Report of the 2023 Asia Pacific Conference on Mosquito and Vector Control: “reimagining vector control—innovations for a changed world”

Abstract

The Asia–Pacific region has had decades of progress in reducing malaria cases and deaths. The region is now accelerating its efforts towards malaria elimination by 2030 using a science-based approach by applying evidence-based best practices alongside existing tools. However, there are concerns of knowledge gaps and external factors challenging this goal. The COVID-19 pandemic served as reminder of the need for a holistic approach. This report summarizes the outcomes of the discussions from the “Asia Pacific Conference on Mosquito and Vector Control” held in Chiang Mai, Thailand from 27 to 30 November, 2023. The conference aims to provide insights into recent research, cutting-edge tools, and the strength of the Asia–Pacific regional mosquito and vector control capacity post-COVID-19 pandemic era. The conference featured discussions on mosquito surveillance, monitoring and control; enabling the resolution of local problems with local expertise and forging new partnerships; and exploring recent research advancements in vector control strategies. More than 500 experts from 55 countries attended.

Background

The coronavirus disease 2019 (COVID-19) pandemic has caused a significant impact on the health systems around the world [1]. At the peak of the pandemic, many public health workers were, inevitably, required to switch their roles to focus on COVID-19 [2]. Major disruptions in medical and public health research were noticeably significant effects due to travel restrictions. These disruptions had a significant impact on the management of vector-borne diseases (VBDs) [2,3,4] which disproportionately affect ill-equipped public health systems of the world that includes the Asia–Pacific region [5]. In this regard, countries hit by both COVID-19 and VBDs were urged not to disengage on the latter [6]. Concerns remain in Asia–Pacific countries over the conflicting low and high levels of VBDs recorded throughout the COVID-19 period from 2020 to 2022 and the alarming epidemics after the period [7].

The Asia Pacific Conference on Mosquito and Vector Control (AMV)-2023 was a significant occasion as it marked the first in-person scientific meeting on mosquito and vector control since the challenges posed by the COVID-19 pandemic. In collaboration with the Department of Disease Control, Ministry of Public Health (MoPH), Thailand, and the Thailand Pest Management Association, Kasetsart University hosted AMV-2023 from November 27th to 30th at the International Convention Center, the Empress Hotel, Chiang Mai. The conference aims to strengthen the Asia–Pacific regional mosquito and vector control capacity and network, forging new partnerships, and exploring new technologies and approaches to address the rapidly changing landscape for mosquito control in the region. It was an honor to have world-class researchers join in exchanging information and providing knowledge and guidelines for controlling mosquitoes and vectors worldwide.

The conference provides insights into both traditional and state-of-the-art techniques in various aspects of mosquito and vector surveillance and control. This is expected to encourage innovation by strengthening connections between countries and regional networks to exchange expertise and knowledge. Furthermore, AMV-2023 encourages innovations in research practices that address the inequality faced by Asia–Pacific scientists and enabling the resolution of local problems with local expertise. This includes combining translational research into practice rather than relying solely on external agendas and strategies. Global collaboration and sustained funding emerged as essential elements in the fight against vector-borne diseases, given their transboundary nature.

AMV-2023 received over 200 abstract submissions and featured 23 separate symposiums, two plenary sessions, four keynote lectures, poster presentations, and remote links. In addition, we hosted a pre-workshop organized by the Global Biodiversity Information Facility, funded by the TDR. Throughout the conference, we explored the latest advancements in vector control strategies, disease surveillance, and public health policies. The conference attracted a diverse and substantial global audience, with a total of 565 participants. The attendance breakdown revealed both online (48) and onsite (517) participation. Noteworthy, participants came from all major continents, including Africa, Asia, Australia, Europe, North America, and South America. Analysis of the registration data revealed a diverse range of presenters, with 154 speakers contributing to the oral sessions, including academic faculty, researchers, master's and doctoral level students, government officers, representatives from non-government organizations, and individuals from the private and commercial sectors.

This report highlights the key outcomes of the AMV-2023 event which have been discussed under three themes composing of: (1) Plenary lectures; (2) Keynote lectures; and (3) Symposium presentations.

Plenary lectures

Dr. Raman Velayudhan, from the Vector Control and Environment Unit, of the Global Neglected Tropical Diseases Programme of the World Health Organization (WHO) highlighted that dengue affects 130 countries, with over 4 billion people at risk and is endemic in over 100 countries. Dengue lacks effective treatments, vaccines, and long-term vector control. Cases surged during the COVID-19 pandemic and have increased eightfold since 2000. In 2023, nearly 5 million cases and 5000 deaths were reported. Dengue fever has been categorized as a Level 3 emergency disease by the WHO, which denotes a severe, large-scale, sudden-onset humanitarian disaster that necessitates system-wide mobilization to increase response and improve overall assistance. The current responses guided by WHO Global Vector Control Response 2017–2030, which focus on collaboration, community engagement, and surveillance, are scaling up tools for dengue control. This talk highlighted that dengue thrives in varied conditions, as seen in Bangladesh’s floods and Brazil's drought. Climate change and water stress impact dengue while urbanization, especially in Africa, poses future challenges.

Prof. Donald Roberts (Uniformed Services University, Bethesda, MD, USA) commented on the adaptability of Aedes aegypti, which was thought incapable of surviving in colder latitudes in the USA, but it is now a permanent resident as far north as Washington, D.C. [8]. These mosquitoes are thought to use extensive underground spaces for overwintering. In warm months, high population densities can be found in intensely used human spaces, for example, in popular outdoor eating places. Comparisons between colonies of Ae. aegypti Rockefeller and Aedes albopictus USUHS confirmed that these two strains exhibit very different egg-hatching strategies.

Keynote lectures

Assoc. Prof. Christina Liew (NEA, Singapore) highlighted that Singapore employs a comprehensive strategy to address dengue occurrences, emphasizing the importance of communication in igniting community action, through mainstream, online, and social media. Although the Aedes House Index has decreased since the 1960s, recent dengue cases are increasing, with 8,734 cases and 3 deaths reported in 2023 by week 46. The control strategy involves four pillars: surveillance, sustainable prevention and control, outbreak management, and public communication and advocacy [9]. Project Wolbachia Singapore employs a suppression strategy, with widespread publicity and stakeholder consultation targeting academia, the medical community, students, and government agencies. According to a post-release household perception survey, 70% of households had heard of the project, and over 90% of households expressed no concerns about the Wolbachia-Aedes’ ongoing release [10].

Dr. Chusak Prasittisuk addressed challenges and opportunities in mosquito vector control in Asia and the Pacific for the next decade. Dengue, Chikungunya, Zika, Japanese Encephalitis, and Lymphatic filariasis remain significant concerns. Urbanization is altering dominant vectors and disease risk, with specific issues noted in India. This talk also highlighted that high diversity and increasing spread of vectors, insecticide resistance, land use reforms, climate change, cross-border malaria citing an example of Thailand-Myanmar border crossings, pose additional challenges to reducing disease burden. Opportunities exist in training, vector identification, collaboration, planning, partnerships, implementation, monitoring and evaluation. The closing message underscored that mosquito vector control is everyone’s responsibility.

Prof. Elizabeth McGraw (Pennsylvania State University, USA) focused on “Thermal stress interactions with Wolbachia and dengue virus in Ae. aegypti”, highlighting that Ae. aegypti serves as an excellent system for studying viruses. Important takeaways from this talk include: Wolbachia pipientis, spreading through cytoplasmic incompatibility, reduces virus replication and works against various viruses, including CHIKV, ZIKV, WNV, YFV, and Plasmodium; both Wolbachia and DENV infections lead to approximately fivefold faster KD time and thermal sensitivity; Wolbachia does not protect against DENV-mediated effects on KD. Notably, HSP expression may not always be useful during heat stress, and Ae. aegypti shows resilience to frequent, short heat exposures, with high heat reducing DENV loads. In conclusion, she reasoned that high heat may reduce viral loads and affect transmission and that thermal sensitivity may affect the geographical range over which Wolbachia can be deployed.

Prof. Chow-Yang Lee (University of California, Riverside, USA), addressed the global resurgence, insecticide resistance, and management of bed bugs in his talk. He highlighted recent media reports of bed bugs in various countries, expressing concern about the long-standing issue of bed bug resurgence. Key points from his presentation include the characteristics of adult bed bugs, their obligate blood-feeding behavior, and the absence of disease transmission. Globally, two major species of public concern are the common bed bug (Cimex lectularius) and the tropical bed bug (Cimex hemipterus). Bed bug management strategies involve chemical control, with insecticide rotation and insecticide mixtures recommended for resistance management. However, the availability of effective active ingredients is limited. The true challenge is controlling bed bugs in their “reservoirs” such as homeless shelters.

Symposium presentations

Epidemiology and control of arthropod-borne diseases

The conference highlighted significant progress in understanding the epidemiology and control of vector-borne diseases. One study employed reverse genetics and detailed intra-host infection kinetics to investigate the function of viral genetic determinants in relation to vector tropism. They identified 11 amino acid residues on pRM, E, NS3, NS4B, and NS5 that are conserved within a subgroup of flaviviruses sharing the same vector (Aedes-borne, Culex-borne, and tick-borne). Detailed infection kinetics analyses suggested that the genetic loci are involved in several infection steps, including virus stability in mosquito midguts, as well as infectivity and maturation during mosquito infection.

In a separate discussion, malaria parasites, vector bionomics, and human behaviours in Lao PDR were linked to an increased risk of malaria transmission. Staying outdoors from 18:00 to 22:00 h and 3:00 to 6:00 h increased human exposure to mosquito bites in villages. Variations in Anopheles vector species, ecotypes, and seasons exacerbated the risk of transmission.

A talk on zoonotic diseases underscored an upsurge of simian malaria, which is attributed to increased human intrusion into forests. The loss of the “dilution effect” due to biodiversity changes, leads to amplified vector-borne disease transmission between humans and other animals. Although the first natural infection of P. knowlesi occurred in Pahang in 1965, simian malaria was expected to remain in the macaques because the vector An. hacker was only zoophagic. Today, several vectors and parasites have been identified. Currently, P. knowlesi, P. cynomolgi, P. inui, and P. fieldi have been reported in humans.

Implication of climate in relation to vector distribution and control

The conference addressed the impact of climate change on vector dynamics. Changing environmental conditions are altering the distribution and behaviour of vector species, presenting new challenges for control efforts. Adaptive strategies that consider these changes are necessary to maintain effective vector control. Using dengue data from 2002 to 2019, a climate-driven spatiotemporal predictive model for dengue was created for four provinces in Thailand and Laos. This model allows for the study of the influence of climate change on dengue. According to the model, there is a discernible rise in temperature between the current decade and the predicted future. In Thailand’s Ubon Province, the temperature was predicted to rise by 1.5 °C in 2020 compared to 2000, then by 3 °C by 2050 and 6 °C by 2090. The discussions underscored the interconnectedness of climate, human activities, and vector ecology in shaping VBD transmission patterns.

Vector control research and beyond

The iDEM (Intervention for Dengue Epidemiology in Malaysia) project which employs a proactive integrated vector management (IVM) approach was discussed. This approach emphasizes the use of auto-dissemination devices for larviciding, targeted outdoor residual spraying for adulticiding, and community engagement activities to control dengue. A 29% reduction in dengue cases during ‘outbreaks’ and a 43% reduction in ‘hotspots’ were recorded. In Malaysia, an outbreak is defined as the presence of two or more dengue cases that occur within a 200-m radius within 14 days of the first case notification date. A dengue hotspot is defined as an outbreak lasting more than 30 days following the start of the outbreak. The iDEM project’s operationalization during COVID-19, together with the difficulties faced and solutions found are among its highlight features [11].

A meta-analysis on volatile pyrethroid spatial repellents against mosquitoes showed that metofluthrin and transfluthrin were the main active ingredients studied, evaluated by either human landing catch or trap density. An overall protective efficacy was 48% (95% CI 41–55%) with higher protective efficacy measured using human landing catch (74%; 95% CI 73–76%) and passive fabric interventions showing the highest efficacy (64%; 95% CI 63–66%). Susceptibility varied across mosquito species, with the highest efficacy seen in Aedes species that were not Ae. aegypti and the lowest in An. funestus. Product format, active ingredient, mosquito species, study type, weather, and study design were highlighted as the evidence gaps. Important technologies discussed consisted of attractive toxic sugar baits, biological pesticides such as Bacillus thuringiensis var. israelensis (Bti), Pseudomonas entomophila, and Beauveria bassiana, Wolbachia, and sterile insect technique (SIT).

Community engagement for vector control

Through various presentations, there was unanimous agreement that community engagement plays a crucial role in the implementation of vector control strategies. Some presenters highlighted community engagement as a crucial part of IVM and climate change-driven vector management. In Cambodia in particular, where the National Malaria Control Program (CNM) and local task forces coordinate efforts, community engagement has made it possible to utilize insecticide-treated bed nets (ITNs) efficiently. Advice is given on cleaning, drying, and storing the nets—all of which are essential for maintaining their integrity and sustainability. Whereas the application of communication for behavioural impact (COMBI) Model to a pilot study delivering volatile pyrethroid spatial repellents and etofenprox insecticide-treated clothing highlighted user preferences. Community-led deployment of a spatial repellent product against Ae. aegypti in Mexico was noted with high satisfaction and efficacy in households. The talk on Singapore’s experience in public engagement for Wolbachia-based dengue control highlighted that emphasis on education, consultation, involvement, and feedback were crucial in the rollout of Wolbachia technology. High levels of awareness and acceptance were observed.

Improved targeting and delivery of vector control and surveillance tools: NextGen technology

The presentations highlighted the state-of-the-art technology in use or under development in vector control and management of VBDs. Cutting-edge technologies, including genetic modification, sterile insect techniques, machine learning, artificial intelligence, and novel insecticides, were showcased as promising tools in vector surveillance and control. Delving into the intricacies of the “Gene Drive for Vector Control” project, the significance of population genetics in developing genetic insecticides through CRISPR/Cas9 technology was emphasized. Population genetics is important for target site selection, understanding the spread of transgenes, population size, and identification of cryptic species. The gene targets for vector control consist of behavioural and sensory genes, immune genes, sex determination genes, and fertility genes.

In Singapore-based studies, presenters demonstrated the use of computational tools and AI-based models for forecasting and spatial risk determination of dengue. The use of machine learning support for Wolbachia releases, focusing on dynamic adjustments based on data has shown considerable gains in closing the time gaps and reducing mosquito density.

In a separate talk, a web-based surveillance for Ae. albopictus and Culex quinquefasciatus was demonstrated, utilizing the “MS-300” mosquito monitor that can specifically and efficiently capture the vectors and monitor their density automatically in real-time. A digital version of the Entomological Surveillance Planning Tool (ESPT), a decision-support tool for planning entomological surveillance activities, interpreting entomological data, and guiding programmatic vector control decisions.

Insect repellents: from lab discoveries to real-world protection

The presenters discussed spatial repellents' modes of action and protection gaps, emphasizing their efficacy in areas where LLINs and IRS are impractical. Citing case studies from the Mekong sub-region, a talk on the spatial repellents for malaria control emphasizing trials and challenges and shaping policy on the use of topical repellents.

The bite interruption toward elimination (BITE) project has played a crucial role in the study of insect repellents, particularly, volatile pyrethroid spatial repellents (VPSRs), evaluated in semi-field and field trials as well as modelling studies. Major findings include: (1) In Thailand, all VPSRs, etofenprox-treated forest ranger uniforms and civilian clothing (long trousers), and the combined intervention (VPSR1 + treated long civilian clothing), suggest potential to offer community protection by preventing diversion to nearby non-users through mosquito disarming. Treated civilian clothing (short trousers) did not reduce landing but did reduce post-exposure blood feeding success and increase 24-h mortality, also suggesting the potential to provide community protection by disarming and preventing diversion. (2) In Cambodia, all the intervention tools offered protection against mosquito bites but VSPR was the most effective with a 95% reduction in biting. Also in Cambodia, overall, Human Biting Rate (HBR) data demonstrated greater biting pressure outside than inside. However, integration of HBR data with Human Behavioural Observation data indicates that while peak biting measured by HLC occurred later in the evening (21:00–00:00 h), the primary gap in protection is during the early evening hours for people outside, awake, not under an ITN.

Insecticide resistance and management

The discussions offered comprehensive insights into the current situation and ongoing efforts. The WHO testing guidelines and the Global Vector Control Response 2017–2030 were particularly recommended as reference guidelines in the management of insecticide resistance. The five IVM elements of advocacy, legislation, and community engagement; cross-sector collaboration; integrated approaches; evidence-based decision making; and capacity-building provide a comprehensive, all of society approach to insecticide resistance management through the “all pest control options”. The presentations highlighted knockdown resistance (kdr) mutations as the major challenge in Ae. aegypti control using pyrethroids. The discovery of new mutations such as the L982W mutation, and concomitant mutations, L982W + F1534C and V1016G + F1534C, exacerbates this challenge.

Conclusion

Discussions throughout the conference explored advancements in vector control strategies, disease epidemiology, and surveillance, the impacts of climate change, insecticide resistance, and public health policies, celebrating successes, acknowledging setbacks, and setting a course for the future. Attendees, including students, young scientists, researchers, private sector colleagues, and academia, benefitted from professional development, knowledge expansion, and communication skills enhancement, through oral and poster presentations. The conference facilitated valuable networking opportunities, allowing participants to connect with professionals, leading to potential collaborations, research opportunities, internships, and job offers. Additionally, the conference served as an ideal platform for businesses to reach their target market, expand internationally, and gain visibility through various promotional activities. A summary of selected topics, presenters and their affiliations from different symposiums have been presented in Table 1. The Asia Pacific Malaria Conference on Mosquito and Vector Control is conducted every three years, and the next one is planned for Thailand in 2026.

Table 1 Selected topics and presenters at the Asia–Pacific Conference on Mosquito and Vector Control