A low-cost repellent for malaria vectors in the Americas: results of two field trials in Guatemala and Peru.
BACKGROUND
The cost of mosquito repellents in Latin America has discouraged their wider use among the poor. To address this problem, a low-cost repellent was developed that reduces the level of expensive repellent actives by combining them with inexpensive fixatives that appear to slow repellent evaporation. The chosen actives were a mixture of para-menthane-diol (PMD) and lemongrass oil (LG).


METHODS
To test the efficacy of the repellent, field trials were staged in Guatemala and Peru. Repellent efficacy was determined by human-landing catches on volunteers who wore the experimental repellents, control, or 15% DEET. The studies were conducted using a balanced Latin Square design with volunteers, treatments, and locations rotated each night.


RESULTS
In Guatemala, collections were performed for two hours, commencing three hours after repellent application. The repellent provided >98% protection for five hours after application, with a biting pressure of >100 landings per person/hour. The 15% DEET control provided lower protection at 92% (p < 0.0001). In Peru, collections were performed for four hours, commencing two hours after repellent application. The PMD/LG repellent provided 95% protection for six hours after application with a biting pressure of >46 landings per person/hour. The 20% DEET control provided significantly lower protection at 64% (p < 0.0001).


CONCLUSIONS
In both locations, the PMD/LG repellent provided excellent protection up to six hours after application against a wide range of disease vectors including Anopheles darlingi. The addition of fixatives to the repellent extended its longevity while enhancing efficacy and significantly reducing its cost to malaria-endemic communities.
Ifakara Health Research and Development Center, Ifakara, Tanzania. smoore@ihrdc.or.tz <smoore@ihrdc.or.tz>
Sarah J
SJ
Moore
Samuel T
ST
Darling
Moisés
M
Sihuincha
Norma
N
Padilla
Gregor J
GJ
Devine
D000818:Animals; D000852:Anopheles / Q000187:drug effects* / Q000502:physiology; D000081005:Cyclohexane Monoterpenes; D003671:DEET / Q000008:administration & dosage*; D005052:Eucalyptus / Q000737:chemistry; D006166:Guatemala; D006801:Humans; D007299:Insect Bites and Stings; D007302:Insect Repellents / Q000008:administration & dosage / Q000737:chemistry / Q000191:economics; D007303:Insect Vectors / Q000187:drug effects* / Q000502:physiology; D008288:Malaria / Q000517:prevention & control*; D008610:Menthol / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000191:economics; D009032:Mosquito Control; D010568:Peru; D010938:Plant Oils / Q000008:administration & dosage* / Q000191:economics; D013729:Terpenes / Q000008:administration & dosage* / Q000191:economics
D000081005:Cyclohexane Monoterpenes; D007302:Insect Repellents; D010938:Plant Oils; D013729:Terpenes; D003671:DEET; D008610:Menthol; C052901:lemongrass oil; C005804:terpin