HAMILTON (AP) — The Swiss-born researcher who gained international recognition for discovering the bacteria that causes Lyme disease has died in western Montana.

A spokesman at the Daly-Leach Chapel said Wilhelm “Willy” Burgdorfer died from complications of Parkinson’s disease Monday in Hamilton. He was 89.

Burgdorfer was educated in Switzerland. He went to the Rocky Mountain Laboratory in Hamilton as a research fellow in 1951 and 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 hopes of uncovering the cause of a spotted fever outbreak in New York, 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 Dr. Tom Schwan. 

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

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

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

Burgdorfer retired in 1986 after authoring more than 225 scientific papers and traveling the world giving lectures and working with fellow scientists. He won numerous awards, including the Robert Koch Gold Medal for excellence in biomedical sciences in 1988, and received an honorary medical degree from the University of Marseille in France in 1991.

Burgdorfer was born June 27, 1925, in Basel, Switzerland, and received doctorates in zoology, parasitology and bacteriology. He served in the Swiss Army for three years before moving to the United States, where he became a citizen in 1957.

In 1953, he married Dale See of Hamilton. They had two children, William and Carl. His wife died in 2005, and he later married Lois Rohr, who survives along with his sons.