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Pinworm Life Cycle

Pinworm Life Cycle

The entire life cycle of a pinworm is completed within 13 weeks. In spite of such a short life span, a pinworm manages to have to devastating consequences on the health of its host. Let us take a look at the life cycle of a pinworm in the following article.
BiologyWise Staff
Pinworms are one of the most common parasites that infect human guts. They are more likely to cause an infection in children than adults. One needs to seek pinworm treatment as the infection can quickly pass on to other members of the family. Although it is not termed as a very serious medical condition, one needs to seek pinworm treatment. It is important to know all about its life cycle, in order to get rid of these parasites for good. Here, we shall take a look at the life cycle of pinworm in humans.

What is a Pinworm?

A pinworm, also known as threadworm or seatworm is a nematode. It is a common human intestinal parasite that belongs to the genus Enterobius. It is a small, white roundworm. The adult female is about 8 to 13 mm long and male is just 2 to 5 mm in length. The females have a pointed posterior end and males have a curved posterior end. They reproduce by laying eggs that are translucent and sticky. They are very small about 50 to 60 micrometers in size and is flat on one side. They are barely visible to human naked eye, and can be seen when they form clumps of more than a thousand eggs.

Life Cycle of a Pinworm in Humans

Pinworm requires a host to complete its life cycle. Without a host the pinworm cannot grow and reproduce. The complete life cycle takes place in the gastrointestinal tract. First the eggs are ingested by the human host. Within 6 to 8 hours the eggs hatch in the duodenum of the host. Here the larvae begins to grow to a size of about 140 mm. It will then travel down through the small intestine into the colon.

While the larvae migrates, it will molt twice. This is a part of the process of turning into an adult worm. The mating takes place in the ileum, after which the male worm dies. The female worm can survive for about 5 to 13 weeks and males live for about 7 weeks. The dead worms are passed out of the system through the stools. The gravid female begins to get comfortable in the ileum, cecum, appendix and colon. She attaches herself to the mucosa and feeds on the colonic contents. Soon, her entire body is filled with eggs. There are about 11,000 to 16,000 eggs in the female body.

After about 5 weeks of entering the human body, the female will lay her eggs. The heavily pregnant worm travels through the colon towards the rectum and emerges out of the anus. As she moves on the skin, she will deposit her eggs around the anus. The process of laying eggs in pinworms is not yet clear. It can occur by contraction that causes the eggs to be expelled from the female body. It may even occur after the death of the female and her body disintegrating, releasing the eggs. Third possibility is that the hosts starts scratching the anus due to irritation and this causes the female body to rupture. This rupture causes the eggs to spill out of the female body. Once the eggs are deposited, the female dies. She travels out of the body to lay eggs as they require oxygen to mature.

Transmission of Pinworms in Humans

Pinworms are transmitted to a human host by ingestion of the pinworm eggs. Pinworm eggs can survive for about 3 weeks in a moist environment. They remain viable in low temperatures but, do not tolerate heat. When the eggs are deposited around the anus, they are ready to enter a host. The anus becomes very itchy, especially at night after the person is asleep. In sleep, the person scratches the anus and the eggs stick to the fingernails, hands, night clothing as well as the bed sheets. These eggs are then able to travel down the water, food, furniture, bathroom fixtures, and all the other things the infected person touches without washing their hands. Many times these eggs stick to pet fur and can enter human nose or mouth through inhalation. Some eggs hatch within the anal mucosa and travel up to the intestines to complete their life cycle. Sometimes, the infected person unknowing puts his fingers in his mouth without being aware the eggs are sticking on to his fingernails. The eggs re-enter the infected person's body, continuing with the cycle. This process is called retroinfection. It is very dangerous, as it tends to increase the load of parasites within the person's bowels. Retroinfection allows the parasite to infect the host indefinitely.

Thus, one should seek pinworm treatment and get rid of the parasite. Even if the person is asymptomatic, it is important to kill the parasites within the intestine. Medications containing albendazole and mebendazole help kill pinworms. There are other medications like pyrantel pamoate, piperazine that help kill adult pinworms. Hygiene is the key in preventing the eggs from getting ingested. Wash hands before eating food, and after using the toilet.