Evaluation of two counterflow traps for testing behaviour-mediating compounds for the malaria vector Anopheles gambiae s.s. under semi-field conditions in Tanzania (original) (raw)
Related papers
PLoS ONE, 2011
Odour baited traps have potential use in population surveillance of insect vectors of disease, and in some cases for vector population reduction. Established attractants for human host-seeking mosquitoes include a combination of CO 2 with L-lactic acid and ammonia, on top of which additional candidate compounds are being tested. In this field study in rural Gambia, using Latin square experiments with thorough randomization and replication, we tested nine different leading candidate combinations of chemical odorants for attractiveness to wild mosquitoes including anthropophilic malaria vectors, using modified Mosquito Magnet-X (MM-X) counterflow traps outside experimental huts containing male human sleepers. Highest catches of female mosquitoes, particularly of An. gambiae s.l. and Mansonia species, were obtained by incorporation of tetradecanoic acid. As additional carboxylic acids did not increase the trap catches further, this 'reference blend' (tetradecanoic acid with L-lactic acid, ammonia and CO 2 ) was used in subsequent experiments. MM-X traps with this blend caught similar numbers of An. gambiae s.l. and slightly more Mansonia and Culex mosquitoes than a standard CDC light trap, and these numbers were not significantly affected by the presence or absence of human sleepers in the huts. Experiments with CO 2 produced from overnight yeast cultures showed that this organic source was effective in enabling trap attractiveness for all mosquito species, although at a slightly lower efficiency than obtained with use of CO 2 gas cylinders. Although further studies are needed to discover additional chemicals that increase attractiveness, as well as to optimise trap design and CO 2 source for broader practical use, the odour-baited traps described here are safe and effective for sampling host-seeking mosquitoes outdoors and can be incorporated into studies of malaria vector ecology.
Journal of Medical Entomology, 2007
Chemical cues play an important role in the host-seeking behavior of blood-feeding mosquitoes (Diptera: Culicidae). A Þeld study was carried out in The Gambia to investigate the effects of human odor or synthetic odor blends on the attraction of mosquitoes. MM-X traps baited with 16 odor blends to which carbon dioxide (CO 2 ) was added were tested in four sets of experiments. In a second series of experiments, MM-X traps with 14 odor blends without CO 2 were tested. A blend of ammonia and L-lactic acid with or without CO 2 was used as control odor in series 1 and 2, respectively. Centers for Disease Control and Prevention (CDC) traps were placed in a traditional house and an experimental house to monitor mosquito densities during the experiments. The MM-X traps caught a total number of 196,756 mosquitoes, with the most abundant species belonging to the genera Mansonia (70.6%), Anopheles (17.5%), and Culex (11.5%). The most abundant mosquito species caught by the CDC traps (56,290 in total) belonged to the genera Mansonia (59.4%), Anopheles (16.0% An. gambiae s.l. Giles, and 11.3% An. ziemanni Grü nberg), and Culex (11.6%). MM-X traps baited with synthetic blends were in many cases more attractive than MM-X traps baited with human odors. Addition of CO 2 to synthetic odors substantially increased the catch of all mosquito species in the MM-X traps. A blend of ammonia ϩ L-lactic acid ϩ CO 2 ϩ 3-methylbutanoic acid was the most attractive odor for most mosquito species. The candidate odor blend shows the potential to enhance trap collections so that traps will provide better surveillance and possible control.
Malaria Journal, 2006
The successful development of odour-baited trapping systems for mosquitoes depends on the identification of behaviourally active semiochemicals, besides the design and operating principles of such devices. A large variety of 'attractants' has been identified in laboratory investigations, yet few of these increase trap catches in the field. A contained system, intermediate between the laboratory and open field, is presented and previous reports that human foot odour induces behavioural responses of Anopheles gambiae confirmed.
Parasites & Vectors, 2013
Background: Mosquitoes that bite people outdoors can sustain malaria transmission even where effective indoor interventions such as bednets or indoor residual spraying are already widely used. Outdoor tools may therefore complement current indoor measures and improve control. We developed and evaluated a prototype mosquito control device, the 'Mosquito Landing Box' (MLB), which is baited with human odours and treated with mosquitocidal agents. The findings are used to explore technical options and challenges relevant to luring and killing outdoor-biting malaria vectors in endemic settings. Methods: Field experiments were conducted in Tanzania to assess if wild host-seeking mosquitoes 1) visited the MLBs, 2) stayed long or left shortly after arrival at the device, 3) visited the devices at times when humans were also outdoors, and 4) could be killed by contaminants applied on the devices. Odours suctioned from volunteer-occupied tents were also evaluated as a potential low-cost bait, by comparing baited and unbaited MLBs. Results: There were significantly more Anopheles arabiensis, An. funestus, Culex and Mansonia mosquitoes visiting baited MLB than unbaited controls (P≤0.028). Increasing sampling frequency from every 120 min to 60 and 30 min led to an increase in vector catches of up to 3.6 fold (P≤0.002), indicating that many mosquitoes visited the device but left shortly afterwards. Outdoor host-seeking activity of malaria vectors peaked between 7:30 and 10:30pm, and between 4:30 and 6:00am, matching durations when locals were also outdoors. Maximum mortality of mosquitoes visiting MLBs sprayed or painted with formulations of candidate mosquitocidal agent (pirimiphos-methyl) was 51%. Odours from volunteer occupied tents attracted significantly more mosquitoes to MLBs than controls (P<0.001).
Attraction of Anopheles gambiae to odour baits augmented with heat and moisture
Malaria Journal, 2010
Background: The search for a standard human surrogate in the form of a synthetic mosquito attractant has been the goal of many laboratories around the world. Besides alleviating the occupational risk subjected to volunteers participating in vector surveillance and control, discovery of potent attractants underpins the development and deployment of mass trapping devices for controlling mosquito-borne diseases.
Malaria Journal
Background When seeking a human for a blood meal, mosquitoes use several cues to detect and find their hosts. From this knowledge, counter-flow odour-baited traps have been developed that use a combination of CO2, human-mimicking odour, visual cues and circulating airflow to attract and capture mosquitoes. Initially developed for monitoring, these traps are now also being considered as promising vector control tools. The traps are attractive to host-seeking mosquitoes, but their capture efficiency is low. It has been hypothesized that the lack of short-range host cues, such as heat and increased local humidity, often prevent mosquitoes from getting close enough to get caught; this lack might even trigger avoidance manoeuvres near the capture region. Methods This study investigated how close-range host cues affect the flight behaviour of Anopheles female malaria mosquitoes around odour-baited traps, and how this affects trap capture performance. For this, a novel counter-flow odour-b...
Parasites & Vectors, 2015
Background: Malaria is the 4 th largest cause of mortality in Madagascar. To better understand malaria transmission dynamics, it is crucial to map the distribution of the malaria vectors, mosquitoes belonging to the genus Anopheles. To do so, it is important to have a strong Anopheles-specific lure to ensure the maximum number of captures. Previous studies have isolated volatiles from the human skin microbiota and found the compound 3-methyl-1-butanol to be the most attractive to the malaria mosquito, Anopheles gambiae, in a laboratory setting; and recommended 3methyl-1-butanol as a compound to increase An. gambiae captures in the field. To date, this compound's ability to lure wild mosquitoes in differing land-use settings has not been tested. In this study, we evaluate the role of the synthetic compound, 3-methyl-1-butanol in combination with field produced CO 2 in attracting Anopheles mosquitoes in varying land-use sites in Madagascar. Methods: CDC miniature light traps in combination with field produced CO 2 were deployed in and around six villages near Ranomafana National Park, Madagascar. To test the role of 3-methyl-1-butanol in luring Anopheles mosquitoes, two traps were set in each land-use site (village, agricultural sites, and forested habitats affiliated with each village). One was baited with the synthetic odor and the other was kept as a non-baited control. Results: While 3-methyl-1-butanol baited traps did capture An. gambiae s.l. in this study, we did not find traps baited with synthetic 3-methyl-1-butanol to be more successful in capturing Anopheles mosquitoes, (including Anopheles gambiae s.l.) than the non odor-baited control traps in any of the land-use sites examined; however, regardless of odor bait, trapping near livestock pens resulted in the capture of significantly more Anopheles specimens. Conclusions: A strong synthetic lure in combination with insecticide has great potential as a mosquito control. Our findings suggest that trapping mosquitoes near livestock in malaria endemic regions, such as Madagascar, may be more successful at capturing Anopheles mosquitoes than the proposed 3-1-methyl-butanol lure.
Journal of the American Mosquito Control Association, 2005
A synthetic blend of chemicals comprising volatiles released by the human body has been shown to be an effective attractant for female Aedes aegypti in olfactometer bioassays with laboratory-reared mosquitoes. We report the laboratory evaluation of Ae. aegypti response to a synthetic blend tested with 4 types of mosquito traps (CDC model 512, CDC model 1012, CFG, and Fay-Prince traps). Aedes aegypti females were attracted significantly by the blend. The higher release rate of attractant (320.2 Ϯ 10.71 mg/h) more efficiently attracted mosquitoes than the lower release rate (42.0 Ϯ 2.3 mg/h). Although both the Fay-Prince and CFG traps caught higher number of mosquitoes than the other traps, only the CFG trap caught a statistically significant greater number of mosquitoes. The results suggest that the synthetic blend is effective in attracting Ae. aegypti females under controlled laboratory conditions (i.e., a closed system). Further studies are needed to evaluate the efficacy of this blend in baited traps under field conditions.
Understanding the long-lasting attraction of malaria mosquitoes to odor baits
PloS one, 2015
The use of odor baits for surveillance and control of malaria mosquitoes requires robust dispensing tools. In this study, the residual activity of a synthetic mosquito attractant blend dispensed from nylon or low density polyethylene (LDPE) sachets was evaluated at weekly intervals for one year without re-impregnation. The potential role of bacteria in modulating the attraction of mosquitoes to odor-treated nylon that had been used repeatedly over the one year study period, without re-impregnation, was also investigated. Significantly higher proportions of female Anopheles gambiae sensu stricto mosquitoes were consistently attracted to treated nylon strips than the other treatments, up to one year post-treatment. Additional volatile organic compounds and various bacterial populations were found on the treated nylon strips after one year of repeated use. The most abundant bacteria were Bacillus thuringiensis and Acinetobacter baumannii. Autoclaving of treated nylon strips prior to ex...