Parasite Prevention

Whether indoor or outdoor, every cat needs protection from the pests of spring

By Eleanor Edwards, DVM

Cat Hospital of Norman

Spring is coming, and it is perhaps my favorite season. There is a promise of warm days, flower blossoms and bugs! We have to take the good with the bad, I guess. While bugs can be pesky for us, they can be even worse for our furry friends. Most people are aware of fleas and ticks, but other parasites we need to protect against for our cats are mosquitoes and the various intestinal parasites such as tapeworms, roundworms and hookworms.

We often hear from clients that their cats are inside only and, hence, not exposed. Unfortunately, this simply is not true. We bring them in on us, our shoes, our dogs, and they come inside on their own accord. We usually do not see them or know they are even around.  We worry about them being on or in our cats because they spread disease to not only our cats but, in some cases, also people. Thankfully, we have options to prevent them, which we will explore later.


I talked about fleas and ticks earlier, and these are perhaps the most common parasites we think of affecting our pets. They also have the most impact by spreading significant disease to pets and people. Fleas carry and transfer bacteria such as Mycoplasma haemofelis that causes hemolytic anemia, fever and in severe cases death. The bacteria attach themselves to the red blood cells and break them apart.

Besides anemia, it causes significant inflammation in the blood vessels; that’s never a good thing. They also carry Bartonella. This is the bacteria that causes “cat scratch fever.” As someone who has had this disease, trust me when I say it’s not fun—holy swollen painful lymph nodes! I luckily had a good immune system, a good doctor, and I didn’t turn into a character from the Ted Nugent song. In someone with a compromised immune system, this disease can be severe, so it’s best to prevent the fleas that carry it from being in your home.


Fleas also carry tapeworms. Those gross golden grains of rice on your cat’s backside likely came from your cat ingesting a flea while grooming. The tapeworm life cycle is interesting. The flea while in its larval stage must ingest a tapeworm egg. They grow and mature together. Once the flea is groomed off by your cat and swallowed, the flea is digested and the tapeworm is free to finish developing inside your cat. It is really kind of remarkable.


Ticks, much like fleas, carry and pass along significant disease to our cats and to us as well. Perhaps the disease of note most currently is Cytauxzoon felis or “bobcat fever.” This is a protozoa that also attaches to blood cells and the lining of blood vessels. It was first noted in Arkansas, and it has slowly spread to surrounding states. The reservoir is bobcats, and it rarely causes significant disease in them.

Unfortunately, in domestic cats it is often fatal. Owners bring their cats in because they are lethargic, are not eating and have a high fever. They may even notice their ears and eyes are turning yellow. This disease has an 60% survival rate approximately, but that is if the disease is caught early and treated aggressively over the course of one to two weeks. It is definitely best to keep your kitties protected from ticks. We people are not immune to the ticks coming in on us or our cats. They also carry somewhat common human ailments such as Lyme disease, Ehrlichia and Rocky Mountain spotted fever. I also have been lucky enough to be diagnosed with this last disease. Again, avoid it at all costs!


Mosquitoes also pose a significant risk to our kitties. They carry heartworm disease. Most people have heard of heartworms in dogs but not cats. Hopefully, this article helps to change that. Cats are indeed susceptible to heartworms, and, worse, there is no treatment for cats. Cat heartworm infections are different from that of dogs. Cats will oftentimes have just a few adult worms or only immature worms, and the worms do not reproduce in cats. However, that does not mean they are any less dangerous to cats. They cause respiratory disease and can cause sudden collapse and death. In fact, sudden death may be the only sign of this disease in cats. It can also cause coughing, wheezing, asthma-like symptoms, vomiting and loss of appetite.

Heartworm testing is also not as straight forward in cats as it is in dogs. The blood test may or may not pick up the presence of worms. Sometimes, they are diagnosed from an ultrasound of the heart along with clinical signs and radiographs. As I said before, there is no treatment for cats, other than supportive care and treating symptoms as they arise. This is why prevention is so important for our cat friends whether they live indoors or out. Remember, mosquitoes have no respect when it comes to staying out of the house.

Intestinal Parasites

If those parasites and the diseases they bring were not enough, here come the intestinal parasites such as hookworms, roundworms and both kinds of tapeworms commonly found in our cats. Yes, even our indoor-only cats are susceptible. Hookworms are very small and can be difficult to see in the stool. The larvae live in soil for weeks to months, and we bring them in on our shoes; dogs can also bring them in. The mother cat can also pass these worms along through her milk to her kittens. Cats being such good groomers will ingest the  larva when cleaning themselves. These worms can produce hundreds of eggs a day. The worms like to attach to the intestinal wall and create inflammation and blood loss. The larva can also burrow through our own skin and cause cutaneous larva migrans. It’s not fatal and is treatable but is very uncomfortable.

Roundworms are maybe the most commonly diagnosed worms in cats on fecal exam. They can be passed in the uterus, through the milk, by swallowing an egg or by eating a host. The most common hosts that cats eat are birds, rodents, earthworms, roaches or other insects. Clearly, there are lots of opportunities for cats to become infected. We people can also develop visceral and ocular larval migrans. Essentially, the larva can tunnel through our tissues, causing significant disease.

I mentioned tapeworms earlier. They can be transmitted through fleas but also from cats eating birds and rodents. Oftentimes, owners will not see the fleas or the critters their cats have eaten. It only takes one flea to infect a cat, and the evidence for the fleas is usually seen from the resulting tapeworms. If your cat is diagnosed with tapeworms, your veterinarian is probably going to recommend that he or she also be treated for fleas. Often, the treatments for these intestinal parasites do not kill all stages of the worms and need to be repeated in two to three weeks.

If you have read this far, thank you, and, hopefully, you aren’t too grossed out. With this information, you can now understand why your veterinarian recommends flea, tick and heartworm prevention and regular deworming for your cats. There are several different products on the market to protect our kitties, the majority being topical or oral. Most are through prescription, but there are a few safe over-the-counter options for some of the preventatives. Some of these products are administered monthly, some bi-monthly and some every three months.

Whether you are purchasing products through your veterinarian or not, please talk with him or her about the different options. Some are labeled for cats, but I would not recommend them for safety or efficacy reasons. (I have yet to find an all-natural or alternative preventative that works well and reliably while still being safe for pets and the owners. It is a hot topic for many owners, but I cannot recommend any alternatives currently. I am a firm believer of Eastern and Western medicine complementing each other but not in this case.) 

We veterinarians are here to help, and prevention is key. Your cats’ health is important and so is yours.


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