The Pet Partners Story

Early authors of the Pet Partners story

Michael and Bill McCulloch


The Pet Partners story began in the mid-1970s as the brainchild of a group of pioneers and visionaries:

  • Dr. Leo K. Bustad, a veterinarian
  • Two brothers, Dr. Michael J. McCulloch, a psychiatrist and Dr. William ‘Bill’ McCulloch
  • Veterinarians R.K. Anderson DVM, Stanley L. Diesch DVM, Joe Quigley DVM, and Alton Hopkins DVM

Long before Animal-Assisted Interventions were documented to improve health these professionals aligned through a shared observation. They all saw that pets were having a positive impact on their human clients’ health and happiness. Each had observed this phenomenon in their own practices (and personal lives).

They theorized there was much more depth to what they were witnessing and recognized that anecdotal stories were not enough to capture the attention of the medical community. They concluded that scientific research was needed.

They searched the journals and found little existed. So, they committed themselves to ensuring research would be completed to further explore the effects that animals have on people’s lives.

Pet Partners Founder who developed the term human-animal bond, Leo Bustad

Leo Bustad

In 1977 the Delta Foundation was formed in Portland, Oregon with Michael J. McCulloch, MD as the President.

In 1981 the organization’s name was changed to Delta Society. This symbolized an expanding group of interested researchers and medical practitioners in both human and animal fields.

At this time Leo K. Bustad, DVM, PhD became President. Bustad is widely credited with introducing the term “human-animal bond.”

Research findings soon began to accumulate. These showed that having a companion animal helped a person in demonstrable ways. Evidence of reduced blood pressure, lower stress and anxiety levels were early findings. The stimulation of the release of chemicals known as endorphins (that trigger positive feelings) was noted when animals interacted with people. The members of Delta Society knew it was time to put their now proven theories into every day application.

In 1981, Bill McCulloch, DVM helped initiate the AVMA Human-Animal Bond Task Force to review the profession’s role in recognizing and promoting the human-animal bond. This AVMA Committee continues to this day.

Delta Society leaders were also instrumental in helping with the passage of the Housing and Urban Rural Recovery Act of 1983. Their testimony in Washington DC and the subsequent passage of the Act by the federal government sent a strong public signal that it recognized the therapeutic value of pets in Americans’ lives.

Through the late 1980’s and early 90’s Delta Society continued to strengthen its presence in this expanding field. New initiatives were developed to build on the organization’s research foundation. These programs focused on providing direct services at the local community level.

In addition, Delta Society developed the Pet Partners® program. This was the the first comprehensive, standardized training in animal-assisted activities and therapy for volunteers and health-care professionals.

In 2012, Delta Society formally changed its name to Pet Partners® in order to convey more clearly its mission. For 35 years as Delta Society and now 5 years as Pet Partners, the organization remains focused on improving human health through positive interactions with therapy animals. The organization has now grown to over 15,000 teams across the US making approximately 3 million visits each year.

Our history is rich with ground-breaking work and we invite you to become part of the next chapter in the Pet Partners story.

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