We therefore conclude that CO2 baits are beneficial when targeting Anopheles spp., as their use may lead to increased capture rates in comparison to non-baited CDC-LT. These findings are consistent with previous studies, which have shown that dry ice baited CDC-LT are a good alternative choice to collect malaria vectors including An. minimus s.l., and An. maculatus s.l. and An. sawadwongporni Rattanarithikul and Green, respectively.In contrast, previous studies on African and Brazilian malaria vectors, specifically An. arabiensis Patton, An. funestus s.l. Giles , An. darlingi Root , and An. aquasalis Curry have shown that CO2 was insufficiently attractive as a standalone bait and that traps using CO2 in mixed odor baits or together with body odors may provide better results. Most of the collected Anopheles mosquitoes were in the unfed state and feeding status did not seem to impact capture efficiency when comparing indoor and outdoor trap locations. This stands in contrast to a previous study that indicated a preferential capture of blood fed mosquitoes and An. funestus by CDC-LT in indoor locations in Zambia, however this may be attributable to the low numbers of blood fed mosquitoes observed in this study and that the captured Anopheles species commonly exhibit a zoophilic host preference. Culex spp. were the most abundant species collected in this study. Overall, there was no significant difference in the capture efficiency of baited or unbaited traps and/ or trap locations . Similar to Anopheles spp. there was a tendency that CO2 baited traps were more efficient than unbaited traps in outdoor locations. When Cx. vishnui was considered separately, capture efficiency was significantly higher in CO2 baited traps. More detailed analysis revealed that this effect was restricted to traps placed outdoors and in the hot season . Cx. vishnui is a main vector of Japanese Encephalitis Virus. It is most commonly found in fragmented forest, rural, and suburban habitats and is exophagic in nature,dutch buckets preferentially feeding on pigs. This may explain why it is more frequently trapped in outdoor locations.

Previous studies have shown improved collected mosquito numbers in CO2 baited traps for Cx. quinquefasciatus in French Polynesia, and Cx. quinquefasciatus and Cx. annulioris Theobald in Kenya. In addition, the use of CDC-LT with dry ice was most effective for trapping of Cx. quinquefasciatus when compared with UV light traps and gravid traps in China. This effect was not observed in the present study but this may be attributable to the low numbers ofCx. quinquefasciatus captured. Traps were mostly placed in villages surrounded by mountains and forests whereas Cx. quinquefasciatus is a mostly urban mosquito species and known to breed in open drains polluted with organic matter. Therefore, the trap setting strategy applied in this study may not have been suitable to capture large numbers of Cx. quinquifasciatus. Armigeres mosquitoes were captured consistently better outdoors in the CO2 baited traps and this effect was consistent across seasons. Ar. subalbatus primarily occurs in plantation areas and forests, and is mainly active during the day particularly in the crepuscular period. This may explain its preferential capture in outdoor locations. Ar. subalbatus is known to transmit Wuchereria bancrofti and several zoonotic filarial worms such as Brugia pahangi. While some previous studies have compared captured Ar. subalbatus numbers using different types of traps, we are not aware of a direct comparison of CO2 vs. nonCO2 and indoor vs. outdoor trap placements for this mosquito species. Overall, the number of Aedes species mosquitoes captured in this study was low and most captured Aedes mosquitoes were Ae. albopictus. Although previous studies have indicated that CDC-LT are amongst the most efficient traps for the capture of some Aedes species these differences were not apparent for Ae. albopictus. CO2 baiting slightly increased Ae. aegypti capture in a comparative trapping study in Manaus. In the present study, there were no statistically significant differences in trapping efficacy with or without CO2 and the placement of the traps. Ae. albopictus seemed to have a tendency of preferential indoor capture . Extended trapping studies would need to be conducted in order to determine whether capture efficiency is improved by CO2 and/or whether indoor/outdoor trap placement is important. Aedes trapping studies commonly use BG traps and it has been shown that these are more effective in capturing Aedes than CDC-LT. This study is limited by several factors.

Trap placement was irregular and the number of trap nights differed considerably between villages and months of year . While most previous studies distinguish between traps by counting absolute mosquito numbers, due to the complex and irregular placement of the traps in this study we compared the rate of mosquito capture per unit time, rather than absolute numbers. Although CDC-LT baited with CO2 were shown to increase capture rate for several mosquito species including several important disease vectors , it should be noted that the traps require daily dry ice and battery changes limiting the scope of trapping studies, as each trap needs to be maintained every day. Over 94 % of female mosquitoes in the trapped population were not blood-fed. It is unclear whether these individuals are newly emerged or parous females that have not yet taken a blood meal. The ratio of nulliparous to parous female mosquitoes may represent an important entomological parameter to be determined in future studies. Normally, An. minimus s.l. and An. maculatus s.l. are regarded as exophilic. A surprisingly small percentage of occupants in the study houses reported using ITNs . We cannot exclude the possibility that concurrent usage of ITN decreased indoor biting, but our analyses did not show such an effect modification, possibly because our sample numbers are too small. Other factors, such as house structures and the presence of domestic animals around houses might further affect mosquito behavior. Further studies should be conducted to comparatively evaluate whether the species composition, and the blood-fed and physiological age distribution of captured mosquitoes is similar for CDC-LT and human landing catches and thus, if CDC-LT are truly capable of capturing representative samples of those mosquitoes relevant for human disease transmission. This study highlights differences in trapping efficiency of CDC-LT for different mosquito species. Our study thus provides important orientation for more targeted future vector trapping studies on the Thai-Myanmar border, an important cross-border malaria transmission region.Human occupants are an important source of microbes in indoor environments. On indoor surfaces, direct contact leads to a rapidly generated signature of the occupants , one that is predictable based on the nature of the human contact. Airborne microbial levels increase when rooms are occupied compared to unoccupied conditions, and humans have been reported to be a source of bacteria and fungi in settled dust samples.

A full understanding of the role that occupancy plays in airborne microbial quantity and composition, particularly in comparison with other sources such as ventilation supply from outdoor air, is just beginning to emerge. While a recent study showed the influence of human body-associated bacteria in office buildings, investigations into the source strength of humans on indoor bioaerosols have predominantly focused on occupied classrooms. Hospodsky et al. showed that human occupancy in a university classroom setting leads to a nearly 10× increase in bacterial genomes and that emissions from human skin make a significant direct contribution to the bacteria in indoor air. More recently, Hospodsky et al.  determined in a sample of children’s classrooms that the emission rates attributable to occupants ranged from 0.8 million to 35 million bacteria cells per person-hour and from 3 million to 57 million fungal cells per person-hour. Two broad routes have been identified through which human occupants emit bioaerosol particles. One route is through direct shedding, which includes particles directly coming off bodies and clothing. The second route is through resuspension from inanimate room surfaces,grow bucket whereby occupants’ movements disturb microbial materials that had previously settled onto or colonized indoor materials. The goal of the present study is to explore the relative contribution of occupancy compared to other sources in shaping indoor bioaerosol composition using replicated experiments conducted under controlled conditions. For one component of the study, we sought to identify how the number and activity of occupants influences the biological components of the indoor air; we report those results here. Elsewhere, we report the emission rates of fluorescent biological aerosol particles from human occupants. We combine information from filter samples subjected to molecular-based analysis of DNA with the real-time size-resolved optical monitoring of total particle number concentrations. Outdoor samples were collected simultaneously and analyzed, which allows us to put the effect of occupants in the context of the contribution of outdoor air, as introduced via the ventilation system. We hypothesized that the signature of human-emitted microbes would increase with the number and activity of occupants, would be greater when the flooring was carpet that was exposed rather than covered with plastic sheeting, and would be stronger for bacteria than fungi. We expected that airborne microbial composition during low occupancy periods would be compositionally similar to that of outdoor air. We also expected that composition during high human occupancy periods would be similar across samples because of the shared signature of the human microbiome and because of the anticipated strong contribution of occupants to total airborne levels.Experiments were conducted in a controlled environmental chamber designed to simulate an office room.

The chamber has a floor area of 30 m2 and the ceiling height is 2.5 m. Ventilation in the chamber is controlled by an independent heating, ventilation, and air-conditioning system. The HVAC system supplies thermally and humidity controlled outdoor air that has passed through filters with a MERV 7 rating. There is no air recirculation with the single-pass ventilation system. The duct length from the outside air inlet to the room is approximately 10 m, and the ventilation air passes through a filter, supply fan, cooling coil, and heating coil in sequence. Outdoor temperatures during the test period ranged from 10 to 20°C. The outdoor humidity conditions were such that the cooling coil temperature was always above the dewpoint and therefore dry. The room was pressurized so that infiltration from adjacent building spaces was negligible. The ventilation fan speed was set to maintain a constant air-exchange rate, which was calculated by the exponential decay of the net CO2 level during the post-experimental period when the room quickly went from being occupied to unoccupied. The air-exchange rate was so determined to be 2.8 ± 0.2 h-1.The chamber floor consisted of closed-loop nylon carpet tiles, and we executed experiments both with the chamber carpet exposed and with it covered in plastic sheeting. To minimize static electricity effects during the walking treatment of the covered floor, we placed rectangular strips of a conductive material on top of the plastic sheeting. Subjects walked only on these strips. The duration of each experiment was two hours, a period of time allowing for sufficient collection of bioaerosol material for community analysis while still a time-resolved sampling period aligned with the particle-based instrumentation The five experimental combinations of occupancy and activity were each replicated three times on two different floor types, for a total of 30 experiments . Participants were members of the university community , including students, researchers, and faculty, and each of the high-occupancy sampling periods included both men and women. Participants provided written informed consent for the research, which was approved by the University of California Committee for the Protection of Human Subjects Protocol ID 2013-01-4927.Bioaerosol samples were collected by drawing air through open-face filters. Analytic filter cups of 47 mm diameter, 0.2 μm pore size cellulose nitrate membrane were suspended upside down at a height of 1.5 m . The attached vacuum pump was set to a flow rate of 25 liters per minute, so that a total volume of 3 m3 of air was sampled per experiment. We note that in sampling the entire 2-hour experimental period, the procedure captures both times when conditions are in transition and when steady-state conditions should prevail. For outdoor samples, the filter cup was suspended upside down, outside a window on the same building face at ~ 5 m from the outdoor air intake for the HVAC system. This sampling approach should only collect particles with diameters smaller than ~ 50 μm .