DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Some Coryneform bacteria, existing in human sweat, are known to produce methanethiols that emanate as both cheese and foot odor. The microbes may be responsible for producing human odors from human perspiration. Evidence for direct microbial involvement in producing the volatile attractants in human hosts has been demonstrated by showing that incubation of sweat enhances its attraction. Therefore, it is very useful to identify these microbes and use these microbes for simulating human odors, as a means for attracting the haematophagous mosquitoes.

[0020] Nectar is the only food source of male mosquitoes, while the females of many species take a sugar meal before engaging in blood feeding. For the host-seeking flight, sugar is presumably the energy source and the initial differences in energy reserves affect the response to host volatiles. Additionally, that CO2 shows non-species limited attraction of mosquitoes has been reported in a dose-dependent response. In this invention, the mosquito attractants include at least a human odor simulator simulating human host volatiles, a sugar source and a CO2 supply source. The human odor simulator is provided by specific bacteria decomposition, while a steady increased CO2 concentration and a flavored sugar meal is provided by yeast fermentation using fruit juice as the culture medium.

[0021] Experimental data:

[0022] Some experiments were applied to mosquitoes, described as following:

[0023] Mosquitoes The Aedes aegypti were maintained and assayed at 23-25° C., 60-80% relative humidity, and 12 hrs light/12 hrs dark. Adults were kept in 30 cm3 gauze-covered cages and fed with a 10% (v/v) sugar solution. In the bioassay 30 of the 4-8 day-old females that had not received a blood meal were released into a dual-port olfactometer. The olfactometer consisted of a flight chamber (1.6 m×0.6 m×0.6 m) in which mosquitoes were released. Air pumped from the room source was filtered by charcoal, passed through two bottles of distilled water, and one of the two ports (5 cm diameter, 30 cm apart), and then released into the flight chamber. The odor source was placed in the port, where the temperature was kept at 30° C. by a water circulation system, while the room temperature was maintained at 23-25° C. The observation time of the bioassay was 15 minutes after releasing mosquitoes. All parts of the olfactometer were cleaned with 75% alcohol and blow with strong fans for 20 minutes between test series. In addition, to counteract the effect of any biased directional response of unknown origin, the positions of the treatment and control were alternated between ports after each test.

[0024] Bacteria Strains of two Coryneform bacteria, Brevibacterium epidermidis (BE) and B. linens (BL), purchased from Deutsche Sammlung von Mikrooranismen and Zellkulturen GmbH, Braunschweig, Germany and Food Industry Research & Development Institute, Hsinchu, Taiwan, ROC, respectively, were used for bioassay. The bacteria were grown in three different mediums: TSB, MB and NB. The ingredients of the three mediums are listed as following: TSB (15 grams of tryptone+5 grams of soytone+5 grams of NaCl/liter, pH 7.3), MB (50 grams of milk powder+2.5 grams of peptone/liter, pH 7.2), and NB (5 grams of peptone+1.5 grams of beef extract+1.5 grams of yeast extract+5 grams of NaCl/liter, pH 7.4) at 30° C., 200 rpm for two days.

[0025] In order to screen the different combinations of bacteria and medium for the highest efficiency of mosquito attraction, 4 ml of the 2-day-old bacterial cultures from different combinations were tested in the olfactometer.

[0026] As shown in Table 1, most Corynebacterial strains grown in any of these three mediums can attract mosquitoes, except for strain BE9585 that did not show attraction. Among them, strain BE9586 is the only one to show attraction with all three growing mediums, of which that cultured with the NB medium had the highest attraction percentage. In general, the attraction efficiency was not higher than 30% in the absence of the heating device. 1

[0027] In order to further identify the attraction of strain BE9586 grown in the NB medium, the supernatant obtained from centrifugation of the bacterial culture was assayed in the olfactometer. Referring to Table 2, up to 86.7% of adult female mosquitoes were attracted toward the supernatant of the bacterial culture. This percentage of attraction was approximately 20% higher than NB medium alone and higher than blank solution without the odor source. It suggests that volatiles emanating from decomposition of the bacterial culture can exclusively attract adult female mosquitoes. In this assay, the heating itself showed 61.7% attraction, higher than previous non-heated odor sources. In addition, the heating device may also function for better evaporation of the bacterial decomposition. 2

[0028] FIG. 1 is a display view of an apparatus according to one preferred embodiment of the present invention. Referring to FIG. 1 , the apparatus 100 is divided into an upper compartment 102 and a bottom compartment 104 , connected by a thumbscrew container 106 . A shield 108 is connected to the top of the upper chamber 102 with a supporting means, such as a supporting stock with extension walls for leading mosquitoes into passing channels. The shield 108 is separated from the upper compartment 102 by a distance of about 1-2 cm. Under the shield 108 , the top of the upper compartment includes a plurality of passing channels 110 that open inward to the internal space of the upper chamber 102 . The passing channels 110 have openings large enough for mosquitoes to pass through, while the channels 110 open inward to prevent the escape of incoming mosquitoes. After the upper compartment 102 is fit into the thumbscrew container 106 , a first bottle 120 is placed inside the upper compartment 102 and on a grid 112 of the thumbscrew container 106 . The first bottle 120 comprises at least odor simulators and a steady source for supplying CO2, as well as a sugar source. Preferably, the human odor simulators and the steady source for CO2 can be provided by the yeast fermentation with a medium. The medium may contain juice, further serving as a sugar source.

[0029] Referring to FIG. 1 , the bottom compartment 104 includes an adjustable heating assembly 114 , comprising at least a time-control means and a temperature-control means. The time-control means can set up an application time based on the user's schedule. The temperature-control means can generate heat to a specific (set-up) temperature and maintain the temperature, and comprises, for example, at least a metallic heater 116 that is controlled by a logic circuit. The adjustable heating assembly 114 can be controlled by the user's set-up to generate a regulated thermal gradient for bacteria incubation and evaporation of the bacterial decomposition components. A second bottle 122 is placed inside the bottom compartment 104 and on the bottom of the bottom compartment 104 . The second bottle 122 comprises host odor simulators, for example, bacterial decomposition. After incubating specific microorganisms (bacteria) with cultivating mediums, bacteria can generate metabolic products or decompose the cultivating medium so as to produce bacterial decomposition, Preferably, Corynebacterial strains and cultivating conditions used in previous experiments are used. For example, strain BE9586 grown in the NB medium [5 grams of peptone+1.5 grams of beef extract+1.5 grams of yeast extract+5 grams of NaCl/liter, pH 7.4] is used to provide bacterial decomposition. The heater 116 is provided inside the bottom compartment 104 and above the second bottle 122 for heating up the chamber of the bottom compartment 104 , thus providing heat for microbe incubation in the second bottle 122 . A conversion funnel 118 is used to gather the heat, provided by the heater 116 , in the chamber of the bottom compartment 104 and transfer heat to the chamber of the upper compartment 102 , thus providing heat for incubating the yeast fermentation. As a result, two different thermal zones are generated in two compartments. Preferably, the thermal zones of the upper and bottom compartments should maintain at about 30° C. and 37° C. respectively. These maintained thermal zones of the two compartments provide heat for microbe incubation of both microorganisms and for helping emanation of the attractants produced in the bacteria culture. Furthermore, the maintained thermal zone can simulate human body temperature and act as an attractant for attracting mosquitoes.

[0030] Experiments performed by the inventors for the effect of heat combined with odor simulators on the mosquito species Aedes aegypti showed that bacterial decomposition along with heat evaporation could attract 60% of the mosquitoes, more than the 44% of mosquitoes attracted by yeast fermentation in a 60 minutes observation. Moreover, the synergistic effect could be observed in the combination of bacterial decomposition, yeast fermentation and heat evaporation, as 85% of mosquitoes were trapped after a 12-hours incubation within the olfactometer. Using bacterial decomposition as the mosquito bait attracts more mosquitoes in a certain period when compared with other baits, probably due to the dominant influence of odors in host-seeking behavior of mosquitoes.

[0031] FIG. 2A is a perspective view of an apparatus according to one preferred embodiment of the present invention, while FIG. 2B is a partially exploded perspective view of the apparatus shown in FIG. 2A .

[0032] Referring to FIG. 2 A, an apparatus 200 is shown with an upper compartment 202 and a bottom compartment 204 , connected by a thumbscrew container 206 .

[0033] Referring now to FIG. 2 B, the apparatus 200 is shown in a partially exploded perspective view to further describe assembly details of the apparatus. A first bottle 220 is mounted on the center of a grid fixture 224 . The thumbscrew container 206 has an upper thumbscrew 226 and a bottom thumbscrew 228 in order to fit the upper compartment 202 and the bottom compartment 204 respectively, as well as a grid 212 between the upper thumbscrew 226 and the bottom thumbscrew 228 . A first O-ring 230 and a second O-ring 232 are used to seal up the upper compartment 202 and the bottom compartment with the thumbscrew container respectively. The grid fixture 224 is placed on the grid 212 , so that the first bottle 220 is located inside the upper compartment 202 after the upper compartment 202 fits with the thumbscrew container 206 . A collecting web 234 can be further included between the grid fixture 224 and the grid 212 for collecting dead mosquitoes. The collecting web 234 may also include a sticky material to trap mosquitoes or insecticides for killing mosquitoes. Furthermore, electric grids can also be included into the upper compartment 202 for killing mosquitoes.

[0034] Referring to FIG. 2 B, the bottom compartment includes a bottle fixture 236 with a removable undercarriage 238 , and a second bottle 222 is locked within the bottle fixture 236 . The removable undercarriage 238 can be dismantled from the bottle fixture 236 , so that the second bottle 222 can be refilled or cleaned. A heater 216 and a conversion funnel 218 are located above the bottle fixture 236 . The conversion funnel 218 has a narrower opening facing the center of the grid 212 and a wider opening facing the chamber of the bottom compartment 204 , so that heat gathered from the chamber can be transferred through the grid 212 to the upper compartment 202 .

[0035] Bait-releasing Unit

[0036] In another preferred embodiment of the present invention, the previously cited apparatus further comprises a bait-releasing means for enhancing the release and evaporation of the mosquito bait. The bait-releasing means, for example, utilizes spraying mechanisms for spreading the bait as finely droplets (e.g. with a diameter of about 5-50 microns) into the environment. Therefore, the diffuse rate and evaporation rate of the bait in a certain space is increased, thus enhancing efficiency of the mosquito bait and increasing the effective distance for attracting mosquitoes.

[0037] A bait-releasing unit is taken as an example for the bait-releasing means of the present invention. FIG. 3 is a display view of a bait-releasing unit in the apparatus according to another preferred embodiment of the present invention. In FIG. 3 , the bait-releasing (bait-spraying) unit 300 is disposed inside the aforementioned apparatus (shown as 303 in FIG. 3 ), either inside the upper compartment, inside the bottom compartment, inside the second bottle or between the upper and the bottom compartment. Moreover, the bait-releasing unit 300 can be coupled with the electric grids.

[0038] The bait-releasing unit 300 comprises at least a spray nozzle 302 , made of stainless steel, and a small air pump 304 . The air pump 304 can be replaced by an air cartridge or by other mechanisms with similar functions. The spray nozzle 302 comprises an outer tube 306 and an inner tube 308 that is telescoped into the outer tube 306 .

[0039] The air pump 304 pressurizes air through a tubing 309 into the inner tube 308 of the spray nozzle 302 . Because the outer tube 306 is immersed in the mosquito bait (in a liquid form) and a crevice 310 is in the bottom of the outer tube 306 , the liquid mosquito bait can be siphoned up to a cap 312 of the spray nozzle 302 . The air pressurized into the inner tube 308 then ejects at a high speed through a small hole 314 , thus spraying out the mosquito bait in a form of very fine droplets (shown as arrow in FIG. 3 ). The droplets have an average diameter of about 5-50, microns, for example. Therefore, the bait is turned to a mist that is volatile and easily diffusive.

[0040] Because the apparatus 303 has an outer shell that can prevent large droplets of the bait from spreading out, only fine droplets of the bait are released into the environment. Therefore, each droplet can quickly and easily evaporate, thus enhancing efficiency of the mosquito bait and increasing the effective distance for attracting mosquitoes.

[0041] Accordingly, the bait-releasing unit sprays out the mosquito bait in a form of fine droplets, so that the diffuse rate and evaporation rate of the bait in a certain space are increased, thus increasing the effective distance for attracting mosquitoes and boosting efficiency of the mosquito bait to a maximum.

[0042] For testing the effect of the bait-releasing unit combined with mosquito attractants, experiments are carried out within a room dimensioned 3.5*3.5*3 meters on the mosquito species Aedes aegypti. The results showed that the mosquito capture rate is increased from 30% (without the bait-releasing unit) to 90% (with the bait-releasing unit).

[0043] Therefore, the bait-releasing unit disclosed in the present invention indeed boosts diffusion of the mosquito bait and improves attraction toward mosquitoes, thereby increasing the capture rate of the mosquitoes.

[0044] Furthermore, instead of the spraying mechanism of the aforementioned bait-releasing means, a foam blowing mechanism can also be used to help spreading out the mosquito bait. Through chemical reactions between specific foaming agents with solutions, gases, for example, carbon dioxide, can be produced to blow the mosquito bait into the surrounding environment. Therefore, it boosts the release of the bait and reinforces the attraction toward mosquitoes. One of the advantages of this foam blowing mechanism is no electrical power is required, thus suitable for outdoor usage in combination with pesticide or sticky materials.

[0045] It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the present invention without departing from the scope or spirit of the invention. In view of the foregoing, it is intended that the present invention cover modifications and variations of this invention provided they fall within the scope of the following claims and their equivalents.