Wilhelm Burgdorfer inoculates ticks at the Rocky Mountain Laboratories of the National Institute of Allergy and Infectious Diseases in 1954. (Associated Press)

Wilhelm “Willy” Burgdorfer, a Swiss-born researcher who gained international recognition for discovering the bacteria that cause Lyme disease, died Nov. 17 in Hamilton, Mont. He was 89.

The cause was complications from Parkinson’s disease, said a spokesman at the Daly-Leach funeral home in Hamilton.

Dr. Burgdorfer went to the Hamilton-based Rocky Mountain Laboratories of the National Institute of Allergy and Infectious Diseases as a research fellow in 1951. He joined the staff as a medical entomologist six years later.

He spent decades researching the connections between animal and human diseases caused by the bites of fleas, ticks and mosquitoes.

In 1982, while he and another researcher were studying deer ticks in the hope of uncovering the cause of a spotted-fever outbreak in New York, Dr. Burgdorfer found the microorganisms, called spirochetes, that would prove to be the cause of Lyme disease.

His previous work on relapsing fever helped him recognize the cause of Lyme disease, said colleague and friend Tom Schwan.

Schwan said Dr. Burgdorfer called his most famous discovery “serendipity.” It was made while looking for something totally different and is a testament to Dr. Burgdorfer’s abilities as a scientist, he said.

The infection caused children living near Lyme, Conn., to develop rheumatoid arthritis. It also causes heart and neurological problems. The spirochete later was named Borrelia burgdorferi, after Dr. Burgdorfer.

Dr. Burgdorfer’s research opened doors to diagnose and treat the disease, Schwan said.

Dr. Burgdorfer retired in 1986 after writing more than 225 scientific papers and traveling the world, lecturing and working with fellow scientists. His awards included the Robert Koch Gold Medal for excellence in biomedical sciences in 1988.

Wilhelm Burgdorfer was born June 27, 1925, in Basel, Switzerland, and received doctorates in zoology, parasitology and bacteriology at colleges in Switzerland. He became a citizen in 1957.

His first wife, Dale See, died in 2005. Survivors include his wife, Lois Rohr; two sons from his first marriage; a brother; and two grandchildren.

— Associated Press