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Communication Dans Un Congrès Année : 2011

A model for bovine babesiosis to test scenarios and control strategies

Résumé

Bovine babesiosis, due to Babesia divergens, constitute a threat to bovine and splenectomized humans. Modelling is a useful tool in epidemiology due to a model’s capacity to gather existing knowledge and test scenarios. As no model has been yet developed for this disease, this study aims at simulating babesiosis spread within a dairy herd, in order to test control scenario. Vector-borne disease modelling results from the coupling between a population dynamics submodel applied to the vector, here the tick Ixodes ricinus, widespread in Europe, and an infection submodel that represents the spread of the protozoa B. divergens. The I. ricinus population dynamics submodel considers the different involved stages (egg, larva, nymph and adult). For each stage except eggs, individuals are successively host questing, feeding and in development. Different processes (hatching, host questing, development, egg laying, mortality) are governing the dynamics. Comparison between model outputs and data collected in a woodland habitat demonstrates that the model allows a realistic simulation of questing nymph densities. This model is thereafter applied to a theoretical landscape considering three habitats: woodland, pasture and ecotone at the interface. Wild hosts, i.e. small (rodents) and large (deer) mammals, migrate between the habitats and results show that these migrations allow the presence of ticks in the pastures. Cattle are then introduced in the system, and their role is shown to be minor, although not negligible. The infection submodel considers only reservoirs of the pathogen, namely susceptible and infectious ticks and cattle. Involved processes are: transmission and acquisition of the pathogen, respectively from tick to cattle and reverse, persistence between the different stages, transovarial transmission and clearance of the pathogen in ticks and cattle. Simulations demonstrate that the model can realistically represent the infection dynamics: simulated prevalence in cattle varies between 0.12 (in winter) and 0.24 (in summer), which is consistent with literature. We use the model to test the impact of a doubling in deer density. Such an increase generates a doubled prevalence in cattle after a ten year simulation. Although deer is not a reservoir for B. divergens, this increase is due to the concomitant increase in tick density and subsequently in the number of infected ticks. This demonstrates an amplification of the infection with nonreservoir host density. The influence of acaricide is also assessed with the model. We consider that acaricide kills 90% of ticks on host at the time of application (spring peak of tick activity) but this efficiency decreases thereafter in a logistic manner. From long-term simulations, acaricide use generates a reduction by half of the prevalence in cattle but no extinction of the infection is simulated. Apart from results on babesiosis, this model constitutes a framework for other tick-borne diseases.
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Dates et versions

hal-02809401 , version 1 (06-06-2020)

Identifiants

  • HAL Id : hal-02809401 , version 1
  • PRODINRA : 44522

Citer

Thierry Hoch, Julien Goebel, Albert Agoulon, Laurence Malandrin. A model for bovine babesiosis to test scenarios and control strategies. 7. Ticks and Tick-Borne Pathogens (TTP) Conference, Aug 2011, Saragosse, Spain. 1 p. ⟨hal-02809401⟩
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