Common Internal Parasites in Cats
Even strictly indoor cats can be exposed to internal parasites, although CAPC (Companion Animal Parasite Council) notes that the likelihood is far lower than for cats that go outdoors. The following are the most common intestinal parasites in cats:
| Parasite | Transmission Route | Common Symptoms | Zoonotic |
|---|---|---|---|
| Roundworm | Swallowing eggs from the environment, through the mother's milk (kittens), eating prey | Abdominal distension, vomiting (may vomit worms), diarrhea, weight loss | Yes |
| Tapeworm | Swallowing infected fleas or eating prey containing larvae | Rice-grain-like segments visible around the anus, may be asymptomatic | Yes (rare) |
| Hookworm | Swallowing larvae from the environment or prey, skin penetration | Bloody stool, anemia, weight loss | Yes |
| Toxoplasma | Hunting, raw meat | Usually asymptomatic (may cause illness in immunocompromised individuals) | Yes |
| Coccidia | Fecal-oral | Diarrhea (more severe in kittens) | No |
| Giardia | Contaminated water, fecal-oral | Chronic soft stool, diarrhea | Rare |
Recommended Deworming Schedule
The two most widely cited guidelines are ESCCAP (European Scientific Counsel Companion Animal Parasites, Europe) and CAPC (North America), and they take different approaches: ESCCAP sets the deworming frequency by each cat's risk group, while CAPC recommends year-round monthly parasite control for every cat. ESCCAP is written for Europe and CAPC for North America, so ask your veterinarian to assess your cat's actual risk.
Kittens
- CAPC: Start at 2 weeks of age and repeat every 2 weeks until the kitten moves onto regular broad-spectrum parasite control
- ESCCAP: Start at 3 weeks of age, then every 2 weeks until 2 weeks after weaning. Kittens at ongoing higher risk (for example, allowed to roam outdoors) continue monthly until 6 months of age
Adult Cats: ESCCAP Deworming Chart
| Cat's situation | ESCCAP recommendation |
|---|---|
| Strictly indoor (or only a fenced patio/garden, unlikely to eat rodents) | 1–2 times a year, or fecal testing and treatment based on results |
| Free to roam outdoors | 4–12 times a year |
| Hunts or eats raw meat | At least 4 times a year, with a product that also covers tapeworms |
| Lives with children under 5–6, or immunocompromised or elderly people | Monthly deworming, or monthly fecal testing |
| No individual risk assessment | At least 4 times a year |
ESCCAP also notes that 1–3 dewormings a year do not provide sufficient protection when risk has not been assessed, and that deworming every 3 months does not necessarily prevent a cat from shedding worm eggs. Keeping your cat indoors puts it in the lowest-risk group.
CAPC does not split cats by lifestyle: it recommends year-round broad-spectrum parasite control (monthly for intestinal parasites) for all cats, including indoor cats, plus fecal examinations at least four times in the first year of life and at least twice a year for healthy adults.
How to Know If Your Cat Has Parasites
- Fecal examination: The most basic screening method. A veterinarian examines the stool under a microscope for parasite eggs. A single negative result does not completely rule out infection — ESCCAP notes that testing samples collected on different days increases sensitivity
- Visual observation: Roundworms may be visible in vomit or stool (resembling thin noodles), and tapeworm segments may be seen around the anus (resembling white grains of rice)
- Clinical signs: Abnormally distended abdomen in kittens, chronic diarrhea or soft stool, weight loss, dull coat
Important Deworming Considerations
- Use veterinary-prescribed deworming medication: Different parasites require different drugs, and over-the-counter "broad-spectrum dewormers" may not cover all types
- Dose accurately by weight: Underdosing is ineffective, while overdosing may cause side effects
- Flea control in tandem: Fleas are the intermediate host for tapeworms — without flea control, tapeworms cannot be eradicated
- Environmental cleaning: After deworming, clean all feces from litter boxes to reduce the risk of reinfection
- Deworm all cats in multi-cat households simultaneously: To prevent cross-infection
Zoonotic Considerations
According to CDC data, some cat parasites can be transmitted to humans:
- Toxoplasma: Infection during pregnancy can affect fetal development. Toxoplasma oocysts don't become infectious until 1–5 days after being shed, so cleaning the litter box daily can greatly reduce the risk
- Roundworm: Young children may become infected through contact with contaminated soil in sandboxes or gardens
- Basic precautions: Wash hands after cleaning the litter box, keep young children away from cat feces, and deworm cats regularly
Related Reading
- Cat flea & tick prevention
- Cat vaccination schedule (FVRCP, rabies, FeLV)
- Litter box cleaning & toxoplasma prevention
- Blood in cat stool: causes & when to worry
- Cat diarrhea home care guide
References
- ESCCAP. Worm Control in Dogs and Cats. ESCCAP Guideline 01, 7th edition, June 2025. esccap.org
- Companion Animal Parasite Council (CAPC). General Guidelines for Dogs and Cats (updated April 2025). capcvet.org
- Companion Animal Parasite Council (CAPC). Ascarid (updated February 2025). capcvet.org
- CAPC Pets & Parasites. Frequently Asked Questions. petsandparasites.org
- CDC. Preventing Toxoplasmosis. cdc.gov
- CDC. Ocular Toxocariasis — United States, 2009–2010. MMWR, 60(22), 2011. cdc.gov