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Updated: Oct 20, 2025
Author Spotlight: Controlled Human Exposure Model for Tick Research and Lyme Disease Studies
Published on: December 1, 2023
Vector competence of human-biting ticks Ixodes scapularis, Amblyomma americanum and Dermacentor variabilis for
Rohit Sharma1,2, Duncan W Cozens1,2, Philip M Armstrong1,2
1Center for Vector Biology & Zoonotic Diseases, The Connecticut Agricultural Experiment Station, 123 Huntington St, New Haven, CT, 06511, USA.
Background:
Powassan virus (POWV; genus Flavivirus) is the sole North American member of the tick-borne encephalitis sero-complex and an increasing public health threat in the USA. Maintained in nature by Ixodes spp. ticks, POWV has also been isolated from species of other hard tick genera, yet it is unclear if these species can serve as vectors. Dermacentor variabilis and Amblyomma americanum share geographic and ecologic overlap with Ixodes spp. ticks and POWV transmission foci, raising the possibility that POWV could become established in these tick species and leading to range expansion and increased human risk. Therefore, we assessed the competency of Ixodes scapularis, D. variabilis and A. americanum for POWV lineage II (POWV II).
Methods:
Larvae from all three species were co-infested on POWV-infected Balb/c mice. The engorged larvae were allowed to molt to nymphs and screened for the presence of POWV II RNA by reverse transcription-qPCR. Eight infected nymphs from each species were allowed to individually feed on a naïve mouse. Mice were screened for the presence of POWV II RNA to determine infection status.
Results:
The results demonstrated that larvae from all three tick species were able to efficiently acquire POWV II via feeding on viremic mice, maintain infection through molting and successively transmit POWV to naïve mice at the nymphal stage at comparable rates across all three species.
Conclusions:
Our findings reveal that non-Ixodes tick species can serve as competent vectors for POWV and highlight the potential role of these species in the ecology and epidemiology of POWV. Future studies examining the possible implications of these findings on POWV epidemiology and the adaptability of POWV in these new vectors are warranted.
Insights
Non-Ixodes ticks, including Dermacentor variabilis and Amblyomma americanum, can efficiently transmit Powassan virus lineage II (POWV II). This finding expands our understanding of POWV vector competence and its potential public health impact.
Area of Science:
- Veterinary Entomology
- Arthropod-borne Diseases
- Viral Ecology
Background:
- Powassan virus (POWV) is a significant public health concern in North America, primarily transmitted by Ixodes ticks.
- The potential role of other hard tick species, such as Dermacentor variabilis and Amblyomma americanum, as POWV vectors remains largely uncharacterized.
- Understanding POWV transmission dynamics is crucial for predicting and mitigating its spread.
Purpose of the Study:
- To evaluate the vector competence of Ixodes scapularis, Dermacentor variabilis, and Amblyomma americanum for Powassan virus lineage II (POWV II).
- To determine if non-Ixodes tick species can acquire, maintain, and transmit POWV II.
- To assess the potential for range expansion and increased human risk associated with POWV transmission by these tick species.
Main Methods:
- Larval ticks of three species (I. scapularis, D. variabilis, A. americanum) were fed on POWV-infected mice.
- Engorged larvae were allowed to molt to nymphs, and their POWV II RNA presence was confirmed via RT-qPCR.
- Infected nymphs were fed on naive mice to assess transmission efficiency.
Main Results:
- Larvae of all three tick species efficiently acquired POWV II from infected mice.
- POWV II infection was maintained through the molting process from larvae to nymphs.
- Nymphs of all tested tick species successfully transmitted POWV II to naive mice at comparable rates.
Conclusions:
- Non-Ixodes tick species, specifically D. variabilis and A. americanum, are competent vectors for POWV II.
- These findings suggest a broader ecological role for various tick species in POWV maintenance and transmission.
- Further research is needed to understand the epidemiological implications of POWV adaptability in these alternative tick vectors.
