Ixodes ricinus ticks collected from the North Sea Island of Ameland, the Netherlands, were screened for the presence of Borrelia spirochaetes. The present authors used IFAT on tick gut preparations and identified Borrelia in 31 per cent of the adult ticks and 16 per cent of the nymphs collected from the dunes and 45 per cent of the nymphs collected from the forests. In vitro cultivation of Borrelia sp. isolated from the adult ticks and its subsequent recognition by B. burgdorferi-specific monoclonal antibodies in western blots, verified that this pathogen is identical with B. burgdorferi, the causative agent of
Lyme Disease. Further research is required to gain an insight into the epidemiology of the
disease and to assess its medical and veterinary significance in the Netherlands.