Biology subjects

Olafson, P. U.

Publications and source records attributed to Olafson, P. U..

7 recordsLinked to original sources

bioRxiv2026

Genome sequencing and multi-stage, blood-feeding, and tissue-specific transcriptome atlas of the Rocky Mountain wood tick provide a critical resource for this vector

Dermacentor andersoni, the Rocky Mountain wood tick, is an important vector for pathogens impacting human and animal health, including bovine anaplasmosis, Colorado tick fever, and Rocky Mountain spotted fever. A better understanding of the biology of this tick is needed for developing disease prevention and vector control strategies. A reference genome was assembled for D. andersoni using high-fidelity (HiFi) long-read PacBio sequences and Hi-C contact mapping, yielding a contiguous assembly in which most contigs matched one of 11 chromosomes. Genome annotation by the NCBI eukaryotic genome annotation pipeline revealed high gene content completeness, yielding a genome completeness score of 94.0% using the Arachnida ortholog dataset. Following genome sequencing, we identified specific genes involved in blood feeding across a range of tissue types and life stages for D. andersoni. To accomplish this, RNA-seq analysis was used to investigate differential gene expression across most organs in adult, nymphal, and larval D. andersoni before and after feeding. Based on this analysis, we identified several gene groups that are involved in blood feeding. Furthermore, we establish sex- and developmental-stage-specific transcriptional profiles. Collectively, this study advances knowledge of D. andersoni biology and enables the development of strategies to limit the spread of diseases transmitted by this tick.

genomics↗

bioRxiv2025

Transcriptome analysis of the winter tick (Dermacentor albipictus) reveals sex-specific expression patterns

The winter tick, Dermacentor albipictus, is a significant ectoparasite of ruminants across North America, posing health risks to wildlife and occasionally humans. Despite its ecological importance, limited genomic resources exist for this species. This study provides the first comprehensive transcriptome analysis of D. albipictus, focusing on early-stage embryos, sexed adults, dissected ovaries, and dissected male reproductive systems. Differential gene expression analyses revealed significant sex-biased expression patterns, and functional annotations identified candidate genes involved in sex determination. Notably, we identified the first documented case of sex-specific splicing of a doublesex-like gene in chelicerates, a mechanism previously thought to be absent in this group. This discovery suggests that ticks may share more insect-like features of sexual differentiation, with implications for understanding the evolution of sex determination pathways in arthropods These transcriptome data serve as a critical resource for understanding the biology of D. albipictus and will facilitate the development of novel genetic control strategies.

genomics↗

bioRxiv2025

Identification of Amblyomma americanum antigens after vaccination with tick extracellular vesicles in white-tailed deer

Anti-tick vaccines represent a promising alternative to chemical acaricides for the management of ticks on wildlife; however little progress has been made to produce a vaccine effective in wild hosts that are critical for tick reproduction, such as the white-tailed deer (Odocoileus virginianus; WTD). To date, most tick antigens have been tested using laboratory models (i.e. rabbits); however, their expression in wild hosts has not been confirmed. We recently tested Amblyomma americanum salivary (SG) and midgut (MG) extracellular vesicles (EVs) as vaccine candidates in WTD, which resulted in on-host female tick mortality. Using a proteomic approach, we show that these SG- and MG-EVs contain a "core-cargo" enriched in chaperones, small GTPases, actin and actin-related proteins, and other proteins previously reported in small EVs. Label-free quantitative proteomics showed significant differences in protein cargo between MG and SG-EVs (333 proteins out of 516). Pre-vaccinated and day 57 post-injection serum samples from three vaccinated and one control WTD were used to immuno-precipitate antigenic proteins from SG- and MG-EV preparations. Proteomic analysis of immunoprecipitated proteins identified thirty antigens with potential for use in anti-tick vaccines, seven of which we have categorized as high priority. These proteins represent promising candidates for anti-tick vaccine design in WTD and other wildlife hosts.

immunology↗

bioRxiv2024

Impaired humidity sensing reduces tick survival by preventing water homeostasis

Off-host periods are critical for ticks, representing a time when environmental stress, particularly dehydration, can impact tick survival. To prevent dehydration, ticks must be able to detect and move into high humidity areas to allow for water vapor uptake. Ionotropic receptor 93a (Ir93a), which is highly expressed in the front forelegs (location of Hallers organ), increases expression following dehydration, suggesting a role for the forelegs in humidity detection. Although the Hallers organ is suggested as the site of humidity detection in ticks, humidity detection has not been extensively examined for ticks. Here, we assessed the ability of ticks to sense humidity and how altered humidity detection impacts tick survival by manipulating the Hallers organ. Permanent (cutting or heat ablation) or temporary blocking (silicone covering) of the Hallers organ impairs the ability of the American dog tick, Dermacentor variabilis, to rest in areas necessary to maintain hydration. Impaired detection of humidity did not impact tick survival when individuals were held under stable optimal conditions. Still, variable conditions (low and high humidity gradient) reduced survival through dehydration stress and decreased energy reserves, as chronic water vapor uptake is energetically expensive. Field validation of these studies in D. variabilis confirmed that humidity detection is critical to tick survival. Lastly, modeling indicates impaired humidity detection will reduce questing tick populations, specifically in the adult stages. These studies confirm that the Hallers organ is critical for humidity sensing in ticks. Without this ability, tick survival will be impaired by potential dehydration or more rapid depletion of energy reserves.

physiology↗

bioRxiv2024

Evaluation of tick salivary and midgut extracellular vesicles as anti-tick vaccines in White-tailed deer (Odocoileus virginianus)

Current tick control measures are focused on the use of synthetic acaricides and personal protective measures. However, the emergence of acaricide resistance and the maintenance of tick populations in wildlife has precluded the efficient management of ticks. Thus, host-targeted, non-chemical control measures are needed to reliably reduce ticks parasitizing sylvatic reservoirs. This project aimed to evaluate extracellular vesicles (EVs) from Amblyomma americanum as vaccine candidates for white-tailed deer (Odocoileus virginianus; WTD). Salivary gland (SG) and midgut (MG) EVs were isolated by ultracentrifugation. Three deer were vaccinated with SG and MG EVs and received two boosters at days 28 and 50. Two control deer were injected with adjuvant and PBS only. On day 58, WTD were infested with 100 A. americanum nymphs, 50 females, and 50 males that were allowed to feed to repletion. On-host and off-host mortality, tick engorgement weight, nymph molting, time to oviposition, and egg hatchability were evaluated. Serum samples were recovered every seven days until the last day of tick drop off, and then at one year (Y1) and 1-year and 1-month (Y1M1). Vaccination resulted in seroconversion and significant increases in total IgG levels that remained significantly higher than controls and pre-vaccination levels at Y1 and Y1M1. No negative effects were observed in nymphs, but on-host mortality of female A. americanum was significantly higher in vaccinated animals. No effects were observed on reproductive parameters. These results indicate that proteins within female tick SG and MG vesicles are not good candidates for vaccine design against nymphs; however, the on-host adult mortality suggests that tick EVs harbor protective antigens against A. americanum females.

immunology↗

bioRxiv2024

Developmental stage and level of submersion in water impact the viability of lone star and winter tick eggs during flooding

Female ticks deposit large egg clusters that range in size from hundreds to thousands eggs each. These clusters are immobile and restricted to a deposition site, usually under leaf litter and other debris. These sites can be exposed to periodic flooding, where the cluster of tick eggs can float to the surface or remain underneath organic debris entirely submerged underwater. Here, we examined the viability of egg clusters from winter ticks, Dermacentor albipictus, and lone star ticks, Amblyomma americanum, when partially or fully submerged in water and in relation to the developmental stages of the eggs. In general, egg clusters that were older and partially submerged had a higher viability than fully submerged, younger eggs. A. americanum was more resistant to water exposure between the two species. These studies highlight that egg clusters for certain tick species can remain viable when exposed to water for at least two weeks. These studies also suggest that distribution by flooding of egg clusters could occur for some species and flooding will differentially impact tick egg survival based on the specific developmental stage of exposure and species.

ecology↗

bioRxiv2019

Functional genomics of the stable fly, Stomoxys calcitrans, reveals mechanisms underlying reproduction, host interactions, and novel targets for pest control

BackgroundThe stable fly, Stomoxys calcitrans, is a major blood-feeding pest of livestock that has near worldwide distribution, causing an annual cost of over $2 billion for control and product loss in the United States alone. Control of these flies has been limited to increased sanitary management practices and insecticide application for suppressing larval stages. Few genetic and molecular resources are available to help in developing novel methods for controlling stable flies.\n\nResultsThis study examines stable fly biology by utilizing a combination of high-quality genome sequencing, microbiome analyses, and RNA-seq analyses targeting multiple developmental stages and tissues. In conjunction, manual curation of over 1600 genes was used to examine gene content related to stable fly reproduction, interactions with their host, host-microbe dynamics, and putative routes for control. Most notable was establishment of reproduction-associated genes and identification of expanded vision, chemosensation, immune repertoire, and metabolic detoxification pathway gene families.\n\nConclusionsThe combined sequencing, assembly, and curation of the male stable fly genome followed by RNA-seq and downstream analyses provide insights necessary to understand the biology of this important pest. These resources and knowledge will provide the groundwork for expanding the tools available to control stable fly infestations. The close relationship of Stomoxys to other blood-feeding (Glossina) and non-blood-feeding flies (medflies, Drosophila, house flies) will allow for understanding the evolution of blood feeding among Cyclorrhapha flies.

genomics↗