How can humans become infected with Toxocara canis?

Humans can become infected with Toxocara canis primarily through the ingestion of eggs. Toxocara canis is the roundworm commonly found in dogs, and it has a lifecycle that includes the production of eggs that are shed in the feces of infected canines. When these eggs contaminate soil, water, or surfaces, they can remain viable for long periods. If a person, particularly a child, unknowingly ingests these eggs—perhaps while playing in contaminated soil or not practicing proper hygiene—they can become infected.

Upon ingestion, the eggs hatch in the intestines, and the larvae can migrate through the body, potentially leading to a condition known as visceral larva migrans, where the larvae can cause damage to various organs. This transmission route underscores the importance of maintaining good hygiene practices, especially around pets and in outdoor environments where dog feces may contaminate the soil.

Other methods of potential transmission, such as through bites from dogs or inhalation of spores, do not play a role in the lifecycle of Toxocara canis, making the ingestion of eggs the most accurate representation of how humans can become infected.