When I was a little girl, my family had a cat named Suki. I loved the animal shelter more than I did visiting the zoo, and I picked Suki out myself.

Suki (left) and Ming (right), the first cats of my childhood.  Photo courtesy Hank Weisman.

Back in the 80s, we didn’t have spot-on flea treatments or any of the other advances in flea control we do today. What we had were flea collars and flea dips you had to bathe your dog or cat in. We also had whole-house foggers that would spew chemicals into the furthest corners of your home, hoping to kill off all of the fleas.

Living in north Florida, we didn’t have the kind of harsh winter that killed off all the fleas like you get in some parts of the country, so fleas were a real problem. When Suki and our dog at the time had a persistent flea infestation, they were both subjected to frequently repeated flea dips to try to get it under control.

One Sunday morning when I was eleven years old, Suki threw up her breakfast. That’s not so unusual for a cat. But what was unusual was that a while later she started convulsing and wouldn’t stop. It went on and on, and it was terrible.

My mother sent my sister and me off to Sunday school with a carpool ride, and she went to the vet. I couldn’t concentrate on anything anyone was saying that morning. I just wanted to know how my beloved cat was. Suki never came home, and I never saw her again even to say goodbye.

Fast forward 30 years or so, and I read a description of permethrin poisoning in cats from flea products. It brought the awful scene from that Sunday morning flooding back. I had the sinking realization permethrin, found in flea dips, had killed Suki.

Permethrin Toxicity

Many flea solutions contain the pyrethrins, an insecticide with an active ingredient permethrin.  This is a synthetic form of a naturally occurring extract from the Tanacetum cinerariifolium flower, part of the chrysanthemum family.

Tanacetum cinerariifolium flower. Image courtesy Wikimedia Commons.

But instead of being a flower, permethrin is a neurotoxicant. It kills fleas by over-exciting their nerves.

Unfortunately, cats are especially sensitive to permeterhins because they can’t metabolize them quickly enough. As a result, permethrin is the most common cause of poisoning of cats in the US. They can cause neurological symptoms like tremors, seizures, and hypersalivation. In some cases, they can even cause death.

Permethrin has been eliminated from most products labeled for cats, though you may still find it today as an ingredient in flea dips labeled for use for both cats and dogs. Products are allowed to be labeled for use in cats when they contain low levels of permethrin. To be safe, always use a product specifically labeled as safe for cats, and avoid pyrethrin and permethrin ingredients.

Cats can be exposed to permethrin by being given a flea product labeled for dogs, or by spending time in close contact with a dog who has had a topical flea product applied. They can also be exposed to it when it is used in insectisides for the garden.

There is no antidote for permethrin/pyrethrin poisoning in cats. Treatment is limited to removing as much of the toxin from the skin as possible to prevent absorbing more and to supportive care.

Questionable Internet Flea Treatment Advice

Today, with the convenience of the internet, it’s easy to reach out to others who love the same things we do for advice and support. As a result, I am often among groups of animal lovers online. Far too often, I see people giving the advice that you can save money on cat flea control by buying a big dog flea medication then splitting the dose up among many cats.

Spot-on flea treamtent. Photo credit: depositphotos/Thamkc

When I see this, I try to warn that it is dangerous, pointing out permethrin poisoning is a risk if you don’t know what is in the dog flea treatment. Answers have ranged from “I’m in rescue and I know what I’m doing” to “I have done it plenty of times and nothing bad has ever happened.” I don’t want to argue with people on the internet, but I don’t want to stand by and watch cats be killed like my Suki, either.

Recently, I have started leaving Facebook groups when this issue comes up because I don’t have the heart to have the same argument over and over again. Even if the person who asked the question reads my warning, the next person who skims past trying to find a quick answer won’t, and I can’t stand to see the tragic results show up in the group later.

A Safer Flea Treatment Plan

If you need to use a flea product for your cat, consider a bath with a few drops of Dawn dish soap, which is often used on kittens too young for flea chemicals. If you use a chemical flea treatment, make sure it’s a flea product labeled for cats and doesn’t contain permethrin. If you are at all unsure about the product, ask your veterinarian about their experience with it.

Also, make sure you know how much your cat weighs. Flea treatment is generally applied by weight, and you can overdose a cat if you guess their weight wrong. Your vet will be happy to set up a weigh-in for your cat if you don’t have an appropriate scale, possibly even at no charge.

Keep your cat safe and happy this flea season!

Research and further reading

Journal of the American Veterinary Medical Association, Toxicosis in cats erroneously treated with 45 to 65% permethrin products.
Journal of Feline Medical Surgery, Feline permethrin toxicity: retrospective study of 42 cases.

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Another friend of ours just had a cat diagnosed with hyperthyroidism, and I wanted to share an overview of the things I shared with her. Having had four hyperthyroid cats in our family, this is something I’m familiar with.

What is hyperthyroidism?

Hyperthyroidism is a hormone disorder in cats, where the thyroid gland produces too much of the thyroid hormone. Cats with hyperthyroidism often lose weight, seem restless or even hyperactive. Some hyperthyroid cats can even seem aggressive.

What you can’t see from the outside is that a hyperthyroid cat’s body has to work a lot harder with all these extra thyroid hormones telling it to go, go, go. That makes the condition hard on a cat’s heart and kidneys.

The thing your vet often doesn’t say is that all hyperthyroid cats have a tumor, usually benign, in their thyroid causing it to overproduce. I had four hyperthyroid cats, including one that went through radioactive iodine treatment, and no one vet said the word tumor to me! This experience doesn’t seem unusual, and as far as I can tell, some vets leave that detail out to keep explanations simple.

What causes hyperthyroidism?

This is a question under much debate. In humans, hyperthyroidism is often caused by the autoimmune disorder Grave’s Disease or by iodine insufficiency. It’s not clear what causes it in cats. It is possible that flame retardants in our furniture and sofas may contribute to this condition in cats. There is also a theory that PBDEs and polychlorinated biphenyls (PCBs), found in the fish ingredients in cat foods, may be to blame.

How is feline hyperthyroidism treated?

There are four ways you can treat a hyperthyroid cat:

• Anti-thyroid medication
• Radioactive iodine (I-131) treatment
• Surgical thyroidectomy
• Prescription food

Anti-thyroid medication

The most common form of treatment is an anti-thyroid drug. This prevents the peroxidase enzyme and iodine in your cat’s system from being used by the thyroid gland to create as much thyroid hormone. Since this treatment reduces the amount of thyroid hormone based on the amount of the drug taken, there is often a period of trial and error to get it adjusted so that it does its job without going too far and making the cat hypothyroid, which can cause other health issues.

Daily pill box with cats printed on it. Photo credit: flickr creative commons/Lisa Risager

This treatment also does not address the underlying issue that there is a tumor in the thyroid gland which will continue to grow. Over time, the thyroid gland can become significantly enlarged, or the tumor itself can change from benign to cancerous.

Radioactive iodine (I-131) treatment

Today, treatment with radioactive iodine (I-131) is considered the treatment of choice for hyperthyroidism in cats. Since iodine is required for the thyroid gland to function correctly and generate thyroid hormones, a radioactive form of iodine that can destroy thyroid cells is used to treat the overactive thyroid. While the thyroid gland stores iodine, no other parts of the cat do, so the treatment is localized and focused to the problem gland. The tumor is destroyed, and the cat is cured of hyperthyroidism.

This kind of treatment is not invasive, but it is performed on an inpatient basis at a specialty veterinarian because of the need for the facility to have special licenses to handle the nuclear material. They generally keep a cat from 3 to 7 days while most of the radiation is emitted from the cat’s body.

My cat, Rhett, had radioactive iodine treatment for his hyperthyroidism.

I-131 treatment isn’t perfect. A small percentage of cats require a second round of treatment when the first isn’t fully effective. Additionally, despite the dose of radioactive iodine used for treatment being less than it was five years ago, there is a possibility of a cat becoming hypothyroid and being unable to create enough thyroid hormone on his own. Many cats who are hypothyroid look great and don’t show any signs of low thyroid. If they do, your vet will advise supplementing with a hormone replacement.

Surgical thyroidectomy

Before I-131 treatment was available, the removal of the thyroid gland by surgery was a treatment employed by veterinarians. Usually, both lobes of the thyroid gland are removed, since otherwise the disease usually recurs within a few years.

This is not considered the favored course of treatment, because it is a long surgery, and patients with hyperthyroidism are often senior or geriatric cats who often also have issues with their heart or kidneys that make extended anesthesia risky. Because this treatment removes both lobes of the thyroid, cats must be supplemented with thyroid hormone for the rest of their lives, which is not ideal.

This treatment is no longer in very much in the US, and some veterinary schools have even stopped teaching students how to perform it.

Prescription food

A newer form of managing hyperthyroidism is through a cat’s diet. Prescription anti-thryoid diets are available that don’t contain iodine. Without iodine, the thyroid doesn’t have all of the necessary ingredients to generate the thyroid hormone, so it can’t overproduce it.

Cat kibble. Photo credit: flickr creative commons/rfduck

This food is controversial, since it does nothing to treat or remove the tumor causing the hyperthyroidism. In order to remove the iodine, most of the protein is removed, as well, and much of the protein is provided from non-animal sources. Although the thyroid overproduction is controlled, muscle wasting continues because when the cat’s diet is too low in protein, the body starts to consume its own muscles for an energy source.

Another problem with this approach is a practical one. Cats don’t like this food. In a cat food manufacturer study, 225 cats began the trial, and after only two weeks, only 60 cats remained because the others rejected the food. Yet to work, a cat has to eat this food and only this food, with no treats or other snacks to prevent any iodine entering the cat’s diet from other food sources. This kind of discipline is hard to make possible, especially in a multi-cat home.

Every cat is different

What’s right for your hyperthyroid cat may be different than mine. What was right for one of my cats wasn’t the same for the next of my hyperthyroid cats. Your vet will guide you through the pros and cons of different treatment options.

The main thing to remember is that as scary as it is to hear that your cat has hyperthyroidism, there are lots of options for helping your cat feel better.

Research and further reading:

Journal of Feline Medicine and Surgery, Hyperthyroidism in cats: what’s causing this epidemic of thyroid disease and can we prevent it?
Environmental Science & Technology, Higher PBDE Serum Concentrations May Be Associated with Feline Hyperthyroidism in Swedish Cats
NAVC Conference 2017, Hyperthyroid Diagnosis and Treatment
American Thyroid Association, Radioactive Iodine
Insights into Veterinary Endocrinology, The Best Diet to Feed Hyperthyroid Cats

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