Market and Online Survey, and Efficacy of fifteen commercially available mosquito repellents in Johannesburg, South Africa.
Authors: Dr Mustapha Halidu Aliero, Professor Robyn L. van Zyl, Professor Shelley Schmollgruber, Professor Lizette Koekemoer
Key words : Malaria, Repellents, Efficacy, Commercial and Mosquito.
Background: The current Covid-19 pandemic has confined us to live indoors, being increasing more exposed and susceptible to the endophilic malaria transmitting vectors capable of transmitting malaria between 0.3 to 22.5 days earlier than outdoor vectors. With this increased potential of being infected, the use of mosquito repellents for personal protections is essential to avoid mosquito bites. Many products are available in our communities, but not all are effective..
Aim: To undertook a survey to determine which repellents are most commonly used and to ascertain the efficacy of fifteen commonly available/used repellents in Johannesburg, South Africa.
Methods: Following ethics approval, a cross-sectional survey was conducted to determine the commonly used products used by South Africans and the information on commercially available mosquito repellents sold online or in markets was collated. From this, the repellent efficacy of fifteen products was assessed against starved female Anopheles gambiae S.S. every fifteen minutes for one hour in the WRIM laboratory. A non-contact method using a plastic-double netted dual choice test chamber was used to house the 20 mosquitoes with the volunteers’ forearms held 1-2cm from the netting. N,N-diethyl-meta-toluamide (DEET; Tabard™) was used as the control repellent. Data was captured in the REDCaP and analysed using SPSS version 26.0.
Results: From the cross-sectional survey of the 637 participants (females : males – 386 : 244), 75.2% (n=479) had used mosquito repellents in the past, with a diethyl toluamide-based product (Peaceful sleep™, 15%) being the most used, 53.8% (n=343). To date, a total of 96 products have been documented from both markets (21.9%) and online shops (71.8%). Of which, only 55.2% were approved by the South African Bureau of Standard (SABS). In the efficacy studies, the control product, 19.5% DEET (Tabard™ lotion) provided a mean protection of 99.1±0.9% for all four tested volunteers; with a slightly higher mean protection of 99.5±0.3% obtained with Medi-scabiol™ soap (citronella oil). After an hour, the three least active products were all-natural products, namely Mosquito-Patch™ (citronella), So-pure™ naturally (vanilla) and No-squito™ (neem and lemongrass oil) lotion. The Kruskal-Wallis H test revealed a statistically significant differences of mean protections among the repellent products (p=0.032); however, the Dunn post-hoc test with Bonferroni’s corrections did not show statistically significant differences between the control repellent and any of the repellent products tested.
Conclusion: This result shows that the citronella-based repellent product is effective for short-term personal protection from mosquito bites; however, DEET remains the gold standard repellent product for long-term protection. Consumers are advised to check for SABS approval for any product they intend to use to ensure optimal protection.