Feline Roundworm Infection: Symptoms, Transmission Routes, and Treatment & Prevention Guide

Infection/ParasitesDiseasesMeongsiljang Veterinary Advisory Board

Feline roundworm infection is an internal parasitic disease caused by Toxocara cati, which lives in the small intestine. It can cause vomiting, diarrhea, and abdominal distension in kittens. Regular deworming and fecal exams can help prevent and detect the condition early.

What is Feline Roundworm Infection?

A kitten receiving a check-up at the veterinary clinic

Feline roundworm infection is an internal parasitic disease caused by the roundworm Toxocara cati, which parasitizes the small intestine of cats. The most important point is that symptoms are much more severe in kittens. Kittens can become infected immediately after birth through their mother’s milk, and if they experience recurring symptoms such as vomiting, diarrhea, and abdominal distension, roundworm infection should be suspected. While adult cats often remain asymptomatic, they can still serve as a source of environmental contamination, making regular testing essential.

How Do Cats Get Infected? — 3 Main Transmission Routes

Milk (lactogenic) transmission: If the mother cat is infected with roundworms during late pregnancy, larvae can be passed to her kittens through the milk. However, in chronically infected mothers, very few eggs appear in the milk, so not all kittens are infected immediately after birth.

Ingestion of eggs from contaminated environments: Roundworm eggs are encased in a thick shell, allowing them to survive for long periods in soil, sand, or contaminated grass. Cats may ingest these eggs while grooming themselves or coming into contact with contaminated surfaces.

Hunting intermediate (paratenic) hosts: When cats hunt and eat small animals like mice, birds, or insects, dormant roundworm larvae in their muscles can enter the cat’s body. This is especially risky for cats that spend a lot of time outdoors or have strong hunting instincts.

Key Symptoms Checklist

Vomiting: Roundworms irritate the stomach and intestines, causing repeated vomiting. You may even see white, thread-like roundworms in the vomit.

Diarrhea: Irritation of the small intestinal lining can lead to small-intestinal diarrhea, such as loose or mucoid stools. In severe cases, this can progress to catarrhal enteritis.

Abdominal Distension: Particularly noticeable in kittens, whose bellies appear prominently swollen.

Poor Growth: By interfering with nutrient absorption, roundworms cause significantly slower weight gain and growth compared to littermates.

Coughing and Respiratory Issues: During the migration phase when larvae pass through the liver and lungs, temporary coughing or rapid breathing may occur.

Lethargy and Loss of Appetite: As the infection worsens, overall health declines, energy levels drop, and appetite decreases.

Checklist of common symptoms of roundworm infection in cats — vomiting, diarrhea, abdominal distension, etc.

Seek Veterinary Care Immediately If You See These Symptoms

If vomiting or diarrhea persists for more than 24 hours, or if you actually see white, thread-like parasites in the vomit or stool, you should seek veterinary care immediately. Kittens are at risk because dehydration and hypoglycemia can progress rapidly, so delays can be dangerous.

Diagnostic Methods — How Is It Confirmed at the Clinic?

Fecal flotation: This basic and highly accurate diagnostic method involves suspending a stool sample in a special solution to identify roundworm eggs under a microscope.

Direct smear: A stool sample is thinly spread on a slide to detect larvae or parasite structures.

Post-deworming observation: If adult worms are expelled in the stool after administering deworming medication, it provides further confirmation of infection.

For kittens, fecal testing should be performed within the first week of adoption. Adult cats should be tested regularly once or twice a year. Testing is essential even if no symptoms are present.

Treatment — Types of Deworming Medications Prescribed by Veterinarians

Roundworm infections are treated with deworming medications prescribed by a veterinarian. Dosage and treatment frequency vary depending on your pet’s weight and age, so it is essential to follow the prescription exactly.

Pyrantel pamoate: Safe for use in kittens.

Fenbendazole: Broadly effective against various types of internal parasites.

Milbemycin oxime: Used for both heartworm prevention and roundworm treatment.

Moxidectin and Selamectin: Available in topical formulations, allowing for stress-free administration.

A pet owner applying a spot-on dewormer to a cat’s back

Home Care and Management

Litter box hygiene: Roundworm eggs are shed in the feces. Scoop the litter daily and thoroughly clean and disinfect the entire litter box at least once a week.

Hand hygiene: Always wash your hands after handling cat feces, as roundworm larvae can also affect humans.

Indoor living: Keeping your cat indoors significantly reduces exposure to contaminated soil and intermediate hosts.

Nutritional support for kittens: After a severe infection, consult your veterinarian about providing a specialized recovery diet to help restore your kitten’s nutrition.

Regular Deworming Schedule to Prevent Reinfection

Start deworming kittens at three weeks of age, repeating every two weeks until they are eight weeks old, and then continue monthly until they reach six months. For adult cats, deworm every three to six months if they live strictly indoors; if they go outdoors or live in a multi-cat household, consult your veterinarian about a three-month interval. Aligning deworming with the vaccination schedule helps ensure you don’t miss any treatments.

Zoonotic Risk — It Can Also Infect Humans

Toxocara cati can also infect humans. Infection typically occurs when eggs are ingested after touching the mouth with hands that have come into contact with contaminated soil or sand. Cases of children becoming infected in sandbox play areas have been reported.

Visceral larva migrans: Larvae migrate through organs such as the liver and lungs, triggering allergic reactions.

Ocular larva migrans: Larvae can penetrate the retina and cause vision loss, requiring particular caution.

When handling cat feces, always wear gloves and wash your hands thoroughly afterward.

Guide to the transmission routes of zoonotic roundworm infections in cats

Reviewed by a veterinarian

Dr. Tony — Punnawat Phongkittirak

Veterinarian

A veterinarian who majored in veterinary medicine at Khon Kaen University, Thailand, and completed the IVSA program at North Carolina State University in the United States. Drawing on clinical experience at animal hospitals, he works in the pet healthcare field and is dedicated to building a digital care environment that connects pet parents with veterinarians.

Frequently Asked Questions

Can even indoor-only cats get infected with roundworms?

Yes, they can become infected. Contaminated soil tracked in on your shoes or clothing, as well as insects that enter the home, can all lead to infection. We strongly recommend regular deworming and fecal exams for indoor cats as well.

I found roundworms in my pet’s stool after giving dewormer. Is this normal?

Yes, this is a normal reaction. Deworming medications paralyze and kill roundworms, which are then expelled in the stool. If you see white, thread-like strands or long, hair-like objects, it means the deworming is working effectively. However, if the worms continue to appear for several days or if the quantity seems excessive, please consult your veterinarian.

Can deworming the mother cat prevent the transmission of parasites to her kittens?

It can be quite helpful. Preventive deworming of the mother during pregnancy and lactation can reduce the risk of larvae being transmitted through her milk. However, since complete prevention cannot be guaranteed, it is essential to start separate deworming for the puppies from three weeks of age after birth. Please consult your veterinarian for the exact schedule.

What should people who live with a cat that has roundworms do?

Alongside your cat’s treatment, thoroughly disinfect the area around the litter box, and always wear gloves and wash your hands when handling feces. If there are immunocompromised individuals or young children in the household, it’s safest for them to consult their own doctor as well.

How often should I give deworming medication for roundworms?

Kittens should begin vaccinations at three weeks of age, with subsequent doses every two weeks until eight weeks old, followed by monthly vaccinations until they reach six months of age. For adult cats, we recommend vaccinations every three to six months if they live exclusively indoors, and every three months if they have outdoor access. The most reliable approach is to establish a precise schedule in consultation with your veterinarian.

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References

[1] Maddison JE et al., Clinical Medicine of the Dog and Cat, 4th Edition, CRC Press, 2022

[2] Little SE (ed.), The Cat: Clinical Medicine and Management, 2nd Edition, Elsevier Saunders, 2022

[3] Bowman DD (ed.), Principles and Practices of Canine and Feline Clinical Parasitic Diseases, Wiley-Blackwell, 2021

[4] Companion Animal Parasite Council (CAPC), Toxocara cati Parasite Guidelines, 2023

[5] Birchard SJ & Sherding RG (eds.), The Veterinary Workbook of Small Animal Clinical Cases, Elsevier, 2020