WO2009146520A2

WO2009146520A2 - Modified trap to capture the main mosquito vector of malaria (anopheles darlingi)

Info

Publication number: WO2009146520A2
Application number: PCT/BR2009/000163
Authority: WO
Inventors: Álvaro Eduardo EIRAS; Renata Antonaci Gama; Ivonete Maria Da Silva
Original assignee: Universidade Federal De Minas Gerais-Ufmg
Priority date: 2008-06-06
Filing date: 2009-06-08
Publication date: 2009-12-10
Also published as: BRMU8801292U2

Description

'MODIFIED TRAP FOR CAPTURE OF MALARIA MAIN MOSQUITO VECTOR Anopheles darlingP'

The present utility model patent proposes an improvement on the mosquito trap described in WO2004054358A2 to increase its efficiency in catching the Anopheles darlingi mosquito, the main malaria vector.

Malaria is an acute febrile infectious disease transmitted by the bite of the female Anopheles mosquito, infected with Plasmodium. Malaria transmission in Brazil is concentrated in the Legal Amazon, where 99.5% of all cases are recorded. This region is composed of the states of Acre, Amazonas, Amapá, Maranhão, Mato Grosso, Pará, Rondônia, Roraima and Tocantins, and totals 807 municipalities. From 1999 to 2002 there was a gradual reduction of malaria cases in the Legal Amazon, with an average of 496 thousand cases / year. During this period, actions were intensified, but there was no sustainability, since from 2003 malaria started to grow again and in 2005 603 thousand cases were notified, with a reduction in 2006, when about 540 thousand cases were registered.

The main vector of malaria in Brazil, the Anopheles darlingi mosquito, known as mosquito, muriçoca, carapanã, capuchin mosquito is a species of wide geographical distribution. It extends from southern Mexico to northern Argentina, and from the eastern slopes of the Andes to the shores of the Atlantic Ocean. It is estimated that over 40% of the world's population is at risk of malaria. In 2006, Brazil recorded 545,696 cases of malaria.

The main method of capturing Anopheles darlingi is through human bait, a technique that consists of exposing a person (collector) to the mosquito during the period of greatest feeding activity (bite). When the mosquito lands on the collector's body it is usually caught by means of a glass tube. This technique has been intensively questioned due to ethical issues in exposing humans to mosquitoes, at the risk of acquiring malaria.

Therefore, the development of efficient pitfalls for malaria vector collection is one of the goals of the Health researchers working with this vector to replace human bait.

Despite the great investment that has been made in this area, the main and effective tool for anopheline monitoring remains the human attraction. Although it is the most efficient method of capture, it has some ethical pitfalls, due to the exposure of field agents to the acquisition of diseases, and practical drawbacks, as it is a tiring and laborious method, and it has wide range of responses since the attractiveness and collection ability vary among individuals (PALIS YR & CURTIS, CF. Evaluation of different methods of caching anopheline mosquitoes in western Venezuela. J. Am. Mosq. Control. Assoe. 8: 261-267, 1992).

Among the pitfalls tested for anopheline monitoring are the Centers for Disease Control (CDC) (SUDIA, WD & CHAMBERLAIN, RW Battery-operated light trap, improved model. Mosquito News, v. 22, p. 126- 129, 1962) and Shannon's trap (SHANNON, RC 1931, The Environment and Behavior of Some Brazilian Mosquitoes. Proceedings of Entomilogical Society of Washington; v.33: p.1-27). C0 ₂ is one of the main attractions used in traps. However, in addition to being a generalist component in attracting most hematophagous insects, its effectiveness is questioned when it comes to anthropophilic species (GILLIES, MT & WILKES.TJ). freshwater area of west Africa Bull of Surrounding Res 61, 389-409, 1972; response to CO2, acetone and 1-octen-3-ol (J. Insect Behavior, 10: 395-407, 1997). Alternatively, some components present in human odor have been tested, such as lactic acid, ammonia and carboxylic acids (GEIER, M. & BOECKH, J. A new y-tube olfactometer for mosquitoes to measure the attractiveness of host odours. Entomol Applic, v. 92, pp. 9-19, 1999; BERNIER, UR; KLINE, DL; BARNARD, DR; SCHRECK, CE. & YOST RA Analysis of human skin emanations by gas chromatography / mass spectrometry. 2 identification of volatile compounds that are candidate attractants for the yeilow fever mosquito (Aedes aegypti). Anal. Chem, v. 72, No. 747-756, 2000; GEIER, M .; BOSCH, OJ & BOECKH, J. Ammonia as an attractive component of host odor for the yeilow fever mosquito, Aedes aegypti. Chem. Senses, v. 24, p. 647-653, 1999), in an attempt to improve the performance and specificity of traps in anthropophilic anopheline collection.

WO2004054358A2, the product of which is known as BG-Sentinel, is a trap developed in Germany for catching mosquitoes (or hematophagous mosquitoes, mainly the dengue vector, among other hematophagous insects). It has been showing good results in the collection of other species of culicidae (pernolved) in field trials (WILLIAMS, CR, LONG, JA, RUSSEL, C, RITCHIE, SA. Field efficacy of the BG-Sentinel compared with CDC backpack aspirators and CO ₂ baited. EVS traps for collection of adult Aedes aegypti in Cairns, Queensland, Australia J. Am. Mosq. Control Assoe 22: 296-300, 2006; MACIEL de FREITAS, R., EIRAS, AE, Lourenço de Oliveira, R. Field evaluation of effectiveness of the BG-Sentinel, a new trap for capturing adults Aedes aegypti (Diptera: Culicidae) Mem. Inst. Oswaldo Cruz.10: 321-325, 2006; KROECKEL, U., ROSE, A., EIRAS , AE, GEIER, M. New tools for surveillance of adult yeilow fever mosquitoes: comparison of trap catches with human landing rates in an urban environment J. Am. Mosq. Control. Assoe 22: 229-238, 2006; WILLIAMS, CR, LONG, JA, WEBB, EC, BITZHENNER, M., GIER, M., RUSSEL, C, RITCHIE, SA Aedes aegypti population sampling using BG- Sentinel trap in North Queensland Australia lia: Statistical considerations for trap development and sampling strategy. J.Med. Entomol 44: 345-350, 2007; MACIEL de FREITAS, R..CODEODE, CT, OLIVEIRA LOURENÇO, R. Daily survival rates and dispersal of Aedes aegypti females in Rio de Janeiro, Brazil. Am. J. Trop. Med. Hyg. 4: 359-665, 2007) and in tests with African anophelines (Grunewald et al., Unpublished data).

Trap efficiency is based on visual stimuli (white in the peripheral part and black in the central cone) and olfactory (synthetic human odor) stimuli. The original BG-Sentinel trap consists of a white cylindrical structure and a black cone in the central part. Inside has a fan that has the function of releasing synthetic attractive from the synthetic human odor (BG-Lure ^® ), which are dissipated to the environment with downward directed flow (GEIER, M .; ROSE, A. & EIRAS, AE A new lure for host-seeking anthropophilic mosquitoes and a novel type of a simple, non-CO ₂ mosquito trap Int. J. Med. Microb, p. 293: 50, 2004; ROSE, A .; , AE & GEIER, M. New attractants for host-finding mosquitoes & innovative designs for non-CO2 traps. The abstract book, 70th Annual Meeting of the J. Am. Mosq. Control. AssocA, 2004), mimicking the format of the plume of human odor, and suction the oncoming insects by retaining them in a compartment in the central part.

The present utility model patent discloses an enhancement to the mosquito trap described in WO2004054358A2 for the specific and efficient capture of the Anopheles darlingi main malaria vector, significantly increasing the capture rate by (inversion) of the trap position. so that the opening is facing downwards, reversing the arrangement of the internal structures; (b) alteration of the coloring pattern of the original trap, which has white body and white and black upper portion, to black body and white upper portion.

The advantages of the utility model patent presented herein may be better understood by the following examples:

Example 1: Evaluation of airflow position in BG-Sentinel trap.

The BG-Sentinel trap (patent WO2004054358A2) was installed at ground level with its opening at 40 cm and the approaching mosquitoes are sucked down and trapped in the collecting bag.

The objective of this experiment was to evaluate if the change in the trap installation position, and consequently in the suction direction of the mosquitoes, interferes with the anopheline capture rate, especially the Anopheles darlingi mosquito. It should be noted that in addition to changing the suction position of mosquitoes, changing the trap installation position It also interferes with the dispersion of the odor plume, an extremely important factor in attracting insects to entrapment. Six treatments were established: (a) usual position, trap installed at ground level with opening upwards at 40 cm from the ground (b) trap with opening upwards at 1.5 m from the ground (having inlet trap as a measure reference); (c) Trap installed sideways at ground level (opening 40 cm from the ground); (d) trap installed sideways at 1.5m from the ground; (e) face down trap with opening 40 cm from the ground and (f) face down trap at 1.5 m from the ground. Traps were baited with C0 ₂ and three replicates were performed.

Carbon dioxide (CO2) was used as attractive in all tests being obtained from dry ice contained in a 250 ml Styrofoam bottle featuring a silicone hose through which the gas was released at an average rate of 25g / hour. The traps were installed in the peridomicile and the experiments were performed from 18:00 to 20:00 hours.

The experiments were carried out during June and July 2007 in Mato Grosso, rural area of Porto Velho (RO), in an area where the anopheline population is usually high and the predominant species is Anopheles darlingi. The area is surrounded by three permanent breeding sites, which keep the anophelic density always high, and has abundant vegetation. It has only one residence where 12 children live, two adults and they raise dogs and chickens. Temperature, relative humidity and average precipitation were respectively 28.6 ° C, 79% and 6.7mm in June and 27.7 ° C, 75% and 17.6mm in July.

All experiments followed the Latin square design and data that were normal after transformation (log X + 1) were analyzed by analysis of variance (ANOVA) and nonparametric by Kruskal-Walis. The statistical program used was Systat 8.0 for Windows.

During this experiment a total of 550 anophelines were collected, being 356 A. darlingi, 192 Anopheles spp. and 2 A. benarrochi (captured at normal position 1.5m). There was no significant difference between the positions tested, however an increase in the mean and total number of A. darlingi (Table 1) and other anophelines (Table 2) collected in the downturned trap 1.5m from the ground, which is why this position is used in subsequent tests.

Table 1: Results of Anopheles darlingi capture using BG-Sentinel trap in various positions and heights.

Table 2: Results of anopheline capture using the BG-Sentinel trap at various positions and heights.

The normal position was not efficient for the capture of anophelines in the soil and in this position at 1.5 m from the soil obtained the worst performance in A. darlingi collections (Figure 2). The side position increased the catch only when placed at 5m from the ground. However, when the position of the trap was inverted downwards, there was an increase in catch at both heights (0.4 and 1.5m from the ground), and in the inverted position at 40 cm from the ground it captured approximately four times more A. darlingi (Table 1) and Anopheles spp. than the normal position.

The highest trap catches were 0 to 2 anophelines for all treatments (Table 3). In the normal position of the BG-Sentinel trap, the largest catch was 15 anophelines and occurred only in one trap, while in the downward position the highest catch were 31, 53 and 58 A. darlingi thus confirming the higher efficiency of the BG-Sentinel trap when placed down to 40 cm at ground level.

Table 3: Frequency of anophelines collected in BG-Sentinel traps in different positions (normal 0.4m, normal 1.5m, side 0.4m, side 1.5m, down 0.4m and down, 5m).

Number of Normal Down

Anopheline 0.4m from Normal 1.5m Side 0.4m Side 1.5m Down 1.5m from captured soil soil soil soil 0.4m soil soil

Classes N% N% N% N% N% N%

0-2 12 66.7 15 83.3 12 66.7 9 50.0 9 50.0 9 50.0

3-5 2 11.1 1 5.6 2 11.1 5 27.8 2 11.1 3 16.7

6-8 3 16.7 1 5.6 3 16.7 2 11.1 1 5.5 1 5.6

9-11 - - - - 1 5.6 0 0.0 - - 2 11.1

12-14 - - - - - - 1 5.6 2 11.1 2 11.1

15-17 1 5.6 - - - - - - - - - -

18-20 - - - - - - 1 5.6 1 5.6 - -

21-23 - - 1 5.6 - - - - - - - - -

24-26 - - - - - - - - - - - -

31-34 - - - - - - - - 1 5.6 - -

53-58 ** - - - - - - - - 2 11.1 1 5.6

Total 18 100.0 18 100.0 18 100.0 18 100.0 18 100.0 18 100.0

** The range was increased due to the reduced (or nonexistent) number of anophelines caught in the intermediate classes.

Example 2: Evaluation of BG-Sentinel Trap Staining. In order to evaluate the effect of variations in the black and white pattern of the trap on the anopheline capture rate, the color of the trap body, the top and the collecting pot were modified. The following treatments were evaluated: (a) all-white trap (BBB); (b) all black trap (PPP); (c) normal trap consisting of white body, white top and black collecting pot (BBP); (d) white body trap, black top and white collecting pot (BPB); (e) white body trap, black top and black collecting pot (BPP); (f) black body trap, black top and white pickup pot (PPB); (g) trap with body black, white top and white pickup pot (PBB); (h) black body trap, white top and black pickup pot (PBP).

All traps were baited with CO ₂ and the experiment had two repetitions. In this test, the traps were installed face down, as this position performed better in example 1.

A total of 1,196 anophelines were collected in this experiment, 709 of A. darlmgi species. No significant difference was observed in anopheline collection by different staining patterns. The trap that obtained the smallest number of captured anophelines was the one with black body, white lid and black pot (PBP) with 69 and only 34 specimens of A. darlingi. The trap in its original configuration (with white body, white lid and black pot, BBP) collected only 88 anophelines, 46 specimens of A. darlingi (Table 4). However, while the normal BG-Sentinel trap captured only 46 A. darlingi, the modified black-body trap with the white lid and pot (PBB) captured 182, with the trap efficiency increasing by approximately 4 times. The same happened with the anopheline capture, while the normal trap captured 88 anopheline, the modified PBB trap captured 313, approximately 3.5 times higher (Tables 4 and 5).

Table 4: Mean (± standard deviation) and Total Anopheles darlingi caught in C0 ₂ -baited BG-Sentinel traps.

Table 5: Mean (± standard deviation) and total anopheline captured BG- ₂ -baited sentinel traps.

Treatments

BBP

BBB (Normal) BPB BPP PPP PPB PBP PBB

Total 119 88 153 129 140 185 69 313 X + ep 7.4 ± 1.67 5.5 ± 1.68 9.6 ± 3.49 8.1 ± 2.17 8.7 ± 2.86 11.6 ± 4.08 4.3 ± 1.58 19.6 ± 7.73 The frequency of anopheline collected by trap ranged from zero to 127, with most traps positive with up to 8 mosquitoes (Table 2). The PPP (all black) trap captured anophelines at all repetitions (minimum 2 anophelines per trap) while PPB had only one trap without anopheline capture, demonstrating that the black color has a major influence on malaria vector capture.

Table 6: Frequency of anophelines collected in BG-Sentinel traps in different colors.

BBP

BBB (Normal) BPB BPP PPP PPB PBP PBB

Classes N% N% N% N% N% N% N% N% N%

0-2 2 12.5 5 31.2 4 25.0 4 25.0 2 12.5 5 31.25 11 68.75 2 12.5

3-5 2 12.5 7 43.7 4 25.0 5 31.2 6 37.5 5 31.25 1 6.25 5 31.25

6-8 8 50.0 1 6.2 3 18.7 3 18.7 4 25.0 1 6.25 1 6.25 1 6.25

9-11 3 18.7 1 6.2 1 6.2 - - 2 12.5 1 6.25 1 6.25 1 6.25

12-14 - - - - 2 12.5 1 6.2 - - - - - - 2 12.5

15-17 - - - - 1 6.25 1 6.25 - - 1 6.25 1 6.25 - -

18-20 - - - - - - - - 1 6.25 - - - - - -

21-23 - - 2 12.5 - - - - - - - - 1 6.25 - -

24-26 - - - - - - - - - - - - - - 2 12.5

27-42 ** 1 6.25 - - - - 2 12.5 - - 1 6.25 - - 2 12.5

43-58 ** - - - - - - - - 1 6.25 2 12.5 - - - -

59-74 ** - - - - 1 6.25

> 75 ** 1 6.25

Total 16 100 16 100 16 100 16 100 16 100 16 100 16 100 16 100

N = Number of traps, and classes are the captured anopheline value ranges.

BRIEF DESCRIPTION OF THE FIGURES

Figure 01. Scheme of variation in BG-Sentinel trap color patterns: (a) all white (BBB); (b) all black (PPP); (c) white body, white top and black collector pot (BBP); (d) white body, black top and white collecting pot (BPB); (e) white body, black top and black collecting pot (BPP); (f) black body, black top and white pickup pot (PPB); (g) black body, white top and white pickup pot (PBB); (h) black body, white top and black pickup pot (PBP).

Claims

1. "MODIFIED TRAP FOR CATCHING THE MAIN VECTOR MALARIA MOSQUITO Anopheles darlingi characterized by understanding improvements in the trap described in WO2004054358A2 by reversing the position of the trap so that the opening is downward, changing the dispersion of the odor plume it attracts the insects until the trap enters and the trap color pattern changes to black body, white top and white pickup pot.