The risk of Lyme borreliosis for humans and susceptible animals is affected by the abundance of tick vectors (Ixodes ricinus, I. persulcatus) which are infected by spirochetes belonging to the Borrelia burgdorferi sensu lato group (acarological risk). Understanding ecological processes, involving ticks and vertebrate hosts, may allow the prediction of acarological risk that, in turn, may be appropriately communicated to the general public, for the adoption of personal prevention measures, and to the medical community to support decision in diagnosis and treatment. In Europe, 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 dynamical model was built to gain insight into conditions underlying dominance of B. lusitaniae (transmitted by lizards) and the maintenance of B. afzelii (transmitted by wild rodents). The model showed the existence of a threshold for the fraction of larvae feeding on a rodent (lizard) below which the persistence of the B. afzelii (lusitaniae) is not possible. Results applied on data collected in Tuscany, Italy, confirmed the persistence of B. lusitaniae, which was detected in human patient in Europe, but whose pathogenicity is still to be clarified. For this combination of host and nymphs densities, the fraction of larvae feeding on rodents needed for the persistence of B. afzelii has to be significantly higher than the fraction of those feeding on lizards necessary for the endemicity of the lusitaniae genospecies. These results are in agreement with field observations. For the protection of public health, it is therefore important to be aware of the presence of B. burgdorferi sl genospecies not associated with small rodents and causing clinical forms which might be different from the most common forms of Lyme borreliosis.
The role of variable densities of vertebrate host on the persistence of Borellia lusitaniae and Borellia afzelii
FERRERI, LUCA;PERAZZO, SILVIA;VENTURINO, Ezio;GIACOBINI, Mario Dante Lucio;BERTOLOTTI, Luigi;MANNELLI, Alessandro
2013-01-01
Abstract
The risk of Lyme borreliosis for humans and susceptible animals is affected by the abundance of tick vectors (Ixodes ricinus, I. persulcatus) which are infected by spirochetes belonging to the Borrelia burgdorferi sensu lato group (acarological risk). Understanding ecological processes, involving ticks and vertebrate hosts, may allow the prediction of acarological risk that, in turn, may be appropriately communicated to the general public, for the adoption of personal prevention measures, and to the medical community to support decision in diagnosis and treatment. In Europe, 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 dynamical model was built to gain insight into conditions underlying dominance of B. lusitaniae (transmitted by lizards) and the maintenance of B. afzelii (transmitted by wild rodents). The model showed the existence of a threshold for the fraction of larvae feeding on a rodent (lizard) below which the persistence of the B. afzelii (lusitaniae) is not possible. Results applied on data collected in Tuscany, Italy, confirmed the persistence of B. lusitaniae, which was detected in human patient in Europe, but whose pathogenicity is still to be clarified. For this combination of host and nymphs densities, the fraction of larvae feeding on rodents needed for the persistence of B. afzelii has to be significantly higher than the fraction of those feeding on lizards necessary for the endemicity of the lusitaniae genospecies. These results are in agreement with field observations. For the protection of public health, it is therefore important to be aware of the presence of B. burgdorferi sl genospecies not associated with small rodents and causing clinical forms which might be different from the most common forms of Lyme borreliosis.
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