Adulticidal, Larvicidal, and Repellent Effects of Ethanolic Azadirachta indica Seed Extract Against Rhipicephalus microplus

Abstract

Ticks, especially Rhipicephalus microplus, are a major threat to livestock, as they cause blood loss, skin damage, poor weight gain, and the spread of tick-borne pathogens. Traditional control measures rely on synthetic acaricides, which have led to resistance after prolonged use, environmental pollution, and residues in animal products. The study evaluates the adulticidal, larvicidal, and repellent properties of an ethanolic extract of Azadirachta indica (Neem) seeds against R. microplus. A crude ethanolic extract (yield: 15.2%) was tested at concentrations ranging from 1.25–20% using adult immersion, larval immersion, and tick-climbing repellency assays. Dose-dependent acaricidal effects were observed to be significantly high with adult mortality of 85% and larval mortality of 92% recorded at 20% extract. The LC₅₀ and LC₉₀ values for adults were 6.23 and 18.75%, respectively, and the LC₅₀ and LC₉₀ values for larvae were 4.85 and 15.42%, respectively. Reproductive parameters were also adversely affected at the highest concentration: hatchability was 28%, and oviposition was inhibited by 88%. The highest repulsive percentage of 82.4 was recorded after 4 hours at 20% extract. These same findings indicate that the ethanolic extract of Neem seeds exhibits strong adulticidal, larvicidal, antireproductive, and repellent efficacy against R. microplus, thereby supporting its potential as a botanical acaricide candidate for further evaluation in tick management.