Locomotor activity in Aedes aegypti with different insecticide resistance profiles

Crude saliva of Amblyomma cajennense sensu stricto (Acari: Ixodidae) reduces locomotor activity and increases the hemocyte number in the females of Aedes aegypti (Diptera: Culicidae)

Aedes aegypti are vector insects of arboviruses such as dengue, Zika, and chikungunya. All available vector control methods have limited efficacy, highlighting the urgent need to find alternative ones. Evidence shows that arachnids like ticks are sources of biologically active compounds. Moreover, chemical modulation of the locomotor and immune systems of vector insects can be used to control arbovirus transmission. The present study evaluated the effectiveness of crude saliva of female Amblyomma cajennense sensu stricto (s.s.) ticks in reducing locomotor activity and inducing an immune response in Ae. aegypti females. Additionally, the study evaluated the protein constitution of tick saliva. For this purpose, the crude saliva obtained from several semi-engorged A. cajennense females was used. A volume of 0.2 nL of crude tick saliva was administered to mosquitoes by direct intrathoracic microinjection. The effect of the tick's saliva on the locomotor activity of the mosquito was observed using Flybox, a video-automated monitoring system, and the hemolymph hemocyte levels were quantified by reading slides under a light microscope. The protein concentration of the crude tick saliva was 1.27 μg/μL, and its electrophoretic profile indicates the presence of proteins with a molecular weight ranging between ∼17 and 95 kDa. Microplusins, ixodegrins, cystatin, actins, beta-actin, calponin, albumin, alpha-globulins, and hemoglobin were the main proteins identified by proteomics in the saliva of A. cajennense. The microinjected saliva had low toxicity for Ae. aegypti females and significantly reduced their locomotor activity, especially in the transition between the light and dark phases. The crude tick saliva did not change the period and rhythmicity of the circadian cycle. The tick saliva significantly increased the number of hemocytes two days after injection and reduced it after five days. These results suggest that further evaluation of the biological properties of tick saliva proteins against Ae. aegypti would be of interest.

Simulation analysis and physiological and biochemical evaluation of Sophora flavescens aboveground against aphids using network pharmacology

Pests cause substantial damage to human environments; therefore, studying insecticidal mechanisms is crucial for improving pest control. However, the use of chemical pesticides can cause irreversible secondary damage. In this study, we used network pharmacology to investigate the effect of Sophora flavescens Alt., as a biological pest control agent, on glucose-6-phosphate 1-dehydrogenase, thymidylate synthase, and a translocation protein in aphids. The stability and reliability of target proteins was analyzed using molecular docking and molecular dynamic simulations. Enzyme activity assays validated the feasibility of network pharmacology to obtain actionable targets. We used interdisciplinary integration to study pest control and network pharmacology to identify how Sophora flavescens Alt. resists aphid attacks. The results show that the use of network pharmacology can increase the accuracy and specificity of our predictions for the molecules targeted by insecticides. This approach will facilitate improved, environmentally friendly pest control development in the future.

Increased Repellent Effect of DEET on Aedes aegypti (Diptera: Culicidae) Field Population

Insecticides and repellents are routinely used in Brazil because of the high rates of arbovirus transmission and the nuisance caused by mosquitoes. However, few studies have assessed the effectiveness of repellents against mosquito populations that have been under exposure to xenobiotics, mainly insecticides and repellents. This study investigated the sensitivity of a field population of Aedes aegypti (Linnaeus, 1762) from a dengue-endemic area under high insecticide pressure to N,N-diethylmethylbenzamide (DEET), the active ingredient in common repellent products. The field (Laranjeiras, Sergipe, Brazil) and laboratory (Rockefeller) populations were characterized for the presence of the Val1016Ile kdr mutation, associated with pyrethroid resistance, and locomotor activity. Repellency bioassays were performed to assess the response of the mosquitoes to human odor by exposing them to 10% DEET applied to the skin in ethanol. Samples from the field population showed higher frequency of the kdr mutation, 21.9% homozygous and 21.9% heterozygous, greater locomotor activity and greater sensitivity to DEET than the laboratory population. These results suggest increased sensitivity to DEET in field populations and a possible interaction between insecticide exposure and sensitivity to DEET.

Body size does not affect locomotor activity of Aedes aegypti and Aedes albopictus females (Diptera:Culicidae)

Intraspecific competition between mosquito larvae can affect several adult traits, particularly size. This study tested the hypothesis that intraspecific competition during the larval stage affects wing length in Ae. aegypti and Ae. albopictus adults, in turn influencing locomotor activity. L1 larvae of both species were reared in trays under conditions of low and high competition. After adults had emerged, the locomotor activity of virgin females of Ae. aegypti and Ae. albopictus was evaluated under light-dark cycles of 12:12 h at 25 °C and 70% relative humidity. At the end of the locomotor activity experiment, the left wings of the mosquitoes were removed to be measured, and wing length was used as an indicator of adult female size. Although the results showed that the wing lengths of Ae. aegypti and Ae. albopictus females reared under low larval competition were significantly greater than those of females reared under high larval competition, this difference did not affect locomotor activity in females of either species, demonstrating that locomotor activity in small Ae. aegypti and Ae. albopictus females is not lower than in larger females. Our findings reinforce the idea that intraspecific competition alters the wing length of Ae. aegypti and Ae. albopictus females and provide new evidence about this effect on the locomotor activity of these species.

Mosquito flight: Escaping attacks in dim light

To avoid fast attackers, animals must move somewhere their pursuer cannot follow or does not expect. A new study shows that female mosquitoes of either a diurnal or a nocturnal species each exhibit a distinct escape strategy matched to the light level they experience as they hunt for blood.