ac-dc-electropenetrography-for-study-probing-ingestion-behaviors

AC-DC Electropenetrography for the Study of Probing and Ingestion Behaviors of <i>Culex tarsalis</i> Mosquitoes on Human Hands

Mosquitoes transmit pathogens that negatively affect human and animal health. A greater understanding of their blood-feeding biology and interactions with ...

Usda Agricultural Research Service

Rift Valley fever virus (RVFV) (Bunyavirales: Phlebovirus) is a prominent vector-borne zoonotic disease threat to global agriculture and public health. Risks of introduction into nonendemic regions are tied to changing climate regimes and other dynamic environmental factors that are becoming more prevalent, as well as virus evolutionary factors and human/animal movement. Endemic to the African continent, RVFV has caused large epizootics at the decadal scale since the early 20th century but has spread to the Arabian Peninsula and shows increasing patterns of interepizootic transmission on the annual scale. This virus can be transmitted by mosquitoes as well as through direct contact with infected tissues and can cause sporadic to widespread morbidity and mortality in domestic ungulate livestock as well as humans. High viremias in infected livestock moved for legal and illegal trade as well as in infected mosquitoes or human travelers can spread this virus worldwide. With increasing global commerce, it is likely RVFV will be introduced to new areas with suitable hosts, mosquito vector species, and environments. However, the strong mosquito component of RVFV epidemiology combined with advancements in vaccines, diagnostics, and virus evolutionary factors create opportunities for strategies to leverage models of connectivity among potential source and emerging regions to target surveillance and mitigation activities to reduce the risk of RVFV introduction, or contain the virus should it be introduced, into new regions.

The increasing threat of Rift Valley fever virus globalization: strategic guidance for protection and preparation.

Culex tarsalis Coquillett (Diptera: Culicidae) mosquitoes are capable of vectoring numerous pathogens affecting public and animal health. Unfortunately, the probing behaviors of mosquitoes are poorly understood because they occur in opaque tissues. Electropenetrography (EPG) has the potential to elucidate these behaviors by recording the electrical signals generated during probing. We used an AC-DC EPG with variable input resistors (Ri levels) to construct a waveform library for Cx. tarsalis feeding on human hands. Biological events associated with mosquito probing were used to characterize waveforms at four Ri levels and with two electrical current types. The optimal settings for EPG recordings of Cx. tarsalis probing on human hands was an Ri level of 10 Ohms using an applied signal of 150 millivolts alternating current. Waveforms for Cx. tarsalis included those previously observed and associated with probing behaviors in Aedes aegypti L. (Diptera: Culicidae): waveform families J (surface salivation), K (stylet penetration through the skin), L (types 1 and 2, search for a blood vessel/ingestion site), M (types 1 and 2, ingestion), N (type 1, an unknown behavior which may be a resting and digestion phase), and W (withdrawal). However, we also observed variations in the waveforms not described in Ae. aegypti, which we named types L3, M3, M4, and N2. This investigation enhances our understanding of mosquito probing behaviors. It also provides a new tool for the automated calculation of peak frequency. This work will facilitate future pathogen acquisition and transmission studies and help identify new pest and disease management targets.

An electropenetrography waveform library for the probing and ingestion behaviors of Culex tarsalis on human hands.

A detailed understanding of mosquito probing and ingestion behaviors is crucial in developing novel interventions to interrupt the transmission of important human and veterinary pathogens, but these behaviors are difficult to observe as the mouthparts are inserted into the skin of the host. Electropenetrography (EPG) allows indirect observation, recording, and quantification of probing and ingestion behaviors of arthropods by visualizing the electrical waveform associated with these behaviors. The study of mosquito probing and ingestion behaviors has been limited to the use of human hands as host, which is not suitable for pathogen transmission studies. Mouse models of mosquito-borne diseases are a widely used and indispensable tool in this research, but previous attempts to use direct current EPG to study mosquito probing behaviors on mice have been unsuccessful. Accordingly, the present study used alternating or direct current (AC-DC) EPG to observe the ingestion behaviors of adult  mosquitoes on a mouse host in real time under BSL-2 containment conditions with enhanced BSL-3 practices. Our results show that waveform families previously identified during  probing and ingestion on human hands were observed using 100 mV of AC at an input resistance (Ri) of 10 Ohms (Ω) on CD1 mice. This work is a proof of concept for using mouse models for studying mosquito probing and ingestion behaviors with AC-DC EPG. In addition, these data show that the experimental setup used in these experiments is sufficient for conducting studies on mosquito probing and ingestion behaviors under BSL-2 containment conditions enhanced with BSL-3 practices. This work will serve as a foundation for using EPG to investigate the effects of pathogen infection on mosquito probing behaviors and to understand the real-time dynamics of pathogen transmission.

AC-DC Electropenetrography as a Tool to Quantify Probing and Ingestion Behaviors of the Yellow Fever Mosquito () on Mice in Biocontainment.

Japanese encephalitis is a disease caused by the Japanese encephalitis virus (JEV) and is a concern for U.S. military personnel stationed in the Republic of Korea (ROK). The recent literature reports a potential shift from GI to GV as the dominant genotype circulating in east Asia. In the ROK, GV has been reported in a few  spp., but not in the main JEV vector, . . The goal of this surveillance was to shed light on the current knowledge of the epidemiology of JEV in the ROK by analyzing mosquito collection data from three consecutive years, 2021-2023, and molecularly detecting and genotyping JEV in all  spp. collected in several military locations across the ROK. In this study, we detected only JEV GI in .  in 2021 samples. In contrast, all 2022 and 2023 positive samples were GV and detected in . , . , and . . Results support a shift in JEV genotype in the ROK and suggest that for GV,  spp. other than .  may be playing an important role.

Article	Year
The increasing threat of Rift Valley fever virus globalization: strategic guidance for protection and preparation. Journal of medical entomology\| PubMed ID: 37862067	2023
An electropenetrography waveform library for the probing and ingestion behaviors of Culex tarsalis on human hands. Insect science\| PubMed ID: 37942850	2024
AC-DC Electropenetrography as a Tool to Quantify Probing and Ingestion Behaviors of the Yellow Fever Mosquito () on Mice in Biocontainment. Comparative medicine\| PubMed ID: 38086541	2023
Japanese Encephalitis Virus Surveillance in U.S. Army Installations in the Republic of Korea from 2021 to 2023. Pathogens (Basel, Switzerland)\| PubMed ID: 39204305	2024

Dana Mitzel

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