Date of Award

January 2022

Document Type

Open Access Thesis

Degree Name

Master of Public Health (MPH)


School of Public Health

First Advisor

Philip Armstrong

Second Advisor

Douglas Brackney


IntroductionDeer Tick Virus—a lineage of Powassan Virus—is an emerging tick-borne flavivirus associated with high rates of morbidity and mortality. Although DTV infection is rare, there has been an observed increase in the number of human cases in recent decades, necessitating more public health attention. Ixodes scapularis ticks are known to be the primary vector of DTV. However, the enzootic cycle has yet to be fully characterized and there is evidence that horizontal transmission alone may be insufficient for DTV maintenance; it is hypothesized that vertical and co-feeding transmission are also necessary for sustained transmission.

MethodsA dynamic model was developed to analyze DTV maintenance in the absence of vertical and co-feeding transmission. Multiple parameters—including host population density, host-to-larva and nymph-to-host transmission rates, and duration of host viremia—were modified to assess their impact on DTV transmission dynamics.

Results/ConclusionsDTV infection rates within the I. scapularis population declined dramatically within the tick population during the first year of the model’s run-time, and DTV prevalence dropped to zero early in the second year. The model output indicates that, in isolation, horizontal transmission is unlikely to be sufficient for sustaining DTV long-term. A combination of increased duration of host viremia, host population density, and transmission rates resulted in DTV stability within the tick population over time. Therefore, in order for viremic transmission to act as the sole form of transmission in nature, a combination of parameters must be modified, including host density, host viremic period, and/or horizontal transmission rates.


This is an Open Access Thesis.

Open Access

This Article is Open Access