What is a common route of entry for helminth infections in humans?

The ingestion of contaminated food or water is a well-documented route for helminth infections in humans. Many parasitic worms, such as roundworms and tapeworms, have life cycles that involve developing in the environment, often in soil or aquatic settings, where they can contaminate food sources or drinking water. For instance, ingesting eggs or larvae present in undercooked meat, contaminated fruits, or vegetables can lead to infection.

This route is particularly common in areas with poor sanitation, where human feces may contaminate local water supplies or food sources. Once ingested, the larvae can mature and establish themselves within the human body, leading to various health issues depending on the specific type of helminth involved.

In contrast, the other routes listed are less associated with helminth transmission; inhalation of infected air is not a typical method for helminth entry, as these parasites do not spread through airborne pathogens. Direct skin contact is relevant for some parasites, such as certain species of schistosomes, but is not as prevalent as the ingestion route for the majority of helminths. Lastly, intravenous injection is not a known method of transmission for helminths, which primarily invade hosts through the digestive system.