Seasonal monitoring of Aedes albopictus: practical applications and outcomes (original) (raw)
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Aedes albopictus (Diptera: Culicidae) Monitoring in the Lazio Region (Central Italy)
Journal of Medical Entomology, 2020
The Asian tiger mosquito Aedes albopictus (Skuse 1894) is assuming an ever-increasing importance as invasive species in Europe and consequently as human health and nuisance concern. In Central Italy, the species has been recently involved in a chikungunya outbreak. A 3 yr Ae. albopictus monitoring was carried out in 21 municipalities of the Lazio region (Central Italy), belonging to three provinces. Samplings were performed on a weekly basis using ovitraps, in order to investigate climatic and spatial variables driving egg abundance and Ae. albopictus period of activity. A temperature of 10.4°C was indicated as lower threshold for the onset of egg-laying activity, together with a photoperiod of 13:11 (L:D) h. The whole oviposition activity lasted 8 mo (May–December), with 95% of eggs laid between early June and mid-November and a peak at the end of August. Egg abundance was positively influenced by accumulated temperature (AT) of the 4 wk preceding sampling and negatively by precipi...
PLOS Neglected Tropical Diseases, 2016
Seasonal-long larvicide treatments and/or outdoor space-spray applications of insecticides are frequently applied to reduce Aedes albopictus nuisance in urban areas of temperate regions, where the species has become a permanent pest affecting people's quality of life and health. However, assessments of the effectiveness of sequential interventions is a difficult task, as it requires to take into account the cumulative and combined effect of multiple treatments, as well as the mosquito seasonal dynamics (rather than mosquito abundance before and after single treatments). We here present the results of the effectiveness assessment of a seasonal-long calendar-based control intervention integrating larvicide treatments of street catch basins and night-time adulticide ground spraying in the main University hospital in Rome (Italy). Cage-experiments and an intensive monitoring of wild mosquito abundance in treated and untreated sites were carried out along an entire season. Sticky traps were used to monitor adult abundance and site-specific eco-climatic variations (by recording water left over in each trap), in order to disentangle the effect of insecticide treatments from eco-climatic drivers on mosquito seasonal dynamics. Despite the apparent limited impact of single adulticide sprayings assessed based on mortality in caged and wild mosquitoes, the results of the temporal analysis showed that mosquito seasonal patterns were initially comparable in the two sites, diverged in the absence of diverging eco-climatic conditions and remained stable afterwards. This allowed to attribute the lack of the expected Ae. albopictus population expansion in the treated site to the combined effect of multiple adulticide sprayings and larvicide treatments carried out during the whole season. The approach proposed was proved to be successful to assess effects of seasonal-long control treatments on adult mosquito population dynamics and could represent a valuable instrument to assess the effectiveness of other control interventions, to evaluate their actual cost-benefits and to possibly minimize space-spraying applications to reduce mosquito nuisance.
Journal of Vector Ecology, 2011
The chikungunya virus outbreak that occurred in 2007 in northern Italy (Emilia-Romagna region) prompted the development of a large scale monitoring system of the population density of Aedes albopictus (Skuse, 1894), comparable at the provincial and municipal levels. In 2007, egg density data presented an aggregated distribution (VMR >1) and Taylor's power law was applied to calculate the minimum number of ovitraps needed to obtain the prefixed precision levels: D=0.2 in the areas where the chikungunya epidemic occurred and D=0.3 in all the other urban areas >600 ha. The estimated minimum ovitrap number was then used to set up a monitoring network at the regional scale in season 2008 (May-October). In 242 municipalities 2,741 ovitraps were activated and the 2008 sampled data showed a similar aggregated distribution as in 2007. The adequacy of the monitoring design was evaluated by recalculating the Taylor's coefficients and the minimum ovitrap number for each urban area >600 ha using the 2008 egg density data. The comparison between the two estimates showed that the minimum ovitrap number calculated in 2007 was underestimated by 2.7% in weeks 22-41 but was overestimated by 29.4% if referring to the period of highest population density (weeks 27-37). The low cost of the proposed monitoring system, based on the use of fortnightly checked ovitraps, could make it economically sustainable even in a non-epidemic season. Journal of Vector Ecology 36 (1): 108-116. 2011.
Aedes albopictus, the Asian tiger mosquito, originates from the tropical and subtropical regions of Southeast Asia. Over the recent decades it has been passively spread across the globe, primarily through the used tyre trade and passive transportation along major traffic routes. A. albopictus is a proven vector for many arboviruses, most notably chikungunya and dengue, with recent outbreaks also in continental Europe. In southern Switzerland, in the Canton of Ticino A. albopictus was spotted for the first time in 2003. Since then the local authorities have implemented a control programme based on larval source reduction. Despite these efforts, mosquito densities have increased over the last decade, casting doubts on the effectiveness of such larval control programmes.
Since its introduction and establishment in Italy during the early 1990s, the Asian tiger mosquito, Aedes albopictus, has spread over large parts of Italy and other Mediterranean countries. Aedes albopictus is both a nuisance and a competent vector for various arthropod-borne pathogens. Although efficient traps for Ae. albopictus exist and are used for population monitoring, their use as a control tool has not yet been studied. We evaluated Biogents BG-Sentinel mosquito traps, used with the BG Lure, as control tools in northern Italy. The trial was performed as a controlled experiment in which 3 intervention sites, equipped with 7 or 8 BG-Sentinel traps each, were matched with 3 comparable control sites. Trap density ranged from 1 trap per 150 m2 to 1 per 350 m2. Mosquito populations were monitored at both the intervention and control sites with weekly human landing collections (HLC) and ovitraps. Between 64% and 87% fewer Ae. albopictus individuals were collected by HLC at the intervention sites with the BG-Sentinel mosquito traps, as compared to the untreated control sites. These results indicate that the sustained use and proper placement of efficient mosquito traps can significantly reduce Ae. albopictus biting pressure.
Parasites & vectors, 2015
In Ticino, a canton located south of the Alps in Switzerland, a surveillance programme on Aedes albopictus (Stegomyia albopicta) started in 2000 seeing that the region was considered at high risk of introduction based on the rapid spread of this mosquito in neighbouring Italy. The surveillance programme, which is still ongoing, was adapted continuously to handle preventive measures of arrival, dispersal and establishment of this invasive species. The monitoring was based on ovitraps supported by reports from the population. The integrated control measures included removal of breeding sites, larvicide applications with Bacillus thuringiensis israelensis or diflubenzuron and, in some circumstances, adulticide applications with permethrin. These measures involved citizens, municipalities and Civil Protection Units. Ae. albopictus was first observed in 2003 in Ticino. We describe the strategies adopted and their adaptations to the evolving problem since year 2000. The approach used allo...
Transactions of the Royal Society of Tropical Medicine and Hygiene, 2011
This study was undertaken to evaluate the effectiveness of four complementary and combined strategies to minimize the presence of the invasive mosquito Aedes albopictus, firmly established in Sant Cugat del Vallès, Catalonia, Spain. A quasi-experimental design including six neighbourhoods was performed in 2008-2009. The abundance of mosquitoes was monitored through ovitraps. The multiple intervention strategy consisted of four actions: source reduction; larvicide treatments (Bacillus thuringiensis israelensis and diflubenzuron); adulticide treatments (alfacipermetrin); and cleaning up uncontrolled landfills. The results showed the number of eggs significantly reduced in the areas with intervention. In 2008, the accumulate median of eggs was 175 and 272 in the intervention and control areas, respectively. In 2009, these medians were 884 and 1668 eggs. In total, 3104 households were visited and 683 people were interviewed. During inspections inside the houses, the cooperation of citizens in 2009 was 16% higher than that in 2008 (95% CI 13-19%). These findings suggest that the strategy was effective in reducing the number of eggs. Citizen cooperation, an essential factor for success, was observed through a high level of collaboration by the home owners, who allowed entry into their private dwellings. This study could be a model for controlling the populations of Ae. albopictus in the Mediterranean region.
Monitoring of Aedes albopictus (Diptera, Cilicidae) in Calabria, Southern Italy
Abstract — A control program currently active in Calabria (southern Italy) was carried out to population density estimation of Aedes (Stegomyia) albopictus (Skuse, 1894) (Diptera, Culicidae). For the first time we report on the spatial and temporal (seasonal) distribution of the mosquito in the urban area of Cosenza and Rende by ovitrap, from May, 2013 through the mid October, 2013. In spring and summer season 2013, ovitraps were activated according to standard and guidelines and were checked on average weekly. The peak of adult abun-dance occurs from July to first part of October. The aim was assess the mosquito population’s aggregation degree, through the application of the Taylor’s power law and to study the distribution and phenology of this mosquito. Index Terms — population density, spatial and temporal (seasonal) distribution, Aedes albopictus
Vector-Borne and Zoonotic Diseases, 2010
The Asian tiger mosquito, Aedes albopictus, has colonized nearly all the regions of Italy as well as other areas of Europe. During the summer of 2007 the tiger mosquito was responsible for an outbreak of Chikungunya in Italy, when this virus was brought in by a tourist of Indian origin returning from an endemic area. To increase the knowledge of tiger mosquito population dynamics, a survey was carried out from April to November 2008 in the municipalities of Arco and Riva del Garda (northern Italy) through a Biogents SentinelÔ (BG)-trap sampling. In particular, the aim of the study was to evaluate the influence of temperature and rainfall on the activity and dynamics of A. albopictus host-seeking females. The seasonal emergence of host-seeking females was strongly influenced by the minimum temperature, and a lower threshold of 138C was identified. In addition, the threshold for the end of adult activity was found at a minimum temperature of 98C. Host-seeking female abundance was positively affected by the accumulated temperatures over the period 3 and 4 weeks before the sampling week, possibly as a consequence of the positive effect of accumulated temperatures on larval density. Instead, accumulated precipitation over 1-4 weeks before sampling was negatively correlated with host-seeking female abundance. Finally, the activity of host-seeking females, estimated by the weekly increment in female abundance, was positively affected by the total abundance of females and by mean weekly temperatures. Our study provides useful information for predicting the dynamics of host-seeking Ae. albopictus females in northern Italy and for designing control strategies for preventing arbovirus outbreaks in areas colonized by Ae. albopictus.
Vector-Borne and Zoonotic Diseases, 2010
Knowledge of the frequency of contact between a mosquito species and its different hosts is essential to understand the role of each vector species in the transmission of diseases to humans and=or animals. However, no data are so far available on the feeding habits of Aedes albopictus in Italy or in other recently colonized temperate regions of Europe, due to difficulties in collecting blood-fed females of this diurnal and exophilic species. We analyzed Ae. albopictus host-feeding patterns in two urban and two rural sites within the area of Rome (Italy). Ae. albopictus was collected using sticky-traps and the blood-meal origin of 303 females was determined by direct dot-ELISA. The blood-fed sample, although representing only 4% of the total Ae. albopictus collected, demonstrates the useful application of sticky-trap in studying the feeding behavior of the species. The human blood index was significantly different among sites, ranging from 79-96% in urban sites to 23-55% in rural sites, where horses and bovines represented the most bitten hosts. The results obtained confirm the plastic feeding behavior shown by Ae. albopictus in its original range of distribution and highlights the high potential of this species as a vector of human pathogens in urban areas of Italy, where both humans and the mosquito itself may reach very high densities.