The influence of distance on movement of tabanids (Diptera: Tabanidae) between horses.

Two studies evaluated the potential use of spatial barriers to reduce the mechanical transmission of disease agents by tabanids in the Pantanal region of Brazil. Tabanids at stations separated by four different distances (5, 10, 25, and 50m) were marked. In the first study, tabanids were marked and allowed to feed until engorgement or natural interruption occurred and captured if they transferred to the other horse. A total of 2847 tabanids belonging to nine different species were marked. The percentage of tabanids that moved between horses was 10.5 at 5m, 6.8 at 10m, and 4.6 at 25m. In the second study, flies were marked, feeding was then interrupted, and the flies were released approximately 50cm from the host. A total of 1274 tabanids belonging to five different species were marked. The percentage of flies that moved between horses was 9.7 at 5m, 9.7 at 10m, and 4.6 at 25m. No tabanids transferred between animals separated by 50m in either experiment. The results of this study strongly support the recommendation that segregation of animals effectively prevents the mechanical transmission of pathogens by tabanids.