关键词: 白纹伊蚊, 诺卡酮, 驱避

Abstract:

Objective To evaluate the repellent effect of the plant-derived repellent nootkatone against Aedes albopictus. Methods In the spatial repellency screening assay using three-part tubes, three replicates each of 20%, 10%, and 5% nootkatone solutions were tested, together with one blank control. For each group, 40 female Ae. albopictus mosquitoes (5 to 8 days post-emergence without blood feeding) were selected. The treatment side of the three-part tube was fitted with a mesh screen impregnated with the respective nootkatone solutions, while the control side was treated with absolute ethanol. Mosquitoes were introduced into the central chamber of the three-part tube, which were covered with green flannels. Then, the partitions to both sides were opened. After 10 minutes, the partitions were closed, and the number of mosquitoes in each side was recorded to calculate the relative repellency rate. The nootkatone solutions with a relatively higher repellency rate were selected for subsequent fabric efficacy and human hand topical application cage tests. For the fabric efficacy evaluation, five replicates were conducted, each utilizing 600 adult mosquitoes (3 to 5 days post-emergence without blood feeding, including 300 males and 300 females). Fabrics in the treatment group were immersed in the repellent at a dose of 7.5 ml/500 cm² for 48 hours, while the control group used untreated fabric from the same batch. The fabric was used to cover a 40 mm × 40 mm observation window on the back of test gloves. Five volunteers wore the gloves and inserted their hands into mosquito cages, and the number of mosquito probing attempts within 30 minutes was recorded. The criterion for complete protection was absence of any probing during this period. The residual efficacy was re-tested on days 5 and 7, and so forth, until protection failed. For the human hand topical application cage test, five replicates were performed, each using 300 female mosquitoes (3 to 5 days post-emergence without blood feeding). A 50 mm × 50 mm area on the back of a volunteer’s hand, aligning with the 40 mm × 40 mm observation window on the test glove, was marked. The volunteer wore a test glove exposing the treated area 2 hours post-treatment with nootkatone solution at a dose of 1.5 μl/cm², inserted their hands into the cage, and the number of probing attempts within 2 minutes was recorded. This test was repeated hourly, with the first occurrence of a probing event defined as the failure criterion, and the duration of effective protection was recorded. For the spatial repellency screening assay using three-part tube, Mann-Whitney U test was used to analyze the difference in mosquito distribution between the two sides under blank control conditions, and chi-square test was used to analyze differences between experimental groups (different concentrations) and the blank control. Results The spatial repellency screening assay using three-part tube showed a 15/15 mosquito distribution ratio between the control and treatment sides under blank conditions (Z = 0.145, P > 0.05). The relative repellency rates of 5%, 10%, and 20% nootkatone were 26.1%, 26.1%, and 57.7% against Ae. albopictus mosquitoes, respectively, with no statistically significant differences compared to the blank control (χ² = 3.112 1, 3.112 1, 0.331 4; P > 0.05). The repellency rate of 20% nootkatone was significantly different from that of both 5% and 10% nootkatone (χ² = 4.978, 4.978; P < 0.05). The fabric efficacy evaluation demonstrated that fabric treated with 20% nootkatone for 48 hours provided complete protection, with a protective duration of 5 days. The human hand topical application test indicated that the average effective protection time was 2.4 hours for 20% nootkatone. Conclusion In the fabric efficacy evaluation, 20% nootkatone provides a complete protection against Ae. albopictus.

Key words: Aedes albopictus, Nootkatone, Repellent