qPCR results from design and partial validation of three novel eDNA qPCR assays for several common North American tick (Arachnida: Ixodida) species

The range expansion of ticks to higher latitudes poses a severe threat to
human health exposing human populations who had no prior contact with
ticks to several harmful tick-borne diseases.  Early detection of
ticks in new areas is critical to help inform the public and medical
professionals of the dangers associated with tick encounters. 
Environmental DNA represents a novel survey method that could provide
reliable records of tick occurrences and timely warnings of their range
expansions.  In this study, we designed three novel eDNA qPCR
assays for three common North American tick species (Dermacentor
variabilis, Amblyomma americanum, and Ixodes scapularis) and tested them
on samples of grasses collected from grasslands and forests in
Illinois.  We provide in silico and in vitro validation of all
three assays, however we were unable to generate any positive detections
from field samples.  Our lack of eDNA detections likely stems
from low eDNA deposition rates coupled with rapid degradation in
grasslands and forests, a problem exacerbated by terrestrial eDNA sampling
methods that are limited by volume of substrate. We provide
recommendations for improving sample collection methods to increase
detection probability in future efforts.  Continued research
should focus on the viability of eDNA to detect small terrestrial
invertebrates, like ticks, and it potential as early warning indicator of
the spread of vector-borne diseases.