DEAR READERS: Many people believe that cats help prevent the spread of bubonic plague by killing the rats that can harbor the disease. In reality, they can help spread it.

This plague, also called the Black Death, is caused by the bacterium Yersinia pestis. It swept through Asia and Europe in the 14th century, killing over 25 million people (a third of the population) in Europe between 1347 and 1352. These days, an average of 10 human plague cases are reported each year in the United States; the majority are from New Mexico, California, Colorado and Arizona.

Yersinia pestis is maintained in the environment in a natural cycle between susceptible rodent species and their associated fleas. Commonly affected species include ground squirrels, prairie dogs, rabbits and wood rats. Cats are usually exposed to the bacteria by oral contact with secretions or tissue of an infected rodent or rabbit -- for example, eating an infected animal -- or by the bite of an infected flea.

To decrease the risk of pets and humans being exposed to plague, pet owners in areas where the disease may be found should keep their pets from roaming and hunting.

While rats and cats were blamed for the plague and killed in the Middle Ages, the disease mainly spread person to person via fleas and lice. But cats can transmit plague to humans by biting or scratching them. People can also be exposed to the illness through direct contact with an infected cat’s draining lymph node material. An infected cat may also carry fleas that can transmit Yersinia pestis to humans by biting them. If a cat has the pneumonic form of plague, it can easily be spread to humans through the air. Owners and veterinarians are at risk of contracting plague when dealing with an infected cat.

There are more than 30 other diseases cats can transmit to humans which, aside from their predation on birds and other wildlife, should mandate owned cats not being allowed to roam our neighborhoods.

DEAR DR. FOX: I am looking for any help for my 22-month-old cocker spaniel. He is my baby, but now I am afraid of him.

I gave him Bravecto one week ago, and he has become very aggressive and has attacked everyone in the house. He went directly after my grandson’s face. He appears fearful and confused at times.

This pill lasts three months. What can I do to help him and get through the next months? I cannot have family over for the holidays. Is there a detox protocol or anything I can do? -- Y.H., Fort Myers, Florida

DEAR Y.H.: This is a most distressing side effect of this widely used insecticide, which is a neurotoxin and should not be given to dogs, in my opinion. Some dogs will panic when they have a strange odor put on them, and show fear and defensive aggression when they experience side effects such as muscle tremors and incoordination.

There is also a condition known as cocker hysteria, which the drug may have triggered in a susceptible dog like yours.

I would have the vet check his thyroid function and prescribe him a low dose of Valium for five to seven days. Keep your dog quiet, with no visitors, and give him 250 mg each of milk thistle, vitamin E and vitamin B complex to help his liver detoxify the Bravecto.

Another veterinarian I consulted, Dr. Ava Frick, suggested an alternative to Valium: the natural herb valerian (namely, the Valerian Complex supplement from the Australian brand MediHerb), which can often reduce the amount of anticonvulsants and sedatives dogs are on. You could also give the dog calcium and magnesium to help calm the nerves.

Keep me posted. This is an unusual side effect of this drug, and I would like to hear from readers with similar experiences.

For details about the risks of these insecticides in our animal companions, check my website (drfoxonehealth.com) for the article entitled “Companion Animal Risks of Flea and Tick Insecticides.”

(Send all mail to animaldocfox@gmail.com or to Dr. Michael Fox in care of Andrews McMeel Syndication, 1130 Walnut St., Kansas City, MO 64106. The volume of mail received prohibits personal replies, but questions and comments of general interest will be discussed in future columns.

Visit Dr. Fox’s website at DrFoxOneHealth.com.)

DEAR DR. FOX: I’ve lost two dogs in the last two years due to illness and age.

They were 40- to 50-pound mixed breeds. One died at 12 years old from probable liver cancer, considering blood test results, and the other at 16 from a weak heart (treated) and other age-related problems.

I’ve lived in a senior community for not quite three years. In that time, it has come to my attention that there have been what I would consider an abnormal number of dogs passing away, from age 8 and up, many due to cancers. It has also come to my attention that weed killers are routinely used around the community where many of us walk our dogs. Roundup was used regularly, until recently, when another brand replaced it due to the controversy about Roundup.

What is your opinion of my suspicion that the weed killer may have contributed to the loss of at least some of these dogs and/or shortened the dogs’ lives? In particular, I’m thinking of my 12-year-old dog with liver cancer. Could his year-and-a-half exposure to weed killer have done it?

All my dogs have lived to 15 or 16 until now. I know there are other factors that can contribute, such as food, vaccinations and flea treatments, etc. Honestly, I’m somewhat fearful of getting another. -- M.J.S., South Bend, Indiana

DEAR M.J.S.: I sympathize with you over the loss of your dogs. But do consider adopting an older one, regardless of the fact that many dogs are dying at a younger age than anticipated because they developed one form of cancer or another. They are like the canaries down in the mine, alerting us to environmental carcinogens also in our food and water, which they share with us.

The high incidence of cancer in young children today is in large part due to pesticides and other carcinogens -- even in the air we breathe -- that have been blithely released for decades and approved by one government after another.

The best preventive approach, for all of us, is to use a good-quality water filter, buy organically certified foods and avoid using herbicides and insecticides in and around one’s living area, both outdoors and in. These pesticides are creating havoc ecologically and, like antibiotics, should only be used as a last resort. Seeing herbicides applied for aesthetic reasons to control so-called “weeds” means a loss of natural biodiversity, and consequential pest and disease problems.

There’s nothing better than letting indigenous wild plants, and the insects and birds who depend upon them, flourish. Get rid of monoculture lawns and decorative plants, many of which are pretreated with neonicotinoid insecticides. These plants may please the eye, but are of no ecological or food value to bees and other beneficial insects.

DEAR DR. FOX: You write about mercury being a problem for cats, especially when they are fed seafoods like tuna. Where does this mercury come from? Stopping the source may be the solution. -- Y.McF., Fort Myers, Florida

DEAR Y.McF.: Mercury can cause birth defects, cancer and brain-development disorders in humans and other animals. It accumulates in the bodies of fish when bigger fish eat smaller ones that are contaminated with this toxin (a process called bioaccumulation). Major sources of mercury are paper pulp mills that discharge into waterways, as well as coal-fired power plants that contaminate the air and waterways. The latter also emit lead and arsenic. Yet the Trump administration is now moving to roll back Obama-era regulations to limit such pollutants from being released by power plants in order to reduce costs and encourage more coal-fired power plant construction.

Mercury (as thimerosal) has also been used as a preservative in vaccines; many health experts sought to outlaw thimerosal, for good reason.

SPEECH PATHOLOGIST’S DOG COMMUNICATES WITH SOUND BOARD

Speech pathologist Christina Hunger developed a sound board that her Catahoula and blue heeler mix dog, Stella, uses to communicate. The dog presses buttons with her paws to indicate her owners’ names, different activities and basic emotions, and Stella can string words together to form short sentences. (The Daily Dot, Nov. 6)

(Send all mail to animaldocfox@gmail.com or to Dr. Michael Fox in care of Andrews McMeel Syndication, 1130 Walnut St., Kansas City, MO 64106. The volume of mail received prohibits personal replies, but questions and comments of general interest will be discussed in future columns.

Visit Dr. Fox’s website at DrFoxOneHealth.com.)

DEAR DR. FOX: I was very inspired when I read in your Animal Doctor column that you hoped your writing would ”help people accept that, just as we are spiritual beings experiencing life in human form, so these other organisms are spiritual beings experiencing life in other forms, and treat them accordingly.”

Outside of my own writings, I seldom see such sentiments regarding the Oneness of all life published in a newspaper. I was moved to read it out loud to my wife. Her face turned all soft as she said, “Oh my gosh, there’s hope.”

It is exactly as I said in my book, “Conversations With God”: “All things are One Thing. There is only One Thing, and all things are part of the One Thing There Is.”

Spotting your column in my mother-in-law’s copy of our local paper on an evening visit to her house brought me to my first awareness of you and your remarkable work. Of course, I checked out your website immediately, and found that we are saying so many of the same things to the world. I had to write you then, just to express my gratitude for the messages you are, and have been for some time, bringing to the world.

Thank you, Dr. Fox, for evidencing the courage of your convictions in the things you say and do. You are making it a better place. -- N.D.W., Medford, Oregon

DEAR N.D.W.: I know from some readers’ responses to my syndicated Animal Doctor columns that they find affirmation of their sense of kinship with all life and that we are facing an ethical and, indeed, spiritual crisis culturally and in our evolution as a species.

Others take offense, believing that only we humans are made in the image of God, and that animals and nature were created for man’s exclusive use: God-given dominion, indeed.

My slideshow on my website (drfoxonehealth.com) entitled “Animals, Nature and Religion” and my book “The Boundless Circle: Caring for Creatures and Creation” -- along with the more recent book “Animals and Nature First” -- call for the kind of stewardship of planet Earth that is necessary today, especially if we are to be worthy of the self-anointed title of Homo sapiens, “man the wise”! The “manifest destiny” and pioneer spirit of colonialism, with destructive exploitation being a presumed God-given right, is antithetical to Albert Schweitzer’s view that, “Until he extends his circle of compassion to all living things, man will not himself find peace.”

As a veterinarian, I feel it is my professional duty to address the ethical and spiritual aspects of our relationships with fellow creatures as part of the great healing, the One Health, that is long overdue.

DEAR DR. FOX: Our beloved yellow Lab will soon be 13 years old and has experienced some incontinence for the past year or so.

This has been kept in check with the prescription of Proin (25 mg, twice daily) until about a month ago. When her nightly bladder leakage reappeared last month, our doctor increased the dosage to 50 mg, twice daily, which seemed to work for a few days. She is now having these occurrences almost nightly again.

Would it be advisable to increase the dosage again, or is there possibly some better alternative? -- S.W., Forsyth, Missouri

DEAR S.W.: I would not increase the dose of Proin for your old dog. Harmful side effects can include vomiting, loss of appetite, diarrhea, excessive salivation, agitation, tiredness, vocalization, confusion, increased water consumption, weight loss, weakness, fever, panting and changes in skin color (flushing or bright pink).

I would have the dog checked for cystitis, purchase doggy diaper pads, and ask your vet to make up a prescription of DES (diethylstilbestrol). This hormonal replacement, given for a few days periodically, can help many dogs suffering from incontinence -- notably, neutered female dogs -- as I can attest with one of our own dogs.

(Send all mail to animaldocfox@gmail.com or to Dr. Michael Fox in care of Andrews McMeel Syndication, 1130 Walnut St., Kansas City, MO 64106. The volume of mail received prohibits personal replies, but questions and comments of general interest will be discussed in future columns.

Visit Dr. Fox’s website at DrFoxOneHealth.com.)