Researchers at the University of Pretoria Institute for Sustainable Malaria Control (UP ISMC) with chemical engineers at the university’s Institute of Applied Materials (IAM) have developed insecticide-impregnated wall linings.   Using wall linings for mosquito control reduces health risks because sprayed insecticides used in the indoor residual spraying (IRS) programme coat dust particles, leading to certain human exposure through contaminated dust on furniture, on floors and in the air. This dust can also contaminate food and water in sprayed homes.  

Impregnated with the insecticides deltamethrin and alpha-cypermethrin the polyethene wall lining is proving successful in protecting homes from mozzies. "Traditionally DDT has been used to combat mosquitos but this is known to have a detrimental effect on our health," advises UP ISMC Director Prof Tiaan de Jager. “Although some toxicity to humans exists with the wall-lining, it’s far less than the current solution.” To limit human contact, linings are installed out of reach of children, and families are instructed not to touch the material.

UP ISMC initiated a six-month pilot study in non-IRS programme communities within malaria hotspot Vhembe, Limpopo to see whether the linings were acceptable to the community. The response has been incredibly positive with researchers deciding to leave the linings in the homes of participants to test long-term efficacy. “These linings have now been in-field for four years," says Prof de Jager.  

The product has been tested further under laboratory conditions. Researchers have found that the linings remain close to 100% effective in killing mosquitoes, even after four years. Specifically, mosquitoes are knocked down within 30 minutes of contact with the lining and die within 24 hours. Importantly, the lining remains well above the World Health Organisation (WHO) recommended minimum effectiveness for internal wall linings. Reports from communities corroborate these results, as community members reported less overall biting and annoyance.  

UP ISMC has commercial and manufacturing partners for further development of this innovative malaria control technology. Working with Huhtamaki to make the light-weight netting and Avima t,o produce and supply the insecticides, the partnerships will see UP ISMC develop and bring the impregnated mesh technology to market.  

Community buy-in

The feedback from community members who participated in the study and have now taken possession of their wall linings. “Those who have moved house have asked if we can move the linings from their original position because it is so effective”, adds Dr Taneshka Kruger, senior project coordinator at the UP ISMC. "Community members have also indicated that if the linings were commercially available and not expensive, they would consider buying and using them."  

Moving ahead

Dr Kruger says the next steps will be: To conduct phase two field trials using test buildings where mosquitoes that die through contact with the lining will be accurately counted To improve how linings are fastened to the walls, and To look at alternative insecticides, especially WHO-approved insecticides.   “The wall linings are going to remain in the huts and the houses for as long as the people want them there and we hope that phase two will start as soon as possible,” closes Prof de Jager.