Blood-feeding patterns of horse flies in the French Pyrenees

Horse flies can mechanically transmit Besnoitia besnoiti, the agent of bovine besnoitiosis. Although previously limited to enzootic areas, especially the French Pyrenees Mountains, bovine besnoitiosis is now considered a re-emerging disease in western Europe. To improve understanding of the role of horse flies as mechanical vectors, this study investigated their blood-feeding ecology in the eastern French Pyrenees, in two high-altitude summer pastures whose main domestic ungulates were cattle, and in a wildlife park with native fauna. Species-specific PCR assays were conducted to identify the sources of blood meals: wild boar, horse, cattle (or bison), sheep (or mouflon), goat, red deer, roe deer and izard (or Pyrenean chamois). In La Mouline pasture, tabanids (N=20) fed on red deer (70%) and cattle (30%). In Mantet pasture, tabanids (N=24) fed on cattle (52%), red deer (20%), wild boar (16%), horse (8%) and sheep (4%). In the wildlife park, Tabanus bromius (N=32), the most abundant species collected, fed on red deer (85%), bison (9%) and wild boar (6%). Despite relatively high densities in both the pastures and in the wildlife park, small wild ungulates (izard, mouflon and roe deer) were not detected as a source of blood meals. Only two mixed blood meals were identified in two specimens of T. bromius: cattle/horse for the specimen collected in the pastures, and bison/wild boar for the specimen collected in the wildlife park. Our findings showed that tabanids display a level of opportunistic feeding behaviour, in addition to a preference for red deer, the latter being particularly true for Philipomyia aprica, the most abundant species collected in the pastures.