Background

Also called enterobiasis, pinworm infection is caused by Enterobius vermicualris, a small, very slender nematode with a sharply pointed tail. In humans, they are found in the appendix, ascending colon, and cecum. Females measure between 8-13mm, while males range between 2-5mm in length. 

Pinworm is predominantly a disease of children, and parents often become infected through their children, as a result of reinfection or incomplete treatment. This infection is common throughout the world particularly in the temperate areas. In the United States, it us the most common helminthic infection.  

The usual modes of transmission are by direct contact with contaminated bedclothes, furniture, bedding, towels, doorknobs, toilets, or other inanimate objects. The parasites occasionally are transmitted sexually. Generally, there are no symptoms due to pinworm infection and asymptomatic carriers are many in number. The rate of cure with treatment is approximately 90-95% with common chances of re-infection if all contracted patients are not simultaneously treated. 

Epidemiology

Pinworm is a common helminthic infestation in the United States, with general prevalence of 0.2 to 20% in children. Living in crowds and institutionalized individuals show higher prevalence rates, with 50-100% occurrence in institutionalized people. Europe equally reports a similar prevalence. It is highly recorded in cosmopolitan areas in the cool and temperate regions. The rate of carrying eggs may vary between countries and with the most at risk category being school-aged children. In adults, the peak incidence of pin worm infection is among 30-39 years, primarily as a result of the children between ages of 5-9 transmitting it to them, Males are infected in 2:1 ratio over females, except in the ages of 5-14. 

Anatomy

Pathophysiology

A prickling sensation or pruritus or in the perianal area that normally occurs at night is actually the most common symptom of pinworm. It is caused by a gravid female pinworm that has migrated towards the anal area to deposit eggs with her tail pin in the mucosa. Enterobius vermicularis is considered to reside mainly in the small intestine, specifically in the ileocecal area. 

Intense local itching is due to the movement of the female pinworm and her eggs. The ova can survive for up to three weeks prior to hatching, and the hatched larvae can migrate back into the lower intestine and anus and reach the site of fertilization. Embryonated eggs can be released onto fomites (e.g., clothing, paper money, bedding, toys), air or onto hands, which then can be placed directly into the mouth leading to autoinfection and helping the worm to enter the small intestines. 

Typically, pinworms present in the cecum and adjoining structures are asymptomatic, but it has been postulated that acute infection might cause diarrhea by inducing inflammation of the wall of the bowel. Although pinworms were found in the appendix during histologic study of acute appendicitis, this relationship is probably coincidental. 

Probable risk factors for pinworm infection include eating without washing hands, poor personal and group hygiene, and living with an egg-positive person. 

Etiology

Infection by the Enterobius vermicularis nematode has been known to result in this condition. The major transmission pathway involves the ingestion of the egg stage of the pinworm, mainly via contaminated hands, food, drink, or fomite. Autoinfection occurs when infective eggs on the hands are transferred to the mouth from scratching the perianal area, and retroinfection results from the migration of hatched larvae into the intestines.

The life cycle consists of infective eggs hatching in the small intestine, larvae developing to adults, and adults laying many eggs, which cause intense itching and are subsequently spread from scratching. The risk factors of pinworm infection are a close contact, poor hygienic actions, environmental contamination, and self-infection. The understanding of pinworm infection helps to effect control and prevention through good personal hygiene, regular handwashing, and a clean-living environment. 

Genetics

Prognostic Factors

Pinworm infection causes serious morbidity rarely unless ectopic infection takes place, which can happen in patients with inflammatory bowel disease. Parasites can penetrate the bowel wall and can be located in extracolonic sites such as vagina, fallopian tubes, inguinal area, liver, male genital tract, omentum, genital area, pelvic peritoneum, salivary glands, lungs, and male genital tract.

Ectopic enterobiasis has been linked with acute appendicitis, eosinophilic gastroenteritis, and eosinophilic colitis. Infestation by pinworm is rarely fatal and the primary cause of death includes effect of secondary infections. It is very hard to eliminate pinworm entirely in the institutionalized individual, and follow-up examination must be persistent. The success of treatment is higher if treatment of the child is done together with his family and classmates. 

Clinical History

History includes prickling or pain in the anal region particularly in the night, severe anal itching, difficulty sleeping or restless sleep, rarely loss of appetite or abdominal discomfort. Other signs may include irritability and vaginal itching in females. However, most patients are asymptomatic. 

Physical Examination

One hospital-based study of children aged 2–12 years found that itching in the perianal area was found to be not notably more common in children who are infected than in children who are uninfected, although persons who are egg–positive for Enetrobius typically consult a doctor due to perianal itching. 

The female pinworm (10 mm) can be easily visualized in the perianal region with naked eye. Oftentimes the worm is mistaken for a cotton thread residue. Unless viewed under the microscope, eggs (30 μm X 50-60 μm) are not visualized. Perianal excoriations from the itching are commonly found. 

Age group

Associated comorbidity

1. Endometritis 
2. Appendicitis 
3. Vulvovaginitis 
4. Urethritis 
5. Salpingitis 
6. Endometritis 
7. Vulvovaginitis 
8. Urinary tract infections 

Associated activity

Acuity of presentation

Differential Diagnoses

Proctitis 

Anusitis 

Laboratory Studies

Imaging Studies

Procedures

Histologic Findings

Staging

Treatment Paradigm

• Approach considerations: Effective anthelmintic agents against Enterobius vermicularis are mebendazole, pyrantel pamoate, and albendazole. Treatment should be symptomatic for itching, irritation, and excoriation. Reinfection is frequent and young pinworms are often resistant to drugs. Therefore, two rounds of medication are required at 2-week intervals to successfully eradicate them. Treatment should involve all infected family members and classmates. All must be treated at the same time and must pay attention to hygiene. Treatment may be repeated at 2-week intervals in stool-disclosed children. Consult a parasitologist or pediatrician. 
• Long-term monitoring: Follow-up examination is indicated in patients with Enterobius vermicularis infection to evaluate reinfection after taking anthelmintic. The first single examination may be negative for Enterobius eggs, but if perianal itching or prickling pain symptoms are still present, a follow-up perianal swab is necessary. 
• Prevention/ Deterrence: For hygiene improvement of the patients and their families to avoid reinfection, advise washing hands before meals, bathing immediately after waking up, discourage children from sucking fingers, thumb-sucking, among other activities that may promote infection, treating all members of the household at one time, washing the bed, the clothing, and towels in ordinary laundry soap to kill the pinworm eggs. The care providers need to be observant of strict handwashing and ensure that bedding, gowns, and stretchers are thoroughly washed. 

by Stage

by Modality

Chemotherapy

Radiation Therapy

Surgical Interventions

Hormone Therapy

Immunotherapy

Hyperthermia

Photodynamic Therapy

Stem Cell Transplant

Targeted Therapy

Palliative Care

• Hygiene practices
  Promote regular handwashing with soap and water, especially after using the toilet and before eating, after changing diapers. Keep the nails short and clean to minimize the risk of eggs getting trapped in the nails and ingested. 
• Cleaning and disinfection
  Regularly disinfect and clean bathrooms, kitchen surfaces, and other rooms with high contact areas. Wash sheets, clothes, and towels in hot water and use the clothes dryer as the high heat will kill any deposited eggs. 
• Environmental controls
  Regularly vacuum the floors and carpets and rinse out the eggs when dusting with a wet cloth. Clean and disinfect toys and any other objects that will make contact with either the mouth or hands. 
• Institutional measures
  Regular screening for pinworm infection should be conducted at schools, daycare centers, and other institutions where children gather. Mass treatment should be organized in such institutions. 

Use of anthelmintics

• Mebendazole: It leads to the death of worms by selective and irreversible blockage of glucose uptake and nutrients from the intestine where these organisms live. 
• Pyrantel pamoate: This is a depolarizing and neuromuscular blocking agent which suppresses cholinesterases leading to the paralysis (spastic) of worms. 
• Albendazole: This drug reduces the production of ATP in worms that leads to immobilization, depletion of energy, and finally death of worms. To overcome the inflammatory reactions in CNS, individuals must be treated initially with high-dose glucocorticoids and anticonvulsants. 

use-of-phases-of-management-in-treating-pinworm-infections

Management of pinworm infections includes several phases like diagnosis, treatment, prevention, and follow-up. Diagnosis is based on clinical evaluation, visual examination, laboratory tests, examination of faeces, and anthelmintics such as albendazole, ebendazole, Pyrantel Pamoate. Symptomatic relief can be provided using antihistamines. Prevention includes personal hygiene maintenance, cleaning fingernails, environmental cleaning by laundering, cleaning, and dusting, among others.

It enables a reduction in the rate of reinfection through mass treatment and educative programs.
The follow-up should then include re-evaluation, repetition of treatment dose, and monitoring of signs and symptoms. All legs are crucial in effectiveness management, reduction of morbidity, and prevention of reinfection. 

Medication

Future Trends

Media Gallary

References

Intestinal Parasitic Infections in 2023 | Ahmed | Gastroenterology Research (gastrores.org)