Cat Parasites

Internal and External Parasites in Cats


Parasites are creatures that live inside or on another organism, known as the host, and feed on it while inflicting harm on it. For a healthy cat, parasite prevention is essential, and having a broad awareness of potential health risks may help protect your cat from a variety of ailments.

Cats are infected with a range of parasites that are divided into two main categories: external and internal parasites. External parasites dwell on the hair and skin of your pet, whereas internal parasites live inside the body, like the intestines.



Fleas are tiny insects that make your cat’s skin their home and feed on their blood, creating considerable discomfort. They are regarded as one of the most dangerous pest families because, in addition to hurting pets with their incessant biting, they may transmit illnesses such as tapeworm and bacterial infections.

Flea infestations may affect any cat, but outdoor cats, cats that live with pets who go outdoors, and cats who live in multi-pet homes are more likely to get fleas. Cats are known to hide flea infestations, although frequent scratching, licking, or biting of the skin are common signs of their presence.

Fleas, thankfully, are readily treated once discovered. Your veterinarian can provide you with both safe and easy spot-on medications, as well as instructions on how to apply them and how often to use them. Flea collars are also available and can be beneficial. Finally, there are medications that you may give to your cat that will kill any fleas on them.


These arachnid parasites have eight legs and are egg-shaped, with a size range of 1mm to 10mm. They’re more frequent in areas with a lot of wildlife, which in turn makes it easier for cats to get ticks. They are active all year round, although pets are more likely to encounter them in the spring and autumn. Ticks may transmit Lyme disease and Mycoplasma to cats and even humans.

Ticks are large enough to spot while looking for lumps and sore spots on your cat’s skin with your hands. A tick feels like a little bump on the surface of their fur. The head, neck, ears, and legs are the most common places where they can be detected.

There are a variety of tick repellents on the market. Including over-the-counter medicines such as spot-on and collars, as well as prescription treatments from your veterinarian. It’s crucial to note that flea and tick treatments meant for canines should never be used on cats since they might be deadly to them.


Mites are little spider-like parasites that reside on the skin of cats and in their ear canals. They can cause severe itchiness, skin problems, and bacterial infections. The ear mite is the most common mite in cats, living in the feline ear canal, though it may also reside in other parts of the body. Scabies and trombiculosis are caused by other types of mites.

Constant scratching, head-shaking, licking, or biting are the most typical signs of mites in cats, and all of these behaviours can lead to sores, scabs, inflammation, and loss of hair.

Anti-parasite medications, monitoring, and regular grooming are the best ways to keep mites at bay in your cat. If you see indications of these parasites, you should have them evaluated by a veterinarian, who will diagnose the type of parasite and offer the appropriate course of treatment.


Internal parasites that make cats their hosts include worm-like parasites like roundworms, tapeworms, heartworms, and hookworms, as well as protozoan parasitic species like giardia, coccidia, and toxoplasma.


Giardia duodenalis is a protozoan parasite that produces giardiasis. It is not a worm, bacteria, or virus, but rather a one-celled parasitic organism that attaches itself to the intestinal wall and causes the disease. Cats become infected by swallowing the parasite’s cyst stage, which is present in the feces of infected animals.

Giardiasis can cause diarrhea, fatty stools, and weight loss in cats. The stool might be mushy or watery, with a green hue and blood in it. Mucus in the feces is quite frequent. Diarrhea is a condition that can be chronic or recurrent. Cats with the disease may become less energetic and develop a fever.

If your cat has giardiasis, your veterinarian will decide the best course of action and prescribe the drugs needed to get rid of the parasite, as well as therapy for dehydration and diarrhea if they occur. The best strategies to avoid giardiasis are to clean the environment and maintain excellent hygiene.


Coccidiosis is caused by the parasite organisms Isospora felis and Isospora rivolta, which are one-celled parasitic organisms. In most cases, cats become sick by swallowing cysts found in feces, other animals (such as mice and flies), or soil. Humans cannot be infected by the common coccidia species that infect cats.

The majority of cats infected with coccidia exhibit no symptoms, however kittens and adult cats with weakened immune systems may experience severe watery diarrhea, dehydration, vomiting, and a loss of appetite. Coccidiosis is identified only after a thorough analysis of the cat’s feces.

The veterinarian will prescribe particular antiparasitic drugs if a cat is diagnosed with coccidiosis. Other treatments may be required, although most cats will not need them.


Toxoplasmosis is caused by the single-celled parasite Toxoplasma gondii, a common parasitic infection in cats that seldom causes illness. The Toxoplasma parasite in its cyst stage found in raw meat infects the majority of cats (this will mostly be in the form of infected prey). Toxoplasmosis may be transmitted from cats to humans, and while most healthy individuals exhibit no symptoms, humans with weakened immune systems and pregnant women are the most vulnerable.

Toxoplasmosis symptoms are most likely to appear in cats with compromised immune systems, such as kittens or cats with FeLV or FIV. Fever, tiredness, and a loss of appetite are all common symptoms. Other symptoms may appear depending on where the parasite resides, such as pneumonia if it attaches to the lungs or jaundice if it attaches to the cat’s liver.

Toxoplasmosis is usually treated with antibiotics, occasionally in combination with steroids if inflammation develops. As soon as the disease is identified, your veterinarian will prescribe a medication, which should be continued for a few days after the symptoms have subsided.


In cats, roundworms, also known as ascarids, are frequent parasites. They’re big, round worms that dwell in the intestines and cause ascariasis, as the name indicates. Roundworms are transmitted to kittens and adults if they ingest larvae found in the excrement of infected animals or in prey that are egg hosts, such as birds, rats, and cockroaches. Humans can be infected with roundworms, although the illness is uncommon.

Diarrhea, tiredness, weight loss, and vomiting are the most frequent symptoms of roundworms. There may be no indications of illness in cats with few worms, although you may find them in the feces or vomit.

Because roundworm infection signs aren’t often obvious, it’s crucial to follow up with yearly wellness checkups, which should therefore include stool analysis. Once identified, ascariasis is generally simple to cure, requiring just a few doses of specialized dewormers. Because cats are constantly in danger of contracting roundworms, deworming should be done on a regular basis as protection, especially if you have an outdoor cat. It’s also a good idea to keep the litterbox clean and minimize bug and rodent infestations.


These parasites are flat, long, segmented creatures that adhere to the small intestinal walls. The Dipylidium caninum species is the most prevalent cause of infection in cats, although there are numerous other kinds that can infect them. Cats catch tapeworms after eating a flea that has been infected with the parasite; this usually occurs while grooming or as a reaction to flea bites. Tapeworms are extremely unlikely to infect humans.

The appearance of worm segments -or proglottids- in the feces and around the anus is the most visible sign of infection; there may also be vomiting, including proglottids, if the worm has gone to the stomach, and occasionally weight loss.

Deworming medicines, either oral or injectable, are used to treat tapeworms. Flea control treatments are the most recommended approach to avoid tapeworm infection in cats, especially in those that have access to the outdoors.


Heartworms, also known as Dirofilaria immitis, are protozoan parasites that reside in the heart and the blood vessels around it. Although cats are more resistant to heartworm infection than dogs, it can nonetheless occur. This sickness is spread by infected mosquito bites, which inject eggs into the pet’s blood and tissues, the larvae then travel for several months before settling in the heart and pulmonary arteries.

Heartworm infection in cats may not present visible symptoms until it is quite advanced. Rapid breathing and coughing episodes are the most prevalent observable symptoms, along with occasional vomiting, lack of appetite, and weight loss. Cats may occasionally faint, suffer seizures, or have difficulty walking. In cats, sudden collapse and death might be the earliest indications of heartworm illness.

Unfortunately, there is no particular medicine for treating heartworm disease in cats, and the drug used to treat heartworm illness in dogs is not suitable for felines. In cats, the standard therapy involves treating the symptoms and stabilizing the animal, which may entail hospitalization if the veterinarian deems it essential. Heartworm infection, on the other hand, may be readily avoided by taking heartworm preventives, which come in a variety of formulations. Before administering this medicine, always visit your veterinarian and get your cat tested for heartworm.


These parasitic worms are tiny (1/8″) and very thin, with hook-shaped mouths that they use to latch onto the intestinal walls where they feed on the blood and tissue fluids of the host. Ancylostoma tubaeforme and Ancylostoma braziliense are the most frequent worms found in cats, however, the dog hookworm can also be found (Ancylostoma caninum) infecting felines.

Hookworm infection occurs when cats ingest the eggs (often while cleaning their paws), they may also burrow through the skin, or by eating infected prey. Kittens can potentially get the disease through their mother’s milk. Internal infection is not possible in humans, however, larvae can burrow into the skin and cause illness.

Anemia, weight loss, diarrhea, a thin haircoat, and blood in the stools are the most frequent symptoms of hookworm infection in cats.

Hookworms are best identified by a stool study, and once diagnosed by a veterinarian, treatment consists of several rounds of deworming treatment. For cats at risk, parasite preventives should be used on a regular basis, as well as periodic deworming, daily litterbox cleaning, and basic cleanliness.

This article provides a summary view of some aspects you need to know about parasites in cats and how to help them. We recommend you take the time to talk in detail with one of our licensed veterinarians. They will provide the best suggestions and strategies for your pet. For an appointment please contact us at (416) 351-1212.