Thanaka (Limonia acidissima) and deet (di‐methyl benzamide) mixture as a mosquito repellent for use by Karen women

Abstract

The prevention and treatment of drug-resistant malaria is becoming increasingly difficult. On the Thai-Myanmar border multi-drug resistant strains of falciparum malaria are increasing and, because the malaria vector Anopheles bite outdoors during early evening, insecticide house-spraying or impregnated bednets provide only limited protection. Therefore, the protective efficacy of repellent formulations containing di-methyl benzamide (deet) and permethrin against local vectors was estimated, when applied to the skin, and their acceptability amongst pregnant Karen women who are at relatively high risk from malaria was assessed. Human landing catches of mosquitoes showed that almost complete protection was achieved using different formulations of 20% deet and 0.5% permethrin for up to 6 h. All-night collections from human subjects indicated that this repellent combination reduced exposure to malaria parasites by at least 65 and 85% for those transmitted by Anopheles minimus and An. maculatus, respectively, the two principal vectors in this area. Pregnant women in the camps preferred repellents which were mixed with 'thanaka', a root paste made from pulp of the wood apple tree, Limonia acidissima, used locally as a cosmetic. Apart from a temporary warming sensation where repellent thanaka was applied to the skin, the repellents were well tolerated. An intervention trial is currently in progress to determine whether deet mixed with thanaka can protect pregnant women against malaria in this part of the world. Bioassays using a laboratory strain of Aedes aegypti demonstrated that thanaka is itself slightly repellent at high dosages and the mixture with deet provides protection for over 10 h. This treatment would therefore also provide some personal protection against dengue, which is increasing locally, transmitted by Ae. aegypti and Ae. albopictus biting during the daytime.

Can Topical Insect Repellents Reduce Malaria? A Cluster-Randomised Controlled Trial of the Insect Repellent N,N-diethyl-m-toluamide (DEET) in Lao PDR

“…Field trials in Thailand and Malaysia show di-ethyl- N,N- toluamide (DEET) concentrations of 15–20% decrease mosquito biting by over 83% [8]–[10]. However few trials have been able to demonstrate an effect on malaria transmission by the use of insect repellent.…”

Malaria in pregnancy in the Asia-Pacific region

“…34,127,145,146 Review dawn, when they may already be awake and active, potentially restricting the protective eff ect of treated nets. 147 Mosquito repellents with N,N-diethyl-metatoluamide (DEET) are safe in pregnancy, 148,149 can reduce exposure to insect bites, 148 and resulted in a nonsignifi cant reduction in the incidence of P falciparum infection in pregnant women in one possibly underpowered study. 142 Mefl oquine chemoprophylaxis gave 86% protection against P falciparum and complete protection against P vivax infection in a double-blind, placebo-controlled study 49 at the Thai-Burmese border when mefl oquine was still fully eff ective.…”

Malaria vector control: from past to future

“…In addition to this, a community-randomized trial with DEET in South America showed no effect on malaria incidence rates (Kroeger et al 1997), while a recent outbreak of malaria in a village in South Africa was controlled by use of DEET as repellent among the affected population (Durrheim and Govere 2002). Another study in ThaiMyanmar border with multidrug resistant strains of P. falciparum malaria, use of a mixture of a root paste made from pulp of the wood apple tree "Thanaka" (Limonia acidissima,) and DEET by Karen pregnant women found to reduce mosquito bites (Lindsay et al 1998). McGready et al (2001a reported lower accumulation of DEET in cord blood (8%, n=50, 95% confidence interval 2.6-18.2) applied regularly to Karen pregnant women during the second and third trimesters of pregnancy without adverse effects on survival, growth, and development at birth and up to 1 year, indicating considerable safety.…”