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

This corrects the article DOI: 10.30802/AALAS-CM-23-000037
When the above article was first published in the Vol 3 No 6 (December 2023) issue of Comparative Medicine, figure images were incorrectly associated with the figure legends. The correct version of this article has been reprinted in full in volume 74, issue 1 of the February issue of Comparative Medicine.
The publisher apologizes for this error and any inconvenience caused.

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

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 Aedes aegypti 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 Ae. aegypti probing and ingestion on human hands were observed using 100 mV of AC at an input resistance (Ri) of 107 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.

Survey of U.S. based veterinarians' knowledge, perceptions and practices about canine giardiasis

Giardia spp. is a protozoal parasite capable of causing diarrhea in mammals. Certain Giardia assemblages are potentially zoonotic. As part of a public health study, a questionnaire-based cross-sectional web survey was distributed among U.S. small and mixed animal veterinarians to assess the perceived prevalence, the preferred testing and treatment methods, the recommended control measures, and the information communicated about the zoonotic potential of canine giardiasis. Between February and June 2021, over 123 veterinarians from 31 U.S. states participated in the survey. 77% of surveyed veterinarians indicated that they are aware of the prevalence of canine giardiasis in their areas of practice. 52% of veterinarians reported that they test all symptomatic dogs for Giardia, while 42.4% test dogs only some of the time. The preferred confirmatory tests were in the following order: commercial diagnostic lab > in-clinic SNAP® Test > in-clinic Direct Smear > in-clinic Fecal Flotation > state/university diagnostic lab. Several combinations of tests are frequently used to confirm diagnosis. Although there are no labelled products available for treating canine giardiasis in the U.S., 54% of respondents preferred using both fenbendazole and metronidazole simultaneously, 15% reported using fenbendazole only, and 20% reported using metronidazole only. 77.0% of respondents indicated they have dealt with treatment refractory cases often or rarely. 92.6% of veterinarians reported mentioning environmental control to pet owners sometimes or always, which included bathing the infected pet, cleaning toys/bowls/bedding, cleaning floors, and bathing other pets. 73.6% of veterinarians communicated to their clients that Giardia was potentially zoonotic. There are conflicting opinions on the importance of zoonotic transmission between humans and canines available to the general veterinary practitioner. Given that children are at a higher risk of developing Giardia infections, it is important for veterinarians to preserve the health of canine companions to protect their human owners. Thus, the contributions of veterinarians in managing canine giardiasis within the framework of One Health initiatives should not be overlooked.

Dengue Virus-2 Infection Affects Fecundity and Elicits Specific Transcriptional Changes in the Ovaries of Aedes aegypti Mosquitoes

Dengue fever (DF), caused by the dengue virus (DENV), is the most burdensome arboviral disease in the world, with an estimated 400 million infections each year. The Aedes aegypti mosquito is the main vector of DENV and transmits several other human pathogens, including Zika, yellow fever, and chikungunya viruses. Previous studies have shown that the pathogen infection of mosquitoes can alter reproductive fitness, revealing specific vector-pathogen interactions that are key determinants of vector competence. However, only a handful of studies have examined the effect of DENV infection in A. aegypti, showing a reduction in lifespan and fecundity over multiple blood meals. To provide a more comprehensive analysis of the impact of DENV infection on egg laying and fecundity, we assessed egg laying timing in DENV-2 blood-fed mosquitoes (infected group) compared to mock blood-fed mosquitoes (control group). We confirmed a significant decrease in fecundity during the first gonadotrophic cycle. To further investigate this phenotype and the underlying DENV-2 infection-dependent changes in gene expression, we conducted a transcriptomic analysis for differentially expressed genes in the ovaries of A. aegypti infected with DENV-2 vs. mock-infected mosquitoes. This analysis reveals several DENV-2-regulated genes; among them, we identified a group of 12 metabolic genes that we validated using reverse transcription-quantitative PCR (RT-qPCR). Interestingly, two genes found to be upregulated in DENV-infected mosquito ovaries exhibited an antiviral role for DENV-2 in an Aedes cell line. Altogether, this study offers useful insights into the virus-vector interface, highlighting the importance of gene expression changes in the mosquito's ovary during DENV-2 infection in the first gonadotrophic  cycle,  triggering  antiviral  responses  that  may  possibly  interfere  with mosquito reproduction. This information is extremely relevant for further investigation of A. aegypti's ability to tolerate viruses since virally infected mosquitoes in nature constitute a powerful source of supporting viruses during intra-epidemic periods, causing a huge burden on the public health system.

Vesicular Stomatitis Virus Transmission: A Comparison of Incriminated Vectors

Vesicular stomatitis (VS) is a viral disease of veterinary importance, enzootic in tropical and subtropical regions of the Americas. In the U.S., VS produces devastating economic losses, particularly in the southwestern states where the outbreaks display an occurrence pattern of 10-year intervals. To date, the mechanisms of the geographic spread and maintenance cycles during epizootics remain unclear. This is due, in part, to the fact that VS epidemiology has a complex of variables to consider, including a broad range of vertebrate hosts, multiple routes of transmission, and an extensive diversity of suspected vector species acting as both mechanical and biological vectors. Infection and viral progression within vector species are highly influenced by virus serotype, as well as environmental factors, including temperature and seasonality; however, the mechanisms of viral transmission, including non-conventional pathways, are yet to be fully studied. Here, we review VS epidemiology and transmission mechanisms, with comparisons of transmission evidence for the four most incriminated hematophagous dipteran taxa: Aedes mosquitoes, Lutzomyia sand flies, Simulium black flies, and Culicoides biting midges.