Small-scale field assessment of efficacy of the autodissemination approach against Aedes sp. in an urban area

This is the first study to evaluate the efficacy of an autodissemination approach, as suggested by WHO. Therefore, the efficacy of an autodissemination approach in small-scale field trials against wild Aedes sp. population was evaluated in an urbanized setting, Malaysia. Lethal ovitraps enhanced with pyriproxyfen were used to control Aedes sp. populations at treatment sites, with the autodissemination activity was assessed using the WHO larval bioassays. Lethal ovitraps enhanced with pyriproxyfen effectively reduced of Aedes sp. population. All autodissemination stations were shown to be visited by Aedes sp. mosquitoes with 100% complete inhibition against eggs and larvae development. In the larvae bioassay, pupae mortality ranged from 14 to 40%. Statistically, a significant reduction of Aedes sp. population in the treatment sites compared to the untreated areas. The study proved for the autodissemination of pyriproxyfen to breeding habitats by wild Aedes sp. This technique is highly potentially for vector control activities. Future evaluation should focus on large-scale field trials. Author Summary Since 2012, Dataran Automobil, Seksyen 15, Shah Alam, was declared as one of the dengue hotspot areas. Major vector control activities were conducted by government, NGOs, social communities, and local authorities, but the number still rising. We conducted a new invention of autodissemination concepts in this area by an entomological study on mosquito populations reduction and dispersal abilities of the technique. We found that the technique has proven to control mosquito populations, but the other factors such as epidemiology link still unclear and need further clarification. Our finding highlighted the effectiveness of autodissemination strategies that can be considered as one of the alternative tools in vector control programme.

Intervention 156 A total of 150 MHS devices were deployed in four blocks on all stairways. Three 157 autodissemination devices were placed diagonally clustering around each trap on the third floor. 158 Autodissemination devices were one to five meters from the nearest ovitrap. Autodissemination 159 device deployment took place from January 2018 to June 2018, coinciding with the rainy season. 160 All MHS devices were removed from the field at the end of month eight. MHS was checked 161 fortnightly throughout the six months of the trials to refill the solution and replace any loss on 162 MHSs. 163 Activity of pyriproxyfen in the field 164 All field samples from ovitrap and autodissemination devices (MHS) were brought back to the 165 laboratory and then filtered to remove organic debris and wild mosquito populations. From each 166 sample, 200ml water was transferred into a bioassay cup to determine pyriproxyfen activity. 167 Twenty laboratory-reared third instars larvae were exposed to the field samples following larval 168 bioassay procedure as described above. Pupal mortality, abnormal morphology, or coloration was 169 recorded to show pyriproxyfen activity in the field samples. In some specimens, the The water samples were then tested with three different points of time-before, 180 ongoing and after the treatment. All larvae bioassays were performed using late third instar larvae 181 of Ae. aegypti. For the negative control, three cups were set up using tap water and 20 larvae per 182 bioassay. Control treatments were treated with 199ml tap water and 1ml of ethanol. The mortality 183 was recorded every 48h until the emergence of adult, while the larvae were also provided with 184 food daily. Experiments were conducted at temperature of 26±2oC and 60±20% RH and preferably 185 a photoperiod of 12h light followed by 12h dark.    The number of single and mixed breeding among the Aedes sp. population in treatment and control 224 sites were compared ( Table 2). The mixed breeding of Ae. aegypti larvae were 1.96% and 6.8% 225 obtained from control and treatment sites, respectively. The number of Ae. albopictus in mixed 226 containers were 6.0 to 11.0 fold lower than Ae. aegypti species. Additionally, there was no

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To understand the role of meteorological factors on Aedes sp. populations, the rainfall data and 234 temperature were extracted from the study sites. Pearson's correlation analysis showed a low 235 association between the parameters selected. However, all parameters used in study areas did not 236 show any significant associations between the meteorological and entomological parameters used 237 (

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The Generalized Linear Model (GLM) with Poisson distribution used to analyze the data showed 271 that the experiment's sites are significantly predictors of the mean number of larvae (p<0.0001).

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The larvae populations were higher in the untreated sites compared to the treated sites during the We also observed that temperature is an important variable in determining the Aedes sp. for fogging has one-way effects [51]. In some areas, larviciding is the most appropriate method to 353 control Aedes sp. population. However, workers often cannot find cryptic and hidden breeding 354 sites during surveillance [52]. Based on these issues, new paradigms in vector control are required.

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An effective control measure against Aedes sp. mosquitoes is in need, which will be able to 356 specifically target adult, larvae and cryptic breeding habitats of mosquitoes.

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The autodissemination approach has become one of the most interesting methods to 358 combine with other vector control strategies.