In a groundbreaking advance that stands to reshape our understanding of tick biology and vector-borne disease transmission, a collaborative team of researchers from Baylor College of Medicine, Texas A&M AgriLife Research, and the U.S. Department of Agriculture Agricultural Research Service (USDA-ARS) have successfully assembled the first ever whole-genome sequence of the soft tick species Ornithodoros turicata. This accomplishment, published recently in G3: Genes | Genomes | Genetics, marks a significant milestone in acarology, vector genetics, and infectious disease research, offering unprecedented insights into a tick species notorious for its role in transmitting human relapsing fever and potentially devastating agricultural pathogens such as African swine fever virus.
Soft ticks, members of the Argasidae family, have long been overshadowed by their hard tick counterparts (Ixodidae) in scientific study, primarily due to their elusive behaviors and reclusive habitats. Unlike hard ticks that attach for extended periods while feeding, soft ticks like O. turicata are nest dwellers—inhabiting animal burrows, caves, root hollows, and even human-made structures like pier and beam buildings. Their secretive lifestyle and ability to survive without a bloodmeal for over five years pose unique challenges to researchers seeking to unravel their biology and epidemiological impact.
The geographical distribution of O. turicata stretches across a remarkably broad swath of North America, with populations firmly established in Florida, Texas, Oklahoma, Kansas, and extending across the southwestern United States into Mexico. This wide range raises intriguing questions about the tick’s dispersal mechanisms, genetic diversity, and adaptability to diverse ecological niches. The availability of a high-quality chromosome-level genome assembly now allows researchers to investigate these questions at the molecular level, with the goal of shedding light on how populations of this species maintain cohesion or diverge across such a broad territory.
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Crucially, O. turicata is recognized as a vector for Borrelia turicatae, the spirochete bacterium responsible for relapsing fever in humans. This disease, characterized by recurring bouts of fever and systemic symptoms, often evades diagnosis due to the cyclical nature of its manifestation. Beyond human health concerns, O. turicata also carries agricultural significance as a potential vector of African swine fever virus (ASFV), a pathogen that has wrought havoc on swine populations globally and poses an ongoing biosecurity threat in regions where the tick and wild suids co-exist.
The genesis of this genome sequencing project traces back to a tick colony established three decades ago from specimens collected in a cave in Travis County, Texas—a site implicated in a relapsing fever case. “This colony has been invaluable for countless research endeavors,” explained Dr. Pete Teel, co-author and Regents Professor at Texas A&M AgriLife Research, underscoring the colony’s unique contribution as a genetic reservoir for the first-ever assembly of the soft tick genome. Maintaining such a colony over decades is a feat in itself, considering the complex biology and long life spans characteristic of these ticks.
From a developmental biology perspective, soft ticks present a labyrinth of challenges. Unlike hard ticks, where sex determination is outwardly discernible, O. turicata’s gender is cryptic during immature stages, becoming ascertainable only upon reaching adulthood. The life cycle begins with eggs hatching into larvae, which feed once before molting into nymphs. Soft ticks undergo as many as six nymphal instars, each requiring a blood meal to progress. The entire journey from larva to sexually mature adult typically spans approximately one year, a protracted development period further complicated by their extended fasting capacity.
One of the primary objectives driving the genome project is to uncover the genetic determinants of sex in this species, including the identification of sex chromosomes or genomic regions implicated in sex determination pathways. Understanding sex differentiation at a molecular level promises to unlock new avenues for controlling tick populations by potentially manipulating reproductive biology or targeting sex-specific vulnerabilities.
Generating a genome sequence of this scope demanded more than just sequencing; it required meticulous post-sequencing processing to ensure a highly contiguous assembly. “The goal was to produce a chromosome-level genome that researchers could reliably work with, rather than a fragmented collection of sequences,” emphasized Dr. Job Lopez, senior author and Associate Professor at Baylor College of Medicine’s National School of Tropical Medicine. Such high-quality assemblies open doors to detailed genetic and functional studies that were previously unattainable for this group.
Beyond mapping the genome, the research propels forward applications in population genetics and surveillance. With a clear genetic baseline established, investigators can investigate patterns of gene flow among populations spread across extensive geographic landscapes—the High Plains, the Southwest, Florida, and Mexico—and understand how populations adapt locally or maintain genetic connectivity. These insights are vital for tracking the spread of pathogens and developing precision control strategies.
The relevance of this work transcends academic curiosity, touching on pressing agricultural concerns. Since the early 2010s, African swine fever has emerged as a catastrophic disease, fueled in part by trade and movement of infected domestic swine. African warthogs serve as natural hosts for ASFV in an asymptomatic wildlife cycle, facilitated by tick vectors. Alarmingly, African warthogs have expanded their range into Texas, where O. turicata ticks and large feral swine populations coexist, potentially setting the stage for establishment of a natural ASFV cycle on U.S. soil. Dr. Lopez succinctly encapsulated this looming risk: “Texas has all the puzzle pieces for the emergence of a natural cycle for African swine fever virus. Understanding the tick vector is essential to thwarting that threat.”
At a molecular level, this genomic resource now enables exploration of physiological, developmental, and reproductive pathways governing O. turicata. Of particular interest is the vertical transmission of pathogens—female ticks can transmit microbes directly to offspring—thereby sustaining pathogen reservoirs independent of horizontal transmission. Dissecting the genetic architecture that enables such transmission is pivotal for interrupting disease cycles.
The high resolution of this genome assembly also facilitates elucidation of chromosomal regions linked to traits impacting vector competence, longevity, and host specificity. Such knowledge may drive innovation in vector control, from gene-targeted interventions to ecological management approaches. With the tick’s elusive nature complicating traditional control methods, molecular tools derived from genomic data offer new hope.
Ultimately, this study exemplifies the power of long-term collaboration and resource sharing, leveraging three decades of tick colony maintenance and cutting-edge sequencing technology under the USDA-ARS Ag100Pest Initiative and SCINet projects. The completion of this genome represents a leap toward comprehensive understanding and management of soft tick vectors and the diseases they perpetuate.
The team includes a roster of dedicated scientists beyond Lopez and Teel, including Mackenzie Tietjen, Amanda R. Stahlke, David Luecke, Perot Saelao, Sheina B. Sim, Scott M. Geib, Brian E. Scheffler, Anna K. Childers, and Alexander R. Kneubehl, collectively forging a path toward integrated vector management informed by genomics.
Contact information for media inquiries is available through Homa Warren at Baylor College of Medicine, providing a point of connection for further dissemination of this vital discovery.
This landmark genomic resource inaugurates a new era in the study of Ornithodoros turicata, positioning researchers to tackle unresolved questions related to vector biology, disease ecology, and host-pathogen dynamics. As threats like African swine fever loom ever larger on the horizon, the implications of this work resonate far beyond the laboratory—in public health, agriculture, and wildlife conservation.
Subject of Research: Animals
Article Title: Genome report: whole-genome assembly of the relapsing fever tick Ornithodoros turicata Dugès (Acari: Argasidae)
News Publication Date: 13-Jun-2025
Web References:
G3: Genes | Genomes | Genetics Article
Texas A&M AgriLife Research
Baylor College of Medicine – National School of Tropical Medicine
References:
Lopez, J. et al. (2025). Genome report: whole-genome assembly of the relapsing fever tick Ornithodoros turicata Dugès (Acari: Argasidae). G3: Genes | Genomes | Genetics, doi:10.1093/g3journal/jkaf103.
Keywords: Diseases and disorders, Genetics, Microbiology, Molecular biology, Parasitology
Tags: acarology advancementsagricultural pathogen transmissionArgasidae family characteristicsepidemiological impact of tickshard vs soft ticks comparisonhuman relapsing fever vectorinfectious disease geneticsOrnithodoros turicata researchsecretive tick behaviorsoft tick genome assemblytick biology insightsvector-borne disease transmission
