Ticks are among the most significant vectors of diseases worldwide, and their impact is increasing as climate change drives their spread into new regions. Traditional surveillance methods, while valuable, are labour-intensive, prone to delays, and often limited to specific areas. Environmental DNA (eDNA) offers a promising alternative, allowing for more rapid and scalable detection of tick populations by identifying genetic material left behind in the environment. This approach could enhance early warnings, reduce response times, and support the One Health goal of protecting human, animal, and environmental well-being.
A Promising Study
A recent study in the United States examined the potential of eDNA for monitoring three medically important tick species: American dog tick (Dermacentor variabili), Lone star tick (Amblyomma americanum), and Black-legged or Deer tick (Ixodes scapularis). The findings highlight eDNA’s role in a One Health context, which recognises the interconnected nature of human, animal, and environmental health in tackling tick-borne diseases.
The Case for Early Detection
As ticks move into previously unaffected areas, they pose growing risks to health systems and ecosystems. Warmer temperatures enable faster tick life cycles, higher reproduction rates, and longer active seasons, accelerating their geographical expansion. Early detection in these new regions allows public health agencies to launch awareness campaigns, refine diagnostic approaches, and prepare healthcare professionals.
However, standard surveillance methods can be slow. Passive surveillance relies on ticks submitted by the public, which may not reflect real-time spread. Active surveillance, though effective, is resource-intensive and can yield false negatives. These factors delay warnings and interventions. In contrast, eDNA’s scalability and sensitivity could fill critical gaps in current surveillance strategies.
Environmental DNA for Tick Monitoring
eDNA techniques detect genetic material shed by organisms into their surroundings, such as vegetation and leaf litter. Unlike traditional collection-based methods, eDNA does not require the physical capture of ticks. Instead, it identifies molecular traces left behind, potentially streamlining surveillance and enabling more timely detection.
In the US study, researchers created species-specific qPCR assays for the three target ticks. Under laboratory conditions, these assays showed high sensitivity and specificity, demonstrating their potential to detect even small amounts of tick eDNA in controlled settings. This breakthrough marks a significant advance in surveillance methodology.
Challenges in the Field
Despite promising laboratory results, field tests revealed notable challenges. Samples collected from grassland and forest sites did not yield detectable tick DNA, even though conventional drag sampling confirmed the presence of the targeted species. This shortfall reflects the inherent difficulties of gathering eDNA in terrestrial environments.
Many ticks, including the Black-legged tick and the American dog tick, spend long periods on vegetation or are buried in leaf litter, shedding minimal DNA. Environmental factors such as UV exposure and rainfall may degrade any DNA present, reducing detectability. Practical issues—like insufficient sampling of plant material and patchy DNA distribution—also limit success in collecting terrestrial eDNA.
Refining eDNA Sampling Methods
To enhance the reliability of eDNA surveillance, researchers are exploring improved sampling techniques. One suggestion involves “grass-rolling,” similar to the standard drag method, but using damp cotton sheets that pick up residual DNA over large vegetation areas. Alternatively, spraying water onto vegetation before collecting run-off for filtering may aggregate DNA fragments for easier extraction.
These techniques could increase sample sizes and boost the probability of detecting trace amounts of tick DNA. More studies—such as controlled experiments in which ticks are exposed to vegetation for set periods—would further clarify how environmental factors affect eDNA degradation, guiding field protocols.
The One Health Advantage
By offering timely insights into tick populations, eDNA complements the One Health framework. Early detection has cascading benefits:
- Human Health: Enhanced diagnostic accuracy for diseases like Lyme disease, reducing misdiagnoses and improving patient outcomes.
- Animal Health: Informed decision-making for veterinarians and wildlife managers anticipating tick-related risks to livestock and wildlife.
- Environmental Monitoring: Better understanding of shifting habitats due to climate change, aiding conservation and resource management.
Because eDNA techniques are more scalable than many current methods, they can enable frequent, proactive surveillance.
Future Directions
Further development of eDNA for tick surveillance will focus on refining sampling and preservation methods to improve reliability in field conditions. Combining eDNA with established tick detection techniques could yield a powerful hybrid approach, merging the advantages of advanced molecular tools with the proven utility of traditional methods.
As climate-driven tick expansion intensifies, innovative approaches like eDNA are vital for safeguarding public, animal, and environmental health. With continued research and field validation, eDNA has the potential to revolutionise tick monitoring, offering a flexible, efficient solution well-suited to the evolving landscape of vector-borne disease.
Leave a Reply