Mitigating Diseases Transmitted by Aedes Mosquitoes: A Cluster-Randomised Trial of Permethrin-Impregnated School Uniforms

Abstract

BackgroundViral diseases transmitted via Aedes mosquitoes are on the rise, such as Zika, dengue, and chikungunya. Novel tools to mitigate Aedes mosquitoes-transmitted diseases are urgently needed. We tested whether commercially insecticide-impregnated school uniforms can reduce dengue incidence in school children.MethodsWe designed a cluster-randomised controlled trial in Thailand. The primary endpoint was laboratory-confirmed dengue infections. Secondary endpoints were school absenteeism; and impregnated uniforms’ 1-hour knock-down and 24 hour mosquito mortality as measured by standardised WHOPES bioassay cone tests at baseline and after repeated washing. Furthermore, entomological assessments inside classrooms and in outside areas of schools were conducted.ResultsWe enrolled 1,811 pupils aged 6–17 from 5 intervention and 5 control schools. Paired serum samples were obtained from 1,655 pupils. In the control schools, 24/641 (3.7%) and in the intervention schools 33/1,014 (3.3%) students had evidence of new dengue infections during one school term (5 months). There was no significant difference in proportions of students having incident dengue infections between the intervention and control schools, with adjustment for clustering by school. WHOPES cone tests showed a 100% knock down and mortality of Aedes aegypti mosquitoes exposed to impregnated clothing at baseline and up to 4 washes, but this efficacy rapidly declined to below 20% after 20 washes, corresponding to a weekly reduction in knock-down and mosquito mortality by 4.7% and 4.4% respectively. Results of the entomological assessments showed that the mean number of Aedes aegypti mosquitoes caught inside the classrooms of the intervention schools was significantly reduced in the month following the introduction of the impregnated uniforms, compared to those collected in classrooms of the control schools (p = 0.04)ConclusionsEntomological assessments showed that the intervention had some impact on the number of Aedes mosquitoes inside treatment schools immediately after impregnation and before insecticidal activity declined. However, there was no serological evidence of protection against dengue infections over the five months school term, best explained by the rapid washing-out of permethrin after 4 washes. If rapid washing-out of permethrin could be overcome by novel technological approaches, insecticide-treated clothes might become a potentially cost-effective and scalable intervention to protect against diseases transmitted by Aedes mosquitoes such as dengue, Zika, and chikungunya.Trial RegistrationClinicalTrials.gov NCT01563640

Novel tools for the surveillance and control of dengue: findings by the DengueTools research consortium

“…Our results from the WHOPES cone tests underpin the potential for ISUs to protect against dengue by reducing the populations of Aedes mosquitoes and hence mosquito-bites: knock-down effect and mortality immediately after impregnation of uniforms with permethrin by the InsectShield® proprietary method were close to 100% [33], consistent with results obtained under laboratory conditions [28]. Furthermore, we documented a significant reduction in Aedes mosquito numbers in the classrooms of the intervention schools in the first month after the start of the trial at the time when the insecticidal activity of impregnated uniforms was still 100%.…”

“…For ISUs to be a viable public health intervention they must withstand regular washing. If the rapid washing-out of permethrin can be overcome by novel technological approaches, ISUs would deserve to be re-evaluated as a potentially cost-effective and scalable intervention [33]. …”

“…Paired serum samples were obtained from 1,655 pupils [33]. We did not find a significant difference in proportions of students having incident dengue infections between the intervention and control schools, allowing for clustering by school.…”

“…We ran a blinded trial over a school term (5 months) in 10 schools in Thailand (5 intervention and 5 control) [33]. The primary endpoint was laboratory-confirmed dengue infections.…”

Pengaruh Seragamisasi Celana/Rok Panjang dalam Mencegah Kejadian Demam Berdarah Dengue pada Siswa Sekolah Dasar

“…Hal ini menunjukkan bahwa seragam sekolah berinsektisida merupakan intervensi yang tepat dalam menerapkan penanggulangan secara mekanik karena waktu sekolah merupakan waktu yang digunakan oleh nyamuk Aedes aegypti untuk menghisap darah. 17 Hasil penelitian dari Orsborne, dkk juga menyatakan bahwa pemakaian baju lengan panjang dan celana panjang dapat mencegah adanya gigitan nyamuk yang dapat menyebabkan demam berdarah dengue dan zika. 18 Rumah dengan keadaan jendela yang tidak terpasang kasa nyamuk, akan memudahkan nyamuk Aedes aegypti untuk masuk ke dalam rumah dan mengigit tubuh manusia terutama anak-anak pada saat tidur siang.…”