Parasitologist wins Nobel Prize

William C. Campbell a long-time AAVP member
Published on
information-circle This article is more than 3 years old

William C. Campbell, PhD, and Satoshi Omura, PhD, have earned half the 2015 Nobel Prize in physiology or medicine for helping discover the avermectin class of drugs commonly used in heartworm preventives and to treat parasitic infections in animals. While not a veterinarian, Dr. Campbell has strong ties to the profession.

William C. Campbell, PhD
William C. Campbell, PhD (Courtesy of University of Wisconsin-Madison)

A native of Ramelton, Ireland, Dr. Campbell came to the United States after completing his undergraduate studies at the University of Dublin’s Trinity College in 1952. In 1954, he received his master’s from the University of Wisconsin-Madison veterinary science program, which has been succeeded by the School of Veterinary Medicine’s Department of Comparative Biosciences. He went on to earn a doctorate in zoology from Wisconsin in 1957.

From 1957-1990, Dr. Campbell worked at the Merck Institute for Therapeutic Research, where he began his collaboration with Dr. Omura. Dr. Campbell is currently an associate fellow with the Research Institute for Scientists Emeriti program at Drew University in Madison, New Jersey, which he joined in 1990.

Early in his career at Merck, Dr. Campbell was investigating how to fight heartworm in dogs, according to a story in the spring 2009 issue of Drew Magazine. Dr. Campbell worked with cell cultures of various strains of the soil bacterium Streptomyces—discovered and cultured by Dr. Omura—and showed that a component of one of the cultures was remarkably effective against parasitic infections in dogs, horses, and livestock. Purified, the agent was named avermectin. Existing anthelmintic medications had to be given daily, but a chemical modification of the new drug, known as ivermectin, and sold by Merck as Heartgard, could be given just once a month.

Ivermectin antiparasitic drug molecule

As an agent of importance to veterinary medicine, ivermectin has been used widely in small animal practice since the 1980s, according to Dr. Sandi Sawchuk, a clinical instructor at Wisconsin’s veterinary school. “Since ivermectin hit the small animal pharmaceutical market other avermectin drugs have been discovered—selemectin, moxidectin and milbemycin. All are used not only for heartworm prevention but also intestinal parasites and ear mites. These drugs have made a huge impact on veterinary practice and pet health. I can’t imagine practicing without them,” Dr. Sawchuk said in a UW press release.

Interestingly, it was the efficacy of the drug on a horse parasite similar to the one that causes river blindness in humans that inspired Dr. Campbell to seek testing of the drug in humans, noted Dr. Bruce Christensen, a professor emeritus of parasitology at Wisconsin’s veterinary school.

Prevalent in sub-Saharan Africa and parts of Central America and South America, the parasite that causes river blindness is transmitted by black flies. The worms live just beneath the skin and eventually migrate to the eyes, causing blindness. After successful clinical trials of ivermectin as a treatment in Africa, Merck marketed the drug as Mectizan in 1987.

Because those who most need the drug are usually the least able to afford it, Dr. Campbell facilitated an international collaboration between Merck, the World Health Organization, and numerous nongovernmental organizations, including the Carter Center, to distribute the drug for free. Merck now gives away about 70 million treatments a year.

The citation from the Nobel Assembly at the Karolinska Institute, which annually confers the Nobel prizes, states that the “importance of ivermectin for improving the health and wellbeing of millions of individuals with river blindness and lymphatic filariasis, primarily in the poorest regions of the world, is immeasurable.”

Dr. Campbell and undergrad student
William Campbell, PhD, Nobel laureate, works one-on-one with a Drew University undergraduate student as part of Drew’s unique Research Institute for Scientists Emeriti program, through which senior scientists work with students in the laboratory. (Photo by Bill Denison/Drew University)

Dr. Campbell, in addition to being a longtime member of the American Association of Veterinary Parasitologists, was recognized with the AAVP-Merial Distinguished Veterinary Parasitologist Award in 1990 and was elected to the National Academy of Sciences in 2002. He also was a board member of the American Heartworm Society from 1983-1986 and was named an honorary member of the AHS in 2009, the heartworm society’s highest honor.

China’s Tu Youyou was awarded the other half of the medical Nobel this year for her discoveries related to the antimalarial drug artemisiner. She works for the China Academy of Traditional Chinese Medicine in Beijing.

To hear the phone interview with William C. Campbell, PhD, following the announcement that he won the 2015 Nobel Prize in physiology or medicine, visit