Health problems in passive smokers have been studied and demonstrated for years. Now, innovative veterinary work shows that pets that breathe air contaminated by tobacco combustion also suffer deterioration in their health. Specifically, exposure to cigarette smoke significantly increases the risk of bladder cancer in Scottish terrier dogs, according to a study led by researchers from the Department of Clinical Veterinary Medicine at Purdue University (United States), whose results have been published in The Veterinary Journal.
The team led by Deborah Knapp, a veterinary oncology expert at Purdue University, analyzed data from a cohort (study group) of 120 Scottish terriers (Scotties) over a three-year period. Among the results, they found that dogs exposed to cigarette smoke were six times more likely to develop bladder cancer than those who were not.
"We studied these dogs for years and then we came back and asked, 'What was the difference between those that developed cancer and those that didn't develop cancer? What were the risk factors?'" explains Deborah Knapp in statements released by her university.
Scottish terriers, famous for being the presidential pets of Presidents George W. Bush and Franklin D. Roosevelt or Jock in Disney's Lady and the Tramp, also stand out for a less happy reason: they develop bladder cancer at a rate 20 times higher than that of other dog breeds.
Deborah Knapp's team studied the selected group in search of data that relates their health to their living conditions. The goal was to discover what could prevent the development of cancer and, at the same time, use that information to see what cancer could affect in other dogs and even humans.
"We know that the genetics of Scottish terriers play a very important role in making them vulnerable to cancer," Knapp said. That strong genetic signal linked to cancer helps researchers isolate other factors that affect the likelihood that any dog, or human, will get cancer, and do so with a smaller number of dogs.
"If we were to do this study with mixed breeds of dogs, it would take hundreds and hundreds of dogs to discover this same risk, which probably exists, but this is more difficult to discern because those dogs are not genetically more exposed to bladder cancer ".
When a dog (or human) is exposed to tobacco smoke, either by breathing it or licking clothing saturated with the odor, its body absorbs the chemicals in the smoke and eliminates them through urine. This causes cancer in the urinary tract, but also offers a way to evaluate smoke exposure. The researchers analyzed the dogs' urine for a metabolite of nicotine and cotinine (a chemical formed by the breakdown of nicotine in the body), and its presence indicated that the dog had been exposed to significant amounts of tobacco smoke. .
Any time there is tobacco smoke in the same room as a dog, the dog inhales the smoke. However, some dogs also had cotinine in their urine when their owners did not smoke. In that case, the dog could have been exposed outside the home. Or it could be that his owners visited places where other people smoked and returned home with smoke on their clothes.
Not all dogs that were around smokers got cancer, and some dogs that weren't around smoke still got cancer. This is also true in humans. Half of human bladder cancer is due to smoking, but not all smokers develop bladder cancer. This discovery gives the Purdue team the opportunity to study how the combined effects of genetics inherited from parents plus environmental exposures lead to cancer.
"What we hope pet owners learn from this is that if they can reduce their dogs' exposure to smoke, that can help the dogs' health," Knapp said. "We hope they stop smoking completely, both for their health and so they can still be around their dogs, but any measures to prevent dogs from smoking will help."
