Aedes albopictus in Italy and possible diffusion of the species into the Mediterranean area

Aedes albopictus (Skuse), the important Asian vector mosquito recently introduced in United States and Brazil, is reported from Genoa, North Italy. The infestation was discovered in a kindergarten pre-school center in September 1990 just after the summer holidays. Many discarded tires, well known to provide excellent breeding places for Ae albopictus, had been left in the school playground to be used as toys by the children. After sampling a few biting mosquito specimens for identification, the local health service carried out on September 18 an extensive indoor/outdoor treatment with pyrethroid insecticide. The extent of the infestation in the city of Genoa and in other areas of the Ligurian region has not been evaluated since the identification of the species was available in October, at the end of Ae albopictus reproductive period. A general survey in various Italian regions is being planned for the 1991 spring-summer period. The present record, together with the previous report of Ae albopictus in Albania, clearly supports the hypothesis of a spreading of the species in the Mediterranean area.     

Are Aedes albopictus or other mosquito species from northern Italy competent to sustain new arboviral outbreaks?

The Asian tiger mosquito Aedes albopictus (Skuse) (Diptera: Culicidae), native to Southeast Asia, has extended its geographical distribution to invade new temperate and tropical regions. This species was introduced in 1990 to Italy and has since become the main pest in urban settings. It was incriminated as a principal vector in the first European outbreak of chikungunya virus (CHIKV) in the province of Ravenna (Italy) in 2007. This outbreak was associated with CHIKV E1-226V, efficiently transmitted by Ae. albopictus . The occurrence of this outbreak in a temperate country led us to estimate the potential of Ae. albopictus to transmit CHIKV and dengue virus (DENV), and to determine the susceptibility to CHIKV of other mosquito species collected in northern Italy. Experimental infections showed that Ae. albopictus exhibited high disseminated infection rates for CHIKV (75.0% in Alessandria; 90.3% in San Lazzaro) and low disseminated infection rates for DENV-2 (14.3% in San Lazzaro; 38.5% in Alessandria). Moreover, Ae. albopictus was able to attain a high level of viral replication, with CHIKV detectable in the salivary glands at day 2 after infection. In addition, the other three mosquito species, Anopheles maculipennis Meigen, Aedes vexans vexans (Meigen) and Culex pipiens L., showed variable susceptibilities to infection with CHIKV, of 0%, 7.7% and 0–33%, respectively. This information on vector competence is crucial in assessing the risk for an outbreak of CHIKV or DENV in Italy.     

Further data on the spread to Genoa of Aedes albopictus]

Further data are presented on the presence of Aedes albopictus in the town of Genoa (Italy) where this oriental mosquito was first reported in September 1990. Scattered foci of Ae albopictus were documented during the 1991 summer months in spite of a rather long and rigid '90-'91 winter season with temperatures frequently below 0 degree C. The newly imported mosquito shows the capacity to become a permanent pest in Italy where it could also increase the probability of transmission of pathogens such as arboviruses and filariae.     

Chikungunya epidemic outbreak in Emilia-Romagna (Italy) during summer 2007

During summer 2007, an outbreak due to the local transmission of CHIKV by Aedes albopictus mosquitoes occurred moreover in Italy, Emilia-Romagna Region, in the areas of Ravenna, Forli-Cesena, Rimini and Bologna cities. The original outbreak developed in Castiglione di Cervia and Castiglione di Ravenna, two small villages divided by a river. The first case was recorded on August 9th the epidemic outbreak then spread out, thus giving rise to smaller secondary outbreaks and further sporadic cases in the same area, for a total of 337 suspected cases, 217 of which confirmed by blood analysis. CHIKV has been isolated and characterized on both blood and mosquito samples.     

Reappearance of Aedes albopictus in Sardinia

Aedes (Stegomyia) albopictus is a vector of major human diseases. From 1979 established populations were found in the Mediterranean Region. The first record of Ae. albopictus in Italy goes back to 1990 and at present it is permanently established in several provinces of central and northern Italy. Ae. albopictus was detected for the first time in Sardinia in 1995, and a new record was reported in 1997. After these two isolated episodes, the "tiger-mosquito" was considered apparently eradicated. At the end of September 2006, two natural breeding populations including adults of Ae. albopictus were recorded in two different localities of South-Sardinia: in the botanical garden of downtown Cagliari and in a private garden of a small village, Teulada, on the south-western coast of Sardinia. The origin of this new introduction of Ae. albopictus in Sardinia is still unclear. In both cases the species has been found in artificial containers in densely populated areas.     

An overview of the lesson learned in almost 20 years of fight against the "tiger" mosquito

Since its introduction in Italy in 1990, Aedes albopictus has spread quickly across the country, being at present reported in scattered foci in all regions below 600 m of altitude. The most important items of the lesson learned in almost 20 years of fight against the "Tiger" in Italy are here reported and discussed.     

Blood-feeding preferences of Aedes albopictus (Diptera: Culicidae) in urban and rural settings within the province of Rome, Italy

We here report the results of field trials carried out in Rome with the aim to obtain data on the feeding behaviour of Aedes albopictus, in relation to different availability and abundance of putative hosts. Human Blood Index values were found higher than 75% in urban areas, where humans represented the most abundant hosts, and lower than 60% in rural areas, where host alternative to humans were frequent. The overall results confirm the generalist feeding-behaviour shown by this species in its original range of distribution and highlighting its high potential as vector of human pathogens in urban areas of Italy.     

Distribution of dengue vectors in neighborhoods with different urbanization types of Manaus, state of Amazonas, Brazil

Aedes aegypti and Ae. albopictus are vectors of dengue viruses, which cause endemic disease in the city of Manaus, capital of the state of Amazonas, Brazil. More than 53 thousand cases have been registered in this city since the first epidemic in 1998. We evaluated the hypothesis that different ecological conditions result in different patterns of vector infestation in Manaus, by measuring the infestation level in four neighborhoods with different urbanization patterns, during the rainy (April), dry (August), and transitional (November) seasons. Ae. aegypti predominated throughout the study areas and sampling periods, representing 86% of all specimens collected in oviposition traps. High frequencies of houses positive for both species were observed in all studied sites, with Ae. aegypti present in more than 84% of the houses in all seasons. Ae. albopictus, on the other hand, showed more spatial and temporal variation in abundance. We found no association between infestation level and house traits. This study highlights the homogeneity of dengue vector distribution in Manaus.     

Importance of Aedes albopictus in veterinary medicine

To assess the role of Aedes albopictus in transmission of filarial nematodes of veterinary importance, researches were carried out in different geographical areas. In Italy a first research was performed to study the susceptibility of Ae. albopictus to Dirofilaria repens, D. immitis and Setaria labiatopapillosa. The development of L3 larvae was longer than in other species of mosquitoes but Ae. albopictus could be a suitable vector of filariae. To understand the role of Ae. albopictus in the natural transmission of Dirofilaria and to assess the risk for animal and human health, in 2000, 2001 and 2002 another study was carried out in the town of Padua. A total of 2,534 Ae. albopictus were caught on human-attracted mosquitoes. Specific primers and sequencing identified filarial DNA as D. immitis; Ae. albopictus was proved a natural vector of D. immitis. Similar results were confirmed in Central Italy also for D. repens. The presence of Ae. albopictus increased the probability of transmission of canine and human dirofilariosis in urban environment and it could change the epidemiology of dirofilariosis, in particular for what concern the time of biting and the risk season. These aspects must be considered to outline a correct prophylaxis.     

Results of a survey to detect the mosquito Aedes albopictus in the French Riviera.

A programme of surveillance was initiated in 1992, in the French Riviera, to detect a possible introduction of Aedes albopictus from Italy and to prevent nuisances caused by mosquitoes in the touristic localities of the C?te d'Azur. In five years, numerous mosquito breeding places have been located. Nine species have been collected: Anopheles claviger, An. plumbeus, Aedes geniculatus, Ae. vittatus, Culex hortensis, Cx. impudicus, Cx. pipiens, Culiseta fumipennis, Cs. longiareolata but no Ae. albopictus was found. Nuisances were mainly due to hypogean populations of Cx. pipiens. Breeding places in urban sites have been controlled or suppressed. The discovery of an important larval population of An. plumbeus in an urban area might further stress the importance of this species already suspected to transmit indigenous malaria in cities.     

Transmission potential of chikungunya virus and control measures: the case of Italy

During summer 2007 Italy has experienced an epidemic caused by Chikungunya virus - the first large outbreak documented in a temperate climate country - with approximately 161 laboratory confirmed cases concentrated in two bordering villages in North-Eastern Italy comprising 3,968 inhabitants. The seroprevalence was recently estimated to be 10.2%. In this work we provide estimates of the transmission potential of the virus and we assess the efficacy of the measures undertaken by public health authorities to control the epidemic spread. To such aim, we developed a model describing the temporal dynamics of the competent vector, known as Aedes albopictus, explicitly depending on climatic factors, coupled to an epidemic transmission model describing the spread of the epidemic in both humans and mosquitoes. The cumulative number of notified cases predicted by the model was 185 on average (95% CI 117-278), in good agreement with observed data. The probability of observing a major outbreak after the introduction of an infective human case was estimated to be in the range of 32%-76%. We found that the basic reproduction number was in the range of 1.8-6 but it could have been even larger, depending on the density of mosquitoes, which in turn depends on seasonal meteorological effects, besides other local abiotic factors. These results confirm the increasing risk of tropical vector-borne diseases in temperate climate countries, as a consequence of globalization. However, our results show that an epidemic can be controlled by performing a timely intervention, even if the transmission potential of Chikungunya virus is sensibly high.     

First finding of Dirofilaria repens in a natural population of Aedes albopictus

The invasive mosquito Aedes albopictus (Skuse) (Diptera: Culicidae) has become widespread in Italy during the past decade. Also Italy has foci of canine filariasis caused by Dirofilaria (Spirurida: Onchocercidae), due to subcutaneous D. repens Railliet & Henry as well as the dog heartworm D. immitis (Leidy) transmitted by various vector mosquitoes (Diptera: Culicidae). In 2002, at Fiumicino, west of Rome (Lazio Region), 17% of dogs were found to have D. repens microfilariae in peripheral blood. To evaluate the role of Ae. albopictus as a vector of Dirofilaria in this area, female mosquitoes were collected daily, June-October 2002, landing on dog or human bait in a rural house at Focene. Mosquitoes were maintained at 27 degrees C and 70% RH for 6 days, to allow development or purging of filaria larvae, then identified and frozen for subsequent molecular assay with filaria-specific ribosomal S2-S16 primers. To distinguish specimens harbouring infective L3 Dirofilaria larvae, DNA was extracted separately from the mosquito abdomen and head-thorax. Dirofilaria species were identified by sequencing, confirmed by polymerase chain reaction of positive specimens using primers specific for D. immitis and D. repens. Dirofilaria DNA was detected in 3/154 (2%) of Ae. albopictus females examined: D. repens DNA in head-thorax and abdomen of one collected 27th July; D. immitis in the abdomen of one collected 24th September; DNA of both D. immitis and D. repens in the head-thorax of one collected 11th October 2002. Thus Ae. albopictus is a potential vector of both Dirofilarias in Italy, representing risks for veterinary and human health.     

Parasitism of Ascogregarina taiwanensis and Ascogregarina culicis (Apicomplexa: Lecudinidae) in larvae of Aedes albopictus and Aedes aegypti (Diptera: Culicidae) from Manaus, Amazon region, Brazil

The aim of the study was to determine the existence of Ascogregarina spp. in larvae of Aedes albopictus and Aedes aegypti collected in urban and suburban areas of Manaus, Amazon region, Brazil. Between May 2004 and July 2005, the mid-gut of 3rd and 4th instar larvae, collected in tire traps in six neighborhoods of Manaus, was examined for the presence of trophozoites of Ascogregarina. Coexistence of Ae. albopictus larvae infected by A. taiwanensis, and Ae. aegypti larvae by A. culicis, was detected in traps in the field. The percentage of Ae. albopictus larvae infected by A. taiwanensis ranged from 21% to 93.5% and of Ae. aegypti larvae infected by A. culicis from 22% to 95%. The mean infection intensity was similar in both species of Aedes. In traps located in Mauazinho, the replacement of Ae. aegypti by Ae. albopictus larvae was observed. In Manaus, Ae. albopictus larvae were parasitized by A. taiwanensis, and Ae. aegypti larvae by A. culicis. Infection rates were high when the species of Aedes were found separately.     

福建省白纹伊蚊中登革病毒的分离与鉴定

近年来福建省登革热(Dengue fever,DF)输入性病例持续存在,且登革热的主要传播媒介白纹伊蚊在全省内广泛分布,为了解福建省福州市登革热的媒介白纹伊蚊携带登革病毒(Dengue virus,DENV)状况,2017年10月7日在福州市台江区元一花园小区内开展伊蚊监测,采用双层叠帐法捕获255只白纹伊蚊蚊体研磨液上清提取核酸后用实时荧光RT-PCR法检测DENV特异性核酸,将检测阳性的蚊体研磨液上清接种C6/36细胞进行病毒分离,成功分离到1株DENV病毒株mosquito13/Fujian/2017;经实时荧光RT-PCR法鉴定所分离病毒株的血清型为I型;利用型特异性引物通过RT-PCR扩增病毒E基因并测序进行分子遗传特性分析;E基因核苷酸和氨基酸同源性分析显示,该毒株与2017年10月17日同小区本地登革热病例血清中分离得到的登革毒株E基因序列完全一致,与越南2014年分离株KT825033/Vietnam/2014核苷酸(99.7%)和氨基酸(99.8%)同源性最高;系统进化树分析表明所分离登革病毒毒株的基因型为I型,与东南亚地区的越南,泰国,柬埔寨等国家进化关系相近,可能输入来源于东南亚国家。本研究证实了登革热外潜伏期的存在以及白纹伊蚊在登革热疫情传播过程中的媒介作用,提示在登革热的防控工作中媒介登革病毒监测、检测的重要性,也提示福建省需要加强输入来源监测,特别是东南亚入境人员的监测。     

The first report of Aedes (Stegomyia) albopictus in Haiti

Aedes albopictus was found in six of the 10 departments of Haiti and in 14 of the 35 communes surveyed. The survey found the larvae of Ae. albopictus in 13 different types of containers. Used tires and tins were by far the most common breeding sites used by this mosquito species. At the breeding sites, Ae. albopictus was associated with other mosquito species, such as Aedes aegypti, Culex nigripalpus and Aedes mediovittatus. The highest proportion of association was with Ae. aegypti. This study represents the first report of Ae. albopictus in Haiti.     

Adaptation of the BG-Sentinel trap to capture male and female Aedes albopictus mosquitoes

In recent years, the remarkable spread of Aedes albopictus (Skuse) (Diptera: Culicidae) throughout the world has drawn attention to this hitherto poorly studied species, particularly after its role in outbreaks of chikungunya fever in the western Indian Ocean and in Italy. Variants of sterile insect technique (SIT), including the release of transgenic males with a dominant lethal gene (RIDL), have been proposed in the search for new and innovative methods of control. Knowledge of male dispersal, mating behaviour and longevity will be critical to the success of this approach. We present an effective and practical method for trapping both male and female Ae. albopictus using a mouse-baited BG-Sentinel trap.     

Preliminary data on the performance of Aedes aegypti and Aedes albopictus immatures developing in water-filled tires in Rio de Janeiro

A monthly survey of Aedes aegypti and Aedes albopictus immatures in discarded tires at a site in metropolitan Rio de Janeiro showed that Ae. albopictus was much more abundant in the rainy season, but Ae. aegypti abundance showed a less clear seasonal pattern. Pupal masses for Ae. albopictus showed a seasonal trend. In contrast, Ae. aegypti pupae did not show any clear trend in weight. Large Ae. albopictus pupae were found in the warmer months, when water volume was higher, pH lower and larval abundance lower. Further studies should be carried out to assess how seasonal variations in body size may impact vector competence of these species in Brazil.     

Aedes albopictus in Rome: results and perspectives after 10 years of monitoring

In 1997, Aedes albopictus (Skuse 1894) was detected in Rome in two opposite areas of the city. In the following 2 years, the species quickly spread. In 2000, scattered foci of the species were reported in the whole urban area and in the outskirts of the capital city. In Rome, Ae. albopictus seems to have found optimal environmental conditions to proliferate and to overwinter through and without diapausing eggs. In ten years Ae. albopictus has colonized the whole urban area through three phases: first massive spread, following maintenance of infestation, and colonization of alternative winter breeding sites with favorable climatic conditions. Data collected during the 2007 show that rainfall is no longer the most important factor for the development of the species, with respect to the past. In fact Ae. albopictus probably has found new alternative larval breeding sites through the colonization of small water collections refilled periodically by human activities. During 2007-2008 winter season, in order to evaluate the species adaptability, a study of eggs hatching and length of larval cycle at low temperatures, was carried out in laboratory and in simulated field conditions. Data and results are showed and discussed also by the light of existing literature.     

Impact of Chikungunya virus on Aedes albopictus females and possibility of vertical transmission using the actors of the 2007 outbreak in Italy

We investigated the impact of CHIKV strains on some Aedes albopictus (Skuse) reproductive parameters and the possibility of vertical transmission. Two strains were collected in the area where the epidemic occurred in 2007, one isolated from mosquitoes, the other one isolated from a viraemic patient. Different types of blood meals, either infected or non-infected, were offered to Ae. albopictus females, that were then analyzed at increasing time post infection. The virus titre, measured by two RT-PCR methods in the blood meals, influenced the rate of infection and the rate of dissemination of CHIKV in Ae. albopictus body. We found individual variability with respect to the infection/dissemination rates and their latency both considering the female's body and appendages. The hatching rate was significantly lower for the eggs laid by the infected females than for the control eggs, while the mortality during the larval development (from first instar larva to adult emergence) was similar among the progeny of infected and non-infected female groups. Our findings seem to support the hypothesis that the vertical transmission is a rare event under our conditions, and that a certain time period is required in order to get the ovarioles infected. Field observations conducted during the Spring 2008 showed no evidence of the presence of infected overwintering progeny produced by Ae. albopictus females infected during the 2007 outbreak.