Aedes japonicus is one of several so-called Aedes invasive mosquitoes, or AIMs, that have spread rapidly across Europe in recent decades. Native to East Asia, the species has colonised large parts of central and western Europe since its first detections on the continent, establishing populations in countries including Germany, Switzerland, Austria, Belgium, the Netherlands, France and Slovenia. In Italy, the mosquito had until now been reported only in the northern part of the country, where it has been expanding alongside another Asian invader, Aedes koreicus. The presence of both species in territories bordering Tuscany raised concerns among public health entomologists that the insects would follow the main transport corridors linking northern Italy to the central regions, and the new study set out to test exactly that hypothesis.

The survey was deliberately designed around the geography of invasion. Rather than sampling randomly across Tuscany, the researchers focused on the province of Massa-Carrara, the northernmost province of the region, and specifically on small villages situated along the roads that connect Tuscany with the adjacent regions where Aedes japonicus and Aedes koreicus had already been reported. This strategy reflects a well-established principle in invasion biology: human-mediated transport along road networks is one of the principal drivers of mosquito range expansion, and the first footholds of a new species are most likely to appear along the routes that funnel traffic from invaded areas into uninvaded ones. The team conducted the fieldwork over just two days, inspecting potential breeding habitats for adult mosquitoes, larvae and pupae.

The results were unambiguous. Morphological identification of 90 adult mosquitoes and 35 larvae, combined with molecular analyses performed on eggs, larvae, pupae and one adult, confirmed the presence of Aedes japonicus japonicus in five municipalities of northern Tuscany. The molecular work relied on standard genetic markers used in mosquito identification, including the internal transcribed spacer 1 region of the nuclear genome and the cytochrome c oxidase subunit I gene of the mitochondrial genome, amplified by polymerase chain reaction. This combination of morphological and molecular confirmation is important because several invasive Aedes species are morphologically similar, particularly in their immature stages, and misidentification can lead to costly delays in surveillance and control responses.

Perhaps the most striking aspect of the finding is what it implies about how long the species has been present. Despite the extremely short duration of the survey, the researchers detected Aedes japonicus across multiple sites and in several different types of artificial breeding containers, including buckets, tyres and a fountain basin. Finding the mosquito in so many locations and habitat types within a two-day window suggests that it is not a recent arrival confined to a single introduction point but is already firmly established in the area. The detection of immature stages co-occurring with larvae of other species, including the Asian tiger mosquito Aedes albopictus, the common house mosquito Culex pipiens, Culex hortensis and Culiseta annulata, further indicates that the species is breeding successfully in its new environment rather than merely being transported there incidentally.

This ecological flexibility is a hallmark of the species and a key reason for its invasion success. Aedes japonicus thrives in container habitats of both natural and artificial origin, tolerates cooler temperatures than many other invasive mosquitoes, and can exploit a wide range of water-holding structures in both rural and peri-urban settings. The fact that the Tuscany survey found it in buckets, tyres and a fountain basin confirms this plasticity in the Italian context and suggests that the species has the potential to spread further south, where it may encounter increasingly favourable climatic conditions during the cooler parts of the year. The coexistence of Aedes japonicus with the Asian tiger mosquito, which is now ubiquitous across Italy, also raises ecological questions about competition between the two invaders, since both exploit similar larval habitats.

From a public health perspective, the establishment of Aedes japonicus in Central Italy carries two main implications. The first is nuisance: the species is an aggressive day-biting mosquito whose females readily feed on humans, and its presence in residential areas can significantly degrade quality of life during the warm season. The second, and more consequential, is its potential role as a disease vector. While Aedes japonicus is not as efficient a vector of dengue or chikungunya as Aedes albopictus, it has been shown experimentally and in field studies to be competent for a range of arboviruses, including West Nile virus, and it has been implicated in the transmission ecology of other pathogens in its native and invaded ranges. The introduction of an additional competent vector into a region that already circulates West Nile virus and other mosquito-borne pathogens adds a new layer of complexity to vector-borne disease risk assessment in Italy.

The authors of the study argue that these findings highlight the need for active surveillance specifically targeting Aedes invasive mosquitoes in Central Italy. Traditional mosquito monitoring in Italy has historically centred on the Asian tiger mosquito, which arrived in the country in the early 1990s and is now monitored through extensive ovitrap networks. However, the detection methods and thresholds optimised for Aedes albopictus are not necessarily suited to detecting a newly arriving species at low density. The Tuscany survey demonstrates the value of a different approach: targeted sampling along invasion corridors, informed by the known distribution of the species in neighbouring territories, can detect a new arrival quickly. The researchers acknowledge the contribution of colleagues from neighbouring regions who provided information on the distribution of invasive Aedes mosquitoes near the Tuscan border and offered suggestions on sampling strategies for the timely detection of Aedes japonicus and Aedes koreicus.

The study was supported by the Tuscany region through a fund dedicated to the regional entomological network for the protection of public health, developed and restructured for the 2026 to 2027 biennium. This institutional backing reflects a growing recognition among Italian regional authorities that invasive mosquito surveillance is a core public health function rather than a purely academic exercise. As climate change alters temperature and precipitation patterns across the Mediterranean, and as international trade and travel continue to move mosquitoes and their eggs across borders, the window for early detection and response is shrinking. The rapid spread of Aedes koreicus through northern Italy in recent years, following a pattern similar to that of Aedes japonicus elsewhere in Europe, illustrates how quickly an established invader can consolidate its range once it gains a foothold.

The first report of Aedes japonicus in Central Italy is therefore best understood not as an isolated discovery but as a milestone in an ongoing continental invasion. The species has now bridged the gap between its northern Italian strongholds and the central regions of the peninsula, and its presence in five municipalities of northern Tuscany, confirmed by both morphology and genetics, indicates that the invasion front has moved decisively southward. Whether the mosquito will establish permanent populations further into Tuscany and beyond will depend on climatic suitability, the availability of breeding habitats and the effectiveness of the surveillance and control measures that regional authorities put in place. What is already clear, the researchers conclude, is that the species is firmly established in northern Tuscany, that it exploits the same artificial containers that have fuelled the spread of other invasive mosquitoes, and that sustained, targeted monitoring is now essential to track and, where possible, contain its further expansion.

Subject of Research: First detection of the invasive mosquito Aedes japonicus in Central Italy and its implications for surveillance and public health

Article Title: New evidence of an ongoing invasion: first report of Aedes japonicus in Central Italy

Article References: Del Lesto, I., Chiavacci, M., De Liberato, C., Rondón, S., Ottolini, N., Carioti, V., Magliano, A., Porchia, B. R., & Romiti, F. (2026). New evidence of an ongoing invasion: first report of Aedes japonicus in Central Italy. Parasites & Vectors. https://doi.org/10.1186/s13071-026-07709-2

Image Credits: AI Generated

DOI: 10.1186/s13071-026-07709-2

Keywords: Aedes japonicus, Asian bush mosquito, invasive mosquitoes, Tuscany, Italy, vector-borne disease, entomological surveillance, biological invasion, Aedes albopictus, public health, mosquito vectors, Massa-Carrara

Colorectal cancer remains a leading cause of cancer death worldwide, and early detection with faecal tests demonstrably reduces mortality. But the benefit of screening hinges on uptake. European guidelines consider a participation rate of at least 45 percent acceptable and 65 percent desirable, yet reported figures across programmes range from roughly 23 to 63 percent, with persistent socioeconomic gaps. In Italy, national participation averaged 34.9 percent in 2023, ranging from 18.9 percent in Lazio to 64.2 percent in Veneto. Tuscany, despite its long-standing programmes, sat at 45.8 percent, comfortably above the minimum but short of the desirable benchmark, leaving a large pool of chronic non-responders whom standard letters had repeatedly failed to reach.

The new trial, part of the BESTcc project evaluating behavioural interventions in Tuscany’s screening programmes, is grounded in dual-process theory. Traditional efforts to boost screening participation have appealed to reflective, deliberative reasoning, the slow System 2 of psychological models. Behavioural economics instead targets the fast, automatic System 1, using small contextual modifications, or nudges, such as feedback on past behaviour or social norm messages, to shape decisions without restricting choice. Two earlier randomized trials in Florence, Rome and Turin had tested such messages among previous non-responders with encouraging but sometimes inconsistent results, and the Tuscan team set out to replicate the approach in a larger, geographically diverse population spanning both urban and rural screening organizations.

The study employed a 2×2 factorial randomized design. Between January 2022 and April 2024, eligible individuals who had not responded to at least two consecutive screening invitations and had never been screened were allocated in a 3:1:1:1 ratio to one of four arms: a control group receiving the standard invitation letter, a feedback group, a minority-norm group, and a combined group receiving both messages. The messages themselves were identical to those used in the previous trials, co-developed and pretested with public and patient representatives through qualitative focus groups. The feedback message gently informed recipients that they had unfortunately not responded to previous invitations while stressing that it is never too late to take care of their health. The minority-norm message noted that in many areas six out of ten people invited accept the invitation and that the recipient belonged to the minority who did not. Exclusions covered personal history of colorectal cancer, adenomas or inflammatory bowel disease, recent colonoscopy, or a recent faecal occult blood test.

The trial was registered with the ISRCTN registry in 2022 and approved by the Ethics Committees of the Local Health Units in Tuscany, with individual informed consent waived because the trial was integrated into routine screening, an Essential Level of Care within the Italian National Health System. Randomization was performed individually with a pseudo-random number generator, and although blinding of researchers and participants was impossible, participants did not know they were part of a study and enrolment staff were blinded to the allocation sequence. Importantly, the team also verified that the added sentences did not compromise clarity, using automated natural language processing readability tools validated by crowd-sourced comprehension testing; the modified letters proved as easy to understand as the standard version.

The primary outcome was the return of a faecal immunochemical test within 90 days of the first invitation, analyzed by intention to treat, which even included people whose letters were returned undelivered. In the control group, 6.5 percent of 42,732 participants returned a test. Uptake was significantly higher in all three intervention arms: 8.4 percent in the feedback condition, 7.4 percent with the minority-norm message, and 7.7 percent in the combined condition. The 2×2 factorial analysis revealed a significant interaction between the two message types, with an odds ratio of 0.80 for the interaction term, prompting the researchers to report each modality separately against the control rather than pooling them.

Because participation rates varied substantially across the ten screening programmes, the statisticians built a mixed-effects logistic regression with random intercepts and random slopes for each programme, a model whose superiority over a single-level alternative was confirmed by likelihood ratio testing. The intraclass correlation attributable to programme-level clustering was 0.0884. In this adjusted model, feedback carried an adjusted odds ratio of 1.31 for participation, the minority-norm message 1.17, and the combination 1.22, all statistically significant relative to control, with no significant differences among the three intervention conditions. Women participated more than men, and people aged 60 to 70 were less likely to respond than those aged 54 to 59.

The age-stratified results carried the most practical weight. Among 60-to-70-year-olds, all three messages worked, and the combined message was the strongest performer there, with an adjusted odds ratio of 1.49. Among the younger 54-to-59 group, only feedback showed a significant effect, with an adjusted odds ratio of 1.21. Translated into absolute terms, feedback produced the best figures: an absolute risk reduction of 1.84 percentage points overall, meaning roughly 54 invitations bearing the feedback sentence were needed to generate one additional screened person, improving to 48 invitations in the older subgroup. The combined message achieved an absolute risk reduction of 2.40 percent and a number needed to invite of 57 among those aged 60 to 70.

Why did stacking the two nudges not outperform either alone? The authors offer several speculative explanations, carefully flagged as such because no process data on message perception or recall were collected. The minority-norm message already contains an implicit feedback element, since telling recipients they are part of the minority who did not participate inherently reminds them of their past behaviour, so the explicit feedback sentence may have added little new information. Longer or more complex combined messages may also have diluted attention, or ceiling effects may have limited further gains. The researchers recommend that future studies incorporate brief process measures, such as recall, perceived relevance and comprehension, and explore factorial designs, message sequencing or qualitative interviews to disentangle these mechanisms, as well as testing more clearly distinct interventions such as deadlines.

The findings arrive with clear caveats and clear strengths. Household spill-over could not be controlled since members of the same family could be randomized to different arms, message placement within the letter may have limited salience, and the analysis was restricted to age and sex without socioeconomic variables such as deprivation, education or health literacy. Nevertheless, the trial’s scale, its objective participation data, its single-region consistency and its focus on the hardest-to-reach group, people who had ignored two consecutive invitations, make the result compelling for screening organizers. The interventions are essentially free, requiring only small edits to existing letters, and the effects were demonstrated in a mix of long-established and newer programmes. The authors caution that organized, population-based faecal-test programmes differ from opportunistic or colonoscopy-based systems, and that cultural norms and trust in health authorities shape how such messages land, so extrapolation elsewhere should be cautious. Within that frame, the message is simple: a reminder of what someone has not done, and an honest account of what their neighbours have, may be enough to bring the reluctant back into the prevention fold.

Subject of Research: Behavioural economics messages to increase participation in population-based colorectal cancer screening among previous non-responders in Tuscany

Article Title: Testing feedback and social norms messages to increase participation: the BestCC randomized controlled trial among non-respondents in population-based colorectal cancer screening programmes in Tuscany

Article References: Gorini, G., Betti, E., Falini, P., Carreras, G., Mallardi, B., Migliori, M., Giorgi, D., Tramalloni, D., Cosimi, A., Venturi, G., Ravelli, A. A., Iossa, A., Battisti, F., Stoffel, S. T., & Mantellini, P. (2026). Testing feedback and social norms messages to increase participation: the BestCC randomized controlled trial among non-respondents in population-based colorectal cancer screening programmes in Tuscany. SSM – Population Health, Article 101974. https://doi.org/10.1016/j.ssmph.2026.101974

Image Credits: AI Generated

DOI: Not provided

Keywords: colorectal cancer screening, behavioural economics, nudge, social norms, feedback messages, FIT test, randomized controlled trial, Tuscany, screening participation, non-responders, public health, health communication