Willy Burgdorfer investigated tick-borne infectious diseases. In 1982 he and collaborators reported a spirochaete isolated from ticks associated with Lyme disease. Infected ticks produced persistent skin lesions in rabbits, and patients' blood serum contained antibodies reacting with the organism in indirect immunofluorescence tests.[ref]
These were complementary observations: finding an organism in a suspected vector, observing an effect after feeding, and detecting a human immune response each supplied a different link in the causal argument. The original report cautiously proposed involvement in Lyme disease; it did not rest its conclusion solely on resemblance under a microscope.
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