Cat. Toxocariasis

 Toxocariasis and cats

Toxocariasis is a human infection caused mainly by the roundworms:

• Toxocara cati (from cats)
• Toxocara canis (from dogs)

Humans become infected by accidentally ingesting microscopic parasite eggs, usually from:

• contaminated soil
• dirty hands
• unwashed vegetables
• contaminated litter or surfaces

You do not usually get toxocariasis from petting a cat directly unless contaminated fecal material is involved.

House cat vs street cat: risk comparison

Indoor house cat

A strictly indoor, well-cared-for cat has a much lower risk of carrying Toxocara.

Risk is especially low if the cat:

• receives regular deworming
• has veterinary care
• does not hunt rodents/birds
• does not roam outdoors
• has a clean litter box

Adult indoor cats are often low risk because:

• repeated exposure decreases worm burden over time
• indoor lifestyle limits reinfection

Still, kittens can carry roundworms even in good homes, because transmission can occur from the mother.

Street cat / feral cat

Street or feral cats generally have a significantly higher risk of carrying parasites including Toxocara cati because they:

• hunt prey
• eat contaminated food
• live in contaminated environments
• rarely receive deworming
• may have repeated reinfections

Areas heavily populated with stray cats can accumulate infective eggs in:

• parks
• gardens
• sandboxes
• soil

The eggs can survive for months or even years in the environment.

Important practical point

The biggest human risk usually comes from:

• contaminated soil
• poor hand hygiene
• children playing in dirt/sand

—not from casual contact with cats themselves.

Children are at highest risk because they may:

• put dirty hands in their mouths
• play in contaminated soil
• have closer contact with ground surfaces

Symptoms in humans

Many infections cause no symptoms.

When illness occurs, it can range from mild to serious:

• fever
• cough/wheezing
• abdominal pain
• enlarged liver
• fatigue
• high eosinophils (a blood finding)

Rarely, larvae migrate into the eye:

• blurred vision
• eye inflammation
• retinal damage

This is called ocular toxocariasis.

How to reduce risk

For house cats

• regular veterinary deworming
• scoop litter daily
• wash hands after litter handling
• keep cats indoors if possible

Around stray cats

• avoid contact with feces
• wash hands after touching outdoor soil
• wear gloves for gardening
• clean children’s sandboxes

Bottom line

• Indoor, regularly dewormed house cats: relatively low toxocariasis risk
• Street/feral cats: substantially higher parasite risk
• The main danger is environmental contamination with microscopic eggs, not simply touching a cat

If you want, I can also explain:

•  how likely transmission actually is
•  whether sleeping with cats is risky
•  toxoplasmosis vs toxocariasis
•  UK prevalence specifically
•  symptoms timeline
•  how eggs survive in litter and soil