Spirochetes belonging to the Borrelia burgdoferi sensu lato (sl) group cause
Lyme Borreliosis (LB), which is the most commonly reported vector-borne
zoonosis in Europe. B. burgdorferi sl is maintained in nature in a complex
cycle involving Ixodes ricinus ticks and several species of vertebrate hosts.
The transmission dynamics of B. burgdorferi sl is complicated by the varying
competence of animals for different genospecies of spirochetes that, in turn,
vary in their capability of causing disease. In this study, a set of difference
equations simplifying the complex interaction between vectors and their hosts
(competent and not for Borrelia) is built to gain insights into conditions
underlying the dominance of B. lusitaniae (transmitted by lizards to
susceptible ticks) and the maintenance of B. afzelii (transmitted by wild
rodents) observed in a study area in Tuscany, Italy. Findings, in agreement
with field observations, highlight the existence of a threshold for the
fraction of larvae feeding on rodents below which the persistence of B. afzelii
is not possible. Furthermore, thresholds change as nonlinear functions of the
expected number of nymph bites on mice, and the transmission and recovery
probabilities. In conclusion, our model provided an insight into mechanisms
underlying the relative frequency of different Borrelia genospecies, as
observed in field studies.Comment: 14 pages, 3 figures, to be published in Theoretical Population
Biolog
