Effects of mosquito age and batch size on knockdown and mortality of laboratory-reared Anopheles dirus, Anopheles minimus, and wild-caught Anopheles harrisoni (Diptera: Culicidae) exposed to transfluthrin using WHO tube and CDC bottle bioassays.

WHO tube and CDC bottle bioassays are currently available for insecticide resistance monitoring and malaria transmission research. Multiple parameters including mosquito density, age, and nutritional status may affect the readout in these bioassays' tests. This study aims to assess the effects of experimental factors on knockdown and mortality measurements in dominant malaria vectors in Thailand following exposure to sublethal and lethal doses of transfluthrin. The effects of (i) 3 different mosquito batch sizes (5, 10, and 20 individuals) and (ii) 2 age groups (3-5 and 20-23 days old) on outcomes measured using the WHO tube (14.7 µg/cm2) and CDC bottle bioassay discriminating concentration (0.006 µg/cm2) against 2 laboratory strains: Anopheles dirus Peyton & Harrison and Anopheles minimus Theobald (species A) and wild-caught Anopheles harrisoni Harbach & Manguin (species C). Our results showed higher knockdown at 1-h exposure using WHO tube and CDC bottle bioassays containing 20 individuals compared to batches containing 10 and 5 individuals. Older mosquitoes showed greater susceptibility than younger test population, especially for An. mininus. Our study supports WHO recommendations for using 3- to 5-day-old mosquitoes. It also validates Praulin et al. (2022) proposal to divide the cohort into smaller batches with more test replicates when it is not practicable to test 25 mosquitoes per replicate.

Effects of transfluthrin-treated jute and cotton clothing against resistant and susceptible Aedes aegypti (Diptera: Culicidae) in a semifield system.

Volatile pyrethroids exert a range of both lethal and behavioral effects on mosquitoes through the passive release of insecticides into the atmosphere. We investigated the protective efficacy (PE) of transfluthrin-treated jute (TI-jute) and cotton (TI-cotton) fabrics, worn at the back of a protective black vest, against laboratory-reared pyrethroid susceptible and resistant strains of Aedes aegypti (L.) in a semifield system (SFS). Each fabric (1,029 cm2) was treated with 1.79 mg/cm2 of transfluthrin as the intervention. Human landing collections were conducted by 2 collectors seated in designated treatment and control compartments of the SFS. The trials were conducted for 41 days, with 16 days partitioned into morning and evening phases. Furthermore, we examined blood feeding behavior and fecundity of the surviving mosquitoes post-exposure. Results showed that in the morning, the PE of TI-jute (49.4%) was higher than that of TI-cotton (36.8%). TI-jute demonstrated a lower PE of 9.6% against the transfluthrin-resistant strain. Remarkably, a significantly higher number of eggs were laid by the transfluthrin-resistant mosquitoes that survived the intervention (36.5 eggs/female) compared to the control group (11.8 eggs/female). These findings suggest that TI-jute can help protect against bites and alter the life traits of Ae. aegypti. The study highlights that the timing of the intervention during the day affected the efficacy of TI-jute and TI-cotton, while sublethal exposure to transfluthrin stimulated egg production in the resistant strain. These are critical challenges that warrant attention in vector control strategies. Investigating this phenomenon in mosquito reproduction necessitates future research at a molecular level.

Transfluthrin and Metofluthrin as Effective Repellents against Pyrethroid-Susceptible and Pyrethroid-Resistant Aedes aegypti (L.) (Diptera: Culicidae).

Aedes aegypti is a major vector of dengue fever in tropical regions. Spatial repellents (SRs) have shown promise in delaying pesticide resistance. Methods for discriminating concentrations (DCs) are well established using various bioassay tools, while data for high-throughput screening system (HITSS) toxicity bioassay (TOX) are absent. In this study, we compared and optimized lethal (LCs) and sub-lethal concentrations (SLCs) of transfluthrin (TFT) and metofluthrin (MFT) on pyrethroid-susceptible (USDA) and pyrethroid-resistant (Pu-Teuy) Ae. aegypti (L.) strains, using the HITSS-TOX. Mean mortality (MT) was 100% at LC99 and DC, compared to LC50 (45.0 ± 3.7%) and LC75 (65.8 ± 7.0%) for the USDA strain. However, the resistant strain (Pu-Teuy) showed reduced susceptibility against TFT and a significantly lower MT at LC50 (12.5 ± 4.4%; t = 5.665, df = 10, p < 0.001), LC75 (9.2 ± 3.5%; t = 4.844, df = 10, p = 0.001), LC99 (55.0 ± 9.9%; t = 4.538, df = 5, p = 0.006), and DC (75.0 ± 5.2%; U = 3.0, p = 0.007). The DC of TFT (0.15222%) was 4.7-fold higher than for MFT (0.03242%) in USDA strain. The baseline DCs established are useful to better understand susceptibility and the efficacy of various repellents against field populations of Ae. aegypti.

Aedes aegypti and Aedes albopictus (Diptera: Culicidae) ecology, biology, behaviour, and implications on arbovirus transmission in Thailand: Review.

Aedes aegypti and Aedes albopictus (Aedes) transmit highly pathogenic viruses such as dengue, chikungunya, yellow fever, and Zika which can cause life-threatening diseases in humans. They are the most important vectors of arboviruses in Thailand. Their vectorial capacity (VC) is highly complex mainly due to the interplay between biotic and abiotic factors that vary in time and space. A literature survey was conducted to collate and discuss recent research regarding the influence of Aedes vector biology, behaviour, and ecology on arbovirus transmission in Thailand. The survey followed guidelines of preferred reporting items of systematic reviews and meta-analyses (PRISMA). All fields, keyword search was conducted in the Web of Science database for the period of 2000-2021. The search yielded 821 records on Ae. aegypti and 293 records on Aedes albopictus, of which 77 were selected for discussion. Genomic studies showed that there is a high genetic variation in Aedes albopictus whereas Ae. aegypti generally shows low genetic variation. Along with genetically unstable arboviruses, the interaction between Aedes and arboviruses is largely regulated by genomic events such as genetic mutations and immune response protein factors. Temperature and precipitation are the major climatic events driving arbovirus transmission. Human exposure risk factors are mainly due to multiple feeding patterns, including endophagy by Aedes albopictus and zoophagic behaviour of Ae. aegypti as well as diverse human-associated breeding sites. Integration of the One Health approach in control interventions is a priority with a rigorous focus on Aedes-arbovirus surveillance as a complementary strategy.

An active and targeted survey reveals asymptomatic malaria infections among high-risk populations in Mondulkiri, Cambodia.

BACKGROUND: Malaria is a mosquito-borne disease that is one of the most serious public health issues globally and a leading cause of mortality in many developing countries worldwide. Knowing the prevalence of both symptomatic and asymptomatic malaria on a subnational scale allows for the estimation of the burden of parasitaemia present in the transmission system, enabling targeting and tailoring of resources towards greater impact and better use of available capacity. This study aimed to determine the PCR-based point prevalence of malaria infection, by parasite species, among three high-risk populations in Mondulkiri province, Cambodia: forest rangers, forest dwellers, and forest goers. METHODS: A cross-sectional survey was performed during the transmission season in November and December 2021. Blood samples collected on filter paper from participants (n = 1301) from all target groups were screened for Plasmodium spp using PCR. RESULTS: Malaria prevalence among all study participants was 6.7% for any Plasmodium species. Malaria prevalence in the forest ranger group was 8.1%, was 6.8% in forest goers, and 6.4% in forest dwellers; all infections were asymptomatic. Plasmodium vivax was detected in all participant groups, while the few Plasmodium falciparum infections were found in goers and dwellers. 81% of all infections were due to P. vivax, 9% were due to P. falciparum, 3% due to Plasmodium cynomolgi, and the rest (7%) remained undefined. Gender was associated with malaria infection prevalence, with male participants having higher odds of malaria infection than female participants (OR = 1.69, 95% CI 1.08-2.64). Passively collected malaria incidence data from the Cambodian government were also investigated. Health facility-reported malaria cases, based on rapid diagnostic tests, for the period Jan-Dec 2021 were 521 Plasmodium vivax (0.89% prevalence), 34 P. falciparum (0.06%) and four P. falciparum + mixed (0.01%)-a total of 559 cases (0.95%) for all of Mondulkiri. CONCLUSION: This reservoir of asymptomatic parasitaemia may be perpetuating low levels of transmission, and thus, new strategies are required to realize the goal of eliminating malaria in Cambodia by 2025.

The effect of transfluthrin-treated jute and cotton emanator vests on human landing and fecundity of Anopheles minimus in Thailand.

Complementary approaches to tackle outdoor and early evening biting mosquitoes are urgently required. Transfluthrin (TFT) is a volatile pyrethroid capable of altering mosquito feeding behavior. This study investigated the efficacy of TFT-treated jute (TFT-J) and cotton (TFT-C) fabrics on human landing activity, feeding and fecundity of Anopheles minimus in Thailand. Jute and cotton fabrics each measuring 1024 cm2 were impregnated with 7.34 × 10-4 g/cm2 TFT (20%, w/v), and evaluated in a semi-field screen house system. Two collectors, wearing an untreated control or TFT-treated vests, conducted human-landing collections of released 100 laboratory-reared adult females of An. minimus from 18:00-00:00 h for 16 consecutive nights. Recaptured mosquitoes were given a blood meal for 30 min. with a membrane feeding system for assessment of blood feeding and fecundity. TFT-J, relative to control, significantly reduced human landings (Odds Ratio (OR) =0.27 (95% Confidence Interval (CI) [0.10-0.74], p = 0.011)), however no significant reduction was observed for TFT-C (OR=0.67 [95% CI 0.24-1.82], p = 0.43). Blood feeding was significantly lower among mosquitoes exposed to TFT-J (12.45% [95% CI, 2.04-22.85], p = 0.029) and TFT-C (13% [95% CI, 0.99-26.84], p = 0.016) relative to control. Impregnated fabrics had no effect on the mean number of egg oviposition. However, egg hatchability was reduced in TFT-J (49.5% [95% CI, 21.74-77.26], p = 0.029) and TFT-C (40.2% [95% CI, 17.21-63.19], p = 0.008) relative to control. TFT-J significantly reduced the landing, blood feeding, and fertility of An. minimus. Further studies are needed to evaluate different treatment methods on fabrics and their incorporation in integrated mosquito management.

Comparable Outcomes Between Native and Periprosthetic Fractures of the Distal Femur.

Despite the rising prevalence of arthroplasty and aging population, limited data exist regarding differences in periprosthetic fracture clinical outcomes compared with native counterparts. This study compares differences in hospital treatment, morbidity, and mortality associated with periprosthetic distal femur fractures at an urban level 1 trauma center. We retrospectively reviewed all adult AO/OTA type 33 fractures (526) that presented to our institution between 2009 and 2018. In total, 54 native and 54 periprosthetic fractures were matched by age and gender. We recorded demographics, operative measures, length of stay (LOS), discharge disposition, and mortality. We used McNemar's and paired t-tests for analysis where appropriate (p < 0.05) (IBM SPSS Statistics for Windows, Version 26.0. Armonk, NY; IBM Corp.). The average age at injury was 74 years ± 12 (native) compared with 73 years ± 12 (periprosthetic). After 1:1 matching, the groups had similar body mass index (31.01 vs. 32.98, p = 0.966 for native and periprosthetic, respectively) and mechanisms of injury with 38 native and 44 periprosthetic (p = 0.198) fractures from low-energy falls. Both groups had 51/54 fractures managed with open reduction internal fixation with a locking plate. The remaining were managed via amputation or intramedullary nail fixation. Mean operative time (144 minutes (±64) vs. 132 minutes (±62), p = 0.96) and estimated blood loss (319 mL (±362) vs. 289 mL (±231), p = 0.44) were comparable between the native and periprosthetic groups, respectively. LOS: 9 days ± 7 (native) versus 7 days ± 5 (periprosthetic, p = 0.31); discharge disposition (to skilled nursing facility/rehab): n = 47 (native) versus n = 43 (periprosthetic, p = 0.61); and mortality: n = 6 (native) versus n = 8 (periprosthetic, p = 0.55). No significant differences were observed. We found no statistical differences in morbidity and mortality in periprosthetic distal femur fractures treated over 10 years at a level 1 trauma center. Native and periprosthetic AO/OTA type 33 distal femur fractures are serious injuries with similar outcomes at a level 1 trauma center.

Comparison of Vector Trapping Methods for Outdoor Biting Malaria Vector Surveillance in Thailand and Vietnam.

The performances of the human-baited double net trap (HDNT) and the human-baited host decoy trap (HDT) methods were compared against the outdoor human landing catch (OHLC) method in Thailand and Vietnam. Two study sites were selected in each country: a rural village and a nearby forest setting. The three outdoor trap methods were rotated nightly between three set trapping positions, in a pre-assigned Latin square design. Volunteers were rotated following the trap rotation to avoid bias. The greatest number of adult mosquitoes was collected from the forest sites in both countries, showing Anopheles minimus (s.s.) Theobald (96.54%) and Anopheles dirus (s.s.) Peyton & Harrison (25.71%) as the primary malaria vectors in Thailand and Vietnam, respectively. At the Thai forest site, OHLC collected significantly more anopheline mosquitoes per trap night than HDNT and HDT, with mean ± standard error values of 14.17 ± 4.42, 4.83 ± 1.56, and 4.44 ± 1.45, respectively, whilst HDNT and HDT were significantly less productive at 0.34 times and 0.31 times, respectively, than OHLC in capturing anopheline mosquitoes. However, there were no significant differences among the three methods of trapping malaria vectors for the village site. At the Vietnamese forest site, HDNT achieved the highest performance in collecting Anopheline mosquitoes at 1.54 times compared to OHLC, but there was no significant difference between the two traps. The results suggested HDNT could be a possible alternative trap to OHLC in this area. Although HDT was less efficient at attracting Anopheline mosquitoes, it was highly efficient at trapping culicine mosquitoes.

Semi-field evaluation of human landing catches versus human double net trap for estimating human biting rate of Anopheles minimus and Anopheles harrisoni in Thailand.

Background: Whilst the human landing catch (HLC) technique is considered the 'gold standard' for estimating human-biting rates, it is labor-intensive and fraught with potential risk of exposure to infectious mosquito bites. This study evaluated the feasibility and performance of an alternative method, the human double net trap (HDNT) relative to HLC for monitoring host-seeking malaria vectors of the Anopheles minimus complex in a semi-field system (SFS). Methods: HDNT and HLC were positioned in two rooms, 30 m apart at both ends of the SFS. Two human volunteers were rotated between both traps and collected released mosquitoes (n = 100) from 6:00 pm till 6:00 am. Differences in Anopheles mosquito densities among the trapping methods were compared using a generalized linear model based on a negative binomial distribution. Results: There were 82.80% (2,136/2,580) of recaptures of wild-caught and 94.50% (2,835/3,000) of laboratory-reared mosquitoes that were molecularly identified as An. harrisoni and An. minimus, respectively. Mean density of An. harrisoni was significantly lower in HNDT (15.50 per night, 95% CI [12.48-18.52]) relative to HLC (25.32 per night (95% CI [22.28-28.36]), p < 0.001). Similarly, the mean density of a laboratory strain of An. minimus recaptured in HDNT was significantly lower (37.87 per night, 95% CI [34.62-41.11]) relative to HLC (56.40 per night, 95% CI [55.37-57.43]), p < 0.001. Relative sampling efficiency analysis showed that HLC was the more efficient trap in collecting the An. minimus complex in the SFS. Conclusion: HDNT caught proportionately fewer An. minimus complex than HLC. HDNT was not sensitive nor significantly correlated with HLC, suggesting that it is not an alternative method to HLC.

Scientific achievements and reflections after 20 years of vector biology and control research at the Pu Teuy mosquito field research station, Thailand.

Additional vector control tools are needed to supplement current strategies to achieve malaria elimination and control of Aedes-borne diseases in many settings in Thailand and the Greater Mekong Sub-region. Within the next decade, the vector control community, Kasetsart University (KU), and the Ministry of Higher Education, Science, Research and Innovation must take full advantage of these tools that combine different active ingredients with different modes of action. Pu Teuy Mosquito Field Research Station (MFRS), Department of Entomology, Faculty of Agriculture, Kasetsart University (KU), Thailand was established in 2001 and has grown into a leading facility for performing high-quality vector biology and control studies and evaluation of public health insecticides that are operationally relevant. Several onsite mosquito research platforms have been established including experimental huts, a 40-m long semi-field screening enclosure, mosquito insectary, field-laboratory, and living quarters for students and researchers. Field research and assessments ranged from 'basic' investigations on mosquito biology, taxonomy and genetics to more 'applied' studies on responses of mosquitoes to insecticides including repellency, behavioural avoidance and toxicity. In the course of two decades, 51 peer-reviewed articles have been published, and 7 masters and 16 doctoral degrees in Entomology have been awarded to national and international students. Continued support of key national stakeholders will sustain MFRS as a Greater Mekong Subregion centre of excellence and a resource for both insecticide trials and entomological research.

Entomological outcomes of cluster-randomised, community-driven dengue vector-suppression interventions in Kampong Cham province, Cambodia.

Cambodia has one of the highest dengue infection rates in Southeast Asia. Here we report quantitative entomological results of a large-scale cluster-randomised trial assessing the impact on vector populations of a package of vector control interventions including larvivorous guppy fish in household water containers, mosquito trapping with gravid-ovitraps, solid waste management, breeding-container coverage through community education and engagement for behavioural change, particularly through the participation of school children. These activities resulted in major reductions in Container Index, House Index, Breteau Index, Pupal Index and Adult Index (all p-values 0.002 or lower) in the Intervention Arm compared with the Control Arm in a series of household surveys conducted over a follow-up period of more than one year, although the project was not able to measure the longer-term sustainability of the interventions. Despite comparative reductions in Adult Index between the study arms, the Adult Index was higher in the Intervention Arm in the final household survey than in the first household survey. This package of biophysical and community engagement interventions was highly effective in reducing entomological indices for dengue compared with the control group, but caution is required in extrapolating the reduction in household Adult Index to a reduction in the overall population of adult Aedes mosquitoes, and in interpreting the relationship between a reduction in entomological indices and a reduction in the number of dengue cases. The package of interventions should be trialled in other locations.

Field Efficacy of Larvivorous Fish and Pyriproxyfen Combined with Community Engagement on Dengue Vectors in Cambodia: A Randomized Controlled Trial.

Evidence on the effectiveness of low-cost, sustainable biological vector control tools for Aedes mosquitoes is limited. Therefore, the purpose of this trial was to estimate the impact of guppy fish in combination with the larvicide pyriproxyfen (PPF) (Sumilarv® 2MR) and communication for behavioral impact (COMBI) activities to reduce entomological indices in Cambodia. In this cluster randomized, controlled superiority trial, 30 clusters comprised of one or more villages each was allocated in a 1:1:1 ratio to receive either 1) all three interventions (guppies, PPF, and COMBI), 2) two interventions (guppies and COMBI), or 3) control (standard vector control). Entomological surveys among 40 randomly selected households per cluster were carried out quarterly. The primary outcome was the population abundance of adult female Aedes mosquitoes trapped using adult resting collections. In the primary analysis, adult female Aedes abundance and mosquito infection rates was aggregated over follow-up time points to give a single rate per cluster. These data were analyzed by negative binomial regression, yielding abundance ratios (ARs). The number of Aedes females was reduced roughly by half compared with the control in both the guppy, PPF, and COMBI arm (AR = 0.54; 95% CI, 0.34-0.85; P = 0.0073); and the guppy and COMBI arm (AR = 0.49; 95% CI, 0.31-0.77; P = 0.0021). The effectiveness demonstrated and extremely low cost of including fish rearing in community-based health structures suggest they should be considered as a vector control tool as long as the benefits outweigh any potential environmental concerns. Sumilarv® 2MR was also highly accepted and preferred over current vector control tools used in Cambodia.

Forced Egg Laying Method to Establish F1 Progeny from Field Populations and Laboratory Strains of Anopheles Mosquitoes (Diptera: Culicidae) in Thailand.

Successful monitoring of physiological resistance of malaria vectors requires about 150 female mosquitoes for a single set of tests. In some situations, the sampling effort is insufficient due to the low number of field-caught mosquitoes. To address this challenge, we demonstrate the feasibility of using the forced oviposition method for producing F1 from field-caught Anopheles mosquitoes. A total of 430 and 598 gravid Anopheles females from four laboratory strains and five field populations, respectively, were tested. After blood feeding, gravid mosquitoes were individually introduced into transparent plastic vials, containing moistened cotton balls topped with a 4 cm2 piece of filter paper. The number of eggs, hatching larvae, pupation, and adult emergence were recorded daily. The mean number of eggs per female mosquito ranged from 39.3 for Anopheles cracens to 93.6 for Anopheles dirus in the laboratory strains, and from 36.3 for Anopheles harrisoni to 147.6 for Anopheles barbirostris s.l. in the field populations. A relatively high egg hatching rate was found in An. dirus (95.85%), Anopheles minimus (78.22%), and An. cracens (75.59%). Similarly, a relatively high pupation rate was found for almost all test species ranging from 66% for An. minimus to 98.7% for Anopheles maculatus, and lowest for An. harrisoni (43.9%). Highly successful adult emergence rate was observed among 85-100% of pupae that emerged in all tested mosquito populations. The in-tube forced oviposition method is a promising method for the production of sufficient F1 progeny for molecular identification, vector competence, insecticide resistance, and bioassay studies.

Report of the 2018 annual meeting of the Asia Pacific Malaria Elimination Network Vector Control Working Group: harnessing skills and knowledge for malaria elimination across the Asia Pacific.

The 2018 Asia Pacific Malaria Elimination Network's Vector Control Working Group (APMEN VCWG) annual meeting took place 3-5 September 2018 in Bangkok, Thailand. It was designed to be a forum for entomology and public health specialists from APMEN country programmes (over 90 participants from 30 countries) to discuss current progress and challenges related to planning, implementing, and sustaining effective vector control (VC) strategies for malaria elimination across the region, and to suggest practical and applicable solutions to these moving forward. The meeting was organised as a joint collaboration between the VCWG host institution-Faculty of Tropical Medicine, Mahidol University, Thailand-and leading partner institutions within the VCWG: Malaria Consortium and the Malaria Elimination Initiative at the University of California, San Francisco, Global Health Group (UCSF Global Health Group), under the leadership of the APMEN Director and VCWG Co-Chairs from ministries of health in Malaysia and India. This report provides an introduction to the role and nature of the VCWG, highlights key themes and topics presented and discussed at the meeting, and outlines the future objectives and focal areas for the VCWG and APMEN at large.

Residual Malaria Transmission in Select Countries of Asia-Pacific Region: Old Wine in a New Barrel.

BACKGROUND: Despite substantial reductions in malaria burden and improvement in case management, malaria remains a major public health challenge in the Asia-Pacific region. Residual malaria transmission (RMT) is the fraction of total transmission that persists after achievement of full operational coverage with effective insecticide-treated bed nets (ITNs)/long-lasting insecticidal nets (LLINs) and/or indoor residual spray interventions. There is a critical need to standardize and share best practices for entomological, anthropological, and product development investigative protocols to meet the challenges of RMT and elimination goals. METHODS: A systematic review was conducted to describe when and where RMT is occurring, while specifically targeting ownership and usage of ITN/LLINs, indoor residual spray application, insecticide susceptibility of vectors, and human and vector biting behavior, with a focus on nighttime activities. RESULTS: Sixty-six publications from 1995 to present met the inclusion criteria for closer review. Associations between local vector control coverage and use with behaviors of human and mosquito vectors varied by locality and circumstance. Consequently, the magnitude of RMT is insufficiently studied and analyzed with sparse estimates of individual exposure in communities, insufficient or incomplete observations of ITN/LLIN use, and the local human population movement into and from high-risk areas. CONCLUSIONS: This review identified significant gaps or deficiencies that require urgent attention, namely, developing standardized procedures and methods to estimate risk exposure beyond the peridomestic setting, analytical approaches to measure key human-vector interactions, and seasonal location-specific agricultural or forest use calendars, and establishing the collection of longitudinal human and vector data close in time and location.

Field Evaluation of a Spatial Repellent Emanation Vest for Personal Protection Against Outdoor Biting Mosquitoes.

Exophilic vectors are an important contributor to residual malaria transmission. Wearable spatial repellents (SR) can potentially provide personal protection in early evening hours before people retire indoors. An SR prototype for passive delivery of transfluthrin (TFT) for protecting humans against nocturnal mosquitoes in Kanchanaburi, western Thailand, is evaluated. A plastic polyethylene terephthalate (PET) sheet (676 cm2) treated with 55-mg TFT (TFT-PET), attached to the back of short-sleeve vest worn by human collector, was evaluated under semifield and outdoor conditions. Field-caught, nonblood-fed female Anopheles minimus s.l. were released in a 40 m length, semifield screened enclosure. Two collectors positioned at opposite ends conducted 12-h human-landing collections (HLC). The outdoor experiment was conducted between treatments among four collectors at four equidistant positions who performed HLC. Both trials were conducted for 30 consecutive nights. TFT-PET provided 67% greater protection (P < 0.001) for 12 h compared with unprotected control, a threefold reduction in the attack. In outdoor trials, TFT-PET provided only 16% protection against An. harrisoni Harbach & Manguin (Diptera: Culicidae) compared with unprotected collector (P = 0.0213). The TFT-PET vest reduced nonanophelines landing by 1.4-fold compared with the PET control with a 29% protective efficacy. These findings suggest that TFT-PET had diminished protective efficacy in an open field environment. Nonetheless, the concept of a wearable TFT emanatory device has the potential for protecting against outdoor biting mosquitoes. Further development of portable SR tools is required, active ingredient selection and dose optimization, and more suitable device design and materials for advancing product feasibility.

Fostering social innovation and building adaptive capacity for dengue control in Cambodia: a case study.

BACKGROUND: The social-ecological systems theory, with its unique conception of resilience (social-ecological systems & resilience, SESR), provides an operational framework that currently best meets the need for integration and adaptive governance as encouraged by the Sustainable Development Goals. SESR accounts for the complex dynamics of social-ecological systems and operationalizes transdisciplinarity by focusing on community engagement, value co-creation, decentralized leadership and social innovation. Targeting Social Innovation (SI) in the context of implementation research for vector-borne diseases (VBD) control offers a low-cost strategy to contribute to lasting and contextualized community engagement in disease control and health development in low and middle income countries of the global south. In this article we describe the processes of community engagement and transdisciplinary collaboration underpinning community-based dengue management in rural primary schools and households in two districts in Cambodia. METHODS: Multiple student-led and community-based interventions have been implemented focusing on empowering education, communication for behavioral change and participatory epidemiology mapping in order to engage Cambodian communities in dengue control. We describe in particular the significance of the participatory processes that have contributed to the design of SI products that emerged following iterative consultations with community stakeholders to address the dengue problem. RESULTS: The SI products that emerged following our interaction with community members are 1) adult mosquito traps made locally from solid waste collections, 2) revised dengue curriculum with hands-on activities for transformative learning, 3) guppy distribution systems led by community members, 4) co-design of dengue prevention communication material by students and community members, 5) community mapping. CONCLUSIONS: The initiative described in this article put in motion processes of community engagement towards creating ownership of dengue control interventions tools by community stakeholders, including school children. While the project is ongoing, the project's interventions so far implemented have contributed to the emergence of culturally relevant SI products and provided initial clues regarding 1) the conditions allowing SI to emerge, 2) specific mechanisms by which it happens and 3) how external parties can facilitate SI emergence. Overall there seems to be a strong argument to be made in supporting SI as a desirable outcome of project implementation towards building adaptive capacity and resilience and to use the protocol supporting this project implementation as an operational guiding document for other VBD adaptive management in the region.

Behavioral responses to transfluthrin by Aedes aegypti, Anopheles minimus, Anopheles harrisoni, and Anopheles dirus (Diptera: Culicidae).

Airborne spatial repellency (SR) is characterized and distinguished from other chemical actions including contact locomotor excitation and toxicity. The use of volatile spatial repellents is a potential new intervention class for combatting mosquito-borne pathogen transmission; therefore, continuing investigations on the actions of these chemicals that modify mosquito host-seeking behavior (i.e., bite prevention) is needed. The objective of this study is to characterize the key behavioral avoidance actions of transfluthrin (TFT) to advance spatial repellent development into practical products. Behavioral avoidance responses were observed for adult laboratory strains of Aedes aegypti, Anopheles minimus and An. dirus, and two field populations of An. harrisoni and Ae. aegypti, respectively. Established TFT sublethal (LC50 and LC75), lethal concentrations (LC99) and discriminating concentrations (DCs) were selected corresponding to each mosquito test species. Spatial repellency and contact excitation ('irritancy') responses on adult mosquitoes to TFT were assessed using an excito-repellency assay system. At LC50, TFT exhibited strong avoidance with An. minimus (60.1% escape) and An. dirus (80% escape) laboratory strains, showing between 12 and 16x greater escape response than Ae. aegypti (5% escape). Repellency responses for field collected Ae. aegypti and An. harrisoni were 54.9 and 47.1% escape, respectively. After adjusting the initial contact escape response (a measure of combined irritancy and repellency) to estimate only escape due to contact, the LC50 and LC99 showed moderate escape irritancy with laboratory Ae. aegypti (41.4% escape) and no contact activity against the field population. Adjustment showed only weak contact activity (16.1% escape) in laboratory An. minimus at LC50. Spatial repellency is the predominant mode of action of TFT among colonized and field mosquitoes used in this study. Established baseline (susceptible) dose-response curves assist in optimizing SR products for mosquito control and pathogen transmission prevention.