Enterobius vermicularis

Transmission

As with many other GI nematodes, pinworms do not need to rely on a vector for transmission. Pinworm infection usually occurs via ingestion of infectious eggs by direct anus-to-mouth transfer by fingers. This is facilitated by the perianal itch (pruritis ani) induced by the presence of pinworm eggs in the perianal folds, and commonly occurs as a result of nail biting, poor hygiene, or inadequate hand-washing.

Retroinfection is also possible, where some of the pinworm larvae which hatch on the anus return to the gastrointestinal tract of the original host, leading to a very high parasitic load as well as ensuring continued infestation.

However, the transfer can also occur by touching contaminated surfaces, such as clothing, bed linen, and bathroom fixtures followed by ingestion, or even through inhalation or ingestion of aerosolized eggs from the aforementioned surfaces. As such, pinworm infections are easily spread among young children with the habits of nail biting and or poor hygiene, and infected children can easily spread the infection to other family members through the mechanisms listed above.