Small-scale field evaluation of transfluthrin-treated eave ribbons and sandals for the control of malaria vectors in rural Tanzania.

BACKGROUND: Early-evening and outdoor-biting mosquitoes may compromise the effectiveness of frontline malaria interventions, notably insecticide-treated nets (ITNs). This study aimed to evaluate the efficacy of low-cost insecticide-treated eave ribbons and sandals as supplementary interventions against indoor-biting and outdoor-biting mosquitoes in south-eastern Tanzania, where ITNs are already widely used. METHODS: This study was conducted in three villages, with 72 households participating (24 households per village). The households were divided into four study arms and assigned: transfluthrin-treated sandals (TS), transfluthrin-treated eave ribbons (TER), a combination of TER and TS, or experimental controls. Each arm had 18 households, and all households received new ITNs. Mosquitoes were collected using double net traps (to assess outdoor biting), CDC light traps (to assess indoor biting), and Prokopack aspirators (to assess indoor resting). Protection provided by the interventions was evaluated by comparing mosquito densities between the treatment and control arms. Additional tests were done in experimental huts to assess the mortality of wild mosquitoes exposed to the treatments or controls. RESULTS: TERs reduced indoor-biting, indoor-resting and outdoor-biting Anopheles arabiensis by 60%, 73% and 41%, respectively, while TS reduced the densities by 18%, 40% and 42%, respectively. When used together, TER & TS reduced indoor-biting, indoor-resting and outdoor-biting An. arabiensis by 53%, 67% and 57%, respectively. Protection against Anopheles funestus ranged from 42 to 69% with TER and from 57 to 74% with TER & TS combined. Mortality of field-collected mosquitoes exposed to TER, TS or both interventions was 56-78% for An. arabiensis and 47-74% for An. funestus. CONCLUSION: Transfluthrin-treated eave ribbons and sandals or their combination can offer significant household-level protection against malaria vectors. Their efficacy is magnified by the transfluthrin-induced mortality, which was observed despite the prevailing pyrethroid resistance in the study area. These results suggest that TER and TS could be useful supplementary tools against residual malaria transmission in areas where ITN coverage is high but additional protection is needed against early-evening and outdoor-biting mosquitoes. Further research is needed to validate the performance of these tools in different settings, and assess their long-term effectiveness and feasibility for malaria control.

Evaluation of a push-pull system consisting of transfluthrin-treated eave ribbons and odour-baited traps for control of indoor- and outdoor-biting malaria vectors.

BACKGROUND: Push-pull strategies have been proposed as options to complement primary malaria prevention tools, indoor residual spraying (IRS) and long-lasting insecticide-treated nets (LLINs), by targeting particularly early-night biting and outdoor-biting mosquitoes. This study evaluated different configurations of a push-pull system consisting of spatial repellents [transfluthrin-treated eave ribbons (0.25 g/m2 ai)] and odour-baited traps (CO2-baited BG-Malaria traps), against indoor-biting and outdoor-biting malaria vectors inside large semi-field systems. METHODS: Two experimental huts were used to evaluate protective efficacy of the spatial repellents (push-only), traps (pull-only) or their combinations (push-pull), relative to controls. Adult volunteers sat outdoors (1830 h-2200 h) catching mosquitoes attempting to bite them (outdoor-biting risk), and then went indoors (2200 h-0630 h) to sleep under bed nets beside which CDC-light traps caught host-seeking mosquitoes (indoor-biting risk). Number of traps and their distance from huts were varied to optimize protection, and 500 laboratory-reared Anopheles arabiensis released nightly inside the semi-field chambers over 122 experimentation nights. RESULTS: Push-pull offered higher protection than traps alone against indoor-biting (83.4% vs. 35.0%) and outdoor-biting (79% vs. 31%), but its advantage over repellents alone was non-existent against indoor-biting (83.4% vs. 81%) and modest for outdoor-biting (79% vs. 63%). Using two traps (1 per hut) offered higher protection than either one trap (0.5 per hut) or four traps (2 per hut). Compared to original distance (5 m from huts), efficacy of push-pull against indoor-biting peaked when traps were 15 m away, while efficacy against outdoor-biting peaked when traps were 30 m away. CONCLUSION: The best configuration of push-pull comprised transfluthrin-treated eave ribbons plus two traps, each at least 15 m from huts. Efficacy of push-pull was mainly due to the spatial repellent component. Adding odour-baited traps slightly improved personal protection indoors, but excessive trap densities increased exposure near users outdoors. Given the marginal efficacy gains over spatial repellents alone and complexity of push-pull, it may be prudent to promote just spatial repellents alongside existing interventions, e.g. LLINs or non-pyrethroid IRS. However, since both transfluthrin and traps also kill mosquitoes, and because transfluthrin can inhibit blood-feeding, field studies should be done to assess potential community-level benefits that push-pull or its components may offer to users and non-users.

Serologic and Molecular Evidence of Vaccinia Virus Circulation among Small Mammals from Different Biomes, Brazil.

Vaccinia virus (VACV) is a zoonotic agent that causes a disease called bovine vaccinia, which is detected mainly in milking cattle and humans in close contact with these animals. Even though many aspects of VACV infection have been described, much is still unknown about its circulation in the environment and its natural hosts/reservoirs. To investigate the presence of Orthopoxvirus antibodies or VACV DNA, we captured small rodents and marsupials in 3 areas of Minas Gerais state, Brazil, and tested their samples in a laboratory. A total of 336 animals were tested; positivity ranged from 18.1% to 25.5% in the 3 studied regions located in different biomes, including the Atlantic Forest and the Cerrado. Analysis of nucleotide sequences indicated co-circulation of VACV groups I and II. Our findings reinforce the possible role played by rodents and marsupials in VACV maintenance and its transmission chain.

Development of the gravid Aedes trap for the capture of adult female container-exploiting mosquitoes (Diptera: Culicidae).

Monitoring dengue vector control by sampling adult Aedes aegypti (L.) recently has been used to replace both larval and pupal surveys. We have developed and evaluated the Gravid Aedes Trap (GAT) through a sequential behavioral study. The GAT does not require electricity to function, and trapped mosquitoes are identified easily during trap inspections. The GAT concept relies on visual and olfactory cues to lure gravid Ae. aegypti and an insecticide to kill trapped mosquitoes. Gravid mosquitoes are lured to a black bucket base containing oviposition attractant (infusion) and are trapped in a translucent chamber impregnated with a pyrethroid insecticide where they are killed within 3-15 min. In semifield observations, the GAT captured a significantly higher proportion of gravid mosquitoes than the double sticky ovitrap. We also demonstrated that the visual cues of the prototype GAT-LgBF (large black base bucket with a black funnel at the top of the translucent chamber) captured a significantly higher proportion of gravid mosquitoes than the other prototypes. The visual contrast created by the addition of a white lid to the top of the black funnel significantly increased the number of captured gravid mosquitoes when compared with the GAT-LgBF in semifield trials. We conclude that the GAT is more efficient in recapturing gravid Ae. aegypti when compared with sticky ovitraps. The GAT is an effective, practical, low cost, and easily transportable trap, features that are essential in large-scale monitoring programs, particularly in areas where funding is limited.

Field validation of the gravid Aedes trap (GAT) for collection of Aedes aegypti (Diptera: Culicidae).

Current surveillance methods for adult Aedes aegypti (L.) are expensive, require electrical power (e.g., the BG-Sentinel trap, BGS), are labor intensive (aspirators), or require difficult to use and costly adhesives (sticky ovitraps). Field trials were conducted in Cairns (Australia) to compare the efficacy of the newly designed Gravid Aedes Trap (GAT) against existing sticky ovitraps (MosquiTRAP and double sticky ovitrap) and the BGS. Latin square design trials confirmed that alarge GAT using a 9.2-liters bucket treated with Mortein Barrier Outdoor Surface Spray ([AI] 0.3 g/kg imiprothrin and 0.6 g/kg deltamethrin) outperformed a smaller 1.2-liters GAT and collected, on average, 3.7x and 2.4X more female Ae. aegypti than the MosquiTRAP and double sticky ovitrap, respectively. Field trials showed that the GAT collected 10-50% less female Ae. aegypti than the BGS trap but 30% more gravid mosquitoes than the BGS. Trials using the BGS and the GAT indicated that there was no difference in capture rates between female Ae. aegypti uninfected and infected with the wMel strain of Wolbachia, and wMel infection rates were nearly identical at >90% to field captured Ae. aegypti. The potential for the GAT to be used for dengue virus surveillance was also demonstrated with dengue virus type 3 RNA detected in five-sixths and six-sixths pools ofAe. aegypti stored in a GAT held at 28 degreeC and 60% relative humidity for 7 and 14 d, respectively. Mosquito knock down in GATs treated with Mortein surface spray set in 30, 70, and 99% shade was comparable for up to 2 mo, with only approximately 10% of adults escaping. The GAT is therefore a useful tool for capturing adult Ae. aegypti and may be suitable for other container-inhabiting species such as Aedes albopictus (Skuse) and Culex quinquefasciatus Say. The low cost and practicality of operation make the GAT suitable for vector surveillance and projects requiring monitoring of mosquitoes for Wolbachia and arboviruses, especially in developing countries.

Development of a New Mosquito Retention System for the BG-Malaria Trap To Reduce The Damage To Mosquitoes.

The BG-Malaria trap was recently modified from the BioGents BG-Sentinel trap to collect Anopheles species, including Anopheles darlingi. However, the captured mosquitoes often lose their hind legs in the collector bag, making them difficult to identify. To develop a new collector system that is capable of maintaining the integrity of the mosquitoes collected in the BG-Malaria trap, we conducted a study in the municipalities of Belém (Pará State [PA]) and Porto Velho (Rondônia State [RO]), Brazil, using carbon dioxide-baited BG-Malaria traps with 4 different mosquito collector systems: standard, no bag, rigid short, and rigid long. Results indicated significant differences among the numbers of mosquitoes captured in the 4 different collectors (P < 0.05). Additionally, significantly fewer insects (P < 0.05) were damaged using the rigid short and rigid long collectors than by using the standard and no-bag collectors. We observed that the longer the insects remained in the collector, the higher the number of damaged insects; this effect was the greatest in the standard collector. The results of this study indicate that rigid long collectors were the best suited for use in the BG-Malaria trap.

Cost-effectiveness of novel system of mosquito surveillance and control, Brazil.

Of all countries in the Western Hemisphere, Brazil has the highest economic losses caused by dengue fever. We evaluated the cost-effectiveness of a novel system of vector surveillance and control, Monitoramento Inteligente da Dengue (Intelligent Dengue Monitoring System [MID]), which was implemented in 21 cities in Minas Gerais, Brazil. Traps for adult female mosquitoes were spaced at 300-m intervals throughout each city. In cities that used MID, vector control was conducted specifically at high-risk sites (indicated through daily updates by MID). In control cities, vector control proceeded according to guidelines of the Brazilian government. We estimated that MID prevented 27,191 cases of dengue fever and saved an average of $227 (median $58) per case prevented, which saved approximately $364,517 in direct costs (health care and vector control) and $7,138,940 in lost wages (societal effect) annually. MID was more effective in cities with stronger economies and more cost-effective in cities with higher levels of mosquito infestation.

Observing the distribution of mosquito bites on humans to inform personal protection measures against malaria and dengue vectors.

BACKGROUND: Understanding mosquito biting behaviours is important for designing and evaluating protection methods against nuisance biting and mosquito-borne diseases (e.g. dengue, malaria and zika). We investigated the preferred biting sites by Aedes aegypti and Anopheles arabiensis on adult volunteers in standing or sleeping positions; and estimated the theoretical protection limits affordable from protective clothing or repellent-treated footwear. METHODS: Adult volunteers dressed in shorts and t-shirts were exposed to infection-free laboratory-reared mosquitoes inside screened chambers from 6am to noon (for day-biting Ae. aegypti) or 6pm to midnight (night-biting An. arabiensis). Attempted bites on different body parts were recorded. Comparative observations were made on same volunteers while wearing sandals treated with transfluthrin, a vapour-phase pyrethroid that kills and repels mosquitoes. RESULTS: An. arabiensis bites were mainly on the lower limbs of standing volunteers (95.9% of bites below the knees) but evenly-distributed over all exposed body surfaces when the volunteers were on sleeping positions (only 28.8% bites below knees). Ae. aegypti bites were slightly concentrated on lower limbs of standing volunteers (47.7% below knees), but evenly-distributed on sleeping volunteers (23.3% below knees). Wearing protective clothing that leave only hands and head uncovered (e.g. socks + trousers + long-sleeved shirts) could theoretically prevent 78-83% of bites during sleeping, and at least 90% of bites during non-sleeping hours. If the feet are also exposed, protection declines to as low as 36.3% against Anopheles. The experiments showed that transfluthrin-treated sandals reduced An. arabiensis by 54-86% and Ae. aegypti by 32-39%, but did not change overall distributions of bites. CONCLUSION: Biting by An. arabiensis and Ae. aegypti occur mainly on the lower limbs, though this proclivity is less pronounced in the Aedes species. However, when hosts are on sleeping positions, biting by both species is more evenly-distributed over the exposed body surfaces. High personal protection might be achieved by simply wearing long-sleeved clothing, though protection against Anopheles particularly requires covering of feet and lower legs. The transfluthrin-treated footwear can reduce biting risk, especially by An. arabiensis. These findings could inform the design and use of personal protection tools (both insecticidal and non-insecticidal) against mosquitoes and mosquito-borne diseases.

Pheromone gland development and pheromone production in lutzomyia longipalpis (Diptera: Psychodidae: Phlebotominae).

The sand fly Lutzomyia longipalpis (Lutz & Neiva) (Diptera: Psychodidae: Phlebotominae) is the main vector of American visceral leishmaniasis. Adult males produce a terpenoid sex pheromone that in some cases also acts as male aggregation pheromone. We have analyzed the correlation between male pheromone production levels and pheromone gland cell morphogenesis after adult emergence from pupae. The abdominal tergites of L. longipalpis males were dissected and fixed in glutaraldehyde for transmission electron microscopy, or the pheromone was extracted in analytical grade hexane. Pheromone chemical analysis was carried out at 3- to 6-h intervals during the first 24 h after emergence and continued daily until the seventh day. All extracts were analyzed by gas chromatography. For the morphological analysis, we used insects collected at 0-6, 9-12, 12-14, and 96 h after emergence. Ultrastructural data from 0- to 6-h-old adult males revealed smaller pheromone gland cells with small microvilli at the end apparatus. Lipid droplets and peroxisomes were absent or very rare, but a large number of mitochondria could be seen. Lipid droplets started to appear in the gland cells cytoplasm approximately 9 h after adult emergence, and their number and size increased with age, together with the presence of several peroxisomes, suggesting a role for these organelles in pheromone biosynthesis. At 12-15 h after emergence, the lipid droplets were mainly distributed near the microvilli but were smaller than those in mature older males (4 d old). Pheromone biosynthesis started around 12 h after emergence and increased continuously during the first 3 d, stabilizing thereafter, coinciding with the period when males are more able to attract females.

Modeling dengue vector population with earth observation data and a generalized linear model.

Mosquitoes propagate many human diseases, some widespread and with no vaccines. The Ae. aegypti mosquito vector transmits Zika, Chikungunya, and Dengue viruses. Effective public health interventions to control the spread of these diseases and protect the population require models that explain the core environmental drivers of the vector population. Field campaigns are expensive, and data from meteorological sites that feed models with the required environmental data often lack detail. As a consequence, we explore temporal modeling of the population of Ae. aegypti mosquito vector species and environmental conditions- temperature, moisture, precipitation, and vegetation- have been shown to have significant effects. We use earth observation (EO) data as our source for estimating these biotic and abiotic environmental variables based on proxy features, namely: Normalized difference vegetation index, Normalized difference water index, Precipitation, and Land surface temperature. We obtained our response variable from field-collected mosquito population measured weekly using 791 mosquito traps in Vila Velha city, Brazil, for 36 weeks in 2017, and 40 weeks in 2018. Recent similar studies have used machine learning (ML) techniques for this task. However, these techniques are neither intuitive nor explainable from an operational point of view. As a result, we use a Generalized Linear Model (GLM) to model this relationship due to its fitness for count response variable modeling, its interpretability, and the ability to visualize the confidence intervals for all inferences. Also, to improve our model, we use the Akaike Information Criterion to select the most informative environmental features. Finally, we show how to improve the quality of the model by weighting our GLM. Our resulting weighted GLM compares well in quality with ML techniques: Random Forest and Support Vector Machines. These results provide an advancement with regards to qualitative and explainable epidemiological risk modeling in urban environments.

Semi-field assessment of the Gravid Aedes Trap (GAT) with the aim of controlling Aedes (Stegomyia) aegypti populations.

The mosquito Aedes aegypti is the main vector of arboviroses and current approaches to control this vector are not sufficiently effective. Adult traps, such as the BG-Sentinel (BGS), have been successfully used for mosquito surveillance and can also suppress vector populations. A new "passive" trap for gravid Ae. aegypti (Gravid Aedes Trap-GAT) has been shown efficient for Aedes collection and suppress Ae. albopictus populations using mass trapping techniques. Here the GAT was evaluated for the first time as a new tool to control Ae. aegypti in semi-field conditions using simulated outdoor environments (SOE). Two identical large screened chambers inside of a SOE containing different numbers and sizes of artificial breeding sites were used to assess the trapping efficiency of the GAT. One hundred mosquitoes were released into the chambers, and recapture rates evaluated after 48h. The parity status of the captured mosquitoes was also recorded. The number of eggs laid, and breeding productivity were also monitored when using different numbers and sizes of breeding sites. The BGS trap was used here as a control (gold standard) trap to compare capture rates to those of the GAT. The GAT recaptured between 50-65% of the mosquitoes independent of the number and sizes of the breeding sites in the SOEs, whereas the BGS recaptured 60-82% of the females. Both traps showed similar results regarding to the parity status of recaptured mosquitoes. Our results confirmed the effectiveness of GAT for the capture of adult female Ae. aegypti in simulated field environments. The BGS trap recaptured gravid Ae. aegypti before egg-laying in different sizes and number of breading sites, whereas the oviposition activity occurred prior to recapture mosquitoes in the GAT. Based on the results, we believe that GAT is a promising candidate for mass-trapping intervention in urban settings, but a source reduction intervention should be made prior trap deployment. Therefore, we suggest future field studies to confirm the use of GAT as a complementary tool in vector control activities.

Evaluation of the New Modular Biogents BG-Pro Mosquito Trap in Comparison to CDC, EVS, BG-Sentinel, and BG-Mosquitaire Traps.

Mosquito surveillance is an essential component of mosquito control and mosquito traps are a universally employed tool to monitor adult populations. The objective of this paper was to evaluate the new modular Biogents BG-Pro mosquito trap (BGP) and compare its performance to 4 widely used traps for adult mosquitoes: the BG-Sentinel (BGS), the BG Mosquitaire (BGM), the CDC miniature light trap (CDC), and the encephalitis vector survey trap (EVS). One semi-field and 9 field Latin square trials were performed in 7 countries. Results showed that the collection performance of the BGP was equivalent to or exceeded that of the BGS, BGM, CDC, and EVS traps in head-to-head comparisons. The BGP uses 35% less power than the CDC and 75% less than the BGS and BGM. This lower power consumption allows it to run at 5 V for 2 days using a small lightweight 10,000-mAh rechargeable power bank. The BG-Pro is an excellent alternative for the surveillance of mosquito species that are usually monitored with BG-Sentinel, CDC, or EVS traps.

Dengue virus 3 genotype I in Aedes aegypti mosquitoes and eggs, Brazil, 2005-2006.

Dengue virus type 3 genotype I was detected in Brazil during epidemics in 2002-2004. To confirm this finding, we identified this virus genotype in naturally infected field-caught Aedes aegypti mosquitoes and eggs. Results showed usefulness of virus investigations in vectors as a component of active epidemiologic surveillance.

Using the intrinsic growth rate of the mosquito population improves spatio-temporal dengue risk estimation.

Understanding geographic population dynamics of mosquitoes is an essential requirement for estimating the risk of mosquito-borne disease transmission and geographically targeted interventions. However, the use of population dynamics measures, such as the intrinsic growth rate, as predictors in spatio-temporal point processes has not been investigated before. In this work we compared the predictive accuracy of four spatio-temporal log-Gaussian Cox models: (i) With no predictors; (ii) mosquito abundance as predictor; (iii) intrinsic growth rate as predictor; (iv) intrinsic growth rate and mosquito abundance as predictors. This analysis is based on Aedes aegypti mosquito surveillance and human dengue data obtained from the urban area of Caratinga, Brazil. We used a statistical Moran Curve approach to estimate the intrinsic growth rate and a zero inflated Poisson kriging model for estimating mosquito abundance at locations of dengue cases. The incidence of dengue cases was positively associated with mosquito intrinsic growth rate and this model outperformed, in terms of predictive accuracy, the abundance and the null models. The latter includes only the spatio-temporal random effect but no predictors. In the light of these results we suggest that the intrinsic growth rate should be investigated further as a potential tool for predicting the risk of dengue transmission and targeting health interventions for vector-borne diseases.

Linking mosquito surveillance to dengue fever through Bayesian mechanistic modeling.

Our ability to effectively prevent the transmission of the dengue virus through targeted control of its vector, Aedes aegypti, depends critically on our understanding of the link between mosquito abundance and human disease risk. Mosquito and clinical surveillance data are widely collected, but linking them requires a modeling framework that accounts for the complex non-linear mechanisms involved in transmission. Most critical are the bottleneck in transmission imposed by mosquito lifespan relative to the virus' extrinsic incubation period, and the dynamics of human immunity. We developed a differential equation model of dengue transmission and embedded it in a Bayesian hierarchical framework that allowed us to estimate latent time series of mosquito demographic rates from mosquito trap counts and dengue case reports from the city of Vitória, Brazil. We used the fitted model to explore how the timing of a pulse of adult mosquito control influences its effect on the human disease burden in the following year. We found that control was generally more effective when implemented in periods of relatively low mosquito mortality (when mosquito abundance was also generally low). In particular, control implemented in early September (week 34 of the year) produced the largest reduction in predicted human case reports over the following year. This highlights the potential long-term utility of broad, off-peak-season mosquito control in addition to existing, locally targeted within-season efforts. Further, uncertainty in the effectiveness of control interventions was driven largely by posterior variation in the average mosquito mortality rate (closely tied to total mosquito abundance) with lower mosquito mortality generating systems more vulnerable to control. Broadly, these correlations suggest that mosquito control is most effective in situations in which transmission is already limited by mosquito abundance.

Artificial Bloodfeeder Glytube: Evaluating Different Types of Membranes and Blood Sources for Feeding Aedes aegypti and Aedes albopictus.

Mosquito colony maintenance in the laboratory is essential for research but presents logistical and ethical problems with the use of live animals for bloodfeeding. The Glytube is an artificial bloodfeeding system for mosquitoes that uses Parafilm-M® membrane and human blood to feed Aedes aegypti. This study evaluated the efficiency of Glytube with different types of membranes and chicken blood to feed Ae. aegypti and Ae. albopictus. We evaluated 2 artificial (thread seal tape [TST], Parafilm-M) and 2 natural membranes (pork, sheep intestine). The results for Ae. aegypti suggest that TST was the best membrane because it presented a high percentage of fed females (63%), a high average number of eggs per female (54.65), and an egg viability rate significantly similar to control (mouse). For Ae. albopictus, there was no significant difference between the membranes and the control; however, the use of TST is suggested due to the low cost and easy manipulation. The treatments that used chicken blood did not present significant differences in the egg viability when compared with the control. The Glytube functionality can be increased by replacing the Parafilm-M membrane by TST and human to chicken blood.

Videographic analysis of flight behaviours of host-seeking Anopheles arabiensis towards BG-Malaria trap.

The BG-Malaria trap (BGM) is an adaptation of the well-known BG-Sentinel trap (BGS) with greater trapping efficiencies for anopheline and culicine mosquitoes. Its continued optimization requires greater understanding of mosquito flight behaviors near it. We used three high-resolution infrared cameras (68 frames/second) to track flight behaviors of laboratory-reared Anopheles arabiensis females in vicinity of the BGM in comparison with BGS. Additional comparisons were done for BGM at 20, 40 and 80cm heights, and for BGMs baited with Ifakara blend plus CO2, CO2 alone, or no bait. More mosquitoes were observed near BGM than BGS. Both BGMs installed 20cm above the floor and baited with CO2 received more visits by host-seeking mosquitoes than the other BGMs evaluated in their respective experiments. Trap designs, height and attractants all influence mosquito activity in vicinity of the traps which can be readily visualized using infrared cameras to accelerate trap development and testing. The greater activity of host-seeking mosquitoes near BGM than BGS supports the proven superiority of BGM traps in field and semi-field settings.

Are light traps baited with kairomones effective in the capture of Lutzomyia longipalpis and Lutzomyia intermedia? An evaluation of synthetic human odor as an attractant for phlebotomine sand flies (Diptera: Psychodidae: Phlebotominae).

Phlebotomine sand flies are often captured with human bait and/or light traps, either with or without an animal bait. More recently, synthetic attractants have been used as bait in traps to improve the capture of phlebotomine sand flies as well as other insects of medical and veterinary importance. The aim of the present study was to evaluate the effects of the kairomone 1-octen-3-ol (octenol) and the synthetic human odor BG-Mesh Lure (BGML--lactic acid, caproic acid and ammonia) baited in modified CDC light traps on the capture of phlebotomine sand flies. The experiments followed the 5x5 Latin square design. Among the species caught, Lutzomyia intermedia apparently presented a dose-dependent response to octenol. The response obtained with the BGML, alone or in combination with octenol (5 mg/h), indicated some degree of attractiveness of these baits to different phlebotomine sand fly species. Octenol seems to be more attractive to L. intermedia than to Lutzomyia longipalpis, while the BGML presented a higher success in capturing L. longipalpis. When the components of the BGML were used separately, there was no increase in catching the female of L. intermedia. Apparently, there was no synergistic effect between the octenol and the BGML. In conclusion, the octenol and the BGML were demonstrated to be possible baits to attract some phlebotomine sand fly species.

Comparison of different uses of adult traps and ovitraps for assessing dengue vector infestation in endemic areas.

This report presents a set of field experiments designed to assess different protocols for the use of ovitrap and MosquiTRAP, a promising new trap for dengue vector monitoring. Percentage of positive houses, calculated either by the use of 2 traps (outside + inside) or 1 trap (outside) per house, tended to increase with time of exposure, at similar rates. When the aim was either to obtain a qualitative index (Aedes aegypti-positive site) or to determine percentage of positive houses in a selected neighborhood, the use of 1 ovitrap per house with only 5 days of exposure at the peridomestic area was quite sensitive. Seven days of exposure was too long, as saturation is expected in some places. The number of eggs collected per site increased with the time of exposure in all sites. At the 3-day trap exposure, we were not able to discriminate neighborhoods in terms of egg productivity per house. At the 5-day trap exposure, a rank of 4 sites was achieved. There was no correlation between the number of adults caught in MosquiTRAPs and number of eggs collected in ovitraps, neither per neighborhood nor per house where both traps were simultaneously exposed for 7 days in the peridomestic area.

Assessment of entomological indicators of Aedes aegypti (L.) from adult and egg collections in São Paulo, Brazil.

We compared the presence and mean number of eggs from oviposition traps with the mean number of Aedes aegypti females captured by manual aspirators and by MosquiTRAPs to determine the sensitivity of each method and to standardize each indicator. The collections of adults and eggs were performed over 23 weeks in six neighborhoods of Mirassol, state of São Paulo, Brazil. A better assessment of indicators required larger number of MosquiTRAPs, but to quantify the number of females per house, one trap was sufficient. The sensitivities of MosquiTRAPs and manual aspirations to detect the presence of A. aegypti females were similar, but were lower compared to oviposition traps. The correlation coefficients between the number of females captured by MosquiTRAPs and manual aspirations and the number of eggs from oviposition traps were low, which may be a consequence of each method showing different stages of the mosquito life cycle.