DEAR DR. FOX: I breed German shepherd dogs, and in the last year, I have taken back three dogs I had placed years prior. All three were loving, loyal and properly socialized -- no history of any aggression, toward humans or animals -- but were returned to me after sudden, tragic incidents. They were each 2 or 3 years old at the time.

One of them, Helmut, spent his first 18 months with his miniature pinscher companion. They were BFFs. The owner relates that she gave Helmut Nexgard early one morning, and at midnight, he attacked and killed the min-pin. I got similar stories about the other two: great dogs one day; the next, confused, aggressive nightmares.

I have to confess, I am no fan of drugs like Nexgard and Bravecto, having lost five of my dogs in a “Bravecto nightmare.” Here’s the progression: I gave all five dogs the chew on the same day. Three hours later, I found Shadow in a grand mal seizure; she died as I was carrying her to the car for an emergency run to the vet. I couldn’t save her. Thirty days later, Max’s liver failed. He was euthanized, followed by Cujo 12 days later. Satan developed rear-leg paralysis, and several months later, I had to make that decision to do the humane thing again. Daisy developed cancers of the liver and spleen. I treated her by putting her on a no-carb diet with immune system-boosting mushrooms and veggies, along with a 1,100-mg therapeutic CBD oil. She passed two years after her Bravecto chew and one year after her cancer diagnosis.

I filed reports with the FDA. My vet said Bravecto had nothing to do with what happened to my dogs. A Merck representative contacted my (ex-)vet, and the dogs’ health records were manipulated to show that they had underlying issues, which couldn’t be further from the truth. Yes, they were seniors between the ages of 12 and 14, but they were healthy, active dogs up to the day they received Bravecto. -- D.M., Collinsville, Oklahoma

DEAR D.M.: I appreciate the details of your experiences using the widely marketed Bravecto on your dogs. With the human-created COVID-19 pandemic taking all our attention right now, the important issue that you raise will hardly get any notice. But it is all part of the Big Problem. More and more veterinarians are blowing the whistle on the government-sanctioned use of these insecticides on companion animals. And a few are making noise over treating livestock with these drugs, with consequential harm to beneficial insects and other organisms in our soils and waters -- and all other wildlife that depend upon such nontarget organisms for food.

Veterinarian Dr. W. Jean Dodds, in this spring’s Animal Wellness journal, advises cat and dog owners to avoid isoxazoline-containing flea and tick meds, including Bravecto, Nexgard, Simparica, Credelio and the recently FDA-approved Revolution Plus.

Other products used to control companion animal parasites include neonicotinoids and avermectins, which get into the environment from animals’ coats and feces. Doctors C.J. Little and A.B. Boxall attest that “the indiscriminate prophylactic use of antiparasitic drugs in companion animals is irrational, wanton, unnecessary, irresponsible and ecologically dangerous. It should not be considered good practice” (statement from their letter, “Environmental Pollution From Pet Parasiticides,” published in the U.K.’s Veterinary Record on Jan. 25).

I consider the marketing of these and other pesticides as criminally negligent behavior, but it is an accepted -- and highly profitable -- norm for all involved, including the mainstream veterinary profession.

Of course, no one wants fleas and ticks harming their companion animals. These pests can set off pandemics and epidemics: Fleas transmitted the Black Death, and ticks infect thousands of people each year with Lyme and other diseases. And these pests are on the rise today thanks to climate change, wildlife mismanagement and the killing of natural pest-controlling birds, bats and other species.

But there are less harmful and more effective approaches. On my website, you will find a series of steps we should all take to minimize the health risks of fleas and ticks to our animals and ourselves. Go to drfoxonehealth.com and look under the title “Preventing Fleas, Ticks and Mosquitoes.”

(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 READERS: On April 22, two cats in New York belonging to different owners tested positive for infection with the coronavirus after showing signs of a mild respiratory infection. The owner of one cat had been diagnosed with COVID-19, but the owner of the other had not. This does not call for people to abandon their cats, but to be responsible and keep them indoors. There is no evidence yet that infected cats can pass the coronavirus to people.

Also on April 22, four more tigers and three lions at New York City’s Bronx Zoo tested positive for the virus. All of the big cats are receiving veterinary care and are expected to recover.

On the human front, there are fears of greater mortalities in poorer communities and refugee camps, where there is overcrowding and poor sanitation. Food riots and anarchy are predicted. The food-production system is foundering in the U.S., as slaughterhouses close down with workers succumbing to the disease.

Some are claiming that this virus spread into the human population following a lapse in security at a biotechnology laboratory in Wuhan, China. But regardless of any truth to that theory, the fact remains that wild animals for sale in China’s meat markets can carry coronaviruses and other diseases that could spread to humans, and that these markets should be prohibited.

The Centers for Disease Control and Prevention estimates that 6 out of 10 infectious diseases in people come from animals, including diseases caused by coronaviruses. Globally, zoonotic diseases have been on the rise for decades. Human interactions with animals have created a perfect storm for increased zoonotic spillover.

For more on this topic, see the article “What SARS-CoV-2 and COVID-19 Disease Are Telling Us: A Holistic Veterinary and One Health View,” posted on my website (drfoxonehealth.com).

DEAR DR. FOX: Your January column regarding feral cat management using megestrol acetate (MA) and FeralStat is problematic. I feel compelled to comment on your column as a feral cat surgeon practicing Trap-Neuter-Vaccinate-Return (TNVR), the retired Service Head of Shelter Medicine at the University of Illinois’ College of Veterinary Medicine, and a member of the Board of Directors of the Alliance for Contraception in Cats & Dogs.

Your column does mention the problem of accurate dosing of MA. There is scientific evidence that reported side effects are dose-dependent; therefore, a big concern would be controlling the daily dose of individual cats, not to mention preventing the dosing of nontarget species. For these reasons, ACC&D (and other animal welfare organizations, such as Alley Cat Allies) cannot recommend MA for use in free-roaming, outdoor and/or colony situations.

Your column also referred to cats’ relationship with wildlife. However, your readers should know that there is substantial scientific evidence that cats’ role as a “super-predator” (your words) is overstated. The reality is that by sterilizing feral cats, there are fewer cats to predate. There is also evidence that managed colonies of feral cats, those provided resources such as food, are less likely to hunt. While I am an advocate for feral cat sterilization (surgical or nonsurgical, when safe alternatives become available), FeralStat only represents false hope.

The compassionate, hardworking individuals who care for free-roaming cats in our communities want to do what is best for the cats. Regrettably, MA does not fall into that category. -- G. Robert Weedon, DVM, MPH; Community Cat Surgeon; Lakeland, Florida

DEAR DR. WEEDON: I always welcome expert opinion and commentary, and commend you for your dedicated work.

I share your reservations about using hormone-laced bait to reduce breeding of free-roaming cats, and agree that surgical sterilization of those cats who can be trapped is preferable.

I strongly disagree with you, however, that these cats, when well-fed by human volunteers, do not kill wildlife. I say this having witnessed two TNR “community cats” released onto our property, and two other stray cats, killing chipmunks and songbirds just after we had fed them (in preparation for trapping them and successfully socializing and re-homing them).

In order for the kind of programs in which you are involved to be ethically acceptable, in my opinion, there should be no wildlife present and at risk. Also, such cats are difficult to re-trap when they need veterinary care, which is a humane issue.

Your reasoning that such groups of nonbreeding cats means that there will be fewer cats in a given area is all very well if those are closed colonies, or if TNR is done on a massive scale. Otherwise, there will always be non-neutered cats moving in, competing with them for food, fighting with them and spreading disease.

The cats in such programs can only be sacrificial animals to the erroneous belief in population control when there is not, in concert, strict legislation and enforcement prohibiting owned cats being allowed off their owners’ property. This is not permitted for dog owners, and the same should hold for cat owners, many of whom need to be educated about making indoor life consonant with cats’ quality of life, health and overall well-being. Cats should only spend time outdoors in a “catio” or similar enclosure, in my opinion.

For relevant documentation, see my articles on this issue posted on my website (drfoxonehealth.com) under “CATS.”

(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: My religion prohibits me from eating certain creatures, but does not say much else about how we should respect and care for them. As a parent and teacher in a secular school (and as a vegan), I find it challenging to get across to children why they should be kind to animals. “Just because we should” isn’t enough; they don’t like “shoulds.” Then there are the contradictions, like: Why is it OK to kill some animals to eat, and to keep others as pets?

So I ask you: What religious faith do you follow, if any? And what advice can you offer to help me educate my students better? -- L.H., Cleveland, Ohio

DEAR L.H.: I embrace any religion that teaches mindfulness of all our relations and respect for life -- human and non-human, plant and animal. At the core is the spirituality of reverence for all living beings from which arises the bioethics of animal rights, protection of the natural world and avoiding harm to others in securing our basic needs.

Mainstream religions continue to limit their potential and responsibility to serve the common good because they are human-centered. The spiritual core is corrupted and displaced by materialism and objectification, especially of animals; so many species are treated as objects and commodities, and everything in the natural world as an exclusive human resource.

Theosophists proclaim that there is no religion higher than truth. But inhumanity can be rationalized and accepted if that truth is exclusive of other living beings and their inherent value and intrinsic rights. We should all examine the truths we live by, be we theists, atheists, agnostics or secular humanists. For more, see my book “The Boundless Circle: Caring for Creatures and Creation,” and view the video on my website (drfoxonehealth.com) entitled “Animals, Nature and Religion.”

For your students, there are some excellent teaching materials and other resources available from the Institute for Humane Education: Write to info@humaneeducation.org.

DEAR DR. FOX: A few years ago, our beautiful black Lab began turning a bronze color, and now her coat looks really dull and brownish red -- only the top of her head and her belly have stayed black and shiny. Our vet recommended giving her a supplement called The Missing Link over a year ago, and there has been no improvement. We have also tried different shampoos and conditioners.

Do you have any thoughts on why this has happened, and what we can do to restore her coat? She is 9 years old, and we feed her Authority Chicken and Rice for mature dogs. She has been on thyroid meds for one year, but her coat started turning years before her thyroid was ever checked. (Her thyroid was checked in the first place after a Google search on what may have caused a bald patch on her tail.) -- J.V., Springfield, Missouri

DEAR J.V.: I always look at what a dog is being fed when faced with any skin/coat issue. The main ingredients in your dry dog food are as follows:

Deboned Chicken, Chicken Meal, Brown Rice, Corn, Oat Groats, Dried Plain Beet Pulp, Corn Gluten Meal, Brewers Rice, Natural Flavor, Chicken Fat, Fish Oil, Powdered Cellulose, Dried Egg Product.

I would not feed my dog such food every day. Your dog might have some nutrient malabsorption issue, which can cause loss of hair pigment called melanin. My home-prepared dog food might make a difference, along with 6 mg melatonin at night.

Some clarification: Melanin is a pigment produced by tyrosine, whereas melatonin is a neurotransmitter produced by tryptophan. The more melanin in the hair and skin, the darker they will be. Melatonin is responsible for maintaining sleep/wake cycles, biological rhythms and the modulation and inhibition of melanin synthesis. In addition, melatonin can repair the cells, which have been damaged by stress and disease, and stop the secretion of certain hormones. Also being an antioxidant, melatonin can destroy microorganisms, and thus it is referred to as disease-fighting hormone.

Your dog could be tyrosine- and tryptophan-deficient. Genetic and other environmental factors can alter hair color; many dogs like to sun-bake, and such exposure could change hair pigmentation. In some cases, acute emotional stress can cause sudden loss of pigmentation.

Be sure your dog is given foods rich in tryptophan and tyrosine, notably eggs, cheese, cottage cheese and turkey. (But note, some dogs are allergic to eggs, which should always be lightly cooked.) These nutrients and others are destroyed by the heat processing of manufactured pet foods, and are deficient in low-grade animal protein ingredients.

(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.)