Martin Geier

Mosquito control is a critical operational requirement for tropical resort islands, where guest comfort, staff wellbeing, and public health depend on effective management of biting insects. In many island tourism destinations, including the Maldives, mosquito control programs rely heavily on routine insecticide space spraying (fogging or misting). While such interventions can temporarily reduce adult mosquito abundance, their effects are often short-lived. High-frequency applications are therefore common practice but may create risks for human health, biodiversity, and fragile island ecosystems. Here, we examine how mosquito control in the Maldivian tourism and hospitality sector could transition from pesticide-dependent approaches toward ecological mosquito management practices. Drawing on operational experience from fourteen Maldivian resort islands and current knowledge of mosquito ecology, we compare conventional insecticide-based control with alternative approaches including surveillance-based management, larval habitat reduction or modification, biological control, mass trapping of mosquitoes, or combinations thereof. The geographically bounded nature of resort islands, combined with centralized management and strong sustainability commitments within the tourism sector, creates unusually favorable conditions for implementing integrated mosquito management strategies. We propose a practical transition framework that prioritizes monitoring, habitat management, and sustained population suppression while reducing or eliminating routine insecticide applications. Importantly, our operational experience demonstrates that implementation can be simple and practical, requiring only modest adjustments to existing resort operations. Such approaches can improve guest and staff safety, protect island biodiversity, reduce dependence on chemical pesticides, minimize the noise, olfactory and visual disturbances associated with routine fogging and mist-blower operations, and strengthen the environmental sustainability credentials of tropical tourism destinations.

Mass trapping of adult mosquitoes is increasingly promoted as an environmentally friendly alternative to insecticide-based vector control, yet quantitative evidence for its long-term population-level effects remains limited. We analyzed adult Aedes mosquito Biogents trap data from four tropical islands (three in the Maldives, one in the Philippines) where mass trapping was implemented at different trap densities. Using equilibrium-constrained population models, we describe how adult Aedes populations differ across trap densities, with outcomes ranging from partial suppression to near-zero levels at higher trap densities. At low to intermediate densities (4–6 traps·ha⁻¹), populations stabilized at non-zero equilibrium levels, whereas operational elimination was consistently observed at densities ≥ 10 traps ha⁻¹. A descriptive curve is shown to illustrate the decline in equilibrium abundance with increasing trap density, while a conceptual sigmoid model is used to illustrate how a transition in the recruitment–removal balance may occur under theoretical conditions. Limited larval source management was implemented on two islands, but elimination was also observed in the absence of larval interventions, indicating that sustained adult removal appears to have been the dominant driver of suppression. These findings indicate that mass trapping, when deployed at sufficiently high densities, is associated with rapid declines to near-zero population levels and may serve as an effective component of integrated vector management, particularly in geographically bounded settings or as a rapid-response intervention during outbreaks of arboviral diseases.

Space spraying and mass trapping represent distinct adult mosquito control strategies with fundamentally different population-level consequences. We developed a density-regulated population model incorporating either pulsed mortality from spraying (efficacy α = 0.2–0.6 per application) or continuous proportional removal through trapping. Parameters were derived from empirical island datasets. Spraying produced rapid but transient reductions and required high-frequency re-application (weekly to daily) to approach structural suppression when α ≤ 0.4. Consistent with model predictions, analysis of Maldivian resort practices indicated that daily spraying is common in operational settings. In contrast, trapping shifted long-term equilibrium density and induced population collapse above a model-estimated threshold density that, under the baseline parameterization used here, corresponded to approximately 8–10 traps per hectare in geographically bounded island systems. Sensitivity analyses demonstrated that qualitative outcomes were robust across plausible parameter ranges. Economic comparison indicated that spraying frequencies required to match threshold trapping substantially increased cumulative cost. In small island settings with negligible immigration, threshold-based mass trapping provides a structurally stable pathway toward sustained suppression, whereas spraying remains primarily a rapid-response tool with limited durability under moderate-efficacy conditions. When potential ecological externalities and human health considerations associated with repeated insecticide use are considered, trapping may offer additional advantages beyond purely economic comparisons.

Aedes albopictus and Aedes aegypti are invasive mosquito species that impose a substantial risk to human health. To control the abundance and spread of these arboviral pathogen vectors, the sterile insect technique (SIT) is emerging as a powerful complement to most commonly-used approaches, in part, because this technique is ecologically benign, specific, and non-persistent in the environment if releases are stopped. Because SIT and other similar vector control strategies are becoming of increasing interest to many countries, we offer here a pragmatic and accessible ‘roadmap’ for the pre-pilot and pilot phases to guide any interested party. This will support stakeholders, non-specialist scientists, implementers, and decision-makers. Applying these concepts will ensure, given adequate resources, a sound basis for local field trialing and for developing experience with the technique in readiness for potential operational deployment. This synthesis is based on the available literature, in addition to the experience and current knowledge of the expert contributing authors in this field. We describe a typical path to successful pilot testing, with the four concurrent development streams of Laboratory, Field, Stakeholder Relations, and the Business and Compliance Case. We provide a graphic framework with criteria that must be met in order to proceed.

As currently implemented, malaria vector surveillance in sub-Saharan Africa targets endophagic and endophilic mosquitoes, leaving exophagic (outdoor blood-feeding) mosquitoes underrepresented. We evaluated the recently developed host decoy trap (HDT) and compared it to the gold standard, human landing catch (HLC), in a 3 × 3 Latin square study design outdoors in western Kenya. HLCs are considered to represent the natural range of Anopheles biting-behaviour compared to other sampling tools, and therefore, in principle, provide the most reliable profile of the biting population transmitting malaria. The HDT incorporates the main host stimuli that attract blood-meal seeking mosquitoes and can be baited with the odours of live hosts. Numbers and species diversity of trapped mosquitoes varied significantly between HLCs and HDTs baited with human (HDT-H) or cattle (HDT-C) odour, revealing important differences in behaviour of Anopheles species. In the main study in Kisian, the HDT-C collected a nightly mean of 43.2 (95% CI: 26.7–69.8) Anopheles, compared to 5.8 (95% CI: 4.1–8.2) in HLC, while HDT-H collected 0.97 (95% CI: 0.4–2.1), significantly fewer than the HLC. Significantly higher proportions of An. arabiensis were caught in HDT-Cs (0.94 ± 0.01; SE) and HDT-Hs (0.76 ± 0.09; SE) than in HLCs (0.45 ± 0.05; SE) per trapping night. The proportion of An. gambiae (s.s.) was highest in HLC (0.55 ± 0.05; SE) followed by HDT-H (0.20 ± 0.09; SE) and least in HDT-C (0.06 ± 0.01; SE). An unbaited HDT placed beside locales where cattle are usually corralled overnight caught mostly An. arabiensis with proportions of 0.97 ± 0.02 and 0.80 ± 0.2 relative to the total anopheline catch in the presence and absence of cattle, respectively. A mean of 10.4 (95% CI: 2.0–55.0) Anopheles/night were trapped near cattle, compared to 0.4 (95% CI: 0.1–1.7) in unbaited HDT away from hosts. The capability of HDTs to combine host odours, heat and visual stimuli to simulate a host provides the basis of a system to sample human- and cattle-biting mosquitoes. HDT-C is particularly effective for collecting An. arabiensis outdoors. The HDT offers the prospect of a system to monitor and potentially control An. arabiensis and other outdoor-biting mosquitoes more effectively.

Determining the abundance and distribution of male mosquitoes in the wild and establishing species seasonality in candidate pilot sites is of particular interest with respect to the use of the sterile-male technique. With the knowledge that using mice as bait in BG-Sentinel traps effectively enhances Aedes albopictus male and female trapping success, the present study was designed to determine whether attractants derived from mouse odour blend could be a viable substitute for live mice to lure Ae. albopictus mosquitoes into traps. The effects of baiting BG-Sentinel traps with mice, carbon dioxide (CO₂), and attractants derived from litter mouse odours (mouse litter (ML)) and a mouse odour blend (MOB) on the efficiency of trapping Ae. albopictus males and females were tested using a Latin square design. The BG-Sentinel trap baited with CO₂ + ML caught a significantly larger number of mosquitoes compared to traps baited with mice only. The BG-Sentinel traps containing only CO₂ or CO₂ + MOB, however, did not catch significantly more mosquitoes compared to the other traps. The proportions of males caught in the BG-Sentinel traps did not differ significantly between the respective attractants. The results from this study confirm that CO₂ bait is efficient to provide a reliable estimation method for Ae. albopictus adult male abundance in the wild, and suggest that mouse litter baits in combination with CO₂ could be used to enhance Aedes trapping success in BG-Sentinel traps.

Monitoring of malaria vector populations provides information about disease transmission risk, as well as measures of the effectiveness of vector control. The Suna trap is introduced and evaluated with regard to its potential as a new, standardized, odour-baited tool for mosquito monitoring and control.