Lyme disease, a tick-borne infection that can lead to chronic arthritis, apparently was present on eastern Long Island more than three decades before doctors recognized its existence in the mid-1970s, a new report says.

The evidence emerged from the corpses of ticks that had been collected on Long Island in the 1940s and preserved in museum collections. The dead ticks still carried genes that could be there only because they were carrying the bacterium that causes Lyme disease.Researchers from Yale University School of Medicine and the Harvard School of Public Health found the genes with a technique called the polymerase chain reaction, which copies and recopies small amounts of DNA into quantities that can be studied.

The researchers tested ticks collected in different parts of the United States between 1925 and 1951. Thirteen ticks collected in the 1940s near Montauk Point on eastern Long Island tested positive, indicating they were carrying the Lyme disease bacterium.

David H. Persing, a former Yale pathologist now with the Mayo Clinic who is the principal author of a report in last week's Science, said that for decades, Long Island doctors used the terms "Montauk knee" and "Montauk spider bite" to describe symptoms that probably resulted from Lyme disease.