Last Updated: 06/05/2025
Everything You Need to Know about Worms in Cats
Click through to learn all about worms in cats and how to keep your cat purr-fectly worm-free!
Author: Dr Carla Paszkowski BVSc (Hons)
Reading Time: 65 minutes - extensive read
It's not always a topic we like to think about, but worms in our pets are important parasites for Australian cat parents to understand. This is due to a number of reasons but one being that some worms are zoonotic, meaning they can be spread from your cat to you! Even indoor cats are at risk of contracting worms and other parasites.
Although worms can lead to serious illness this is easy to prevent with regular treatment. Read on to learn more about these unwanted parasites and learn how to keep your cat purr-fectly worm-free!
In this article, we'll discuss:
3. What Do Cat Worms Look Like?
6. What to expect after worming your cat
7. Can Humans Get Worms from Cats?
How Do Cats Get Worms?
Cats most commonly contract worms after coming into contact with parasite eggs or infected faeces. Depending on the species of worm, cats may also catch worms from their mother's milk, soil contaminated with faeces, fleas, hunting prey animals, of via cross-species transmission.
Can Indoor Cats Get Worms?
Indoor cats can still catch worms, as they may still be exposed to parasite-transmitting species such as lizards or mice. They can also potentially catch worms from soil walked in on your shoes.
Read more in our article How Do Cats Get Worms?
Types of Worms in Cats
In Australia, there are three main types of worms your can cat can get. These include:
- Intestinal worms- worms that live in the gastrointestinal tract including roundworm, hookworm and tapeworm
- Heartworm - worms that live in the heart and blood vessels
- Lungworm - worms that live in the lungs of cats
1. Intestinal worms
ROUNDWORM
Roundworms, the most common intestinal parasite in cats, are long and round with an appearance resembling spaghetti. A single female adult roundworm can shed up to 200,000 eggs per day in the faeces of infested cats, and these eggs can survive in the environment for several years. Cats can become infested with roundworm in various ways:
- Through ingesting worm eggs from the soil, generally through normal grooming
- Consuming a prey animal, often a rodent, carrying worm larvae
- Nursing from an infected mother cat (a common route of transmission for kittens)
HOOKWORM
These nasty critters can inflict damage to the intestine where they attach and feed on the cat's blood. In extreme cases this blood-feeding parasite can lead to fatal blood loss, particularly in young kittens. Transmission to cats can occur through various means:
- Ingestion of larvae from the environment
- Ingestion of prey animals containing infective larvae in their tissues
- Infection can also occur through larval penetration of the cat's skin
- Nursing from an infected queen
TAPEWORM
Tapeworms are so named for their flat ribbon-like bodies. The worms reside in the cat's gut and feed off the nutrients in there. Some cats may display no symptoms at all but others may exhibit mild signs of infestation. Sometimes you may be unfortunate enough to notice motile worm segments in your cats' faeces or the fur around their bottom. Cats become infested with tapeworm when they ingest an intermediate host infested with these parasites. The type of intermediate host varies with the different tapeworm species. For example:
- Dipylidium caninum (the flea tapeworm) infestation occurs when cats ingest an infected flea during grooming.
- Taenia taeniaeformis (the cat tapeworm) infestation occurs when cats prey on and consume rodents or birds infested with this parasite.
Read more in our article Tapeworms in Cats
2. Heartworm
Unlike dogs, cats are not the natural host of heartworm; however they can still contract the infection through a mosquito. The cat's effective immune system usually fights the infection. Many cats won't show symptoms however if symptoms do arise, they may include coughing, lack of appetite, or weight loss. Unfortunately in some cats the first sign that may be seen is sudden death.
Read more in our article Heartworm in Cats & Dogs
3. Less common species
• Lungworms are very rare in Australia. These parasites are typically transmitted through slugs, snails, often reaching cats when they hunt and consume an animal, such as a rodent or bird, that has ingested an infected mollusc or earthworm. Outdoor cats with hunting tendencies face the highest risk of contracting this parasite. While some cats can live with a high worm burden, others may exhibit respiratory signs like coughing, wheezing and breathing difficulties.
• Flukes, particularly liver flukes such as Fasciola hepatica, are parasitic flatworms that can infect various mammals, including cats. These flukes are not common in urban and metropolitan areas of Australia, but have a complex life cycle, often involving intermediate hosts such as snails and plants. Cats can become infected by ingesting contaminated water, plants, or raw fish containing the infectious stage of the fluke. Once inside the cat's body, the fluke larvae migrate through the intestinal wall into the liver, where they mature into adults and lay eggs. Infections with flukes in cats can lead to liver damage, causing symptoms such as jaundice, weight loss, and lethargy if left untreated. Preventive measures such as avoiding contaminated water sources and properly cooking food can help reduce the risk of fluke infections in cats.
• Bladder Worms are relatively rare in Australia and favour cold, cool environments in Europe and North America. Scientifically known as Capillaria feliscati, or Dioctophyme renale, bladder worms parasitic roundworms that primarily inhabit the kidneys and urinary tract of mammals, including cats. These worms have a complex life cycle that typically involves an aquatic intermediate host such as a freshwater crustacean. Cats can become infected with bladder worms by eating the intermediate host or by consuming raw fish or other aquatic animals harboring the parasite. Once ingested, the larvae of bladder worms migrate through the digestive tract and penetrate the intestinal wall, eventually reaching the abdominal cavity and migrating to the kidneys. Inside the kidneys, the worms mature and can cause significant damage, leading to symptoms such as blood in the urine, abdominal pain, and urinary tract infections. Regular deworming of cats and preventing access to raw or undercooked fish can help reduce the risk of bladder worm infections.
What do cat worms look like?
It's important to note that while some worms may be visible in the cat's faeces or around the anus, others may be present internally and not visible without the aid of a microscope. Cat worms can vary significantly in appearance depending on the species:
- Roundworms (Toxocara spp) are typically creamy white or pale brown in colour and have a spaghetti-like appearance. They can range in size from a few millimeters to several centimetres long.
- Tapeworms (Dipylidium caninum and Taenia species) are flat and segmented, resembling grains of rice or small flat cucumber seeds. The segments may sometimes be seen moving near the anus or in the cat's feces.
- Hookworms (Ancylostoma species and Uncinaria stenocephala) are small, thin worms with hook-like mouthparts. They are usually whitish or reddish-brown and are difficult to see with the naked eye.
- Whipworms (Trichuris species) are thin, whip-like worms with a tapered end. They are usually whitish or pale brown in colour and are typically smaller than roundworms or tapeworms, measuring 3-4.5 cm long.
Symptoms of Worms in Cats
Common signs of intestinal worms:
- Your cat has diarrhoea (sometimes with blood)
- Worms, or worm segments, visible in your cat's stool or around anus
- Weight loss
- Distended (pot-bellied) tummy
- Your cat is vomiting or regurgitating
- Weakness
- Anaemia
- Dull coat
- No signs (many infected cats may not display any symptoms)*
It is important to note that your cat might not show any symptoms at all, and evidence of worms may not always appear in their faeces. In certain rare instances, your cat may actually vomit up a worm - in which case it's advisable to take the expelled worm to your veterinarian for identification. You may also spot worm segments in the faeces. However, the most conventional method of diagnosing intestinal worms is by identifying worm eggs in the faeces which is done through faecal testing by your veterinarian.
Can worms cause blood in stool in cats?
Yes, blood in the stool is a common cause of worm infestation in cats.
Causes of blood in the stool in cats include:
- Parasites such as roundworms, hookworms, whipworms, and tapeworms can lead to irritation and inflammation in the gastrointestinal tract, resulting in bloody stools
- Dietary Issues: Abrupt dietary changes, food allergies, or intolerances can cause gastrointestinal upset and inflammation, leading to blood in the stool
- Inflammatory Bowel Disease (IBD) IBD is a chronic inflammatory condition of the digestive tract that can cause diarrhea, vomiting, and bloody stools in cats
- Bacterial or Viral Infections like bacterial gastroenteritis or viral enteritis can cause inflammation and bleeding in the intestines, resulting in bloody stools
- Colitis: Inflammation of the colon, known as colitis, can result from various factors such as dietary indiscretion, stress, infections, or inflammatory conditions.
- Trauma or Injury: Gastrointestinal tract trauma, such as ingesting a foreign object or rectal injury, can lead to blood in the stool
- Tumors or Polyps: Benign or malignant growths in the gastrointestinal tract, like tumors or polyps, may cause bleeding and result in bloody stools
- Blood Clotting Disorders: Disorders affecting blood clotting, such as hemophilia or thrombocytopenia, can lead to abnormal bleeding including blood in the stool
- Anal Gland Issues: While rare in cats, impaction, infection, or inflammation of the anal glands can cause discomfort and lead to blood in the stool, especially if the glands become impacted or abscessed
Do worms make cats lose weight?
Yes, weight loss is a common side effect of worm infestation and is particularly common with tapeworms. Other causes of weight loss in cats include kidney disease, hyperthyroidism, cancers such as lymphoma, infectious diseases such as Feline Immunodeficiency Virus (FIV), Stress and Anxiety, or malnutrition.
Can worms cause blood in cat's urine?
While it's uncommon for worms to directly cause blood in a cat's urine, certain types of worms or parasitic infections can indirectly contribute to urinary issues that may result in bloody urine. For example, severe infestations of certain parasites, such as bladder worms, may lead to kidney damage or urinary tract obstruction, which can manifest as bloody urine. Additionally, some parasites, like certain types of flukes, can migrate through the body and potentially cause damage to organs such as the kidneys or bladder, leading to urinary bleeding.
However, the most common causes of blood in a cat's urine are urinary tract infections, urinary stones or crystals, bladder inflammation (cystitis), trauma to the urinary tract, or underlying medical conditions such as urinary tract cancer.
Read more in our article Feline Urinary Tract Disease
Can worms cause gas in cats?
Yes, worms can potentially cause gas in cats, although it's not a common symptom associated directly with worm infestations. However, severe infestations of certain types of worms, such as roundworms or hookworms, can lead to gastrointestinal disturbances, including bloating, flatulence, and abdominal discomfort in cats. If worms are the culprit, flatulence is usually accompanied by other signs such as diarrhoea, blood in the stool, or constipation.
Can worms cause paralysis in cats?
No, not typically. It's essential to note that while worms can lead to various health issues in cats, paralysis is not a common symptom associated with most types of worm infestations. Other neurological conditions or injuries are more likely causes of paralysis in cats - and in Australia, the paralysis tick is one of the most common. If you suspect your cat is experiencing paralysis or any other severe symptoms, it's crucial to seek immediate veterinary attention for a proper diagnosis and appropriate treatment.
Read more in our article about Paralysis Ticks in Cats.
Can worms in cats cause eye problems?
Yes, certain types of worms in cats can cause eye problems, although it's not as common as other symptoms associated with worm infestations.
One example is Toxocara cati, a species of roundworm that can infect cats. In severe cases of toxocariasis (infection with Toxocara cati), the larvae of these worms can migrate through various tissues in the body, including the eyes. When the larvae reach the eye, they can cause inflammation and damage to the ocular tissues, leading to symptoms such as uveitis, retinal damage, and chorioretinitis.
Eye problems in cats are more likely to be caused by an infection, trauma, or kidney disease. If your cat is showing signs of an eye problem, seek veterinary attention for a proper diagnosis and treatment.
Can worms cause cats to vomit?
Yes, worms can potentially cause vomiting in cats, although it's not one of the most common symptoms associated with worm infestations. When cats are infested with worms, particularly severe infestations or certain types of worms, it can lead to gastrointestinal disturbances that may include vomiting, due to irritation of the gastrointestinal tract, blockages or obstruction, or secondary infections.
Much more common causes of vomiting in cats include dietary indiscretion, hairballs, gastrointestinal infections, inflammatory bowel disease, and other underlying medical conditions.
Can worms cause constipation in cats?
While it isn't a common symptom of worm infestation, worms can potentially cause constipation in cats. Severe infestations of certain types of worms or specific circumstances related to the infestation can lead to gastrointestinal disturbances, including constipation. Worms may cause constipation due to physical blockages in heavy infestations, intestinal irritation and inflammation, or dehydration.
Read more about the common causes of constipation in our article Constipation in Cats.
Can Humans Catch Worms from Cats?
Yes, humans can potentially catch certain types of worms from cats. These parasitic infections are known as zoonotic diseases, meaning they can be transmitted from animals to humans. Some common worms that can be transmitted from cats to humans include hookworm, roundworm, and tapeworm. Each worm is spread in a different way, which are outlined below.
- How do humans catch different types of worms from cats?
- Roundworms (Toxocara spp.): Roundworm eggs shed in the faeces of infected cats can contaminate the environment. Humans, particularly children, can accidentally ingest these eggs from contaminated soil, sand, or surfaces, leading to toxocariasis. Symptoms in humans can include fever, abdominal pain, coughing, and in severe cases, organ damage.
- Hookworms (Ancylostoma spp and Uncinaria spp.): Hookworm larvae can penetrate the skin of humans upon direct contact with contaminated soil or sand. This can lead to skin irritation and the development of a condition known as cutaneous larva migrans, which presents as itchy, raised tracks on the skin.)
- Tapeworms (Dipylidium caninum and Taenia spp.): Humans can become infected with tapeworms by ingesting fleas infected with tapeworm larvae. Cats can acquire tapeworms by ingesting infected rodents or grooming themselves after flea infestations. In humans, tapeworm infections may cause abdominal discomfort and, in some cases, the passage of tapeworm segments in the stool.
The lesson here is to worm your cat regularly, and wash your hands after petting or changing your cat's litter tray. It's also best not to let your children play in a sandpit or in the dirt if stray cats roam the area!
How are worms treated and prevented?
Treatment involves administering a dewormer to your cat. Regular treatment with a vet-recommended worming product is essential to help keep your cat worm-free, as they will continually be at risk for reinfection due to their natural behaviours of roaming, grooming, and hunting.
Products that treat intestinal worms include: NexGard Spectra, Milbemax, Milpro, Drontal, and Profender.
It's also vital to treat your cat for fleas, because fleas carry and transmit tapeworm. When a cat ingests a flea infected with tapeworm larvae, the larvae can develop into adult tapeworms within their intestine. Grotesquely, the same can occur inside your intestines!
*It is important to be aware that some worming products do not kill hydatid tapeworm. Tapeworm is large and more difficult to kill than smaller worm species, requiring a specific medication called Praziquantal. The selected products kill all important worm species, including tapeworm.
For more parasite protection recommendations read Which Flea and Worming Product Does Your Cat Need?.
Can you crush worming tablets for cats?
Yes, there is no contraindication for crushing worming tablets into your cat's food, provided they consume the entire dose. For tips on giving your cat a pill safely and quickly, read our article and view our helpful video How to Pill a Cat.
Can you overdose a cat on worming tablets?
Yes, it is possible to overdose a cat on worming tablets if they are administered in excessive amounts. Overdosing on worming medication can lead to various adverse effects and potential health risks for the cat. Giving a large cat dose to a small cat, or giving a dog wormer to a cat, are common reasons for overdose.
If you suspect that your cat has been overdosed on worming medication or is experiencing adverse effects after treatment, it's crucial to seek veterinary attention immediately. Contact your veterinarian or an emergency veterinary clinic for guidance on how to proceed and provide any relevant information about the type and amount of medication administered.
Can I worm my pregnant or nursing cat?
Yes! Worming is particularly important for pregnant and nursing cats due to the risk of infecting the kittens. Worming should be done at a few points throughout the pregnancy:
- When to Worm a Pregnant Cat
- Before mating, a female cat should receive her intestinal deworming as normal (for more information, read all about how often you should worm your cat.)
- During pregnancy, worming should be done every 3 weeks unless specified by your vet. It is vital you only use a wormer safe for pregnancy (see the section below for a list!)
- While nursing, the mother cat should be wormed every 3 weeks with a lactation-safe wormer and the kittens must be wormed at 2 weeks of age.
For everything to do with pregnant cat care, read our article Pregnant Cat Guide.
Is My Indoor Cat At Risk Of Getting Worms?
Many assume that if their cat remains indoors, the risk of parasitic infections is low. However, indoor cats are still vulnerable to various parasites through different avenues.
Intestinal worms: Worm eggs can be inadvertently carried indoors on shoes and clothing. Additionally, cats can also acquire tapeworm indirectly via fleas carried inside by outdoor pets or through activities like hunting lizards. Roundworms and tapeworms can also be transmitted to cats through the consumption of undercooked or raw meat or consuming pests such as small rodents which may enter the home.
Heartworm: Every indoor cat is at risk of heartworm infection, as it is transmitted via mosquitoes, which can easily access indoor spaces.
Lungworm: Indoor cats can still contract lungworm, particularly if rodents are present in the indoor environment or if the cat has access to a balcony where birds or carriers like mollusks or earthworms may be encountered.
What to Expect After Deworming Your Cat
How long do cat worming tablets take to work?
The time it takes for cat worming tablets to work can vary depending on the type of worm being targeted and the specific medication used. In general, most deworming medications for cats are designed to start working relatively quickly, with visible effects occurring within hours to days after administration.
If your cat has whipworms or roundworms, you may notice dead worms being passed in the cat's faeces shortly after treatment. Hookworms are not usually visible due to their tiny size. Tapeworms may appear in the faeces in the form of small segments, or a whole worm in its entirety within a few treatments.
Does worming cause diarrhoea in cats?
Yes, worming medication can potentially cause diarrhoea in cats as a side effect. While diarrhoea is not a common side effect of all worming medications, it can occur in some cats as a reaction to the treatment. The severity and duration of diarrhoea can vary depending on factors such as the type of medication, the cat's individual sensitivity, and the presence of other underlying health conditions.
If the diarrhoea persists or is accompanied by other concerning symptoms such as vomiting, lethargy, or blood in the stool, it's crucial to contact your veterinarian for advice.
Ultimately, worms pose a significant danger for cats and it's crucial to stay vigilant with preventative measures. If you see any signs
Further Reading
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