Comparison of Field and Laboratory-Based Tests for Behavioral Response ofAedes aegypti(Diptera: Culicidae) to Repellents

Abstract

The repellent and irritant effects of three essential oils-clove, hairy basil, and sweet basil-were compared using an excito-repellency test system against an insecticide-resistant strain of Aedes aegypti (L.) females from Pu Teuy, Kanchanaburi Province. DEET was used as the comparison standard compound. Tests were conducted under field and controlled laboratory conditions. The most marked repellent effect (spatial noncontact assay) among the three test essential oils was exhibited by sweet basil, Ocimum basilicum L. (53.8% escaped mosquitoes in 30-min exposure period) under laboratory conditions while hairy basil, Ocimum americanum L. and clove, Syzygium aromaticum (L.) Merill et. L.M. Perry from laboratory tests and sweet basil from field tests were the least effective as repellents (0-14%). In contrast, the contact assays measuring combined irritancy (excitation) and repellency effects found the best contact irritant response to hairy basil and DEET in field tests, whereas all others in laboratory and field were relatively ineffective in stimulating mosquitoes to move out the test chambers (0-5.5%). All three essential oils demonstrated significant differences in behavioral responses between field and laboratory conditions, whereas there was no significant difference in contact and noncontact assays for DEET between the two test conditions (P > 0.05).

Synergistic Behavioral Response Effect of Mixtures of Andrographis paniculata, Cananga odorata, and Vetiveria zizanioides against Aedes aegypti (Diptera: Culicidae)

“…As previously described, the design of the contact chamber offered the determination of a combined contact excitation (‘irritancy’) and non-contact repellency. To estimate the true irritancy, the escape percentage was therefore adjusted again by comparing the numbers of mosquitoes that successfully escaped in each paired contact and non-contact trial [ 19 ] using the following equation: (1 − [number of contacts in test × number of non-contact escapes/number of non-contacts in test × number of contact escapes]) × 100. This measurement, a reciprocal of the Henderson–Tilton (H–T) formula designed to measure the effects of toxic chemicals on populations, enables the adjustment of the ‘crude’ contact escape percentage to provide an estimate of the escape percentage due to contact irritancy to exclude those effects due to repellency [ 33 ].…”

“…Several extracts and essential oils from botanical sources can repel Ae. aegypti mosquitoes, such as catnip, citronella, clove, eucalyptus, ginger, cinnamon, basil, kaffir lime, lemongrass, mountain pepper, weeping paperbark, orange, plai, vetiver, ylang-ylang, nutmeg, turmeric, and fah talai jone [ 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 ]. The repellent efficacy of essential oils can be improved by combining several essential oils from different plants, leading to a synergistic effect [ 24 ].…”

Time of Test Periods Influence the Behavioral Responses of Anopheles minimus and Anopheles dirus (Diptera: Culicidae) to DEET

“…Consequently, the crude contact escape percent was further adjusted to more closely approximate the response resulting from direct tarsal exposure causing irritancy alone to account for any unequal sample sizes between pairings using the equation: (1 − [# contact in test × # noncontact escape/# noncontact in test × # contact escape]) × 100. This calculation, a reciprocal of the Henderson-Tilton (H-T) formula (Henderson and Tilton 1955) [38], was formulated to measure the effects of toxic chemicals on arthropod populations, wherein we compare mosquitoes that successfully escaped the chambers in paired contact and noncontact designs by excluding the repellency effects and provide a better estimate of true contact irritancy [39]. After adjusting, an estimation of percent effect due to contact excitation alone was calculated by dividing the adjusted contact escape (alone) with the pre-adjusted (combined effects) percentage escape for each compound and time interval period.…”

“…The greater impact of time was seen in spatial repellency than contact irritancy due to "true irritancy effect" (percentage of escape present in contact excitation (excluding the repellency effect)). Normally, by contact test design, contact irritancy actually represents a measure of combined contact irritancy and noncontact repellency [39].…”

Behavioral responses ofAnophelesspecies (Culicidae: Diptera) with varying surface exposure to pyrethroid-treated netting in an excito-repellency test system

“…Likewise, when control mortality was between 5 and 20%, the final mortality percent in insecticide exposed samples was also adjusted accordingly. The contact escape percent (a measure of combined irritancy and repellency) was adjusted further using the following equation: (1 – [# contact in test × # non‐contact escape/ # non‐contact in test × # contact escape]) × 100 (Sathantriphop et al ). This calculation provides the percent effect of escape due to contact compared to the estimated effect of spatial repellency in the contact test.…”