Scaling up of
insecticide treated nets has contributed to a substantial
malaria decline. However, some
malaria vectors, and most arbovirus vectors,
bite outdoors and in the early evening. Therefore, topically applied
insect repellents may provide crucial additional protection against mosquito-borne pathogens. Among topical repellents,
DEET is the most commonly used, followed by others such as
picaridin. The protective efficacy of two formulated
picaridin repellents against mosquito
bites, including arbovirus and
malaria vectors, was evaluated in a field study in Cambodia. Over a period of two years, human landing collections were performed on repellent treated persons, with rotation to account for the effect of collection place, time and individual collector. Based on a total of 4996 mosquitoes collected on negative control persons, the overall five hour protection rate was 97.4% [95%CI: 97.1-97.8%], not decreasing over time.
Picaridin 20% performed equally well as
DEET 20% and better than
picaridin 10%. Repellents performed better against Mansonia and Culex spp. as compared to aedines and anophelines. A lower performance was observed against Aedes albopictus as compared to Aedes aegypti, and against Anopheles barbirostris as compared to several vector species. Parity rates were higher in vectors collected on repellent treated person as compared to control persons. As such, field evaluation shows that repellents can provide additional personal protection against early and outdoor biting
malaria and arbovirus vectors, with excellent protection up to five hours after application. The heterogeneity in repellent sensitivity between mosquito genera and vector species could however impact the efficacy of repellents in public health programs. Considering its excellent performance and potential to protect against early and outdoor biting vectors, as well as its higher acceptability as compared to
DEET,
picaridin is an appropriate product to evaluate the epidemiological impact of large scale use of topical repellents on arthropod borne diseases.