Cats As Sentinels of Poor Air Quality
By Mariah Smith

Throughout the years, the use of animal species as sentinels for human health problems has become more and more widespread. Many extraordinary sentinel cases have been brought to the attention of the public, and a few have become famous.

An animal sentinel is described as a nonhuman organism that can react to an environmental contaminant before the contaminant impacts humans. The term sentinel species is sometimes used interchangeably with indicator species or surrogate species.

The most well-known application using a sentinel for monitoring human health hazards is probably the proverbial canary in the coal mine. The canary was used to warn of potentially lethal carbon monoxide concentrations in coal mines. Another fascinating use of sentinels occurred in the 1950s in Japan. Cats in Minamata Bay displayed neurobehavioral symptoms from eating methylmercury-contaminated fish. The cats went into uncontrollable fits, frothing at the mouth and showing signs of greatly impaired motor coordination. The behavior of the cats was called the “dancing disease,” and although many residents of the area found it strange, they never considered the antics of the cats in regards to their own health. A few years later, some of the same symptoms of methylmercury poisoning began to show up in the human inhabitants of Minamata Bay. This case illustrates the connection between instances in animals and the possibility of associated human health risks.

There are many advantages to using a sentinel species as indicators of human health hazards. Animals share the human environment, and are therefore exposed to many of the same dangers as humans. They often consume the same foods or water as humans and breathe the same air. Animal species and humans often react to many toxic agents in similar ways, and regularly respond to the toxins by developing comparable diseases.

However, animals usually develop environmentally induced pathological conditions more rapidly than humans. Because animals generally have a shorter lifespan than humans, their diseases progress more rapidly and their susceptibility to toxic chemicals can increase more readily. Sentinel animals can provide an early warning of potential risks to humans before the human population is actually effected. All of these factors show the potential value of sentinel species; they can provide early warning of situations which may require further study, and can also suggest potential causes and effects.

Man’s best friend may be a dog, but American Veterinary Medical Association statistics show that cats are the favorite pet in the US; with nearly 79 million living in homes throughout the country. Since cats live in almost identical environments to their owners, the potential for their use as a sentinel species are endless.

Recently, studies have been conducted examining domesticated animals and companion animals, or pets. Dogs were looked at in regards to cancer, especially bone cancer. Bone cancer in dogs is identical to the disease in humans, but the rate at which it progresses is much faster so research can be done more quickly. Because over seventy percent of pet owners have reported treating their pets like children (1995 survey by the American Association of Animal Hospitals), owners often catch symptoms which years ago would have gone undetected and untreated. Today there are hundreds of pet specialists, and pets now have access to nearly every medical procedure that humans do.

Since the issue of air quality is an increasingly hot topic, the possibility of using cats as indicators of bad air quality may hold promise. Cats develop what is called feline asthma syndrome (FAS). FAS is a clinical condition characterized by recurrent bouts of coughing and wheezing. According to Dr. Mei Mei Welker, DMV, a practicing veterinarian at the Cats on Broadway Hospital in Missoula, MT, asthma in cats is very similar to asthma in humans.

“With most kitties, it’s associated with some sort of allergy, and it’s usually some sort of airborne allergy, either smoke in the household or mold,” she said. “It’s generally just things in the environment.”

Welker explained that the immune system overreacts to an allergen and causes the lungs to become inflamed. “It causes the smooth muscles around the airways to just clamp right up, and it also increases the mucus that’s in the airways and just makes it hard to breathe and also to cough.”

Welker said that in her opinion, cats are more sensitive to air quality than dogs.

“I would say yes [they are] because I work at a cat clinic now, but I worked at a dog and cat clinic prior to this in Portland and saw far more asthmatic kitties than dogs,” she said. “I think it has something to do with the type of cells they have in their lungs, lining the lungs. I think those cells are a little more reactive to things that are in the air.”

The health condition of cats can often parallel that of humans. Welker mentioned a case where a man, who was sick, brought in his cat who had bronchopneumonia. The two had just moved into a new apartment a few weeks before, and Welker hypothesized that there was something in their new environment that was irritating both of them.

Welker said she sees the most cases of feline asthma in the late fall or early winter.

“I attribute this to everyone closing up the house so there’s less ventilation and the air isn’t quite as clean.” She said she hasn’t really seen much of a connection between bad air quality resulting from smoke, like during the summer fire season, and a worsening of asthma. However, this observation may vary from veterinarian to veterinarian and is definitely an idea that warrants monitoring.

“The smoke might be enough to kind of irritate things a little bit and make them ultra-sensitive to other things in the environment,” she said. “They may not be specifically allergic to the smoke, but it might cause inflammation that makes them really sensitive to other things.”

Oftentimes, cat owners may not bring their cats in for treatment because they aren’t aware that they have asthma. Welker said there are most likely a substantial number of cats that aren’t brought in for observation.

“A lot of times the coughing that they do when they’re beginning to have asthma sounds a lot like when they have a hairball, so a lot of the time they’ll just keep on giving hairball medication and eventually the cough goes away,” she said. “Sometimes that means the allergen has gone away or something has changed in the environment.”

Although no direct correlation between bad air quality and the health of cats in relation to humans has been proven, it is most definitely a research topic that deserves further scrutiny. Cats could potentially be used to detect and indicate poor air quality. They may even eventually become as important a sentinel species as dogs.