Researchers at the University of Pretoria Institute for Sustainable Malaria Control have developed insecticide-impregnated wall linings to protect residents in Vhembe, Limpopo. The wall linings have been so successful at reducing mosquito bites that residents have kept them in their homes for the long-term.
Researchers at theUniversity of Pretoria Institute for Sustainable Malaria Control (UP ISMC), and specifically chemical engineers in theInstitute of Applied Materials (IAM) at UP, have developed apolyethylene wall lining that is impregnated with insecticidal chemicals. This innovative mesh material was installed in homes in the Vhembe district to test their efficacy, and to get feedback from the community.
Using wall linings for mosquito control reduces health risks because normal sprayed insecticides coat dust particles, leading to unavoidable human exposure through contaminated dust on furniture, on floors and in the air. This dust can also contaminate food and water in sprayed homes.
The UP ISMC initiated a six-month pilot study to see whether the linings were acceptable to the community. The response was positive so the researchers decided to leave the linings in the homes of participants to see how long they remained effective. These linings have now been in the field for the last four years, and the results have far exceeded the researchers’ expectations. This pilot project was undertaken in an area of a village where insecticides were not sprayed.
The linings contain the insecticides deltamethrin and alpha-cypermethrin, which show some toxicity to humans, but to a far lesser extent than a commonly used insecticide like DDT. To limit human contact, linings are installed out of reach of children, and families are instructed not to touch the material.
The 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 linings, and die within 24 hours in laboratory tests. Importantly, the linings remain well above the World Health Organisation (WHO)’s recommended minimum effectiveness for internal wall linings. Reports from communities corroborate these results, as community members reported less biting and less annoyance overall.
The feedback from community members who were included in the study and have now taken possession of their wall linings, has been overwhelmingly positive. “Those who have moved house have asked if we can move the linings from their original position because it is so effective”, saidDr Taneshka Kruger, senior project coordinator at the UP ISMC.
The UP ISMC now has a commercial partner for further development of this innovative malaria control technology. The company has also conducted their own tests on the wall linings to better understand its qualities, including how long the linings will remain effective after washing.
Dr Kruger says the next steps will be 1) to conduct phase two field trials using trial buildings where mosquitoes that die through contact with the lining can be counted accurately, 2) to improve how the linings are fastened to the walls, and 3) to look at alternative insecticide options - 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,” said Dr Kruger.
The insecticide-impregnated wall linings inside a mud hut. Image credit UP ISMC
The wall linings as they look inside a modern house in Vhembe. Image credit UP ISMC.