  Dengue fever is increasing in geographical range, spread by invasion of its
vector mosquitoes. The trade in second-hand tires has been implicated as a
factor in this process as they act as mobile reservoirs of mosquito eggs and
larvae. Regional transportation of tires can create linkages between rural
areas with dengue to disease-free urban areas, potentially giving rise to
outbreaks even in areas with strong local control measures. In this work we
sought to model the dynamics of mosquito transportation via the tire trade, in
particular to predict its role in causing unexpected dengue outbreaks through
vertical transmission of the virus across generations of mosquitoes. We also
aimed to identify strategies for regulating the trade in second-hand tires,
improving disease control. We created a mathematical model which captures the
dynamics of dengue between rural and urban areas, taking into account the
movement, storage time of tires, and mosquito diapause. We simulate a series of
scenarios. First a mosquito population is introduced to a dengue-free area via
movement of tires, either as single or multiple events, increasing the
likelihood of a dengue outbreak. An endemic state can be induced regardless of
whether urban conditions for an outbreak are met, and an existing endemic state
can be enhanced by vector input. Finally we assess the potential for regulation
of tire processing as a means of reducing the transmission of dengue fever
using a specific case study from Puerto Rico. Our work demonstrates the
importance of the second-hand tire trade in modulating the spread of dengue
fever across regions, in particular its role in introducing dengue to
disease-free areas. We propose that regulation of tire storage and movement can
play a crucial role in containing outbreaks and dengue spread.
