FINAL REPORT LETHAL OVITRAPS WITH ATTRACTANT FOR AEDES AEGYPTI MOSQUITO CONTROL IN THE DOMINICAN REPUBLIC
Recommended Citation: The Zika AIRS Project (ZAP). Lethal Ovitrap Report. Rockville, MD. The Zika AIRS Project, Abt Associates Inc. Contract: GHN-I-00-09-00013-00 Task Order: AID-OAA-TO-14-00035 Submitted to: United States Agency for International Development
Abt Associates Inc. 1 6130 Executive Boulevard 1 Rockville, Maryland 20852 1 T. 301.347.5000 1 F. 301.913.9061 1 www.abtassociates.com
Table of Contents
1 Introduction ...... 4 2 Study Area ...... 4 3 Objectives ...... 5 4 Tools ...... 6 5 Methodology ...... 6 5.1 Experimental Design ...... 6 5.2 Vector Control ...... 8 6 Results ...... 8 6.1 Entomological surveillance ...... 8 6.2 Field Study ...... 10 6.3 Vector Control ...... 14 7 Discussion...... 16 8 Discoveries, Challenges, and Recommendations ...... 17 9 Bibliography ...... 18 10 Annex ...... 19
1 Introduction
The Dominican Republic (DR) is a Caribbean nation that shares the island of Hispaniola with the Republic of Haiti. With a population of approximately 10.6 million and an area of 48,670 square kilometers, the country is densely populated and increasingly urbanized. Due to its tropical location, the DR experiences elevated temperatures and humidity consistently throughout the year. Most of the country’s land mass sits less than 500 meters above sea level, and there are abundant sources of water. These environmental conditions make the DR an ideal location for the proliferation of mosquitoes and other vectors that may be involved in the transmission of communicable diseases.
The goal of integrated vector management (IVM) is to combine different chemical, biological, environmental, and behavior measures to address variable components of the vector transmission cycle, improving efficiency in cost effectiveness, environmental management, and sustainability. Typically, an IVM program addresses specific goals for each region and its economical, logistical and technical capabilities. In this respect, it is necessary to design and implement new, viable and sustainable alternatives for limited resource countries that interrupt the Aedes aegypti life cycle reducing the transmission of arboviruses such as dengue, Zika, and Chikungunya, while keeping the risk of other highly lethal diseases (like yellow fever) at a minimum.
ZAP DR has supported the Centro de Control de Vectores y Zoonosis (CECOVEZ, previously CENCET) since 2017 in the integration of the entomological surveillance method with ovitraps, measuring the adult mosquito density through egg collection and counting. Studies performed in six provinces of the Dominican Republic (La Altagracia, Azua, Espaillat, San Cristóbal, Santo Domingo, and Santiago de los Caballeros), have proven that hay infused ovitraps attract more Aedes mosquitoes than plain water ovitraps.1
The entomological surveillance of the Aedes aegypti mosquito is performed through entomological surveys at the breeding sites, where the classic aedic indexes are determined: household index, container index, and Breteau index. This information provides infestation levels as an additional entomological surveillance measure.
Considering ovitraps high efficiency to capture Aedes mosquito eggs, the ZAP Project, using the lab facilities of the Universidad Autónoma de Santo Domingo (UASD), designed an IVM strategy incorporating lethal ovitraps focused on reduction of mosquito reproduction. The lethal ovitraps for this study consisted of dark colored plastic containers with a roughened surface containing Bti and 10% hay infusion that works as an attractant for pregnant females for oviposition.
2 Study Area
The study area for this pilot is the Monte Plata municipality, in the Monte Plata province. This municipality is located in the south-central area of the island, with geographic coordinates of: 18° 45' 00'' N - 69° 51' 00'' W (See Figure 1 below). Weather is tropical, with an average temperature of 25.9°C and average rainfall of 1,924 mm. Monte Plata has 46,723 inhabitants, the municipal district has 26,192 people according to the 2010 national population and housing census.
1 Entomological surveys, with ovitraps, October - December 2017, ZAP Project, in 6 sentinel sites (Manoguayabo Oeste, Azua, Moca Higuey, Area 1 and Area 3 of Santiago de los Caballeros), of the Dominican Republic.
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The last entomological survey performed in the third quarter of 2017 by the Dirección Provincial de Salud de Monte Plata (local health department), found an index of 5 for A. aegypti infestation. Infestation level combines three indexes (house, container, Breteau) on a scale of 0-9. A score of 5 therefore means an elevated infestation level. Figure 1. Location of the Monte Plata province in the Dominican Republic, and division of the 4 study areas (3 intervention and 1 control).
Control 2 1
3
3 Objectives
General Objective The main objective of this pilot study was to establish the effectiveness of lethal ovitraps as part of an integrated mosquito control strategy, determining its feasibility and sustainability in the Dominican Republic.
Specific Objectives To develop new technical tools and procedures that complement entomological surveillance and integrated vector management in the Dominican Republic; To determine the degree of attraction for mosquitoes in the oviposition stage to different Bti and hay infused combinations; To define the residual effect of different Bti concentrates with and without infusions on A. aegypti larvae; and To evaluate the impact of a mosquito control strategy that integrates lethal ovitraps and reduction of breeding sites over the aedic infestation indexes and adult mosquito density.
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4 Tools
The following tools were necessary to support this study: Plastic100ml (1 liter) capacity black Digital scale from 1 to 1000 grams colored containers 2.5 liter capacity plastic containers Pellon paper Droppers Hay bales “jamos” bug nets Bacillus thuringiensis isrraelensis (1 kilo) Prokopack aspirators GPS BG traps Area maps Tables 20X magnifiers 250ml capacity container cages Flashlights 1 stereoscope (Nexius ZOOM 5 liter buckets NZ.1902-S) Sensitive precision balance (from 0.001) cellphones
5 Methodology
5.1 Experimental Design The lethal ovitraps pilot consisted of three phases: laboratory, semi-field, and field phases.
5.1.1 Laboratory Phase During the laboratory phase, we tested differences in the level of attraction of gravid mosquitoes in oviposition, using ovitraps with different concentrations of Bti, with and without hay infusion as attractant. The tests were conducted at the entomology laboratory of Universidad Autónoma de Santo Domingo.
5.1.1.1 Preference of oviposition on Bti and Bti with attractant In this experiment, differences in attraction for female gravid mosquitoes in oviposition were determined comparing the following combinations of ovitraps attractant: plain water, concentrations of 3ppm or 6ppm Bti and 10% hay infused with 3ppm or 6ppm Bti.
For the oviposition experiments, San Cristobal strain 5-day-old female mosquitoes were used and kept in insectarium conditions of 26-29 C temperature, and 70-90% relative humidity. These mosquitoes were previously mated and subsequently blood-fed for 3 hours. For this, three mice of the Mus musculus species were introduced.
Two days after being blood-fed, 10 randomly picked mosquitoes were introduced in a 30 cm x 30 cm cage (Bug Dorm, BioQuip) around 4 pm, and were removed 72 hours later. Inside each of the cages, three 500 ml capacity plastic containers were introduced; one with the Bti solution (3 or 6 ppm), another one with attractant infusion + Bti (3 or 6 ppm) and a final one with water (control). Three experiments with 3 replica each were performed at different time intervals for each concentration, rotating the containers position as shown in figure 2. With the objective of reducing the randomness of the results, the hay and Bti preparations were done at different time intervals for each one of the experiments and replicas. However, each container was kept with the same solution volume. Inside each cage damped cotton with a sugar solution was also introduced.
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Once the pellon papers were removed, the eggs were counted using stereoscope microscopes. Figure 2. Container rotation to assess oviposition preference by gravid mosquitoes.
Each replica had a container located in a different position, until a full rotation for all three positions is completed. 1. BTI + ATR: 10% hay infused content and 3 or 6ppm Bti; 2. BTI: Bti solution at a 3 ppm or a 6 ppm concentration content (same concentration employed in combination with the attractant); WATER: Does not contain Bti or infusion (Control).
5.1.1.2 Residuality of Bti with attractant To measure residuality, four groups with five (5) 10% hay infused +Bti replica were prepared, each one used weekly for bioassays, with groups of 20 larva of second instar (Table 1). The bioassays consisted of exposing mosquito larva for a period of a maximum of 72 hours, with mortality rate counted every 24 hours.
Table 1: Description of performed activities in the Bti residuality experiment with attractant
WEEK REPLICAS NUMBER OF LARVAE Week 0 20 prepared Bti solutions + attractant; 0 8 only attractant solutions (controls) Week 1 5 lethal solutions; 2 controls with only 140 attractant Week 2 5 lethal solutions; 2 controls 140 Week 3 5 lethal solutions; 2 controls 140 Week 4 5 lethal solutions; 2 controls 140
5.1.2 Semi-field Phase The semi-field phase was done with the objective of ensuring that no larvae or pupae developed during implementation of controlled field activities. This experiment was done during a month in the Yaguate municipality, San Cristóbal province, where 40 ovitraps with 6ppm Bti were used. These were distributed in 10 dwellings (2 indoors and 2 outdoors). Volunteers participating in the investigation signed an informed consent. Before the installation, we completed an entomological survey and Prokopack aspirator adult collection to establish a baseline. Also, on the installation day we performed environmental cleanup to discard household waste. Entomological surveys were done weekly, and adult collection with Prokopack aspirators indoor and outdoor of dwellings were done every 15 days.
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5.1.3 Field Phase For the field study, the Monte Plata municipality was divided in 4 blocks with 50 dwellings, each selected randomly, trying to cover a representative area inside the study sites, but keeping a minimum of 100 meters between dwellings, for a total of 200 houses.
For this investigation, 19 people were selected together with the DPS (local health department): 16 field technicians, 2 group leaders and a supervisor. These personnel were selected based on performance during field practice among 38 candidates trained in entomological surveillance. In parallel, we led coordination meetings with community leaders. These representatives from the communities participated in awareness raising sessions prior to implementation of the field study.
To determine the impact on Aedic indexes, a baseline was obtained through entomological monitoring assessments done prior to starting the intervention. These activities continued during and after the intervention with lethal ovitraps. Specifically, we completed weekly visits to 50 houses (16.6%) selected in each one of the three intervention blocks.
In addition, a control area without lethal ovitraps, 50 houses from an additional 300-houseblock, was selected. In this area we performed entomological monitoring only (larvae surveys and collections with Prokopack aspirators). Entomological monitoring data as well as data from the control site were registered on mobile phones through the ODK Google Play app. Ovitrap locations and households were monitored through a Google Maps app.
5.2 Vector Control To conduct vector control activities, four sentinel sites were selected, set by blocks in the Monte Plata municipality (3 intervention and 1 control), each one composed of 300 continuous households.
In each of the selected households in the three intervention blocks we set up four ovitraps with a 10% hay infused 3mg/l Bti bio larvicide dose, with two placed outdoors (roof) and the remaining two inside the dwellings. In addition to the four sentinel sites, we conducted breeding site elimination and delivery of awareness raising messages aimed at behavioral change. Vector control technicians replaced the oviposition pellon paper as well as the larvicide and attractant solution on a monthly basis, randomly doing an egg count on 13% of the visited dwellings.
The process included social mobilization activities together with the Dirección Provincial de Salud (local health department) where an informed consent was handed out to elicit participation in the study. Upon agreement by the head of the household field technicians proceeded to carry out planned activities. The lethal ovitrap intervention had a duration of three months, starting from the baseline assessment. As noted earlier, a group of 19 people was involved, including 12 technicians, 2 team leaders, 1 supervisor, plus 4 mobilizers. In preparation for field work, we conducted a coordination meeting with the Monte Plata health department as well as meetings with neighborhood committees in the target areas. 6 Results
6.1 Entomological surveillance 6.1.1 Laboratory Phase
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In the laboratory experiments with the San Cristobal strain where Bti or Bti + 10 % hay infusion as an attractant were used, there was no significant difference between 3ppm and 6ppm concentrations of Bti. The difference in attraction was only 4% (Figure 3).
Figure 3. Percentage of Oviposition preference (n= 30 mosquitoes)
9.0% 22.8%
26.0% 16.1% 61.1% 65.0%
Water Water Bti (3ppm) + water Bti (6ppm) + water Bti (3ppm) + infusion Bti (6ppm) + infusion
A 100% fatality rate was also observed for mosquitoes after 24 hours of exposure, and a residual effect of mortality above 90 % during a 4-week period was maintained when a 6ppm concentration was used (Figure 4).
Figure 4. Fatality of A. Aegypti larvae exposed to hay infused and Bti solutions. Fatality rate for 100 A. Aegypti larvae exposed for 72 hours to a 6ppm Bti solution, combined with a 10% hay infusion. The solution was prepared in the same day, but it was used throughout the four weeks. As a control, 100 larvae (blue line) were used, being only exposed to a 10% hay infusion.
100 100 98 98 80 90
60
40
20 5 8 0 3 0 Week 1 Week 2 Week 3 Week 4
Percentage (%) of mortality mortality of(%) Percentage Control Bti (6 ppm) + Infusion
6.1.2 Semi-field Phase After a 1-month observation period, no larvae or pupa were found on any of the 40 installed ovitraps, which confirmed Bti application was an effective method for control of Aedes laravae.
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6.2 Field Study During implementation of the field phase we observed a reduction of the Aedic indexes among the sentinel intervention sites and in the control site. Block 2 did not demonstrate measurable effects, however. (Table 2 and Figure 5).
Table 2. House index (HI), Container Index (CI) and Breteau Index (BI) in entomological monitoring sentinel sites between August - December 2018
August September Site Index Period Period Period Period Period Period Period Period 1 2 3 4 5 6 7 8 HI 68.0% 52.0% 44.0% 42.0% 42.0% 32.0% 58.0% 54.0% Block 1 CI 98.3% 97.8% 13.5% 7.8% 9.0% 5.6% 8.7% 11.0% BI 116 88 122 76 84 52 102 112 HI 46.0% 48.0% 36.0% 38.0% 42.0% 40.0% 40.0% 42.0% Block 2 CI 67.3% 52.4% 21.4% 16.2% 16.2% 16.5% 16.8% 15.9% BI 70 86 86 64 84 76 76 78 HI 26.0% 34.0% 26.0% 22.0% 24.0% 26.0% 20.0% 34.0% Block 3 CI 100.0% 100.0% 10.0% 6.0% 6.3% 10.4% 9.8% 14.5% BI 66 72 46 30 32 52 40 80 HI 66.0% 38.0% 50.0% 44.0% 40.0% 46.0% 42.0% 36.0% Block 4 CI 93.3% 97.8% 15.1% 14.2% 14.3% 12.9% 12.2% 9.4% (Control) BI 112 90 76 74 78 76 70 64
October November December Inde Site x Period Period Period Period Period Period Period Period Period Period 9 10 11 12 13 14 15 16 17 18 HI 46.0% 50.0% 44.0% 42.0% 42.0% 38.0% 36.0% 40.0% 40.0% 30.0% Block 1 CI 9.1% 9.8% 6.4% 7.6% 8.7% 5.7% 5.9% 8.3% 7.7% 5.7% BI 76 92 60 64 74 54 52 64 66 48 HI 40.0% 40.0% 40.0% 30.0% 34.0% 48.0% 46.0% 44.0% 42.0% 38.0% Block 2 CI 17.6% 18.9% 15.5% 14.5% 15.2% 23.0% 19.3% 21.8% 22.4% 24.2% BI 66 76 66 58 58 82 78 72 72 74 HI 14.0% 22.0% 26.0% 16.0% 10.0% 24.0% 10.0% 10.0% 12.0% 6.0% Block 3 CI 5.2% 10.3% 10.2% 7.7% 3.8% 9.9% 5.9% 4.9% 7.3% 4.5% BI 20 42 46 28 14 34 20 16 22 14
Block 4 HI 38.0% 52.0% 32.0% 26.0% 10.0% 24.0% 18.0% 12.0% 30.0% 20.0% (Control) CI 6.7% 12.0% 9.6% 6.9% 2.3% 7.7% 4.3% 3.4% 6.5% 6.1%
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October November December Inde Site x Period Period Period Period Period Period Period Period Period Period 9 10 11 12 13 14 15 16 17 18 BI 56 72 52 36 14 36 22 14 34 24
Figure 5. Container index in the entomological monitoring from August-December 2018
120.0%
100.0%
80.0%
60.0%
40.0% ContainerIndex
20.0%
0.0%
Period 2 Period Period 1 Period 3 Period 4 Period 5 Period 6 Period 7 Period 8 Period 9 Period
Period 10 Period 11 Period 12 Period 13 Period 14 Period 15 Period 16 Period 17 Period 18 Period August September October November December
Block 1 Block 2 Block 3 Block 4 (Control)
The container index in this study reflects the effects of lethal ovitraps on inducing Aedes mosquitoes to change oviposition sites due to preference for 10% hay infusion + Bti. The observed drop in Figure 5 may be explained by frequent household visits to all blocks where educational messages were delivered and breeding sites were eliminated.
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Figure 6. Breteau Index in entomological monitoring from August- December 2018 140
120
100
80
60
BreteauIndex 40
20
0
Period 1 Period 2 Period 3 Period 4 Period 5 Period 6 Period 7 Period 8 Period 9 Period
Period 10 Period 11 Period 12 Period 13 Period 14 Period 15 Period 16 Period 17 Period 18 Period August September October November December
Block 1 Block 2 Block 3 Block 4 (Control)
This graph shows a drop in the Breteau index, however the reduction in all blocks (including control) suggests that this decrease is subject to behavior change at the household level, due to repeated visits by field technicians.
Figure 7. House index for entomological monitoring from August- December 2018 80.0%
70.0%
60.0%
50.0%
40.0%
House Index 30.0%
20.0%
10.0%
0.0%
Period 2 Period Period 1 Period 3 Period 4 Period 5 Period 6 Period 7 Period 8 Period 9 Period
Period 10 Period 11 Period 12 Period 13 Period 14 Period 15 Period 16 Period 17 Period 18 Period August September October November December
Block 1 Block 2 Block 3 Block 4 (Control)
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Although a decrease on the house index is noted, this is not a conclusive result since elevated numbers can be observed with several positive containers or with a single positive container. This index is not sensitive to variations in larvae density in the same household or among households.
Table 3. Adult mosquito capture using Prokopack aspirators indoors and outdoors from August-December 2018
A greater number of mosquitoes was collected indoors. However, we did not observe a reduction in mosquito life expectancy. The prevalence of a semi-gravid digestive state indicated that adult females continued biting and ovipositioning.
Number of female Aedes Blood-digestion stage in aegypti female Aedes aegypti Period Sentinel Site Indoors Outdoors Stage Percentage Total Proko Proko Proko Proko Block 1 74 1 75 Gravid 36% Block 2 47 11 58 Half Gravid 38% August Block 3 80 1 81 Gravid 33% Block 4 (Control) 94 25 119 Gravid 28% Block 1 98 12 110 Half Gravid 42% Block 2 37 5 42 Half Gravid 38% September Block 3 72 1 73 Half Gravid 58% Block 4 (Control) 108 5 113 Half Gravid 57% Block 1 143 2 145 Half Gravid 61% Block 2 63 6 69 Half Gravid 54% October Block 3 86 1 87 Half Gravid 59% Block 4 (Control) 132 10 142 Half Gravid 46% Block 1 77 1 78 Half Gravid 54% Block 2 43 7 50 Half Gravid 62% November Block 3 31 0 31 Half Gravid 61% Block 4 (Control) 44 4 48 Half Gravid 50% Block 1 12 0 12 Half Gravid 83% Gravid/Half Block 2 10 50% December 10 0 Gravid Block 3 0 0 0 N/A 0% Block 4 (Control) 9 0 9 Half Gravid 67%
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6.3 Vector Control During the three intervention months, a target of 1,200 household visits per month was established. A total of 1,200 were treated in September, 1,182 in October, and 1,149 in November. By the second and third months, we found a total of 6 closed dwellings, 21 rejections, and 42 uninhabited homes. Total population covered was 4,032, of which 2,050 were female.
Vector control activities included ovitrap setup, physical elimination of breeding sites, and education for behavior change. For this intervention, 3,600 ovitraps had to be installed; 1,800 indoors and 1,800 outdoor. The latter was not possible because around 50% of the intervened dwellings did not have an outdoor area. In September, 1,800 indoor ovitraps were installed, 1,725 in October and 1,606 in November. In September, 980 were installed outdoors, 913 in October and 784 in November.
During the three intervention months a total of 8,292 breeding sites were found, distributed as 6,002 water tanks, 815 buckets, 301 bottles, 233 water gallons, 150 cans, 126 cisterns, 122 tires, 36 flower vases, 23 small water pools, 21 Bromelia plants, 11 jars and 452 other. In the target area, water tanks represent the largest number of breeding sites with a 6,002 total, of which 3,287 were positive. We observed that the amount of breeding sites in dwellings decreased as the interventions evolved. Field technicians, while locating the breeding sites, also covered, cleaned and eliminated containers during their recurring control activities (Table 4).
Table 4. Lethal Ovitraps September – November 2018 period. Total of visited houses (closed, rejected, uninhabited), total of reached population, number of deposits (negative, positive to larvae and pupae, positive to pupae, positive to pupae only, positive to larvae only, cleaned, covered, eliminated, emptied), total installed ovitraps in and outdoors (active, evaporated, spilled and not found), and number of in and outdoor found eggs.
Achieved results September October November
Total of treated houses 1,200 1,182 1,149 Total of closed houses 0 2 4 Total of rejected houses 0 11 10 Total of uninhabited houses 0 5 37 Total of visited houses 1,200 1,200 1,200 Total of reached population 3,954 80 0 Total of emptied deposits 184 140 38 Total of eliminated deposits 125 115 73 Total of covered deposits 488 439 350 Total of washed deposits 254 237 51 Total of larvae only positive deposits 144 112 49 Total of pupae only positive deposits 17 6 15 Total of larvae and pupae positive deposits 167 142 141 Total of negative deposits 1,982 1,791 1,232 Total deposits 1,051 931 512 Total of active indoors ovitraps 1,796 1,687 1,569 Total of evaporated indoors ovitraps 2 16 19 Total of spilled indoors ovitraps 0 22 18 Total of not found indoors ovitraps 2 641 692
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Total of not found indoor eggs in ovitraps 0 40,186 43,784 Total of indoors installed ovitraps 1,800 1,725 1,606 Total of active outdoors ovitraps 980 874 754 Total of evaporated outdoors ovitraps 0 16 12 Total of spilled outdoors ovitraps 0 23 18 Total of not found outdoors ovitraps 0 1,452 1,514 Total of outdoor eggs in ovitraps 0 21,088 17,793 Total of outdoors installed ovitraps 980 913 784
During the course of the intervention, three random follow-up visits were done in 50 dwellings per block, the first one being done 15 days after installing the first ovitraps. The objective of the visits was to supervise and review the status of the ovitraps (spilled, evaporated or active) and replace them if necessary.
During the visits, 6 positive ovitraps of the first and second instar were found, representing 0.01%; 4 ovitraps showed Syrphidae diptera larvae or flower flies feeding with organic matter; 1 female adult mosquito was found dead in one of the traps, probably during ovipositioning. Starting on the second installation month, a random count in 294 dwellings was done, representing 13% of the intervened houses, counting a total of 122,851 eggs.
Figure 8. Egg count – Lethal ovitraps during the September-November 2018 period
35,000 31,339
30,000 26,961 25,670 25,000
20,000 17,714
15,000 12,026 9,141 10,000
Number of eggs inovitraps 5,000
0 Block 1 Block 2 Block 3
Indoor Outdoor
This figure shows that, among all three intervened blocks, indoor ovipositioning was preferred due to favorable conditions such as humidity, dark spaces, and proximity to humans.
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Figure 9. Lethal ovitraps amount reviewed during the September-November 2018 period 160 144 140 131 124 120 96 100 74 80 68 60
40
20 Numberof ovitraps egg with count
0 Block 1 Block 2 Block 3
Indoor Oudoor
Biggest amount of installed ovitraps was indoor, due to a 50% approximate of intervened dwellings in the studies municipality not having an outdoor area.
7 Discussion
Laboratory entomological results show the effectiveness of Bti + hay infusion to attract gravid A. aegypti during the pilot study. Although eggs could hatch within the ovitraps, larvae died and did not develop to adult forms.
The residuality study done in the lab allowed us to observe that Bacillus thuriengiensis remained active for a period greater than one month. This result was also observed in the semi-field and field phases.
Entomological data shows a reduction of breeding sites but this cannot be attributed only to lethal ovitraps. Other activities, such as follow-up visits, environmental cleanup, and elimination of yard waste triggered behavioral changes among families, included the control area.
During the intervention months a reduction on the container index was observed among all sentinel sites, as shown in Figure 5.
Mosquito preference to lay eggs in lethal ovitraps is suggested by a sample of 13% of counted pellons with a total of 122,851 eggs, instead of ovipositioning in common breeding sites (water tanks, buckets, others). This is an important factor during the intervention because the development of eggs to adult phases was halted. This fact confirms the impact of lethal ovitraps on a reduction of immature mosquito forms.
Lethal hay infused ovitraps turned out to be an effective attractant for Aedes oviposition, and Bti applied at a 3mg/l dose prevents mosquito larvae to develop in the ovitraps. Thus, we can conclude that installation of lethal ovitraps can be a complementary measure for integrated vector management.
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8 Discoveries, Challenges, and Recommendations
DISCOVERIES: An integrated vector management program that combines vector control methods is essential to achieve an effective and lasting impact on mosquito abundance. Aedes aegypti egg collection in the intervention period is an important factor that interrupts hatching of possible mosquitoes in common recipients. Approximately 50% of dwellings did not have an outdoor area, which made comparing data with the obtained indoor egg count figures difficult.
CHALLENGES: Lack of understanding from the population of lethal ovitrap importance as a vector control method, hampered the study. Change of lethal ovitraps locations by the property owners. The need to store water in the houses may lead to an increase of breeding sites in dwellings. Complaints from the property owners, who reported higher mosquito density after ovitrap installation, due to attractant. The presence of domestic animals affected the monthly deployment of ovitraps. Issues with local mobile service caused delays in real time data collection in some study areas.
RECOMMENDATIONS: Larvicide application in key containers, environmental cleanings/junk disposal combined with installation of lethal ovitraps can be a comprehensive methodology for Aedes larvae reduction. Intersectoral collaboration enhances opportunities for integrated vector management For future studies, it is recommended to include larvae and pupae density as a measurement method, instead of house index.
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9 Bibliography
1. Zeichner, B.C. and M.J. Perich, Laboratory testing of a lethal ovitrap for Aedes aegypti. Med Vet Entomol, 1999. 13(3): p. 234-8.
2. Perich, M.J., et al., Field evaluation of a lethal ovitrap against dengue vectors in Brazil. Med Vet Entomol, 2003. 17(2): p. 205-10.
3. ZAP Project’s entomological surveys, done during the October - December 2017 period, based on ovitraps in 6 sentinel sites (Manoguayabo Oeste, Azua, Moca Higuey, Santiago de los Caballeros Area 1 and Area 3 ), of the Dominican Republic.
4. Paz-Soldan, V.A., et al., Design and Testing of Novel Lethal Ovitrap to Reduce Populations of Aedes Mosquitoes: Community-Based Participatory Research between Industry, Academia and Communities in Peru and Thailand. PLoS One, 2016. 11(8): p. e0160386.
5.Barrera, R., et al., Sustained, area-wide control of Aedes aegypti using CDC autocidal gravid ovitraps. Am J Trop Med Hyg, 2014. 91(6): p. 1269-76.
6. Regis, L.N., et al., Sustained reduction of the dengue vector population resulting from an integrated control strategy applied in two Brazilian cities. PLoS One, 2013. 8(7): p. e67682.
7. Lorenzi, O.D., et al., Reduced Incidence of Chikungunya Virus Infection in Communities with Ongoing Aedes Aegypti Mosquito Trap Intervention Studies - Salinas and Guayama, Puerto Rico, November 2015- February 2016. MMWR Morb Mortal Wkly Rep, 2016. 65(18): p. 479-80.
8. Regis, L., et al., Developing new approaches for detecting and preventing Aedes aegypti population outbreaks: basis for surveillance, alert and control system. Mem Inst Oswaldo Cruz, 2008. 103(1): p. 50-
9. Sithiprasasna, R., et al., Field evaluation of a lethal ovitrap for the control of Aedes aegypti (Diptera: Culicidae) in Thailand. J Med Entomol, 2003. 40(4): p. 455-62.
10. Procedures manual for entomological surveillance and Integral Vector Management (Manual de Procedimientos de Vigilancia Entomológica y Manejo Integral de Vectores) ,Ministerio de Salud Pública (Public Health Ministery), Centro Nacional de Control de Enfermedades Tropicales (CENCET 2017)
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10 Annex
Physical elimination of breeding sites.
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* During ovitrap identification.
Pellon sample with mosquito eggs. During recipient supervision.
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