Poster De Conférence Année : 2019

Brucellosis dynamics in Alpine ibex: all caused by females?

Elodie Petit
  • Fonction : Auteur
  • PersonId : 1391007
Anne Thébault

Résumé

Heterogeneity in pathogen transmission occurs when a small proportion of the population is responsible for the majority of transmission, whereas the rest of the population only generates few secondary cases. Such heterogeneity can arise at the individual level, as a result of various traits such as age, sex, behaviour, immunity or genetic. In particular, for several infectious diseases, male hosts play a key role in transmission. Quantifying the contributions of individual or classes of individuals responsible for the majority of transmission can help refine management strategies, by targeting those that are most responsible for transmission. The unique situation of the Alpine ibex (Capra ibex) population of the Bargy area (French Alps) constitutes the very first reported case of self-sustained infection with Brucella melitensis in wildlife in Europe and elsewhere. The public health and economic concerns, as well as the conservation issues for this recently restored and protected species, raise many questions in terms of disease management in this population. We developed an individual-based and metapopulation model of Brucella transmission in our population to determine the relative importance of the various transmission routes, and to quantify transmission heterogeneity among classes of individuals. This model integrated six years of demographic and epidemiological data from the study site, as well as data on space use and spatial movements from GPS collars. In particular, the population was divided in five socio-spatial units, with females always staying in their unit whereas males are more prone to move between units, especially during mating. We formulated the hypothesis that males and females could play different epidemiological roles. On the one hand, females could maintain the infection there through bacterial shedding following abortion or birth. On the other hand, males could play a role of transmission between socio-spatial units through venereal transmission during mating. The results of our model showed that the average proportion of new cases caused by bacterial shedding following abortion or birth was around 70%, whereas venereal transmission caused between 15 and 20% of new cases. Inside each socio-spatial unit, females were responsible for around 90% of new cases, confirming our hypothesis that females maintain the infection inside each unit. However, between-unit transmission happened in less than 5% of cases, and was both caused by males and females (about 40 versus 60%). Indeed, transmission happened from females to males during both the mating season and the abortion period, two periods when susceptible males moved to other units than their own and met infected females. These results were not in accordance with our hypothesis that males were responsible for between-unit transmission. Instead, it seems that, contrary to other host-pathogen systems, females are a critical group in our system, both maintaining the infection inside each unit and being responsible for most of the between-unit transmission. Understanding and quantifying this heterogeneity between genders will help designing and evaluating disease management strategies for brucellosis in Alpine ibex.
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Dates et versions

hal-04889533 , version 1 (15-01-2025)

Identifiants

  • HAL Id : hal-04889533 , version 1

Citer

Sébastien Lambert, Emmanuelle Gilot-Fromont, Carole Toïgo, Pascal Marchand, Clément Calenge, et al.. Brucellosis dynamics in Alpine ibex: all caused by females?. Rencontres annuelles du LabEx Ecofect, May 2019, Lyon, France. ⟨hal-04889533⟩
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