Dear Dr. Fox: I have adopted a young cat, and I wonder what cat litter is best for her. I see so many kinds at the pet store. I was given a bag of clay litter when I adopted her. It is very dusty and tracks everywhere.

R.K., Arlington County

DF: Sodium bentonite, silica and other small particle materials in clay litter might lead to respiratory disease. Unlike some other kinds of litter, clay litters do not recycle well, can clog drains and involve mining, which can be ecologically harmful.

Some kinds of litter might be contaminated with cancer-causing aflatoxin from moldy corn. A representative with World’s Best cat litter (made from corn byproduct) informs me that they do test for aflatoxin but not for glyphosate. This herbicide, widely applied by corn producers, has been designated a probable carcinogen and might play a role in chronic bowel disease. Litters made from wheat byproduct might also be contaminated with mold and agri-chemicals.

Manufactured cat litter derived from recycled wood and paper products comes from the timber industry, a major contaminator of the environment for decades. However, there are eco-friendly paper options.

According to Healthy Pet Chief Executive Ted Mischaikov, “Pulp mills have a variety of pollutants, but our fiber is sourced separate from those distilling/chemical processes and contains only water and minute amounts of white fiber. Specific to our paper pellet cat litter, I also want to stress that there is no post-consumer waste, ink or other contaminants. I am glad and proud that we can help reduce the landfill and/or burning of paper fiber from pulp mills via repurposing into healthy and safe pet products.”

Although some cat litters, such as those from Healthy Pet, can be safely and effectively processed into garden compost, they are generally best disposed of in biodegradable bags placed with household trash. Disposal by flushing down the toilet might clog drains and spread diseases such as toxoplasmosis, which has been linked to often-fatal infections in California’s sea otters and other marine mammals.

SMELLY CAT

Dear Dr. Fox:I have a 13-year-old cat that I took in after her owner died. She is the nicest little indoor cat, except for the fact that she smells like an outhouse! I believe it is more than expelling gas, because it appears to be a constant odor.

She loves to sit on my lap, but sometimes the odor becomes overwhelming. She grooms herself regularly, so I doubt that is the reason. I’ve had cats all my life yet never experienced this before. What could cause this?

R.R., Sterling

DF: Good for you for taking in this older cat after her human companion died. As an old-school veterinarian, I was trained to use all my senses, especially my nose, to help diagnose certain conditions in animals. A healthy animal should smell great and certainly have no nauseating odor.

The first possible cause to have checked is your cat’s oral cavity. Gum and tooth diseases are very common in cats. They can have bacteria and saliva with pus that gets all over their fur as they groom themselves, accounting for their nauseating odor. Think how these poor animals feel! Waste no time and have your cat seen by a veterinarian.

Other causes of cats becoming smelly include chronic kidney disease and manufactured cat foods that are not biologically appropriate for cats and yet are widely sold. For information, go to www.feline-nutrition.org and www.drfoxvet.net.

ALIEN BEHAVIOR

Dear Dr. Fox:Was my dad’s cat kidnapped by aliens? I’m hoping you can explain my father’s — now my — cat’s abrupt behavior change.

My parents, veteran cat lovers, adopted a brother and sister about 12 years ago. The sister got out and disappeared, and the brother became a complete curmudgeon. Whenever we visited, either with or without my young kids, the cat would hiss, spit and run away, or simply hide under the bed and growl at us. If I tried to pet him, he’d lash out and try to bite me. He behaved this way to everyone except my father and mother.

Fast-forward a bit: About four years ago, my mother died, and my father developed dementia. My father accidentally let the cat out of the house, and we thought he was gone. Then, he abruptly returned after two weeks and settled back in the house. Soon, he spent long periods alone when my dad went first to an apartment and then to a nursing home within a few months. I continued to feed the cat but couldn’t pet him or pick him up.

In the end, we had to choose to adopt him or take him to a shelter, because he couldn’t stay with my dad in the nursing home. We decided to adopt him. Because we had a 4-year-old female cat and a 2-year-old dog, plus two youngish kids, we figured he’d spend the rest of his life under our beds or in the basement, but that would be better than having him put down. Who would adopt such a mean cat?

This is where the alien abduction comes in. The cat that we brought into our home is a totally different cat. He purrs, he cuddles without discrimination, he doesn’t mind the dog, he plays with the other cat, he hangs out with strangers, he lets us pick him up and he purrs so loudly we have to put him out of the bedroom at night.

What on earth could cause such a swing in behavior? We are the same people. But is he the same cat? My explanation is that he was kidnapped and replaced by an alien cat during those weeks of freedom.

It has been two years since he moved in, and we still marvel that it is the same animal my parents had in their home. If you have any theories as to how a cat could change so drastically, I’d love to hear them.

C.T., Webster Groves, Mo.

DF: What an interesting and rather sad feline saga you document.

My Web site (www.drfoxvet.net) has the article “Cat Behavior: Cognitive Disassociation and Social Disruption,” which might give you some deeper understanding of cat psychology.

In essence, my interpretation of this kind of sudden personality switch is related to the individual cat’s situation and degree of fear triggered by a change in the environment and social relationships. The cat seeing your dog and cat being relaxed, friendly and not fearful of you may have facilitated his “recovery.” This is one reason why I advocate group housing for shelter cats.

Your letter is also an important reminder that so-called behavioral/temperament tests of cats alone in cages in shelters have serious limitations. Cats that undergo these tests and are considered unadoptable are either euthanized or set free under the dubious banner of trap-neuter-release, when, given more time to adapt and be with other friendly cats in a group might lead to their recovery — and increase their chances of being adopted.

CORRECTION

I recently responded to a reader who had been bitten by her dog and was diagnosed with the same infection that causes cat scratch fever. I wrongly named it bordetella. The organism responsible is actually the bacterium bartonella, which can be harbored by fleas and possibly transmitted to humans, especially children, by flea bites, as well as from bites and scratches from cats. Bordetella causes primarily respiratory diseases and is rarely transmitted from animals to humans.

Michael W. Fox, author of a newsletter and books on animal care, welfare and rights, is a veterinarian with doctoral degrees in medicine and animal behavior. Send letters to animaldocfox@gmail.com or write to him at United Feature Syndicate, 1130 Walnut St., Kansas City, Mo. 64106.

2015 United Feature Syndicate