This case was diagnosed as an infection with the nematode Enterobius vermicularis (Enterobiasis). Nematodes are often described as “roundworms” and are members of the Helminths which include the Cestodes (“tapeworms”) and the Trematodes (“flatworms”).
Enterobius vermicularis is ubiquitous and most apt to cause infections in small children. Infections with Enterobius vermicularis not common in adults but in households with children infections in adults are quite possible. In the case of this cook, he and his wife were very active caretakers of their grandchildren. Children contract Enterobius vermicularis by contaminating their hands with the eggs present in the soil or other contaminated material and placing contaminated hands in their mouth leading to the accidental ingestion of the infectious eggs. The ingested embryonated eggs will hatch in the duodenum and release a larval form that incubates and grows in the mucus of the intestine. The larvae will migrate down through the small intestine, molting twice as it makes its way to the colon eventually as an adult worm. Fertile females will move to the perianal area of the human host to deposit their eggs.
Infections with Enterobius vermicularis can be asymptomatic. However, in a significant number of infections symptoms are present. Some of these symptoms can be gastrointestinal related such as stomach pain and/or nausea. But the chief complaint is perianal pruritus, and insomnia leading to irritability and restlessness in children due to a lack of, or quality of, sleep. The anal itching is due to the nocturnal propensity of the female worm to migrate from the ascending colon / cecum of the large intestine (where the worms are localized) to the anal area where they lay their eggs. Many times these children will be restless and irritable in their school classes, adversely affecting learning and their ability to get along with classmates and teachers. The result is parents being notified about their children having learning and behavioral problems. Heavy chronic infections can adversely affect a childs development. In addition to the previous symptoms of an infection, there are cases where the worms can find their way to the vaginal area resulting in vaginitis-like symptoms. Worms can block the lumen in the appendix producing an inflammation leading to appendicitis. And lastly, intense itching of the perianal area can many times lead to secondary infections.
While in this case it was the worm that was detected, the detection of the Enterobius vermicularis worm is uncommon. But when detected the worm will almost invariably be the female worm which is significantly larger than the male worm. Females are 8-13 mm in length while the males are 2-5 mm in length. Male worms are rarely seen. The female worms will have a pointy pin-like tail of which the name pinworm originated from, and numerous undeveloped eggs can be seen within its body as seen in the image below.
The worms are delicately thin, opaque white, and described as “thread-like”. Because of this appearance, the worm in some circles, specifically England and Australia, is named threadworm. The most common name used to describe Enterobius vermicularis is pinworm. Seatworm is another name used to describe Enterobius vermicularis infections but is less commonly used. And as noted in the case presentation given in part one, the appearance of the worms on the surface of the stool submitted by the cook were indeed delicate and “thread-like”. It wasn’t until I placed a worm under the microscope that I could see that in fact it was a worm and was able to easily appreciate its internal structures.
As previously mentioned before, Enterobius vermicularis worms are not commonly detected. Their recovery in stool ova and parasite determinations is low. Because eggs are deposited on the perianal area of the host by the females, eggs are also rarely seen in ova and parasite examinations. The diagnostic method of choice is the detection of eggs on the perianal area utilizing a clear scotch-tape (sticky side down) gently pressed to the perianal area and then gently placed (sticky side down) on a clean glass slide. There are other similar methods manufactured that provide similar results such as the “Pinworm Paddle”. The Pinworm Paddle is a plastic paddle that has an adhesive sticky side for pressing against the perianal region. The paddle is then observed under a microscope for the presence of pinworm eggs. The photo below is a photo of a positive tape-prep for Enterobius vermicularis eggs. Note the eggs at 11 and 4 that exhibit the characterisitic translucent appearance and flattened side. The image after it is a photo of eggs removed from the worms that were found on the cooks stool, and exposed to Lugols iodine. Because of the nocturnal nature of the female worms and their egg deposition, tape preps are best done upon waking up, before a shower, and prior to defecation to ensure that there is the optimal recovery of the eggs.
Treatment of infections is with either mebendazole, pyrantel pamoate, or albendazole. But treatment/eradication of infections can be fraught with failure. Repeat treatments are not uncommon. Treatments normally involve two doses with each given two weeks apart. The eggs of Enterobius vermicularis can extensively contaminate a household and therefore treatment needs to be seriously considered for others in the house even if they are showing no symptoms. Household bedding material, undergarments, etc… need to be washed in hot water and heat dried to eliminate any potential recontamination of the environment. Surfaces need to be treated with disinfectants containing accelerated hydrogen peroxide or chorine dioxide. It is also important to know that the eggs, once released from the perianal area, can easily become airborne. This is an important mode of transmission in the house where the eggs can also enter the host via inhalation as well as provide for an extensive area of contamination. Thus, the manipulation of bedding material (most importantly) and other possibly contaminated material should be done with great care to prevent eggs from becoming airborne.
The cook in this case study was immediately relieved of his duties in the kitchen until he completed the treatment regimen. Unfortunately he had to be out of work for an extended amount of time because the eradication of the infection was difficult between all family members. He and family members had to take a months worth of treatment along with a continuous extensive cleaning of the household(s). It wasn’t until there was proof of complete eradication that he was allowed back to work.
References:
Rawla P, Sharma S. Enterobius Vermicularis. [Updated 2023 Aug 1]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2025 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK536974/
CDC. About Pinworm Infection. US Centers for Disease Control and Prevention. Available at https://www.cdc.gov/pinworm/about/. September 9, 2024; Accessed: October 8, 2024.