak needs four conditions: sufficient susceptible humans, abundant Aedes vector, dengue virus introduction, and conducive climate. Can Aedes aegypti establish themselves again in Europe in the near future if they are introduced? How do the current and future climate affect dengue transmission globally, and regionally as in Europe? This thesis tries to answer these questions.

Methods Two process-based mathematical models were developed in this thesis. Model 1 describes a vector’s ability to transmit dengue – vectorial capacity – based on temperature and diurnal temperature range (DTR). Model 2 describes vector population dynamics based on the lifecycle of Aedes aegypti. From this model, vector abundance was estimated using both climate as a single driver, and climate together with human population and GDP as multiple drivers; vector population growth rate was derived as a threshold condition to estimate the vector’s invasion to a new place.

Results Using vectorial capacity, we estimate dengue epidemic potential globally for Aedes aegypti and in Europe for Aedes aegypti and Aedes albopictus. We show that mean temperature and DTR are both important in modelling dengue transmission, especially in a temperate climate zone like Europe. Currently, South Europe is over the threshold for dengue epidemics if sufficient dengue vectors are present. Aedes aegypti is on the borderline of invasion into the southern tip of Europe. However, by end of this century, the invasion of Aedes aegypti may reach as far north as the middle of Europe under the business-as-usual climate scenario. Or it may be restricted to the south Europe from the middle of the century if the low carbon emission – Paris Agreement – is implemented to limit global warming to below 2°C.

Conclusion Climate change will increase the area and time window for Aedes aegypti’s invasion and consequently the dengue epidemic potential globally, and in Europe in particular. Successfully achieving the Paris Agreement would considerably change the future risk scenario of a highly competent vector – Aedes aegypti’s – invasion into Europe. Therefore, the risk of transmission of dengue and other infectious diseases to the mainland of Europe depends largely on human efforts to mitigate climate change.

Abstract [sv]

Bakgrund Klimatförändringar tillsammans med en ökad frekvens av globala resor och handel har gynnat spridningen av Aedes-myggor och möjliggjort att de sjukdomar som de överför (dengue feber, Chikungunya, Zika och gul feber) etablerar sig i tidigare oinfekterade områden. Det två största utbrotten av dengue i Europa inträffade i Aten 1927 och på den portugisiska ön Madeira 2012 orsakades av Aedes aegypti, men i de allra flesta delar i Europa finns inga rapporter om Aedes aegypti. Ett utbrott av dengue kräver att fyra villkor uppfylls: tillräckligt mottagliga människor, rikligt med Aedes-vektorer, introduktion av dengue-virus, och ett gynnsamt klimat. En stor fråga idag är om Aedes aegypti kan etableras igen i Europa i ett förändrat klimat, och hur nuvarande och framtida klimatförhållanden möjligör dengue smittspridning globalt och regionalt i Europa. Denna avhandling försöker svara på dessa frågor.

Metoder Två processbaserade matematiska modeller utvecklades i arbetet med denna avhandling. En av modellerna beskriver vektorns förmåga att överföra dengue – vektorkapaciteten – baserat på temperatur och dyngstemperaturens varation (DTR). Den andra modellen beskriver vektorpopulationens dynamik baserat på myggans livscykel. Myggornas populationsdynamik och populationstäthet uppskattades med en modell baserat på enbart klimat, samt en modell baserat på klimat, mänsklig befolkning och BNP. Vektorgruppens tillväxthastighet härleddes som ett tröskelvärde för att uppskatta vektorernas invasionsbenägenhet till nya områden i takt med att klimatet förändras.

Resultat Med hjälp av vektorkapacitetmodellen uppskattade vi den epidemiska potentialen av dengue smittad av Aedes aegypti globalt och i Europa av Aedes aegypti och Aedes albopictus. Vi visar att den genomsnittliga temperaturen och DTR båda är viktiga för dengue myggornas kapacitet att starta epidemier, särskilt i tempererade klimatzoner, så som Europa. För närvarande är Syd-Europa tillräckligt gynnsamt för dengueepidemier vissa tider på året om myggpopulationerna är tillräckligt stora. Vi visat att Aedes aegypti möjligen kan etablera sig längs Europas södra utkanter idag. I slutet av detta århundrade kan invasionen av Aedes aegypti nå så långt norrut till mitten av Europa om vi inte begränsar klimatutsläppen mer än vad vi gör idag. Om vi följer klimatavtalet från Paris 2015 där den globala uppvärmningen begränsar till under 2 grader kan invasionen troligtvis förhindras, eller i vilket fall kraftigt begränsas i Europa.

Slutsats Ett varmare klimat kommer att öka antalet geografiska områdena i Europa som är gynnsamt för Aedes aegypti. Det kommer även öka tidsfönstret för vektorernas epidemiska potential globalt, och i synnerhet för Europa. En framgångsrik implementering av klimatavtalet från 2015, som riktar sig mot att begränsa uppvärmingen till under 2 grader, skulle väsentligt minska risken för en framtida invasion av dengue, zika och chikungunya i Europa. Därför beror risken för dengueöverföring och andra infektionssjukdomar i södra Europa till stor del på mänskliga ansträngningar för att med utsläppsminskningar av växthusgaser kontrollera klimatförändringen.

Ort, förlag, år, upplaga, sidor
Umeå: Umeå universitet , 2018. , s. 100
Serie
Umeå University medical dissertations, ISSN 0346-6612 ; 1931
Nyckelord [en]
dengue, mathematical modelling, vectorial capacity, DTR, Aedes aegypti, Aedes albopictus, climate change, Europe, vector invasion, abundance
Nyckelord [sv]
dengue, matematisk modellering, vektorkapacitet, DTR, Aedes aegypti, Aedes albopictus, klimatförändring, Europa, vektor invasion
Nationell ämneskategori
Folkhälsovetenskap, global hälsa, socialmedicin och epidemiologi
Forskningsämne
epidemiologi
Identifikatorer
URN: urn:nbn:se:umu:diva-143764ISBN: 978-91-7601-798-2 (tryckt)OAI: oai:DiVA.org:umu-143764DiVA, id: diva2:1172083
Disputation
2018-02-02, Hörsal D, Tandläkarhögskolan, By1D, 9 tr, Norrlands universitetssjukhus, Umeå, 09:00 (Engelska)
Opponent
Handledare
Tillgänglig från: 2018-01-12 Skapad: 2018-01-09 Senast uppdaterad: 2018-06-09Bibliografiskt granskad
Delarbeten
1. Vectorial capacity of Aedes aegypti: Effects of temperature and implications for global dengue epidemic potential
Öppna denna publikation i ny flik eller fönster >>Vectorial capacity of Aedes aegypti: Effects of temperature and implications for global dengue epidemic potential
2014 (Engelska)Ingår i: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 9, nr 3, artikel-id e89783Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

Dengue is a mosquito-borne viral disease that occurs mainly in the tropics and subtropics but has a high potential to spread to new areas. Dengue infections are climate sensitive, so it is important to better understand how changing climate factors affect the potential for geographic spread and future dengue epidemics. Vectorial capacity (VC) describes a vector's propensity to transmit dengue taking into account human, virus, and vector interactions. VC is highly temperature dependent, but most dengue models only take mean temperature values into account. Recent evidence shows that diurnal temperature range (DTR) plays an important role in influencing the behavior of the primary dengue vector Aedes aegypti. In this study, we used relative VC to estimate dengue epidemic potential (DEP) based on the temperature and DTR dependence of the parameters of A. aegypti. We found a strong temperature dependence of DEP; it peaked at a mean temperature of 29.3°C when DTR was 0°C and at 20°C when DTR was 20°C. Increasing average temperatures up to 29°C led to an increased DEP, but temperatures above 29°C reduced DEP. In tropical areas where the mean temperatures are close to 29°C, a small DTR increased DEP while a large DTR reduced it. In cold to temperate or extremely hot climates where the mean temperatures are far from 29°C, increasing DTR was associated with increasing DEP. Incorporating these findings using historical and predicted temperature and DTR over a two hundred year period (1901–2099), we found an increasing trend of global DEP in temperate regions. Small increases in DEP were observed over the last 100 years and large increases are expected by the end of this century in temperate Northern Hemisphere regions using climate change projections. These findings illustrate the importance of including DTR when mapping DEP based on VC.

Ort, förlag, år, upplaga, sidor
San Francisco: Public Library of Science, 2014
Nationell ämneskategori
Folkhälsovetenskap, global hälsa, socialmedicin och epidemiologi
Identifikatorer
urn:nbn:se:umu:diva-87872 (URN)10.1371/journal.pone.0089783 (DOI)000332483600022 ()24603439 (PubMedID)
Tillgänglig från: 2014-04-15 Skapad: 2014-04-14 Senast uppdaterad: 2018-06-08Bibliografiskt granskad
2. Climate change and Aedes vectors: 21st century projections for dengue transmission in Europe
Öppna denna publikation i ny flik eller fönster >>Climate change and Aedes vectors: 21st century projections for dengue transmission in Europe
Visa övriga...
2016 (Engelska)Ingår i: EBioMedicine, ISSN 0360-0637, E-ISSN 2352-3964, Vol. 7, s. 267-277Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

Warming temperatures may increase the geographic spread of vector-borne diseases into temperate areas. Although a tropical mosquito-borne viral disease, a dengue outbreak occurred in Madeira, Portugal, in 2012; the first in Europe since 1920s. This outbreak emphasizes the potential for dengue re-emergence in Europe given changing climates. We present estimates of dengue epidemic potential using vectorial capacity (VC) based on historic and projected temperature (1901–2099). VC indicates the vectors' ability to spread disease among humans. We calculated temperature-dependent VC for Europe, highlighting 10 European cities and three non-European reference cities. Compared with the tropics, Europe shows pronounced seasonality and geographical heterogeneity. Although low, VC during summer is currently sufficient for dengue outbreaks in Southern Europe to commence–if sufficient vector populations (either Ae. aegypti and Ae. albopictus) were active and virus were introduced. Under various climate change scenarios, the seasonal peak and time window for dengue epidemic potential increases during the 21st century. Our study maps dengue epidemic potential in Europe and identifies seasonal time windows when major cities are most conducive for dengue transmission from 1901 to 2099. Our findings illustrate, that besides vector control, mitigating greenhouse gas emissions crucially reduces the future epidemic potential of dengue in Europe.

Ort, förlag, år, upplaga, sidor
Elsevier, 2016
Nyckelord
Dengue, Vectorial capacity, Aedes aegypti, Aedes albopictus, Temperature, Climate change
Nationell ämneskategori
Folkhälsovetenskap, global hälsa, socialmedicin och epidemiologi
Identifikatorer
urn:nbn:se:umu:diva-118643 (URN)10.1016/j.ebiom.2016.03.046 (DOI)000377459700039 ()27322480 (PubMedID)
Forskningsfinansiär
EU, FP7, Sjunde ramprogrammet, 282589
Anmärkning

This study is part of the DengueTools project funded by the European Union Seventh Framework Programme FP7/2007-2013 under grant agreement no. 282589.

Originally included in thesis 1 as submitted manuscript.

Tillgänglig från: 2016-03-28 Skapad: 2016-03-28 Senast uppdaterad: 2018-06-07Bibliografiskt granskad
3. Estimating past, present and future trends in the global distribution and abundance of the arbovirus vector Aedes aegypti
Öppna denna publikation i ny flik eller fönster >>Estimating past, present and future trends in the global distribution and abundance of the arbovirus vector Aedes aegypti
2019 (Engelska)Ingår i: Frontiers In Public Health, ISSN 2296-2565, Vol. 7, artikel-id 148Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

Background: Aedes aegypti is the principal vector for several important arbovirus diseases, including dengue, chikungunya, yellow fever, and Zika. While recent empirical research has attempted to identify the current global distribution of the vector, the seasonal, and longer-term dynamics of the mosquito in response to trends in climate, population, and economic development over the twentieth and the twenty-first century remains to be elucidated.

Methods: In this study, we use a process-based mathematical model to estimate global vector distribution and abundance. The model is based on the lifecycle of the vector and its dependence on climate, and the model sensitivity to socio-economic development is tested. Model parameters were generally empirically based, and the model was calibrated to global databases and time series of occurrence and abundance records. Climate data on temperature and rainfall were taken from CRU TS3.25 (1901–2015) and five global circulation models (CMIP5; 2006–2099) forced by a high-end (RCP8.5) and a low-end (RCP2.6) emission scenario. Socio-economic data on global GDP and human population density were from ISIMIP (1950–2099).

Findings: The change in the potential of global abundance in A. aegypti over the last century up to today is estimated to be an increase of 9.5% globally and a further increase of 20 or 30% by the end of this century under a low compared to a high carbon emission future, respectively. The largest increase has occurred in the last two decades, indicating a tipping point in climate-driven global abundance which will be stabilized at the earliest in the mid-twenty-first century. The realized abundance is estimated to be sensitive to socioeconomic development.

Interpretation: Our data indicate that climate change mitigation, i.e., following the Paris Agreement, could considerably help in suppressing risks of increased abundance and emergence of A. aegypti globally in the second half of the twenty-first century.

Ort, förlag, år, upplaga, sidor
Frontiers Media S.A., 2019
Nyckelord
Aedes aegypti, mathematical model, vector abundance, temperature, precipitation, climate change, socioeconomic factors, global vector abundance
Nationell ämneskategori
Folkhälsovetenskap, global hälsa, socialmedicin och epidemiologi
Identifikatorer
urn:nbn:se:umu:diva-143762 (URN)10.3389/fpubh.2019.00148 (DOI)000472667800001 ()31249824 (PubMedID)
Forskningsfinansiär
EU, Horisont 2020, 734584Vetenskapsrådet, 2015-03917Forskningsrådet Formas, 2017-01300
Anmärkning

Originally included in thesis in manuscript form.

Tillgänglig från: 2018-01-09 Skapad: 2018-01-09 Senast uppdaterad: 2020-05-06Bibliografiskt granskad
4. Climate change may enable Aedes aegypti infestation in major European cities by 2100
Öppna denna publikation i ny flik eller fönster >>Climate change may enable Aedes aegypti infestation in major European cities by 2100
2019 (Engelska)Ingår i: Environmental Research, ISSN 0013-9351, E-ISSN 1096-0953, Vol. 172, s. 693-699Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

Background: Climate change allows Aedes aegyptito infest new areas. Consequently, it enables the arboviruses the mosquito transmits - e.g., dengue, chikungunya, Zika and yellow fever – to emerge in previously uninfected areas. An example is the Portuguese island of Madeira during 2012–13.

Objective: We aim to understand how climate change will affect the future spread of this potent vector, as an aidin assessing the risk of disease outbreaks and effectively allocating resources for vector control.

Methods: We used an empirically-informed, process-based mathematical model to study the feasibility of Aedes aegypti infestation into continental Europe. Based on established global climate-change scenario data, we assess the potential of Aedes aegypti to establish in Europe over the 21st century by estimating the vector population growth rate for five climate models (GCM5).

Results: In a low carbon emission future (RCP2.6), we find minimal change to the current situation throughout the whole of the 21st century. In a high carbon future (RCP8.5), a large parts of southern Europe risks being invaded by Aedes aegypti.

Conclusion: Our results show that successfully enforcing the Paris Agreement by limiting global warming to below 2 °C significantly lowers the risk for infestation of Aedes aegypti and consequently of potential large-scale arboviral disease outbreaks in Europe within the 21st century.

Ort, förlag, år, upplaga, sidor
Elsevier, 2019
Nyckelord
Aedes aegypti, Vector invasion, Europe, Climate change
Nationell ämneskategori
Folkhälsovetenskap, global hälsa, socialmedicin och epidemiologi Klimatforskning
Identifikatorer
urn:nbn:se:umu:diva-143763 (URN)10.1016/j.envres.2019.02.026 (DOI)000468377500079 ()30884421 (PubMedID)
Forskningsfinansiär
Vetenskapsrådet, 2015-03917Forskningsrådet Formas, 2017-01300
Anmärkning

Originally included in thesis in manuscript form with title "Climate change may enable Aedes aegypti mosquitoes infestation in major European cities by 2100"

Tillgänglig från: 2018-01-09 Skapad: 2018-01-09 Senast uppdaterad: 2019-06-20Bibliografiskt granskad

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