Abstract
In the last decades, several European countries where arboviral infections are not endemic have faced outbreaks of diseases such as chikungunya and dengue, initially introduced by infectious travellers from tropical endemic areas and then spread locally via mosquito bites. To keep in check the epidemiological risk, interventions targeted to control vector abundance can be implemented by local authorities. We assessed the epidemiological effectiveness and economic costs and benefits of routine larviciding in European towns with temperate climate, using a mathematical model of Aedes albopictus populations and viral transmission, calibrated on entomological surveillance data collected from ten municipalities in Northern Italy during 2014 and 2015.We found that routine larviciding of public catch basins can limit both the risk of autochthonous transmission and the size of potential epidemics. Ideal larvicide interventions should be timed in such a way to cover the month of July. Optimally timed larviciding can reduce locally transmitted cases of chikungunya by 20% - 33% for a single application (dengue: 18–22%) and up to 43% - 65% if treatment is repeated four times throughout the season (dengue: 31–51%). In larger municipalities (>35,000 inhabitants), the cost of comprehensive larviciding over the whole urban area overcomes potential health benefits related to preventing cases of disease, suggesting the adoption of more localized interventions. Small/medium sized towns with high mosquito abundance will likely have a positive cost-benefit balance. Involvement of private citizens in routine larviciding activities further reduces transmission risks but with disproportionate costs of intervention. International travels and the incidence of mosquito-borne diseases are increasing worldwide, exposing a growing number of European citizens to higher risks of potential outbreaks. Results from this study may support the planning and timing of interventions aimed to reduce the probability of autochthonous transmission as well as the nuisance for local populations living in temperate areas of Europe.
Highlights
During the last decade, Europe has faced outbreaks of mosquito-borne diseases (MBD) such as dengue and chikungunya, following the continuous importation of human cases in areas with established competent vectors such as the invasive mosquito Aedes (Stegomyia) albopictus (Skuse) [1]
Larvicides are a key tool to prevent the growth of mosquito populations and decrease both the risks of outbreaks of mosquito-borne diseases and the nuisance deriving from bites
In order to assist municipalities from temperate areas in Europe in effectively planning vector control programs, we modelled the effect of larviciding in public areas on populations of Aedes albopictus using mosquito collection data from 10 municipalities in Northern Italy, over two years with very different temperature conditions
Summary
Europe has faced outbreaks of mosquito-borne diseases (MBD) such as dengue and chikungunya, following the continuous importation of human cases in areas with established competent vectors such as the invasive mosquito Aedes (Stegomyia) albopictus (Skuse) [1]. Adulticide spraying rapidly reduces the number of mosquitoes, but its effect is short-lived [2] For this reason, it is indicated in situations where the transmission risk needs to be reduced drastically and quickly, such as when an individual is diagnosed with an MBD, to prevent or curtail an outbreak [3]. The main limit to larviciding as a control option is the proportion of breeding sites that are accessible to interventions by public health authorities. To overcome this limit, education campaigns may be carried forward to encourage citizens to remove and treat potential breeding sites from their private premises during the mosquito season [6, 7]. Mathematical modelling of MBD associated with cost-effectiveness analyses can help optimizing routine vector control interventions [8] with respect to constraints in human and financial resources [9]
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