Roundworms are common intestinal parasites found in dogs, particularly puppies. These parasites, primarily Toxocara canis, reside in a dog’s intestines and can grow to several inches in length. Humans can contract roundworms from dogs. Transmission occurs not through direct contact with the dog itself, but through accidental ingestion of microscopic roundworm eggs shed by infected animals into the environment.
How Humans Contract Roundworms
Infected dogs release millions of microscopic eggs into their feces. These eggs are initially not infectious but mature in the environment, typically in soil or sand, over two to four weeks, becoming capable of causing infection. Their robust outer layer allows them to survive outdoors for months or even years, under suitable conditions. Humans become infected by accidentally ingesting these eggs. This often occurs after touching contaminated soil, playing where infected dogs have defecated, or consuming unwashed produce grown in contaminated ground.
Health Effects in Humans
Once ingested, roundworm eggs hatch into larvae within human intestines. Unlike in dogs, these larvae do not mature into adult worms in the human body. Instead, they migrate through various tissues and organs, a condition known as larva migrans.
Visceral Larva Migrans (VLM) occurs when larvae travel to organs like the liver, lungs, or brain. This migration can cause inflammation and tissue damage, leading to symptoms such as fever, coughing, wheezing, abdominal pain, or an enlarged liver. Many individuals, especially adults, experience no VLM symptoms, but severe cases can occur, particularly in young children.
Ocular Larva Migrans (OLM) occurs when larvae migrate to the eye. This can cause inflammation, retinal damage, and potentially permanent vision loss, often affecting only one eye. Symptoms of OLM include eye irritation, redness, seeing spots or flashes of light, or decreased vision. While many infections are asymptomatic, the potential for serious health consequences, especially vision impairment, highlights the importance of prevention.
Preventing Transmission
Preventing human infection centers on consistent hygiene and responsible pet care. Thoroughly washing hands with soap and water is important, especially after outdoor activities, gardening, handling pet waste, or before eating. Children should be taught hand hygiene and discouraged from eating dirt.
For pet owners, regular deworming of dogs, especially puppies, is a key preventive measure recommended by a veterinarian. Puppies are often dewormed every two weeks up to 12 weeks of age to prevent egg shedding. Promptly cleaning up dog feces from yards and public spaces helps reduce environmental contamination, as eggs need time to become infectious. Covering sandboxes when not in use prevents dogs from defecating in them, minimizing exposure for children.