Control effectiveness of APL formulation against dengue- and Zika-transmitting Aedes mosquitoes in Gia Lai province, Vietnam

Abstract Background Dengue fever and Zika are two of the Aedes -borne diseases. Despite being widely used, synthetic mosquitocides become abortive for the mosquito control due to growing resistance and environmental pollution. In Gia Lai province (dengue-endemic area), a huge amount of cashew nut shell waste with roughly 100,000 tons/year has been disposed of into the environment, potentiating a high risk of pollution. Methodology/Principal findings To utilize it, anacardic acid was extracted and combined it with ethanol extract of the local lime peel, which contains limonene, to generate APL formulation. APL robustly exhibited inhibition of egg hatching, larvicidal effect, and repellent effect against female mosquitoes from oviposition sites in the laboratory and field. The results showed that, at a dose of 12.5 ppm, the APL formulation after 24 hours of treatment demonstrated oviposition deterrence against Ae. aegypti (43.6%) and Ae. albopictus (59.6%); inhibited egg hatching of Ae. aegypti (49.6%) and Ae. albopictus (59.6%); caused larval lethality in Ae. aegypti (LC 50 = 9.5 ppm, LC 90 = 21 ppm) and Ae. albopictus (LC 50 = 7.6 ppm, LC 90 = 18 ppm). Under natural field conditions, it showed a 100% reduction in larval density after 48 and 72 hours of the APL treatment at a tested concentration of 120 mg a.i./m 2 and maintained a mortality rate of 100% in the next 14 days. Conclusions/Significance The APL formulation is promisingly to become an environmentally friendly and highly effective biological product for future management programs of dengue and Zika-transmitting vectors. Here offer prospects in controlling critical illnesses transmitted by several mosquito species in dengue-endemic areas. Author summary The use of synthetic insecticide to control the dengue and Zika vector population has contributed to drug resistance and caused negative impacts on the environment. The plant-based insecticide should be beneficial for mosquito management in the current situation. Gia Lai province in Vietnam is a dengue-endemic area. A large amount of cashew nut shell waste gets discarded in the area every year, which imposes an increased risk of pollution. The authors took advantage of this by extracting anacardic acid to combine with ethanol extract of local lime peel (containing limonene) to produce APL formulation. This formulation demonstrated potential activities and efficiency in controlling mosquitoes transmitting disease. In the laboratory condition, at a low dose of 12.5 ppm, APL showed activities in inhibiting egg hatching, larviciding, and repelling female Aedes aegypti and Aedes albopictus . In the field condition, APL at a dose of 120 mg a.i./m 2 thoroughly reduced the dengue larval density after two days of contact, and this effect lasted to the next 14 days. APL is a promising and environmentally friendly larvicidal product that is highly effective in controlling dengue and Zika vectors and can play as an alternative measure for vector-borne dengue in the locality.