Auto infection occurs in

The infection of a primary host with a parasite, particularly a helminth, in such a way that the complete life cycle of the parasite happens in a single organism, without the involvement of another host is called autoinfection.  Autoinfection occurs by scratching the perianal area and transferring infective eggs to the mouth with contaminated hands.  Dwarf tapeworm (Hymenolepis nana, also known as Rodentolepis nana, Vampirolepis nana, Hymenolepis fraterna, and Taenia nana) is a cosmopolitan species though most common in temperate zones, and is one of the most common cestodes infecting humans, especially children. Infection is acquired most commonly from eggs in the feces of another infected individual, which are transferred in food, by contamination. Direct contaminative infection by eggs is probably the most common route in human cases. The nematode (roundworm) Enterobius vermicularis is widely known as the human pinworm due to the female’s long, pointed tail.  Infection occurs via self-inoculation (transferring eggs to the mouth with hands that have scratched the perianal area) or through exposure to eggs in the environment (e.g. contaminated surfaces, clothes, bed linens, etc.) Taeniasis in humans is a parasitic infection caused by the tapeworm species Taenia saginata (beef tapeworm), Taenia solium (pork tapeworm), and Taenia asiatica (Asian tapeworm). Humans can become infected with these tapeworms by eating raw or undercooked beef (T. saginata) or pork (T. solium and T. asiatica). People with taeniasis may not know they have a tapeworm infection because symptoms are usually mild or nonexistent.Taenia solium tapeworm infections can lead to cysticercosis, which is a disease that can cause seizures Ref :https://www.cdc.gov/parasites/taeniasis/index.html https://www.cdc.gov/parasites/pinworm/biology.html     https://en.wikipedia.org/wiki/Hymenolepis_nana