Local Variation in Adulticidal Susceptibility of <i>Anopheles</i> spp. to <i>Artemisia scoparia</i> Essential Oil in Batagarawa LGA, Katsina State, Nigeria

Abstract

Malaria remains a major public health burden in Nigeria, exacerbated by increasing insecticide resistance among Anopheles spp. Plant-derived essential oils are increasingly being investigated as environmentally sustainable alternatives for vector control. This study evaluated the adulticidal susceptibility of Anopheles spp. to Artemisia scoparia essential oil (ASEO) across five localities in Batagarawa Local Government Area (LGA), Katsina State, Northwestern Nigeria. Larvae and pupae were collected from 31 breeding sites distributed across Batagarawa localities, reared to adulthood under standardized insectary conditions, and tested using WHO tube bioassays. Four replicates of 25 non-blood-fed adult female Anopheles spp. were exposed per locality to 0.50% ASEO-impregnated filter papers. Knockdown times (KDT₅₀ and KDT₉₅) were estimated using probit regression analysis, while locality differences were analyzed using one-way ANOVA at p < 0.05. Breeding-site physicochemical parameters including temperature, pH, dissolved oxygen, conductivity, and turbidity were also evaluated. Significant variation was observed in breeding-site pH (p = 0.0128) and temperature (p = 0.0067) among localities. Mosquito knockdown responses differed significantly across localities, with KDT₅₀ values ranging from 33.08 (95% CI: 29.56 - 37.02) to 59.15 (95% CI: 48.58 - 72.01) minutes (p = 0.0271). However, 24-hour mortality remained consistently low across all localities, ranging from 4% to 16% (p = 0.2167). The findings indicate that although ASEO induced measurable knockdown effects, its adulticidal efficacy at 0.50% concentration was inadequate under the tested formulation and exposure conditions. These results suggest that A. scoparia essential oil may currently serve better as a complementary component in integrated vector management strategies than as a stand-alone adulticide.