When Janet Riordan returned home from a European vacation in January, she expected a storm of tail wagging and barking from her 7-year-old golden retriever, Reggie. The moment she saw him, she knew something was wrong.
“He came to me in my arms and appeared to be sobbing. I had never seen an animal behave like that,” said Riordan, who lives in Mequon, a suburb of Milwaukee, Wis.
A veterinarian confirmed her fears: Reggie had an aggressive form of lymphoma, a cancer of the white blood cells.
Riordan knew the toll that lymphoma could take. Four years earlier her father died of it.
“It was devastating,” Riordan said. “I never thought I would lose my dad and my dog to the same disease.”
Pet owners share their homes, their exercise habits and sometimes even their food with their four-legged companions. And increasingly, they are sharing the same diseases: Dogs and cats suffer from obesity, diabetes, heart disease, cancer and asthma, just like humans.
Now researchers are examining the role that pollutants and other environmental factors play in these dual diseases. Doctors and veterinarians have begun to work together to identify common risk factors, such as pesticides, air pollutants, cigarette smoke and household chemicals.
“Because our pets share our environments, they are exposed to many of the same pollutants as us,” said Melissa Paoloni, a veterinary oncologist at the National Cancer Institute in Maryland.
Pets, like many young children, often have higher exposures to lawn and garden pesticides and to household chemicals that can accumulate in dust or on carpets.
Scientific research is beginning to reveal some links between their environment and their health. Lawn care chemicals may increase the risk of canine lymphoma and bladder cancer. Cats exposed to flame retardants have a higher rate of thyroid disease, according to one study. And researchers are launching the Golden Retriever Lifetime Study, the largest project ever to tackle disease prevention and treatment in dogs.
“People are beginning to realize the untapped resource that companion animals present for research in human health,” said Rodney Page, director of the Colorado State University’s Animal Cancer Center.
Studies in pets can never replace studies in humans, but they can present corroborating evidence. Linking pollutants to human health effects can prove controversial, “but if we can find the same links in dogs or cats, that can have a powerful effect,” said John Reif, a Colorado State University veterinarian and epidemiologist. “It’s one more piece of evidence that the link is a real one.”
Riordan will never know what caused Reggie’s lymphoma. Golden retrievers generally have a high rate of cancer, most likely for genetic reasons. But some research suggests that environmental chemicals may play a role in the development of lymphoma in dogs.
Researchers at the University of Massachusetts and the Tufts University Cummings School of Veterinary Medicine questioned the owners of more than 700 dogs about use of pesticides. Roughly one-third of the dogs had been diagnosed with canine malignant lymphoma, while the other two-thirds had either benign tumors or were undergoing non-cancer surgeries.
Dogs whose owners reported use of professionally applied lawn pesticides were 70 percent more likely to have lymphoma, according to the study published in the journal Environmental Research in January.
Dogs also were at higher risk of lymphoma if their owners used self-applied insect growth regulators on their yards, such as Nylar, Precor and Gentrol, which control cockroaches, fleas and other pests. However, dogs exposed to flea powders, sprays and on-spot treatments were no more likely to develop lymphoma than those whose owners did not use them,