SC Johnson Guardian™ spatial repellent shows one-year efficacy against wild pyrethroid resistant Anopheles arabiensis, with similar blood-feeding inhibition efficacy to Mosquito Shield™ in a Tanzanian experimental hut trial

Johnson Kyeba Swai^1,2,3*Watson Samuel Ntabaliba¹Emmanuel Mbuba^1,2,3Hassan Ahamad Ngoyani¹Noely Otto Makungwa¹Antony Pius Mseka¹John Bradley⁴Madeleine Rose Chura⁵Thomas Michael Mascari⁵Sarah Moore^1,2,3,6

• ¹Ifakara Health Institute, Ifakara, Tanzania
• ²Swiss Tropical and Public Health Institute, Basel, Switzerland
• ³University of Basel, Basel, Switzerland
• ⁴London School of Hygiene and Tropical Medicine, University of London, London, London, United Kingdom
• ⁵S. C. Johnson & Son, Inc., Racine, Wisconsin, United States
• ⁶School of Life Sciences and Bioengineering, Nelson Mandela African Institution of Science and Technology, Arusha, Tanzania

Background: 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) demonstrated a 33% protective efficacy against malaria in Kenya. Mosquito Shield lasts for one month, but a longer duration product is needed for malaria control programs. SC Johnson’s Guardian™ (Guardian), is designed to provide longer continuous protection from disease-transmitting mosquitoes. Methods: we conducted experimental hut trials to i) evaluate the efficacy of Guardian over 12-months (between May 2022 and May 2023) and ii) assess the potential public health utility of Guardian by comparing it to Mosquito Shield over one month (midway through the Guardian evaluation) in November 2022) against wild pyrethroid resistant malaria vector mosquitoes. The primary endpoint was the number of blood-fed An. arabiensis, while secondary endpoints were proportion of An. arabiensis dead at 24-hours and proportion blood-fed. For Guardian, the number of mosquito landings was also evaluated by human landing catch, a method routinely used in community or implementation studies. Results: Over 12 months continuous use, Guardian reduced numbers of An. arabiensis blood-feeding by 82.7% (95% Confidence Interval (78.5 – 86.1)) and landing by 65.1% (59.4 – 70.0). Guardian also induced 20.1% mortality (18.4 – 21.8). Guardian was found to be superior to Mosquito Shield in reducing the number of blood-fed An. arabiensis with similar proportions blood-fed and dead at 24-hours. Conclusion: Guardian was effective in reducing blood-feeding and landing of wild pyrethroid resistant malaria vectors for 12-months and shows superior protective efficacy to Mosquito Shield in reducing the overall number of blood-feeding mosquitoes. 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.