Modulation of La Crosse Virus Infection in Aedes albopictus Mosquitoes Following Larval Exposure to Coffee Extracts

A Scoping Review on the Epidemiology of Orthobunyaviruses of Canadian Public and Animal Health Relevance in the Context of Vector Species

Background: Mosquito-borne orthobunyaviruses are a growing priority for public and animal health in Canada. It is anticipated that disease incidence will increase due to a warming climate, given that habitats are expanding for reservoir hosts and vectors, particularly in Canada. Little is known about the ecology of primary vectors that perpetuate these orthobunyaviruses, including the viral transmission cycle and the impact of climatic and landscape factors. Methods: A scoping review was conducted to describe the current state of knowledge on the epidemiology of orthobunyaviruses relevant to Canada. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for Scoping Reviews guidelines was used to characterize studies focused on vector species. A literature search was conducted in six databases and gray literature. Eligible studies characterized orthobunyavirus epidemiology related to vector species, including viral competency, geospatial distributions, seasonal trends, and/or risk factors. Results: A total of 1734 unique citations were identified. Screening of these citations revealed 172 relevant studies, from which 87 studies presented primary data related to vectors. The orthobunyaviruses included Cache Valley virus (CVV), Jamestown Canyon virus (JCV), Snowshoe Hare virus (SHV), and La Crosse virus (LACV). Surveillance was the predominant study focus, with most citations representing the United States, specifically, LACV surveillance in Tennessee, followed by CVV and JCV in Connecticut. Orthobunyaviruses were detected in many mosquito species across multiple genera, with high vector specificity only being reported for LACV, which included Aedes triseriatus, Aedes albopictus, and Aedes japonicus. Peridomestic areas were positively associated with infected mosquitoes compared with dense forests. Orthobunyavirus infections, coinfections, and gut microbiota affected mosquito feeding and breeding behavior. Conclusion: Knowledge gaps included Canadian surveillance data, disease modeling, and risk projections. Further research in these areas, especially accounting for climate change, is needed to guide health policy for prevention of orthobunyaviral disease.

Biological, histological and immunohistochemical studies on the toxicity of spent coffee grounds and caffeine on the larvae of Aedes aegypti (Diptera: Culicidae)

The mosquito Aedes aegypti is a primary vector for major arboviruses, and its control is mainly based on the use of insecticides. Caffeine and spent coffee grounds (CG) are potential agents in controlling Ae. aegypti by reducing survival and blocking larval development. In this study, we analyzed the effects of treatment with common CG (CCG: with caffeine), decaffeinated CG (DCG: with low caffeine), and pure caffeine on the survival, behavior, and morphology of the midgut of Ae. aegypti under laboratory conditions. Third instar larvae (L3) were exposed to different concentrations of CCG, DCG, and caffeine. All compounds significantly affected larval survival, and sublethal concentrations reduced larval locomotor activity, delayed development, and reduced adult life span. Damage to the midgut of treated larvae included changes in epithelial morphology, increased number of peroxidase-positive cells (more abundant in DCG-treated larvae), and caspase 3-positive cells (more abundant in CCG-treated larvae), suggesting that the treatments triggered cell damage, leading to activation of cell death. In addition, the treatments reduced the FMRFamide-positive enteroendocrine cells and dividing cells compared to the control. CG and caffeine have larvicidal effects on Ae. aegypti that warrant field testing for their potential to control mosquitoes.

Ameliorative Effects of Phytochemical Ingestion on Viral Infection in Honey Bees

Simple Summary

Virus infection is among the many stressors honey bees are experiencing in the modern agricultural landscape. Although some promising treatments are currently under development, no reliable cure currently exists. Here, we investigated the effects of various phytochemicals (plant-produced chemical compounds) on the survivorship of virus infected honey bees. Our results showed that, when consumed at natural concentrations like those found in flowers, caffeine is capable of significantly reducing the mortality of infected bees. It is important to note that caffeine did not clear the infected bees of all viruses and should, therefore, not be considered a virus cure. Rather, caffeine represents a potential antiviral therapeutic agent that should be studied further to improve understanding of virus-phytochemical interactions.

Abstract

Honey bee viruses are capable of causing a wide variety of devastating effects, but effective treatments have yet to be discovered. Phytochemicals represent a broad range of substances that honey bees frequently encounter and consume, many of which have been shown to improve honey bee health. However, their effect on bee viruses is largely unknown. Here, we tested the therapeutic effectiveness of carvacrol, thymol, p-coumaric acid, quercetin, and caffeine on viral infection by measuring their ability to improve survivorship in honey bees inoculated with Israeli acute paralysis virus (IAPV) using high-throughput cage bioassays. Among these candidates, caffeine was the only phytochemical capable of significantly improving survivorship, with initial screening showing that naturally occurring concentrations of caffeine (25 ppm) were sufficient to produce an ameliorative effect on IAPV infection. Consequently, we measured the scope of caffeine effectiveness in bees inoculated and uninoculated with IAPV by performing the same type of high-throughput bioassay across a wider range of caffeine concentrations. Our results indicate that caffeine may provide benefits that scale with concentration, though the exact mechanism by which caffeine ingestion improves survivorship remains uncertain. Caffeine therefore has the potential to act as an accessible and inexpensive method of treating viral infections, while also serving as a tool to further understanding of honey bee–virus interactions at a physiological and molecular level.