In a study led by Purdue veterinarian Deborah Knapp, experts have found that exposure to cigarette smoke significantly elevates the risk of bladder cancer in dogs, particularly Scottish terriers.
The researchers tracked 120 Scottish terriers over three years, revealing that those exposed to cigarette smoke were six times more likely to develop bladder cancer compared to unexposed dogs.
Investigating the risk factors
Knapp, a renowned expert in veterinary medicine and a leader in comparative oncology research, emphasized the interplay of genetics and environmental factors in cancer development.
“Cancer is a combination of what you are born with – your genetics – and what you are exposed to – your environment,” Knapp explained. “In this case, we studied these dogs for years at a time, and then we went back and asked, ‘What was different between those that developed cancer and those that did not develop cancer? What were the risk factors?’”
Genetic vulnerability to cancer
Scottish terriers are particularly prone to bladder cancer, with a rate 20 times higher than other dog breeds. Bladder cancer is often very aggressive in these dogs, similar to muscle invasive bladder cancer in humans, noted the researchers.
“We know that Scotties’ genetics play a huge role in making them vulnerable to cancer,” said Knapp. This strong genetic signal helps researchers isolate other factors that affect the likelihood of any dog, or human, getting cancer.
“If we were to do this study with mixed breeds of dogs, it would take hundreds and hundreds of dogs to uncover this same risk, which is probably there, just more difficult to discern because those dogs are not already inclined genetically to get bladder cancer.”
Focus of the study
The research team, including Scottish terrier expert Marcia Dawson, delved into the impact of tobacco smoke exposure on dogs. The experts studied 120 Scottish terriers, analyzing their health, environment, food, activity, and any factors they may affect their cancer risk.
Dogs can inhale secondhand smoke or ingest chemicals through licking smoke-infused clothing, leading to the absorption and urinary elimination of harmful compounds like nicotine metabolites.
“If someone goes out to a smoky concert or party, then comes home and their dog hops up on their lap to snuggle with them, the dog can be exposed to the particulate material in smoke through the person’s clothing,” explained Knapp.
Key findings
Some dogs showed exposure to smoke even in non-smoking households, suggesting indirect exposure through environments visited by their owners.
The study also revealed a complex relationship between smoke exposure and cancer development. Not all dogs exposed to smoke developed cancer, mirroring the variability seen in human smokers. This complexity provides the Purdue team with an opportunity to further investigate the interplay of genetics and environmental factors in cancer development.
Knapp emphasized that this discovery is a new one. Dog owners, who almost universally want the best for their dog, did not knowingly put their dogs at risk of cancer by smoking around them. However, with this new information, they may be able to better protect their pets going forward.
Encouraging results
Contrary to previous research, the experts did not find a connection between lawn chemicals and bladder cancer.
“That’s likely because we are working with pet owners who are aware of the risk of lawn chemicals, so they took precautions to keep the dogs safe, like not treating parts of the lawn where the dog tends to be or keeping the dogs off the lawn for longer,” said Knapp. “That is encouraging! People love their pets. There are people taking steps to keep their dogs healthier.”
Study implications
Ultimately, understanding the link between cigarette smoke and cancer can lead to more informed decisions to protect pets’ health.
“What we hope pet owners will take from this is that if they can reduce the exposure of their dogs to smoke, that can help the dogs’ health,” said Knapp. “We hope they stop smoking altogether, both for their health and so they will continue to be around for their dogs, but any steps to keep smoke from the dogs will help.”
The study was funded by the National Institutes of Health’s National Cancer Institute, the Scottish Terrier Club of America and gifts made to Purdue University for canine bladder cancer research.
The research is published in The Veterinary Journal.
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