Human Landing Collections Research Articles

The Mosquitoes (Diptera: Culicidae) of Sonora: Distribution, Ecology, and the First Records of Aedes deserticola Zavortink and Toxorhynchites septentrionalis (Dyar and Knab) in México

The diversity and distribution of mosquitoes from Sonora, Mexico, was documented through entomologic surveys conducted in the four physiographic regions and sub-regions of Sonora: the Sonoran Plain, the Sierra Madre Occidental, the Northern Mountains and Plains, and the Pacific Coastal Plain. Immature stages were collected from aquatic habitats, while adult mosquitoes were collected using Shannon traps, resting in vegetation, and by human landing collections. Overall, 11,316 specimens, which comprised 493 larvae, 224 larval exuviae, 400 pupal exuviae, 33 pupae, 4552 females, 5607 males, and seven male genitalia, were identified. Two subfamilies: Anophelinae and Culicinae, seven tribes, 10 genera, 23 subgenera, and 56 species are reported below. Of these, one tribe, one genus, five subgenera, and 15 species were recorded for the first time in Sonora. Two species, Aedes deserticola Zavortink and Toxorhynchites septentrionalis (Dyar and Knab), are the first recordings of their kind nationwide. Toxorhynchites septentrionalis was also barcoded with the cytochrome oxidase subunit 1 (COI) gene. The presence of Psorophora columbiae (Dyar and Knab) is confirmed in Mexico. Taxonomic notes, new geographic distribution limits of mosquitoes in Sonora, and information regarding their importance as disease vectors are provided. By adding Ae. deserticola and Tx. septentrionalis and confirming Ps. columbiae in Mexico, there are currently 251 mosquito species in the Country.

Mark-Release-Recapture Trial with Aedes albopictus (Diptera, Culicidae) Irradiated Males: Population Parameters and Climatic Factors.

Aedes albopictus is considered one of the major invasive species in the world and can transmit viruses such as dengue, Zika, or chikungunya. The Sterile Insect Technique (SIT) can be used to suppress the native populations of Ae. albopictus. Mark-release-recapture (MRR) studies are crucial to support the development of the release strategy during the SIT application. Meanwhile, weather conditions can affect the MRR trial's results and it is critical to understand the influence of climatic factors on the results. In October 2022, 84,000 irradiated sterile males were released for three consecutive weeks in Faro, Southern Portugal. Mosquitoes were recaptured by human landing collection (HLC) one, two, four, and six days after release. Generalized linear models with a negative binomial family and log function were used to estimate the factors associated with the number of recaptured mosquitoes, prevalence ratios, and the 95% confidence intervals (CIs). A total of 84,000 sterile male mosquitoes were released, with 528 recaptured (0.8%) by HLC. The prevalence of recaptured mosquitoes was 23% lower when the wind intensity was moderate. Marked sterile males had an average median distance travelled of 88.7 m. The median probability of daily survival and the average life expectancy were 61.6% and 2.1 days, respectively. The wild male population estimate was 443.33 males/ha. Despite no statistically significant association being found with humidity, temperature, and precipitation, it is important to consider weather conditions during MRR trial analyses to obtain the best determinant estimation and a more efficient application of the SIT in an integrated vector management program.

Species diversity of mosquitoes (Diptera: Culicidae), larval habitat characteristics, and potential as vectors for lymphatic filariasis in Central Bengkulu Regency, Indonesia.

Lymphatic filariasis (LF) is a vector-borne disease in various regions of Indonesia. The transmission dynamics within a locality are intricately linked to the presence of the pathogen (microfilaria), definitive host (humans), intermediate host (mosquitoes), reservoir, and environmental factors. The geographic landscape of Central Bengkulu Regency, which is characterized by plantations, marshlands, and forests, serves as a suitable habitat for mosquitoes. Understanding species diversity, vector behaviors, habitat characteristics, and microfilarial presence is crucial for devising effective and efficient control strategies. This study aimed to identify species diversity, assess biting patterns, characterize larval habitats, and detect microfilarial presence in mosquitoes. Mosquito collection was conducted using human landing collection (HLC) and resting collection indoors and outdoors for 6 months at a frequency of twice monthly from November 2022 to May 2023. The larvae were collected using dippers and pipettes. Adult mosquitoes and larvae were identified at the species level and analyzed using diversity indices. The measured larval bioecological parameters included physical, chemical, and biological conditions. The mosquito density obtained through HLC was calculated using the man-hour density (MHD) and man-biting rate (MBR) formulas. The presence of microfilaria was confirmed using a polymerase chain reaction. A total of 808 adult mosquitoes from five genera and 18 species were captured, along with 485 larvae from four genera and eight species. The mosquito diversity was moderate. The dominant adult species included Armigeres subalbatus (44.8%), whereas Aedes albopictus (25.4%) and Ar. subalbatus (22.3%) were abundant larvae. The highest larval density was observed in natural ponds. The average MBR was three mosquitoes per person per night, with fluctuating nightly activity (mean MHD of 1.8 mosquitoes per person per hour). Larval habitats had temperatures of 25.4°C-28.7°C, illumination of 224-674 lx, and pH of 7.1-7.9, with over half being turbid and nearly two-thirds lacking predators. Microfilariae were not detected in the tested mosquitoes. The presence of mosquitoes, their habitat, and the high density of Ar. subalbatus contributes to the transmission of LF in Central Bengkulu Regency, Indonesia.

Longitudinal survey of insecticide resistance in a village of central region of Burkina Faso reveals co-occurrence of 1014F, 1014S and 402L mutations in Anopheles coluzzii and Anopheles arabiensis

BackgroundPyrethroid resistance is one of the major threats for effectiveness of insecticide-treated bed nets (ITNs) in malaria vector control. Genotyping of mutations in the voltage gated sodium channel (VGSC) gene is widely used to easily assess the evolution and spread of pyrethroid target-site resistance among malaria vectors. L1014F and L1014S substitutions are the most common and best characterized VGSC mutations in major African malaria vector species of the Anopheles gambiae complex. Recently, an additional substitution involved in pyrethroid resistance, i.e. V402L, has been detected in Anopheles coluzzii from West Africa lacking any other resistance alleles at locus 1014. The evolution of target-site resistance mutations L1014F/S and V402L was monitored in An. coluzzii and Anopheles arabiensis specimens from a Burkina Faso village over a 10-year range after the massive ITN scale-up started in 2010.MethodsAnopheles coluzzii (N = 300) and An. arabiensis (N = 362) specimens collected both indoors and outdoors by different methods (pyrethrum spray catch, sticky resting box and human landing collections) in 2011, 2015 and 2020 at Goden village were genotyped by TaqMan assays and sequencing for the three target site resistance mutations; allele frequencies were statistically investigated over the years.ResultsA divergent trend in resistant allele frequencies was observed in the two species: 1014F decreased in An. coluzzii (from 0.76 to 0.52) but increased in An. arabiensis (from 0.18 to 0.70); 1014S occurred only in An. arabiensis and slightly decreased over time (from 0.33 to 0.23); 402L increased in An. coluzzii (from 0.15 to 0.48) and was found for the first time in one An. arabiensis specimen. In 2020 the co-occurrence of different resistance alleles reached 43% in An. coluzzii (alleles 410L and 1014F) and 32% in An. arabiensis (alleles 1014F and 1014S).ConclusionsOverall, an increasing level of target-site resistance was observed among the populations with only 1% of the two malaria vector species being wild type at both loci, 1014 and 402, in 2020. This, together with the co-occurrence of different mutations in the same specimens, calls for future investigations on the possible synergism between resistance alleles and their phenotype to implement local tailored intervention strategies.

The potential role of the Asian bush mosquito Aedes japonicus as spillover vector for West Nile virus in the Netherlands

BackgroundIn recent years the Asian bush mosquito Aedes japonicus has invaded Europe, including the Netherlands. This species is a known vector for a range of arboviruses, possibly including West Nile virus (WNV). As WNV emerged in the Netherlands in 2020, it is important to investigate the vectorial capacity of mosquito species present in the Netherlands to estimate the risk of future outbreaks and further spread of the virus. Therefore, this study evaluates the potential role of Ae. japonicus in WNV transmission and spillover from birds to dead-end hosts in the Netherlands.MethodsWe conducted human landing collections in allotment gardens (Lelystad, the Netherlands) in June, August and September 2021 to study the diurnal and seasonal host-seeking behaviour of Ae. japonicus. Furthermore, their host preference in relation to birds using live chicken-baited traps was investigated. Vector competence of field-collected Ae. japonicus mosquitoes for two isolates of WNV at two different temperatures was determined. Based on the data generated from these studies, we developed a Susceptible-Exposed-Infectious-Recovered (SEIR) model to calculate the risk of WNV spillover from birds to humans via Ae. japonicus, under the condition that the virus is introduced and circulates in an enzootic cycle in a given area.ResultsOur results show that Ae. japonicus mosquitoes are actively host seeking throughout the day, with peaks in activity in the morning and evening. Their abundance in August was higher than in June and September. For the host-preference experiment, we documented a small number of mosquitoes feeding on birds: only six blood-fed females were caught over 4 full days of sampling. Finally, our vector competence experiments with Ae. japonicus compared to its natural vector Culex pipiens showed a higher infection and transmission rate when infected with a local, Dutch, WNV isolate compared to a Greek isolate of the virus. Interestingly, we also found a small number of infected Cx. pipiens males with virus-positive leg and saliva samples.ConclusionsCombining the field and laboratory derived data, our model predicts that Ae. japonicus could act as a spillover vector for WNV and could be responsible for a high initial invasion risk of WNV when present in large numbers.Graphical

Biodiversity, ecology, and bionomic aspects of Anopheles mosquitoes during the dry season in southern Sumatra

Abstract. Dalilah D, Anwar C, Syafruddin D, Saleh I, Pahlepi RI. 2024. Biodiversity, ecology, and bionomic aspects of Anopheles mosquitoes during the dry season in southern Sumatra. Biodiversitas 25: 1644-1654. South Sumatra and Lampung are western parts of Indonesia’s provinces that are endemic to malaria. This study aimed to determine Anopheles mosquitoes’ diversity, ecology, and biting behavior in both provinces. Understanding the diversity, ecology, and bionomy of Anopheles supports malaria elimination in endemic areas as well as surveillance of vectors in malaria-eliminated areas. The study was conducted during the dry season from June to July 2023. Mosquitoes were collected from southern Sumatra, Indonesia, i.e. Segara Kembang Village in Ogan Komering Ulu (OKU) District, South Sumatra Province, as well as Gayau and Durian Villages in Pesawaran District, Lampung Province. Adult mosquitoes were caught by human landing, resting, and cattle bait collection, while larvae were collected with dippers in the breeding habitat. A total of 4426 mosquitoes from 8 species of Anopheles were identified based on their morphology. The diversity index of Anopheles from all sample areas during this season was low (H’<1). Anopheles barbirostris s.l. and An. vagus found in habitats such as paddy fields and former fish ponds in OKU and Pesawaran District. As for abandoned shrimp ponds in Pesawaran, An. sundaicus s.l. and An. subpictus s.l. were the dominant ones. Mosquito An. sundaicus s.l seems to have a greater tendency to bite humans, whereas An. subpictus s.l was generally zoophilic. An. vagus was always present in all collection methods in all villages, with the greatest abundance in OKU. The finding indicates An. vagus appears to be the most variable in the behavior of all captured mosquitoes; therefore, in the future, it may be able to act as a major vector if transmission is not prevented.

Modelling the dynamic basic reproduction number of dengue based on MOI of Aedes albopictus derived from a multi-site field investigation in Guangzhou, a subtropical region

BackgroundMore than half of the global population lives in areas at risk of dengue (DENV) transmission. Developing an efficient risk prediction system can help curb dengue outbreaks, but multiple variables, including mosquito-based surveillance indicators, still constrain our understanding. Mosquito or oviposition positive index (MOI) has been utilized in field surveillance to monitor the wild population density of Aedes albopictus in Guangzhou since 2005.MethodsBased on the mosquito surveillance data using Mosq-ovitrap collection and human landing collection (HLC) launched at 12 sites in Guangzhou from 2015 to 2017, we established a MOI-based model of the basic dengue reproduction number (R0) using the classical Ross-Macdonald framework combined with a linear mixed-effects model.ResultsDuring the survey period, the mean MOI and adult mosquito density index (ADI) using HLC for Ae. albopictus were 12.96 ± 17.78 and 16.79 ± 55.92, respectively. The R0 estimated from the daily ADI (ADID) showed a significant seasonal variation. A 10-unit increase in MOI was associated with 1.08-fold (95% CI 1.05, 1.11) ADID and an increase of 0.14 (95% CI 0.05, 0.23) in the logarithmic transformation of R0. MOI-based R0 of dengue varied by month and average monthly temperature. During the active period of Ae. albopictus from April to November in Guangzhou region, a high risk of dengue outbreak was predicted by the MOI-based R0 model, especially from August to October, with the predicted R0 > 1. Meanwhile, from December to March, the estimates of MOI-based R0 were < 1.ConclusionsThe present study enriched our knowledge about mosquito-based surveillance indicators and indicated that the MOI of Ae. albopictus could be valuable for application in estimating the R0 of dengue using a statistical model. The MOI-based R0 model prediction of the risk of dengue transmission varied by month and temperature in Guangzhou. Our findings lay a foundation for further development of a complex efficient dengue risk prediction system.Graphical

Diversity of disease-carrying mosquito vectors in potential areas of dengue fever in Palembang City, South Sumatra, Indonesia

Abstract. Listiono H, Damiri N, Kamaluddin T, Irsan C. 2024. Diversity of disease-carrying mosquito vectors in potential areas of dengue fever in Palembang City, South Sumatra, Indonesia. Biodiversitas 25: 474-481. Mosquitoes (Diptera: Culicidae) are biting insects commonly found in many areas on earth in subtropics and tropics, especially around residential areas. So far, more than 2500 species have been recorded from various parts of the world. They are the main vectors of many diseases in humans and livestock caused by viruses and parasites. Mosquito diversity and disease transmission are influenced by landscape modifications, namely vectors and pathogens. The study aimed to evaluate the distribution, prevalence and abundance of mosquito species in potential dengue fever districts in Palembang city. The study was conducted in 2 two sub-districts in Palembang City, namely Gandus and Seberang Ulu I that represent housing environment, schools and gardens. Mosquito capture was done during three periods 06.00-10.00, 15.00-18.00, and 19.00-21.00 to align with their active hours. This involved active human landing collection method. 200 ovitraps were set up in both regions to assess the density of mosquitoes. The results showed that the diversity index values in Gandus and the Seberang Ulu I sub-districts were 0.781 and 0.756, respectively. Both values were categorized as low diversity index. Furthermore, the dominance index in Gandus and Seberang Ulu 1 sub-district were 0.105 and 0.031, respectively. It meant that there were no dominant mosquito species in both sub-districts. Based on the results of Independent t-test analysis, it was found that the average number of mosquito populations in Gandus sub-district was 25.07 and Seberang Ulu I sub-district was 13.29. From the results of the analysis it was found that there was no difference in average number of mosquito populations between Gandus and Seberang Ulu I sub-district, with a p-value of 0.367. Further research needs to be directed at uncovering mosquito distribution patterns and their potential as disease vectors, the risk of infectious diseases, and the need for further prevention to reduce the number of disease incidences.

Late morning biting behaviour of Anopheles funestus is a risk factor for transmission in schools in Siaya, western Kenya

BackgroundChildren in Kenya spend a substantial amount of time at school, including at dawn and dusk when mosquitoes are active. With changing vector behaviour towards early morning biting, it is important to determine whether there is an additional risk of transmission in schools. This study sought to understand whether late morning biting by Anopheles funestus, previously documented in households in western Kenya, was replicated in schools.MethodsFrom the 4th to the 6th of August 2023, human landing collections were conducted hourly in four schools in Alego Usonga sub-County, Siaya County. The collections were conducted in and outside five classrooms in each school and ran for 17 h, starting at 18:00 until 11:00 h the next morning.ResultsAnopheles funestus was the predominant species collected, forming 93.2% (N = 727) of the entire collection, with peak landing between 06:00 and 07:00 h and continuing until 11:00 h. More than half of the collected An. funestus were either fed or gravid, potentially indicative of multiple bloodmeals within each gonotrophic cycle, and had a sporozoite rate of 2.05%.ConclusionSchool children spend up to 10 h of their daytime in schools, reporting between 06:00 and 07:00 h and staying in school until as late as 17:00 h, meaning that they receive potentially infectious mosquito bites during the morning hours in these settings. There is a need to consider vector control approaches targeting schools and other peridomestic spaces in the morning hours when An. funestus is active.

Mosquitoes, Lymphatic Filariasis, and Public Health: A Systematic Review of Anopheles and Aedes Surveillance Strategies.

Lymphatic Filariasis (LF) affects over 120 million people in 72 countries, with sub-periodic filariasis common in the Pacific. Wuchereria bancrofti has three physiological races, each with a unique microfilarial periodicity, and each race is isolated to a specific geographical region. Sub-periodic W. bancrofti is transmitted by various Aedes mosquito species, with Aedes polynesiensis and Aedes samoanus being the primary vectors in Samoa. The Aedes scutellaris and Aedes kochi groups are also important vectors in the South Pacific Islands. Anopheles species are important vectors of filariasis in rural areas of Asia and Africa. The Anopheles gambiae complex, Anopheles funestus, and the Anopheles punctulatus group are the most important vectors of W. bancrofti. These vectors exhibit indoor nocturnal biting behaviour and breed in a variety of habitats, including freshwater, saltwater, and temporary water bodies. Effective vector surveillance is central to LF control and elimination programs. However, the traditional Human Landing Collection (HLC) method, while valuable, poses ethical concerns and risks to collectors. Therefore, this review critically analyses alternative trapping tools for Aedes and Anopheles vectors in LF-endemic regions. We looked at 14 research publications that discussed W. bancrofti vector trapping methods. Pyrethrum Spray Catches (PSC), one of the seven traps studied for Anopheles LF vectors, was revealed to be the second most effective strategy after HLC, successfully catching Anopheles vectors in Nigeria, Ghana, Togo, and Burkina Faso. The PSC method has several drawbacks, such as the likelihood of overlooking exophilic mosquitoes or underestimating Anopheles populations. However, exit traps offered hope for capturing exophilic mosquitoes. Anopheles populations could also be sampled using the Anopheles Gravid Trap (AGT). In contrast, the effectiveness of the Double Net Traps (DNT) and the CDC Light Trap (CDC LT) varied. Gravid mosquito traps like the OviArt Gravid Trap (AGT) were shown to be useful tools for identifying endophilic and exophilic vectors during the exploration of novel collection techniques. The Stealth trap (ST) was suggested for sampling Anopheles mosquitoes, although specimen damage may make it difficult to identify the species. Although it needs more confirmation, the Ifakara Tent Trap C design (ITT-C) showed potential for outdoor mosquito sampling in Tanzania. Furvela tent traps successfully captured a variety of Anopheles species and are appropriate for use in a variety of eco-epidemiological settings. By contrast, for Aedes LF vectors, no specific sampling tool was identified for Aedes niveus, necessitating further research and development. However, traps like the Duplex cone trap, Resting Bucket Trap (RB), and Sticky Resting Bucket trap (SRB) proved effective for sampling Aedes albopictus, offering potential alternatives to HLC. This review emphasises the value of looking into alternative trapping methods for Aedes and Anopheles vectors in the LF-endemic region. Further research is required to determine the efficacy of novel collection techniques in various contexts, even if PSC and AGT show promise for sampling Anopheles vectors. The identified traps, along with ongoing research, provide valuable contributions to vector surveillance efforts in LF-endemic regions, enabling LF control and elimination strategies to advance.

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.

Bionomics of malaria vectors in Lao PDR, 2018–2020: entomological surveillance as a key tool for malaria elimination

BackgroundThe Lao PDR National Strategic Plan for malaria control and elimination for year 2021–2025 emphasizes the importance of routine entomological surveillance being conducted in areas with high transmission and in active malaria foci in elimination targeted areas. The collection of entomological surveillance data that is closely linked to recent epidemiological data is crucial for improving impact, as it contributes to the evidence package that supports operational and strategic decision-making of national malaria programmes, as they accelerate their last mile of elimination.MethodsThe Center for Malariology Parasitology and Epidemiology (CMPE) entomology team conducted entomological surveillance activities at 13 sentinel sites in 8 provinces and at active transmission foci sites from 2018 to 2020. The techniques used for the mosquito collection were indoor and outdoor human landing collections (from houses and from cultivation areas) and cattle baited net trap collections.ResultsThere were 5601 Anopheles mosquito females captured and identified throughout the study, on both human and cow bait. They represented 15 different species or species complexes. The primary malaria vectors as well as the secondary vectors were present in all collection sites in the south, indicating that people living in these rural areas with high malaria incidence are exposed to the vectors. The vectors were highly zoophilic, but they still bite humans throughout the night with a high peak of activity before midnight, both indoors and outdoors. Overall, 17% of the malaria vectors were collected indoors when the people are sleeping. This confirms the importance of bed net use during the night. Thirty-two percent of primary and secondary vectors were collected outdoors at times when people are usually awake and outdoors, which shows that people are exposed to potentially infectious mosquitoes and the importance of personal protection at these times. The findings showed that residual transmission may occur outdoors in the villages, and outside the villages in cultivation fields and forested areas. Epidemiological data showed that transmission was higher in surveillance sites which were targeted as part of a malaria response rather than sentinel sites.ConclusionsUnderstanding where and how transmission is persisting, monitoring and mapping vector species distribution in areas with active transmission, monitoring biting trends, and designing evidence based and effective vector control interventions are critical to accelerating progress toward malaria elimination. In this context, the role of entomological surveillance combined with epidemiological data should be considered as a cornerstone in achieving malaria elimination.

Species Composition and Population Dynamics of Culicidae during their Peak Abundance Period in Three Peri-Urban Aquatic Ecosystems in Northern Spain

For a better understanding of the transmission cycles of mosquito-borne diseases, it is essential to explore the species composition and population dynamics, mainly during their peak abundance period. These investigations do not normally include peri-urban areas, despite their significant epidemiological interest. To address these gaps, an entomological survey was carried out in 2016 and 2017 in three aquatic ecosystems located on the outskirts of the city of Logroño, in northern Spain: the Iregua River and La Grajera (La Rioja) and Las Cañas Reservoirs (Navarra). Mosquitoes were captured using BG-Sentinel traps baited with CO2 and BG-lure, as well as through the human landing collection method. In total, 6793 mosquito specimens were captured, representing 24 taxa within six genera. A specific PCR based on the ITS2 gene was used to differentiate members of the Anopheles claviger complex, and all individuals were identified as An. claviger sensu stricto. La Grajera had the most diverse culicid fauna, with 19 taxa, followed by Las Cañas (n = 15) and the Iregua River (n = 13). The composition and abundance of Culicidae varied across the aquatic ecosystem. We observed that the different hydrological management practices of each environment could play a key role in determining the abundance of mosquito genera. The overall risk of mosquito bites in the study area is expected to be relatively low and will depend on the freshwater ecosystem and the time of year.

Anopheles funestus sensu stricto Giles (Diptera:Culicidae) bites after sunrise at two rural villages in northern Malawi and its implications for malaria vector control.

Malawi has scaled up distribution and use of LLINs but their effectiveness depends on vector behaviour. This study reports information on where and when peak biting takes place by Anopheles vectors at two study sites in northern Malawi. The study was carried out at a single village each in Nkhata Bay and Karonga districts, northern Malawi. Monthly, three teams of four people each sampled mosquitoes using Human Landing Collections (HLCs) from 6.00 pm to 6.00 am. Mosquitoes were counted and identified by PCR. Plasmodium falciparum sporozoites were detected by ELISA and an entomological inoculation rate was estimated. A total of 4,668 and 2,079 mosquitoes were sampled in Nkhata Bay and Karonga districts respectively. An. funestus s.s was common (91.3%; n = 2,611) in Nkhata Bay while An. arabiensis was common (96.9%; n = 706) in Karonga. Pf sporozoite rates varied from 0.8% (4/484) to 3.3% (51/1558). Individuals in Nkhata Bay received more bites (approx. 200 bites/ person/ night) compared to Karonga (approx. 50 bites/ person/ night). An. funestus was more likely to bite indoors (p=0.002) while An. arabiensis was (p=0.05) more likely to bite outdoors. Furthermore, An. funestus peak biting was in the early morning hours from 4:00 am (approx. 331 and 177 bites/ person/ night indoors and outdoors respectively) and remained high till 6:00 am. An. arabiensis peak biting (approx. 63 and 62 bites/ person/ night indoors and outdoors respectively) was around mid-night (12:00). An EIR of 108.4 infective bites/ person/ year was estimated for Nkhata Bay compared to 9.1 infective bites/ person/ year for Karonga. An. funestus s.s. had a considerable Pf sporozite infection rate and EIR. The shift in biting behaviour shown by this species poses a challenge to malaria control. Further studies are required to understand the biting behaviour of Anopheles vectors in Malawi.

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.

Distribution and behavior of Anopheles maculatus and its potential as a Malaria vector in Indonesia

Background: Anopheles maculatus is one of the mosquito species that has been confirmed as a malaria vector in Indonesia. The potential of a mosquito as a vector is influenced by its behavior. Information on the distribution and behavior of An. maculatus needs to be carried out to determine the potential for malaria transmission transmitted by the species in an area. The study aimed to obtain information on the distribution, behavior, and potential of maculatus as a malaria vector in several provinces in Indonesia. Method: Mosquito collection was carried out using human-landing collection, animal-baited trap, cattle-bait, light-trap, and resting morning. A survey of mosquitoes was carried out in 29 provinces in Indonesia. Mosquitoes were identified for the species and detected the blood-sucking behavior with an Enzyme-linked immunosorbent assay and the presence of Plasmodium using a Polymerase Chain Reaction. Results: The results showed that An. maculatus was found in the Riau Islands, Lampung, Bangka Belitung, West Java, Central Java, East Java, and Central Sulawesi. Anopheles maculatus has known to suck the blood of humans and animals with a predominance of animals. Anopheles maculatus is also known to suck blood outdoors predominantly. In general, the activity of An. maculatus sucking blood begins around 18.00 in the evening. Central Java Province was the province with the highest density of An. maculatus mosquitoes, thereby increasing the potential for transmission of malaria cases. Conclusion: Anopheles maculatus was spread in Riau Islands, Lampung, Bangka Belitung, West Java, Central Java, East Java, and Central Sulawesi. This species was known to suck the blood of people and humans, and its blood-sucking activity starts around 18.00 in the evening.

Seasonal assessment on the effects of time of night, temperature and humidity on the biting profile of Anopheles farauti in north Queensland, Australia using a population naive to malaria vector control pressures

BackgroundAnopheles farauti is one of the major vectors of malaria in the Southwest Pacific region and is responsible for past outbreaks in Australia. With an adaptable biting profile conducive to behavioural resistance to indoor residual spraying (IRS) and insecticide-treated nets (ITNs), its all-night biting behaviour can switch to biting mostly in the early evening. With limited insight into the biting profile of An. farauti populations in areas that have not encountered IRS or ITNs, the aim of this study was to develop insights on the biting behaviour of a malaria control naive population of An. farauti.MethodsBiting profiles of An. farauti were conducted at Cowley Beach Training Area, in north Queensland, Australia. Initially, encephalitis virus surveillance (EVS) traps were used to document the 24-h biting profile of An. farauti and then human landing collections (HLC) were used to follow the 18.00–06.00 h biting profile. The human landing catches (HLC) were performed at both the end of the wet (April) and dry (October) seasons.ResultsData exploration using a Random Forest Model shows that time of night is the most important variable for predicting An. farauti biting activity. Temperature was found to be the next important predictor, followed by humidity, trip, collector, and season. The significant effect of time of night and peak in time of night biting, between 19.00 and 20.00 h was also observed in a generalized linear model. The main effect of temperature was significant and non-linear and appears to have a positive effect on biting activity. The effect of humidity is also significant but its relationship with biting activity is more complex. This population’s biting profile is similar to populations found in other parts of its range prior to insecticide intervention. A tight timing for the onset of biting was identified with more variation with the end of biting, which is likely underpinned by an endogenous circadian clock rather than any light intensity.ConclusionThis study sees the first record of a relationship between biting activity and the decreasing temperature during the night for the malaria vector, Anopheles farauti.

The need for larval source management accompanying urban development projects in malaria endemic areas: a case study on Bioko Island

BackgroundIn 2017, several new housing districts were constructed on Bioko Island, Equatorial Guinea. This case study assessed the impact construction projects had on mosquito larval habitats and the effectiveness of larval source management in reducing malaria vector density within the surrounding area.MethodsAnopheline larval presence was assessed at 11 new construction sites by the proportion of larval habitats containing Anopheline pupae and late instar larval stages. Bacillus thuringiensis israelensis (Bti) larvicide was applied weekly to nine locations for 30 weeks, while two locations received no larvicide and acted as controls. Adult mosquito density was monitored via human landing collections in adjacent communities of six construction sites, including the two control sites.ResultsThe sites that received Bti had significantly lower observation rates of both pupae (3.2% vs. 18.0%; p < 0.001) and late instar Anopheles spp. mosquitoes (14.1 vs. 43.6%; p < 0.001) compared to the two untreated sites. Anopheles spp. accounted for 67% of mosquitoes collected with human landing collections and were captured at significantly lower levels in communities adjacent to treated construction sites compared to untreated sites (p < 0.001), with an estimated 38% reduction in human biting rate (IRR: 0.62, 95% CI IRR: 0.55, 0.69). Seven months after the start of the study, untreated sites were treated due to ethical concerns given results from treatment sties, necessitating immediate Bti application. The following week, the number of habitats, the proportion of larval sites with Anopheles spp. pupae, late instars, and adult biting rates in adjacent communities to these sites all decreased to comparable levels across all sites.ConclusionFindings suggest larval source management represents an effective intervention to suppress mosquito populations during infrastructure development. Incorporating larval source management into ongoing and planned construction initiatives represents an opportunity to fine tune vector control in response to anthropogenetic changes. Ideally, this should become standard practice in malaria-endemic regions in order to reduce viable mosquito habitats that are common by-products of construction.

Field Evaluation of Novel Spatial Repellent Controlled Release Devices (CRDs) against Mosquitoes in an Outdoor Setting in the Northern Peruvian Amazon.

U.S. military troops are exposed to mosquito-borne pathogens when deployed to endemic regions. Personal protective measures such as permethrin-treated uniforms and dermal repellents are the cornerstones of mosquito-borne disease prevention for the U.S. military. These measures have limitations and additional personal protection tools, such as spatial repellent devices to decrease the risk of vector-borne pathogen transmission, are required. Novel spatial repellent controlled-release devices formulated with metofluthrin were evaluated in an outdoor setting in the northern Amazon of Peru to evaluate performance under field conditions. The metofluthrin emitting devices lowered the number of mosquitoes captured in protected human landing collections (HLC) compared to blank devices, although there were effect differences between Anopheles spp. and species in other mosquito genera. A computational-experimental model was developed to correlate HLC and active ingredient (AI) concentrations as a function of time and space. Results show a strong correlation between the released AI and the decrease in HLC. This model represents the first effort to obtain a predictive analytical tool on device performance using HLC as the entomological endpoint.

Field Performance Assessment of Irradiated Aedes albopictus Males Through Mark-Release-Recapture Trials With Multiple Release Points.

Mark–release–recapture (MRR) trials have been conducted in Northern Italy to evaluate the capacity of radio-substerilized Aedes albopictus males to survive, disperse, and engage in mating in the field. Two MRR sessions with the human landing collection method (HLC) were conducted with the simultaneous release of irradiated males marked with four different pigment colors. The survival and dispersal rates seem to be influenced more by environmental factors such as barriers, shading, and vegetation rather than weather parameters. In this study, we confirmed a positive linear relationship between the sterile adult male’s daily survival rate and the relative humidity previously reported in similar experimental conditions and a different dispersal capacity of the released A. albopictus males in low- (NDVI index <0.4) and high (NDVI index >0.4)-vegetated areas. Consistent with previous studies, A. albopictus males have their maximal dispersion in the first days after release, while in the following days the males become more stationary. The similar field performances obtained with marked and unmarked radio-sterilized and untreated A. albopictus males on similar environments confirm the negligible effects of irradiation and marking procedures on the quality of the males released. The similar sterile to wild (S/W) male ratio measured in high- and low-vegetation areas in the release sites indicates a similar distribution pattern for the wild and the released sterile males. According to the MRR data collected, the Lincoln index estimated different A. albopictus mean population densities in the study areas equal to 7,000 and 3,000 male/ha, respectively.