Preventing roundworms comes down to breaking the cycle between contaminated soil, unwashed hands, and your mouth. Roundworm eggs are extraordinarily tough, surviving months in soil and resisting freezing, bleach, and desiccation. But with consistent hygiene habits, proper food preparation, and regular pet care, the risk of infection drops dramatically. Nearly 294 million people worldwide are infected with the most common human roundworm species, so these precautions matter more than many people realize.
How Roundworms Spread
Understanding transmission is the foundation of prevention. The roundworm species most relevant to humans include Ascaris (the human intestinal roundworm) and Toxocara (the dog and cat roundworm). Ascaris spreads when someone swallows microscopic eggs from contaminated soil or unwashed produce. Toxocara works similarly: dogs and cats shed unembryonated eggs in their feces, and those eggs mature into an infectious stage in soil over one to four weeks. Humans are accidental hosts who pick up the eggs by touching contaminated dirt and then touching their mouths, or by eating undercooked meat from animals that carried larvae.
Some Toxocara cases have been linked to undercooked beef, lamb, chicken, and duck, particularly organ meats like liver. This means prevention isn’t limited to handwashing. It extends to your kitchen, your garden, your children’s play areas, and your pets’ veterinary care.
Handwashing Is Your Best Defense
Roundworm eggs are sticky and cling to skin effectively. Lab research on Ascaris egg removal from hands found that even rinsing with plain water removed about 83% of eggs, while washing with detergent solutions pushed removal rates above 95%. The key factors are soap, friction, and duration. Wash your hands with regular soap and water for at least 20 seconds, paying attention to fingernails and between fingers where soil can hide.
The most important times to wash are after gardening or any contact with soil, after handling pets or cleaning up animal waste, after using the bathroom, and before eating or preparing food. For children, building this habit early is especially important since they’re the age group most likely to put dirty hands in their mouths.
Keeping Produce Safe
Raw fruits and vegetables grown in or near soil can carry roundworm eggs on their surfaces. The FDA and CDC recommend washing all produce under clean running water, rubbing the surface to create friction. Peeling root vegetables and leafy greens that grow close to the ground adds another layer of protection. Chemical sanitizers like bleach solutions are effective against bacteria but have questionable effectiveness against parasite eggs specifically, so mechanical removal through thorough rinsing and scrubbing is more reliable.
If you grow your own vegetables, avoid using uncomposted animal manure as fertilizer. Properly composted material reaches temperatures high enough to kill parasite eggs, but raw or partially composted waste does not.
Cook Meat Thoroughly
Roundworm larvae in meat die at relatively modest temperatures. The USDA recommends cooking pork to an internal temperature of 71°C (160°F), which kills parasites almost instantly. For other meats that could harbor Toxocara larvae, particularly game meat and organ meats, the same temperature threshold applies. Use a meat thermometer rather than judging by color. Larvae can survive in meat that looks cooked on the outside but hasn’t reached a safe temperature internally.
Deworm Your Pets Regularly
Dogs and cats are the primary source of Toxocara eggs in the environment, making pet parasite control one of the most effective prevention strategies for your household. The Companion Animal Parasite Council recommends deworming all adult dogs and cats four times per year with a broad-spectrum antiparasitic. Puppies and kittens need more aggressive treatment: deworming should start at two weeks of age, repeat every two weeks until two months old, then continue monthly until six months old, and quarterly after that.
Year-round parasite control is important even for indoor pets. Dogs that visit parks, sniff other animals’ feces, or walk on contaminated grass can pick up infections quickly. A single infected dog can shed millions of eggs per day, and those eggs become infectious in soil within weeks.
Pick up your dog’s feces promptly, ideally within 24 hours. Fresh feces aren’t immediately dangerous because the eggs need one to four weeks in the environment to mature into their infectious form. But once those eggs embryonate in the soil, they can persist for years.
Protecting Children in Play Areas
Sandboxes are a well-documented source of Toxocara exposure because cats and other animals use uncovered sand as a litter box. The single most effective step is covering sandboxes when they’re not in use. A fitted cover or tarp prevents animals from depositing feces in the sand overnight.
Research from daycare play areas found that practical prevention requires maintaining fences and gates to keep animals out and immediately removing any fecal material found in sand or soil. Chemical cleaning agents have not proven effective at destroying Toxocara eggs in sand, but direct sunlight does help kill them over time. Turning sand over regularly and replacing it periodically reduces contamination levels.
Teach children not to eat sand or soil, and make handwashing automatic after outdoor play. These habits alone significantly reduce the chance of accidental egg ingestion.
Cleaning Contaminated Surfaces
Roundworm eggs are among the hardest parasites to kill on surfaces. They resist freezing, surviving five freeze-thaw cycles at -15°C with no loss of viability. Undiluted household bleach applied for 90 minutes does not reliably kill them on its own. However, recent research has found that combining bleach with desiccation (letting the surface dry completely for at least one day after treatment) is effective. The bleach damages the outer egg layers, and the drying stresses the egg’s protective lipid barrier, and together the two treatments succeed where either alone fails.
Heat is more reliable. Roundworm eggs lose viability when heated above 62°C (144°F), which makes steam cleaning an effective option for surfaces that can tolerate it. For outdoor areas contaminated with animal feces, such as decks or patios, removing visible material, applying bleach, and allowing thorough drying in sunlight is a practical approach.
Soil and Garden Precautions
Contaminated soil is the primary reservoir for roundworm eggs, and once eggs are in soil, they can survive for years. Areas where dogs, cats, raccoons, or other animals defecate regularly should be treated as potentially contaminated. Wear gloves when gardening, especially in areas where animals have access. Avoid sitting or lying directly on soil in areas frequented by pets or wildlife.
Dried-out soil is not safe soil. Roundworm eggs survive complete desiccation for at least six months at room temperature. Simply waiting for contaminated ground to dry out does not eliminate the risk. If you’re dealing with a known contamination site, such as an area under a deck where raccoons have been nesting, the most effective approach is removing the top layer of soil entirely.
Who Faces the Highest Risk
Children between ages one and five are the most vulnerable group because of their tendency to play in soil and put their hands in their mouths. People who work with soil professionally (gardeners, farmers, construction workers) also face elevated exposure. Pet owners who skip regular deworming create ongoing risk for their households.
Globally, Southeast Asia carries the heaviest burden, accounting for over 55% of people needing preventive treatment for soil-transmitted roundworms. India alone represents 38% of the global need. In higher-income countries, Toxocara from pets is the more common concern, while Ascaris remains prevalent in regions with less access to sanitation infrastructure. Regardless of where you live, the prevention principles are the same: clean hands, clean food, treated pets, and covered play areas.