Waveforms from stylet probing of the mosquito Aedes aegypti (Diptera: Culicidae) measured by AC-DC electropenetrography

Authors: WAYADANDE, ASTRI - Oklahoma State University; Backus, Elaine; NODEN, BRUCE - Oklahoma State University; EBERT, TIMOTHY - University Of Florida

Submitted to: Journal of Medical Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/28/2019
Publication Date: 11/1/2019
Citation: Wayadande, A.C., Backus, E.A., Noden, B.L., Ebert, T. 2019. Waveforms from stylet probing of the mosquito Aedes aegypti (Diptera: Culicidae) measured by AC-DC electropenetrography. Journal of Medical Entomology. 57(2):353-368. https://doi.org/10.1093/jme/tjz188.
DOI: https://doi.org/10.1093/jme/tjz188

Interpretive Summary: Vector-borne pathogens are responsible for about 20% of all infectious diseases worldwide, causing almost a million deaths annually. While some, such as malaria and dengue, have stably impacted human populations for centuries, others (e.g., yellow fever) have re-emerged, or (e.g., chikungunya and zika viruses) have invaded new regions of the world. New approaches are needed to manage or eliminate such diseases by developing unique and novel targets in the disease cycle, either in people and/or mosquito vectors. One new research area has focused on mosquito-host interactions that occur through the attraction and feeding process. Yet, the most rigorous method for studying feeding of piercing-sucking insects has not been fully applied to mosquitoes. This work introduces AC-DC electropenetrography for study of mosquito feeding, and performs benchmark research to define EPG waveforms representing different stages of the feeding process. Behaviors occurred in the following order: surface salivation (waveform family J), mouth part penetration through the outer skin (K), penetration of deeper tissues and location of capillary blood vessels (L), active fluid uptake and swallowing (M), and an unknown behavior that terminates the mosquito bite (N). Probabilities of occurrence of each waveform demonstrated differences among individuals for waveforms L and M, which were alternated. This variation among individuals suggests that mosquitoes could feed differently on different people or in response to different treatments. Now that waveforms for mosquito feeding has been defined, EPG can be used as a tool for improved management of mosquito-borne diseases.

Technical Abstract: Electropenetrography (EPG) has been used for many years to visualize stylet probing behaviors of plant-feeding piercing-sucking insects, primarily hemipterams. Yet, EPG has not been extensively used with blood-feeding insects. In this study, an AC-DC electropenetrograph with variable input resistors (Ri), i.e., amplifier sensitivities, was used to construct a waveform library for the arbovirus vector, Aedes aegypti, while feeding on human hands. EPG waveforms representing feeding activities were: 1) electrically characterized, 2) defined by visual observation of biological activities, 3) analyzed for differences in appearance by Ri level, and 4) quantified. Electrical origins of waveforms were identified from five different Ri levels and two types of applied signal (AC and DC). Mosquitoes produced short stylet probes (“bites”) that typically contained five waveform families, but not all waveforms were performed by every insect. Behaviors occurred in the following order: surface salivation (waveform family J), stylet penetration through the outer skin (K), penetration of deeper tissues and location of capillary vessels/pathway activities (L), active ingestion with engorgement (M), and an unknown behavior that terminated the probe (N). A kinetogram of conditional probabilities for waveform performance demonstrated variation among individuals in L and M, which were alternated. Now that EPG waveform for mosquito feeding have been defined, EPG can be used as a tool for improved management of the scourge of mosquito-borne diseases.