Field Evaluation of Picaridin Repellents Reveals Differences in Repellent Sensitivity between Southeast Asian Vectors of Malaria and Arboviruses

Abstract

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.

EPA-Registered Repellents for Mosquitoes Transmitting Emerging Viral Disease

“…aegypti, A . albopictus, and Culex spp . Four studies of permethrin‐treated clothing provided favorable protection time (4–6 wks) compared with placebo/untreated or DEET alone .…”

Safety of a topical insect repellent (picaridin) during community mass use for malaria control in rural Cambodia

“…Children from 2 to 10 years were given picaridin 10% (as a milky lotion); all individuals above 10 years received picaridin 20% (in spray formulation). Both formulations applied at a dosage of 0.5ml/1000cm 2 were shown to provide an effective protection during at least five hours [15]. No placebo repellent was used in the control arm as its use would have created a false perception of protection.…”

Mosquito repellents for malaria prevention

“…These products include mosquito coils, long-lasting formulated repellent lotions, and insecticide treatments for clothing. Mosquito repellents are currently recommended by the WHO as the first-line malaria-prevention tool for travellers (WHO 2012), and they are commonly used by expatriates in tropical developing countries.…”

“…Repellents interfere with mosquitoes' olfactory reception, affecting their ability to locate and feed on a human host. Approved active ingredients for mosquito-borne disease prevention are DEET (chemical name: N,N-diethyl-m-toluamide or N,N-diethyl-3-methyl-benzamide); icaridin (KBR 3023 [Bayrepel] and picaridin inside the USA; chemical name: 2-2-hydroxyethyl-1-piperidinecarboxylic acid 1-methylpropyl ester); PMD (para-methane-3,8-diol); and IR3535 (chemical name: 3-[N-butyl-N-acetyl]-aminopropionic acid, ethyl ester) (CDC 2014; WHO 2012). The Environmental Protection Agency (EPA) estimates that approximately 200 million people use DEET worldwide every year (WHOPES 1998).…”