Biology subjects

Foy, B. D.

Publications and source records attributed to Foy, B. D..

8 recordsLinked to original sources

bioRxiv2026

Biparental vertical transmission of Aedes anphevirus, Guadeloupe mosquito virus, and verdadero virus in colonized Aedes aegypti

Aedes aegypti mosquitoes can be infected by arboviruses that can be transmitted to and cause disease in vertebrates. Ae. aegypti can also be infected by insect-specific viruses, which do not infect vertebrates, but may impact mosquito biology and vector competence. In this study we characterized the viromes of Ae. aegypti populations that had been maintained in laboratory colonies for 4 to 18 years. Mosquitoes were originally collected in Tapachula, Poza Rica and Merida, Mexico and New Orleans, USA. We used metagenomics to characterize the viruses present in the colonies, then quantified the vertical transmission efficiencies of the viruses by performing crosses between populations. The viruses infecting these colonies included Aedes anphevirus, Guadeloupe mosquito virus, and verdadero virus. These viruses were at high prevalence in infected populations, with over 75% of individual adult mosquitoes infected. All three viruses exhibited biparental vertical transmission: both infected mothers and infected fathers transmitted infection to their offspring, but in all cases maternal transmission was more efficient than paternal. We also identified evidence of possible horizontal transmission between adult mosquitoes that had cohabited during crosses. Efficient transgenerational transmission likely contributes to the ability of these viruses to persist in laboratory populations and nature. Because of their efficient vertical transmission and minimal apparent fitness costs, these viruses could be good candidates for gene delivery to mosquito populations, including for vector control. Author summaryAedes aegypti mosquitoes are responsible for transmission of many dangerous pathogens, including dengue virus, Zika virus, and yellow fever virus. These mosquitoes also carry viruses that do not pose a threat to public health, but might influence mosquito biology. In this study, we identified viruses that persistently infected 4 long-established Ae. aegypti colonies in our insectary. These viruses were at high prevalence in these laboratory populations, and did not appear to harm infected mosquitoes. The viruses exhibited an ability to efficiently transmit from parents to offspring, both from infected mothers and infected fathers. This provided an explanation for how these mosquitoes were able to persist so successfully in laboratory populations, and by extension in nature. Given their ability to efficiently spread and minimal apparent fitness costs, these viruses represent promising candidates for use in mosquito control or other practical applications.

microbiology↗

bioRxiv2025

Evaluation of the safety and insecticidal efficacy of ivermectin-treated bird feed formulations in different avian species

BackgroundWest Nile virus (WNV) is maintained in an enzootic cycle between reservoir host birds and Culex (Cx.) spp. mosquitoes. This relationship presents a potential target for vector control strategies. Ivermectin (IVM), an endectocidal drug that selectively affects invertebrates while remaining safe at high concentrations in mammals and birds, can be delivered to Cx. tarsalis via blood meals from birds fed IVM-treated bird feed. In this study we evaluated the safety, efficacy, and utility of IVM-treated bird feed as a novel vector control strategy by assessing its impact on multiple bird species and mosquitoes. MethodsMosquitoes were collected during peak WNV transmission season in Northern Colorado and DNA extracted from blood meals to determine host species. Chickens, pigeons, zebra finches, and house sparrows were fed different formulations of IVM-treated bird feed and observed for clinical signs, and their sera were fed to Cx. tarsalis mosquitoes to evaluate mosquitocidal efficacy. Feeding rates and IVM serum concentrations in birds were analyzed by unpaired t-test and one-way ANOVA, and mosquito survivorship was analyzed by Kaplan-Meier curves and compared using paired log-rank tests. IVM serum concentration and mosquito survivorship were compared using Spearman correlation. ResultsSpeciation analyses conducted on blood meals from Cx. tarsalis collected during peak WNV transmission season in Northern Colorado determined that they feed primarily on songbird species that commonly visit bird feeders, with house sparrows representing the most frequent blood meal host. In laboratory experiments using multiple formulations and doses of IVM, chickens, pigeons, zebra finches, and house sparrows ate comparable amounts of IVM-treated bird feed compared to untreated feed, had similar weight gain, and exhibited no clinical signs of toxicity. Both colony-reared and locally captured Cx. tarsalis showed significant mortality after feeding on sera from IVM-treated birds compared to controls. ConclusionsThese results suggest that targeting songbirds with IVM-treated bird feed should be safe for wildlife and may elicit high rates of IVM-induced mortality by reaching a large proportion of WNV vector mosquitoes via their proclivity for feeding on passerine birds.

microbiology↗

bioRxiv2025

Anopheles mosquitoes exposed to long-acting antimalarials via drug-spiked bloodmeal absorb drug but do not suffer fitness costs

The World Health Organizations recommendations regarding the use of antimalarials for the prevention of malaria in endemic areas have greatly expanded, allowing more flexibility in the demographic groups and regions where chemoprevention and mass treatment are acceptable. An overlooked aspect of expanding human population-level drug exposure is the downstream impact of ingested drug on the mosquito vector. Data suggest both infected and uninfected Anopheles mosquitoes re-feed often with [≥]4 blood meals during their lifespan. This provides repeated opportunities for mosquitoes to ingest drug via bloodmeals taken from people with antimalarials in the bloodstream and raises questions as to whether exposure may impact the mosquito itself, and/or parasites developing within the infected mosquito. We investigated the impact of exposure to physiologic levels of commonly used long-acting human antimalarials in the Anopheles mosquito via drug-spiked blood feeds. We did not observe any significant differences in mosquito feeding, behavior, fertility, or viability after ingestion of amodiaquine, desethylamodiaquine, piperaquine, and sulfadoxine-pyrimethamine in either lab-reared An. gambiae or field-derived An. coluzzii mosquitoes. Interrogating drug distribution within mosquitoes utilizing LC-MS/MS, desethylamodiaquine, the longer-acting active metabolite of amodiaquine, was fed at 2 concentrations (1/2X and 2X Cmax) with drug subsequently detected in a dose-dependent manner in pooled whole mosquitoes, midguts and hemolymph. This was significant for whole mosquitoes harvested at 24hrs and 120hrs, and midguts harvested at 24hrs. Between 24 to 120 hrs, drug decreased in midguts but increased in hemolymph. Our results show biochemical evidence of antimalarial absorption into Anopheles hemolymph following bloodmeal ingestion. These studies lay the foundation for future work to assess the impact of vector-stage antimalarial drug exposure on parasite progression throughout development in the mosquito, which could in turn have important implications for transmission dynamics and drug resistance spread. Author summaryDrug resistance to first-line antimalarials has emerged in multiple African countries. A better understanding of antimalarial drug resistance emergence and spread is critical in preventing further morbidity and mortality. Millions regularly receive antimalarials for prophylaxis and mass treatment that are purposefully long-acting. Anopheles mosquitoes re-feed frequently, and these malaria vectors (both infected and uninfected) routinely feed on people whose blood contains these long-acting antimalarials. Parasites take approximately 10 days to develop within the mosquito. There is published precedent that several antimalarials can act upon vector-stage parasites, yet any potential impact of antimalarials on mosquitoes and/or parasites developing within has been largely overlooked. We questioned whether antimalarials ingested in mosquito bloodmeals could influence parasite development and drug resistance selection. As initial investigations, we exposed uninfected Anopheles mosquitoes to commonly used long-acting antimalarials via drug-spiked bloodmeals, mimicking predicted physiologic drug exposure. Investigated drugs did not impact mosquito viability. However, mass spectrometry confirmed drug absorption in whole mosquitoes, as well as within midguts and circulatory fluid, several days after feeding, demonstrating that mosquitoes can ingest key drugs without suffering fitness costs, and these drugs can persist in mosquitoes. This highlights the potential for antimalarials to impact parasite development and drug resistance selection within the mosquito.

microbiology↗

bioRxiv2025

West Nile virus dissemination among individual wild mosquito vectors in Northern Colorado, 2023

West Nile virus (WNV) transmission risk is typically estimated from pooled whole-mosquito infection data, which may overestimate the proportion of mosquitoes capable of transmission. To assess natural viral dissemination in field-collected Culex tarsalis, we tested infection rates in tissues of 1,793 individual mosquitoes collected from Northern Colorado in August 2023. Abdomens were screened for WNV RNA, and corresponding thorax and head tissues from positive mosquitoes were tested. Fifteen mosquitoes had detectable abdominal infections, but WNV RNA was detected in only 53% (8/15) of both the thorax and head tissues, while another 27% (4/15) had WNV RNA detected in either the thorax or the head alone. Logistic regression suggests an inconsistent relationship between abdominal viral ribonucleic acid (RNA) load and virus dissemination, whereas receiver operating characteristic analysis identifies a threshold of [~]59,000 RNA copies in the abdomen predictive of dissemination (AUC 0.80, 95% CI: 0.545, 1). These results suggest whole-body RNA detection may overestimate transmission potential from field-captured mosquitoes, and that incorporating infection data could refine surveillance-based risk indices for WNV.

ecology↗

bioRxiv2025

Effect of pharmacokinetically-relevant ivermectin concentrations on survivorship and fecundity of Anopheles coluzzii and Aedes aegypti in Burkina Faso: a laboratory experimental study

BackgroundThe control of vector-borne diseases is increasingly challenged by widespread insecticide resistance. Therefore, innovative vector control strategies with alternative modes of action are urgently needed. Ivermectin (IVM), an endectocide, has demonstrated toxicity to mosquito species such as Anopheles and Aedes when they feed on treated humans or livestock. In this study, we conducted a laboratory experiment to assess the effect of IVM, at concentrations equivalent to human plasma levels following mass drug administration (MDA), on the survival and fecundity of Anopheles coluzzii and Aedes aegypti in Burkina Faso. MethodsTwo laboratory experiments were conducted using 3-5-day old wild-derived female An. coluzzii and Aedes aegypti. Each experiment included four replicates per IVM concentration and was performed on separate dates. Mosquitoes were fed via membrane feeding on rabbit blood treated with five concentrations of IVM (C=112 ng/ml, C2=29 ng/ml, C3=15 ng/ml, C4=6.5 ng/ml, C5=2.5ng/ml), corresponding to the mean human plasma levels at 2, 4, 7, 14, and 28 days post-MDA with IVM at a dose of 300 g/kg. A negative control (C6=0.0 ng/ml) was also included. Mosquito mortalities were recorded daily for 7 days. Fecundity was measured by counting both laid eggs and developed eggs (via ovary dissection). ResultsIVM significantly reduced the survival of An. coluzzii compared to the control group (p<0.001), with the risk of death increasing from 4.2-fold at the lowest concentration (2.5 ng/ml) to 64.2-fold at the highest (112 ng/ml). In contrast, IVM had no significant effect on Aedes aegypti (p>0.05). Additionally, in An. coluzzii, IVM significantly reduced both egg laying and egg development (p<0.0001 and p<0.001, respectively), whereas no significant impact on fecundity was observed in Ae. aegypti (all p>0.80). ConclusionIvermectin concentrations typically achieved in human plasma during mass drug administration campaigns were sufficient to significantly reduce both survival and fecundity of wild type An. coluzzii, but had no measurable effect on recently colonized Ae. aegypti. These findings highlight the species-specific efficacy of ivermectin and support its potential role in integrated vector control strategies targeting malaria vectors in Africa.

zoology↗

bioRxiv2025

Pixel intensity of wing photos used to predict age of Anopheles gambiae caught during the RIMDAMAL II clinical trial

Mosquito age-grading is important for evaluating mosquito control efforts and estimating pathogen transmission risk. We previously developed a simple, low-cost, and high-throughput method to age-grade mosquitoes by computing the pixel intensity (PI) of wing photos, which reflects wing scale loss over time. Here the technique was refined and used to understand wild Anopheles gambiae population structures from the RIMDAMAL II clinical trial. Wing photos from lab-reared An. gambiae had narrower PI ranges compared to wild An. gambiae s.l., but the PI distributions reflected wild population structures where most have lower PI values and very few high PI values. A model was then fitted to samples from lab mosquitoes of known ages and used to interpolate unknown ages from the wild populations (median age of 4.96 [0.8-14.93] days old). Analyses from the RIMDAMAL II trial indicate that while ivermectin mass drug administrations in the intervention arm may have modestly influenced PI and predicted age relative to controls, distributions of new dual-chemistry bed nets in both arms were associated with a strong effect on PI and predicted age structure. These data suggest this method can be used to rapidly age-grade wild mosquito populations and infer the efficacy of vector control interventions.

microbiology↗

bioRxiv2021

The Role of Action Potential Waveform in Failure of Excitation Contraction Coupling

Excitation contraction coupling (ECC) is the process by which electrical excitation of muscle is converted into force generation. Depolarization of skeletal muscle resting potential contributes to failure of ECC in diseases such as periodic paralysis, ICU acquired weakness and possibly fatigue of muscle during vigorous exercise. When extracellular K+ is raised to depolarize the resting potential, failure of ECC occurs suddenly, over a range of several mV of resting potential. While some studies have hypothesized the sudden failure of ECC is due to all-or-none failure of excitation, other studies suggest failure of excitation is graded. Intracellular recordings of action potentials (APs) in individual fibers during depolarization revealed that APs do not fail in an all-or-none manner. Simultaneous imaging of Ca2+ transients during depolarization revealed failure over a narrow range of resting potentials. An AP property that closely correlated with the sudden failure of the Ca2+ transient was the integral of AP voltage with respect to time. We hypothesize the close correlation is due to the combined dependence on time and voltage of Ca2+ release from the sarcoplasmic reticulum. The quantitative relationships established between resting potential, APs and Ca2+ transients provide the foundation for future studies of depolarization-induced failure of ECC in diseases such as periodic paralysis.

physiology↗

bioRxiv2020

Partitiviruses infecting Drosophila melanogaster and Aedes aegypti exhibit efficient biparental vertical transmission

Partitiviruses are segmented, multipartite dsRNA viruses that until recently were only known to infect fungi, plants, and protozoans. Metagenomic surveys have revealed that partitivirus-like sequences are also commonly associated with arthropods. One arthropod-associated partitivirus, galbut virus, is extraordinarily common in wild populations of Drosophila melanogaster fruit flies. To begin to understand the processes that underlie this viruss high global prevalence, we established colonies of wild-caught infected flies. Infection remained at stably high levels over three years, with between 63-100% of individual flies infected. Galbut virus infects fly cells and replicates in tissues throughout infected adults, including reproductive tissues and the gut epithelium. We detected no evidence of horizontal transmission via ingestion but vertical transmission from either infected females or infected males was ~100% efficient. Vertical transmission of a related partitivirus, verdadero virus, that we discovered in a laboratory colony of Aedes aegypti mosquitoes was similarly efficient. This suggests that efficient biparental vertical transmission may be a feature of at least a subset of insect-infecting partitiviruses. To study the impact of galbut virus infection free from the confounding effect of other viruses, we generated an inbred line of flies with galbut virus as the only detectable virus infection. We were able to transmit infection experimentally via microinjection of homogenate from these galbut-only flies. This sets the stage for experiments to understand the biological impact and possible utility of partitiviruses infecting important model organisms and disease vectors. ImportanceGalbut virus is a recently discovered partitivirus that is extraordinarly common in wild populations of the model organism Drosophila melanogaster. Like most viruses discovered through metagenomics, most of the basic biological questions about this virus remain unanswered. We found that galbut virus, along with a closely related partitivirus found in Aedes aegypti mosquitoes, is transmitted from infected females or males to offspring with ~100% efficiency and can be maintained in laboratory colonies over years. This represents one of the most efficient means of virus transmission described, and likely underlies the successful spread of these viruses through insect populations. We created Drosophila lines that contained galbut virus as the only virus infection and showed that these flies can be used as a source for experimental infections. This provides insight into how arthropod-infecting partitiviruses may be maintained in nature and sets the stage for exploration of their biology and potential utility.

microbiology↗