Biodiversity, dilution effect and tick-borne diseases: analysis of the relationship between prevalence of pathogens, tick and host diversities along a landscape gradient

The project explores the links between the ratio of wood, meadow, crop surfaces within each landscape window (considered as major environmental factors) and the biodiversity of host, vectors and pathogens. 

Among investigations on the interlinkage between biodiversity and health, as for example in the case of tick-borne diseases, the dilution effect concept hold a central place but is still debated. Indeed, numerous vertebrates species contribute to tick-borne epidemiology either as pathogens reservoirs or/and as feeding hosts for ticks. The dilution effect suggest that a high diversity of vertebrates as tick hosts should reduce infection risk due to a lower prevalence of the bacteria being the etiological agent of Lyme disease (Borrelia spp.).

Methodology

To the left, satellite picture of the “Zone Atelier Plaine & Val de Sèvre” with 3 landscape windows illustrating different ratios of wood/meadow/crop surfaces. The 3 white stars show 3 sampling sites of ticks on the vegetation within each window.

To the right, representation of the interaction among the 3 communities involved in the patho-system : the hosts (here 3 small mammals species), the vectors (here 3 tick species) and pathogens (Borrelia spp.)

BIODILUTICK tests the hypothesis that the increase of specific diversity within host and tick communities produce a dilution of Borrelia spp. and thus a  diminution of the likelihood of transmission of those bacteria to humans. The ticks are collected on the vegetation. Small mammals are captures to estimate their abundance and diversity, collect ticks attached to those animals and characterized pathogen prevalence in ticks and small mammals. Livestock (that are hosts of adult ticks) density in the sampled meadows is assessed with the help of the farmers. Finally, camera-traps are placed to determine the presence of middle size mammals (roe deer, small mammal predators such as red foxes, mustelids, feral cats…).

The different pathogens (including Borrelia spp.) are looked for in the ticks collected on the vegetation and in the small mammals.

Participants

INRAE structures

• SA Department
  • UMR BIOEPAR
• SPE Department
  • USC CEBC – Résilience

Contacts - Coordinator :

• Olivier Plantard  (UMR BIOEPAR)
• Sabrina Gaba  (UMR CEBC)