What is Enterobiosis?

Enterobiosis (enterobius vermicularis from Greek. Enteron – intestines, bios – life, from lat. Vermis – worm) – a parasitic disease of a person, characterized by intestinal lesions, itching around the anus and allergization of the body.

Causes of Enterobiosis

The causative agent of enterobiosis is pinworm – Enterobius vermicularus (Linnaeus, 1758; Leach, 1853).

The name Enterobius comes from the Greek enteron – intestines and bios – life, vermicularis – reduced from Latin – a worm living in the intestines of a worm.

Pinworm is a small nematode of a spindle-shaped milk (milk) of white color, the cuticle of which has a transverse striated.

The length of the adult female reaches 9–12 mm, the male 3–5 mm, the tail end of the female is pointed, the male is blunt and hooked. Sharp lateral keels extending along the length of the helminth body form head vesicles at the anterior end. The helminth’s digestive system is represented by a mouth opening limited by three lips, a cylindrical esophagus with a bulbous extension extending into the intestine and ending in the anus in the back of the body.

The esophagus bulbus and vesicles form a suction device that secures the fixation of adult helminths to the intestinal wall.

The female reproductive system consists of a paired ovary, a uterus that passes into the vagina, and ends with a vulva. The vagina has muscle pulp, which is in a spasmodic state in the anoxic environment of the human intestine. Therefore, parasitic females, while in the intestinal lumen, do not secrete eggs. The male reproductive system is represented by the testis, which ends with a long spicule.

Pinworm eggs have an oblong, somewhat asymmetric shape, one side more flat. The size of the eggs is 50-60 x 20-30 microns. They are covered with a thin double-circuit colorless smooth shell.

Adult helminths live in the lower part of the small intestine, in the cecum and in the upper part of the colon. As a rule, only females parasitize, males after copulation are excreted with feces. Helminths feed on the contents of the intestines and are optional hematophages. The number of individuals parasitizing in the intestines varies widely from several tens to hundreds and thousands. K.I. Skryabin, V.P. Podyapolskaya and R.S. Schulz described a case when 2750 parasites were found in the intestines during autopsy of a child. Intensive infestations are associated with repeated self-infections.

Human infection with enterobiosis occurs when swallowing mature pinworm eggs, which contain motile larvae. Under the action of digestive enzymes of the small intestine, the larvae are released from the eggs, descending into its lower parts, 2-3 molts pass. Here the process of copulation is completed, and the males passively leave the intestines. And young female pinworms are attached to the mucous membrane with the help of head vesicles and the suction action of the bulb of the esophagus. Eggs form and accumulate in the uterus of the fertilized female, the number of which reaches 5-17 thousand. A stretched enlarged uterus squeezes the bulb of the esophagus, displaces it, as a result of which the helminth loses its ability to stay on the mucosa and, under the action of peristalsis, falls into the lower part of the large intestine. Further, during the active migration of helminth in the rectum, the eggs in the uterus ripen to the stage of a tadpole-like larva.

Overcoming the resistance of the sphincter of the rectum, the female creeps out onto the perianal folds and perineal skin of the invaded. The presence of atmospheric oxygen relaxes the genital tract of the helminth, as a result of which the creeping female secrete eggs that achieve invasiveness directly on the host’s body. As the female moves, heaps of eggs 100 to 300 in each remain on the skin of the invaded.

Pinworms creep out more often at night, when falling asleep and during sleep, when the muscles of the anus sphincter are somewhat weakened.

With considerable humidity and untidiness around the anus, oviposition is delayed, and pinworms continue to wander, sometimes crawling along the perineum not only into the vagina, but even through the uterus and fallopian tubes into the pelvic cavity, where they were found encapsulated on the peritoneum.

The individual life of the female who has secreted eggs ends, she dries, turning into a shapeless lump.

The itching that occurs with the movement of helminths leads to scratching of itchy places, contamination of the hands, getting eggs into the subungual beds, where the conditions for development to the invasive stage are also favorable.