Location: Arthropod-borne Animal Diseases Research
2023 Annual Report
Objectives
Objective 1: Conduct surveillance and evaluate the effect of nocturnal dipteran pests on dairy cattle and estimate their impact on production by quantifying defensive behaviors. These studies are intended to inform development of insect management strategies.
Objective 2: Develop new and improved strategies to reduce transmission risk between livestock and biting midges that are vectors of Bluetongue and Epizootic Hemorrhagic Disease.
Objective 2A: Describe species abundance, diversity, and habitat associations of larval and adult Culicoides communities collected on agricultural and wild sites in Northeastern Kansas which will facilitate improved, more targeted control strategies for midges.
Objective 3: Determine the risk of bacterial pathogen transmission by house flies and develop strategies to mitigate pathogen transmission.
Approach
Among insects, Dipteran species that significantly impact livestock and human health. The studies presented here focus on three key dipteran pests: mosquitoes, biting midges and house flies. Hematophagous mosquitoes and biting midges cause direct damage to the host during blood feeding, while vector species transmit disease agents that cause morbidity and mortality. House flies are nuisance pests to humans and livestock, and annoyance is exacerbated when animals are confined in high density. Being filth-associated, house flies also disseminate and transmit a wide variety of microbes, including pathogenic or antimicrobial-resistant species, especially in operations with poor waste management. The common purpose of the proposed project is to understand key components of the host-pathogen-vector cycle to: (1) estimate pest impact on livestock and/or human health, (2) inform mitigation and management strategies for reducing host contact and pest populations and (3) ultimately reduce or prevent pathogen transmission. The mosquito projects will quantify fitness and economic impacts using wearable technology while also evaluating efficacy of novel management strategies. The biting midge research uses transcriptomics to explore how virus infection alters sensory perception and neurological function in midges, providing information key to developing or modifying control methods. The house fly studies utilize both next-generation sequencing and culture-based approaches to characterize the bacterial microbiome in flies collected from cattle operations across four US climate zones. Data will be used to perform risk assessment, pathogen and antimicrobial-resistance surveillance and to identify biotic and management variables associated with changes in the fly associated microbial community.
Progress Report
Objective 1. Research under this objective was transferred to another ARS location in 2021.
Objective 2. Single-midge RNA isolation protocols were developed to assess transcriptome-level responses of individual female biting midges to vesicular stomatitis virus or bluetongue virus infection. From this same sample, assessment of infection status, i.e., via detection of viral RNA is also accomplished. A new bioinformatic pipeline was developed which will facilitate and improve differential expression analyses.
Sub-objective 2A. Field collections of adult and larval Culicoides midges for this objective were completed in November 2022. All specimens have been identified to species, sex, and (where applicable) physiological status. 17 Culicoides species were found in larval collections and 22 species were found in adult collections. Preliminary analyses of larval data indicate that multiple putative vector species are showing an association with spring habitats, which are a particularly abundant habitat type present in this tallgrass prairie biome. Seasonality of adult collections indicate that populations typically begin emerging in April with peak activity occurring in July-August and a sharp decline through November annually. Formal data analysis is ongoing and will aim to evaluate how the community and population structure changes throughout the year in both agricultural and sylvatic habitats and how this may correspond with the likelihood of disease transmission.
Objective 3. Comparative statistical analyses of microbial communities in house flies collected from Florida, North Carolina and Tennessee dairy farms is ongoing. Initial characterizations of bacterial operational taxonomic units (i.e., molecular identification of bacteria via 16S sequencing) demonstrated common “core microbial communities” in flies from any dairy farm, irrespective of collection date and location. These shared taxa are likely attributable to commonalities in microbial communities in dairy cattle rumen microbiomes and manure (sources of many microbes for filth-breeding flies). In a separate study, culture-based approaches were used to identify and characterize multidrug (MDR) resistant bacteria carried by house flies collected at Kansas beef and dairy operations. Preliminary results suggest that the widest variety of coliform species in house flies were phenotypically dual-resistant to tetracycline and ampicillin. Also most MDR coliforms were identified as Escherichia coli, and this species also had the largest variety of MDR phenotypes. Final analysis will further evaluate the correlation between genotypic and phenotypic resistance for each coliform, as well as compare resistance mechanisms identified in coliforms with similar resistance phenotypes.
Accomplishments
1. Microbes, soil properties and animal disturbance affect the presence of biting midges. Biting midges are tiny insects that spread diseases to livestock, causing significant economic losses. Their larvae grow in semi-aquatic habitats like the shorelines of ponds and springs, but what exactly attracts midges to these places is not known. Understanding the factors that influence where midge larvae are found can help scientists and farmers develop better strategies to control their populations and therefore the diseases they transmit. ARS researchers in Manhattan, Kansas, in collaboration with Kansas State University, studied soil microbiomes, soil chemistry and midge presence in ponds and springs with different animal grazing activities. The types of habitats, grazing by animals like cattle or bison, and soil chemical properties influenced both the types of microbes that were present and whether midges would be found. Certain groups of microorganisms were found to either increase or decrease in the presence of midges, which provides important clues about the relationship between microbes and midge survival. Researchers can further explore how manipulating microbes or other aspects of the habitat can lessen or even inhibit usage by midges, which will help in managing midge-transmitted diseases.
2. House flies from Kansas, Oklahoma and Texas dairy cattle operations carry human and cattle pathogens. House flies flourish in dairy cattle operations where they have unlimited access to food and reproductive sites. Prior studies demonstrated that house flies are reservoirs and potential transmitters of bacteria both within the production operation and off site to nearby human habitation. ARS researchers in Manhattan, Kansas, collaborated with researchers at Oklahoma State University and Texas A&M University to determine the bacterial communities carried within female house flies collected from dairy cattle operations in Kansas, Oklahoma, and Texas across 4 months in 2020. Across all sites, house flies carried human pathogens that cause foodborne illness and some cattle pathogens associated with pink eye and bovine respiratory disease. Interestingly, the types of bacteria within the flies represented a snapshot of the bacteria found in their surrounding environment. These findings show that house flies not only are a problem in carrying and disseminating pathogens, but also can help us monitor threats to both livestock and human health at these cattle operations.
3. House flies have a unique mechanism for regulating immune genes that are consistently activated. House flies have evolved an impressive immune system to adapt to their filth-associated lifestyle. Unlike other insects, house flies possess a multitude of genes coding for antimicrobial defenses, providing them with a superior repertoire. The activation of these defense genes, including where, when and how much product is made, is carefully regulated to ensure optimal protection without squandering valuable energy resources. ARS scientists in Manhattan, Kansas, in collaboration with researchers from the University of Houston, discovered that some immune genes in flies are activated on an as-needed basis through classical immune response mechanisms seen among other insects. However, other genes which require constant activation use a mechanism different from these typical immune-induction pathways. This unique mechanism could play a crucial role in the fly's survival and potentially serve as a vulnerability that could be targeted for controlling flies in the future.
Review Publications
Neupane, S., Davis, T.M., Nayduch, D., McGregor, B.L. 2023. Habitat type and host grazing regimen influence the soil microbial diversity and communities within potential biting midge larval habitats. Environmental Microbiome. 18(1):5-21. https://doi.org/10.1186/s40793-022-00456-8.
Nayduch, D., Neupane, S., Pickens, V., Purvis, T.J., Olds, C. 2023. House flies are underappreciated yet important reservoirs and vectors of microbial threats to animal and human health. Microorganisms. 11(3). Article 583. https://doi.org/10.3390/microorganisms11030583.
Neupane, S., Hall, B., Brooke, G.M., Nayduch, D. 2022. Sex-specific feeding behavior of adult house flies, Musca domestica L. (Diptera: Muscidae). Journal of Medical Entomology. 60(1):7-13. https://doi.org/10.1093/jme/tjac161.
Asgari, D., Saski, C.A., Meisel, R.P., Nayduch, D. 2022. Identification of constitutively-expressed immune effectors in the house fly (Musca domestica L.) and the transcription factors that regulate them. Insect Molecular Biology. 31(6):782-797. https://doi.org/10.1111/imb.12804.
Swanson, D.A., McGregor, B.L. 2022. Life history metrics for Culex tarsalis (Diptera: Culicidae) and Culicoides sonorensis (Diptera: Ceratopogonidae) are not impacted by artificial feeding on defibrinated versus EDTA-treated blood. Journal of Medical Entomology. 60(1):224-227. https://doi.org/10.1093/jme/tjac171.
