SC Johnson Guardian™ spatial repellent shows one-year efficacy against wild pyrethroid-resistantAnopheles arabiensis, with similar blood-feeding inhibition efficacy to Mosquito Shield™ in a Tanzanian experimental hut trial
Authors: Swai Johnson Kyeba , Ntabaliba Watson Samuel , Mbuba Emmanuel , Ngoyani Hassan Ahamad , Makungwa Noely Otto , Mseka Antony Pius , Bradley John , Chura Madeleine Rose , Mascari Thomas Michael , Moore Sarah Jane 
Published: November 2024

Spatial repellents (SR) that passively emanate airborne concentrations of an active ingredient within a space disrupt mosquito behaviors to reduce human-vector contact. A clinical trial of SC Johnson’s Mosquito Shield™ (Mosquito Shield) has demonstrated 33% protective efficacy against malaria in Kenya. Mosquito Shield lasts for one month, but a longer duration product would be advantageous for deployment by malaria control programs. SC Johnson’s Guardian™ (Guardian), is designed to provide longer continuous protection from disease-transmitting mosquitoes. We conducted an experimental hut trial to evaluate the efficacy of Guardian over 12 months and compared it to Mosquito Shield over one month against wild pyrethroid resistant malaria vector mosquitoes, using entomological surrogates of clinical efficacy to assess the potential public health utility of Guardian. The primary endpoint was the number of blood-feedingAn. arabiensis, while secondary endpoints were number landing proportion ofAn. arabiensismortality and proportion blood-fed. Over 12 months of continuous tests, Guardian reduced numbers ofAn. arabiensisblood-feeding by 83% (95% Confidence Interval (79 – 86)) and landing by 65% (59 – 70). Guardian also induced 20% mortality (18 – 22). Guardian was found to be superior to Mosquito Shield in reducing the number of blood-fedAn. arabiensis, and had similar proportions of blood-fed mosquitoes and 24-hours mortality. Results indicate that Guardian effectively reduces blood-feeding and landing of wild pyrethroid resistant malaria vectors for 12-months and shows superior protective efficacy to Mosquito Shield on the blood-feeding endpoint. Experimental hut studies are suitable for comparative evaluations of new spatial repellent products because they precisely estimate entomological endpoints elicited by spatial repellents known to significantly impact vectorial capacity and disease transmission.

Key questions

What is already known on this topic?

There is increasing evidence that spatial repellents have public health value. Randomized control trials have shown that SC Johnson Mosquito Shield™ (Mosquito Shield), a transfluthrin based spatial repellent, is effective in reducing malaria and dengue transmission. A WHO policy recommendation for the spatial repellent intervention class would follow a WHO-commissioned systematic review of the data from clinical trials.

Mosquito Shield is effective for 30 days but malaria transmission lasts for 6 to 12 months in most endemic regions. Therefore, a longer lasting product required only one deployment per transmission season would be more operationally feasible, especially in remote areas of Africa where malaria burden is highest.

What are the new findings?

This is the first study to provide evidence of a spatial repellent product that can reduce the number of wild pyrethroid resistantAn. arabiensisblood-feeding by 83% and landing by 65% while inducing a 20% delayed mortality at 24 hours for a duration of one-year.

The study also demonstrated that Guardian was superior to Mosquito Shield (tested in RCTs) in reducing number of blood-fedAn. arabiensis.

Impact on vector control practice or policy

Guardian meets the preferred product characteristics for a public health spatial repellent. It lasts a full year, and it does not require daily user interaction. This likely will result in higher adherence and coverage with lower operational cost for implementation compared to Mosquito Shield or other shorter-duration spatial repellents.

Guardian is expected to have public health value by impacting disease transmission when used as a vector control tool against malaria because it showed superior performance when compared to Mosquito Shield, which has demonstrated malaria reduction in clinical trials.