Since Aedes mosquitoes, which transmit the Zika virus, tend to bite during the daytime, bed-nets provide only limited protection. Repellent clothing has been recommended as a practical additional prevention measure.  Currently, commercially available repellent clothing does not provide adequate protection in a user-friendly formulation. We are interested in exploring the potential to develop novel repellent technologies that combine effective bite-reduction with broad appeal among Zika-risk groups.

“As a medical entomologist I am excited to be working on this programme because this current Zika epidemic appeared very quickly and taken us by surprise. We need to think of new techniques to outsmart the Aedes mosquito.”

Dr. James Logan, London School of Hygiene & Tropical Medicine

Overall Objectives

To protect pregnant women against Aedes mosquito bites, novel, wash-in detergent formulations and long-lasting plastic technologies containing repellents for the treatment of clothing and other wearable repellent technologies are being developed using new microencapsulation techniques.

Specific Objectives

  • Perform a focus group studies in the cities of Cali and Villavicencio, Colombia, with several cohorts, including pregnant women, non-pregnant women and men, on proposed wearable repellent technologies to determine the most acceptable option,
  • Investigate and develop novel detergents containing repellents that can be used during laundry to allow active repellents to be applied to everyday clothing during each wash for protection against Aedes mosquitoes,
  • Investigate new wash-resistant technologies, including novel silica-shell, polymer fibres and microencapsulated formulations to determine whether repellent active ingredients can be retained in fabrics for multiple washes,
  • Develop plastic wearable repellent technologies including flip-flops, wrist bands, necklaces using a plastic silica technology for protection against Aedes mosquitoes,
  • Perform a modelling study to determine what level of protection (i.e. reduction in biting rate) is required to reduce Zika transmission in pregnant women.

Results and Achievements

To understand more about the potential acceptability of a repellent-based control strategy in Latin America, a series of qualitative studies have been done in Colombia to examine the attitudes of single women and couples of reproductive age towards Zika virus and its prevention.

Societal implications of the work

The data generated from these studies suggest that people who are consistently exposed to the threat of arboviral diseases may be reluctant to adopt new mosquito bite-reduction practices. This adds impetus to the development of technologies that can achieve results with minimal impact on people’s daily routines – like the use of a wash-in repellent– and do not require significant behavior change.

Ongoing focus group studies will explore this phenomenon further and help to identify which kinds of repellent strategies are likely to be the most socially acceptable and will inform any behavior change interventions that would be required to increase uptake.

Repellent Testing

  • A range of repellent actives have been tested and candidates were found with activity at particularly low concentrations when applied to fabrics. Moreover, a synergist-repellent combination that increases the potency of the repellent has been identified.
  • Initial testing of the repellent, as a fabric-softener additive, has produced low levels of repellency, but these tests have not utilized textile binding agents.
  • The experiments have also involved testing commercially available wash-in formulations, which appear to produce low levels of repellence. Once base-line repellency data for an efficacious wash-in prototype has been obtained, work will be undertaken with mathematical modelers to determine what up-take rates and efficacy levels will be required to achieve significant levels of arbovirus protection.
  • Together with qualitative data sets, this will mean that an informed prediction can be made concerning the utility of this approach at a population level.
  • Two insecticides have been identified that may be of particular interest for long-lasting textiles, with high biological activity at low concentrations. Further experiments will investigate the possibility of using cyclodextrins and metal-organic frameworks (MOFs) to strongly bind these to textiles and plastics.

Participating Organisation

Group leader: Prof. James Logan, London School of Hygiene & Tropical Medicine

Senior Researcher: Dr. Thomas Ant