Enterobiasis
Encyclopedia
A pinworm infection or enterobiasis is a human parasitic disease and one of the most common childhood parasitic worm
infections in the developed world. It is caused by infestation with the parasitic roundworm Enterobius vermicularis, commonly called the human pinworm. Infection usually occurs through the ingestion of pinworm eggs, either through contaminated
hands, food, or less commonly, water. The chief symptom is itch
ing in the anal
area. The incubation time from ingestion of eggs to the first appearance of new eggs around the anus is 4 to 6 weeks. Pinworms are usually considered a nuisance rather than a serious disease. Treatment is straightforward in uncomplicated cases, however, elimination of the parasite from a family group or institution often poses significant problems—either due to an incomplete cure or reinfection. Pinworm infection has no association with any socioeconomic level, race or culture.
. The main symptoms are pruritus ani
and perineal
pruritus, i.e., itch
ing in and around the anus and around the perineum
. The itching occurs mainly during the night, and is caused by the female pinworms migrating to lay eggs around the anus. Both the migrating females and the clumps of eggs are irritating, but the mechanisms causing the intense pruritus have not been explained. The intensity of the itching varies, and it can be described as tickling
, crawling sensations, or even acute pain. The itching leads to continuously scratching the area around the anus, which can further results in tearing of the skin and complications such as secondary bacterial infections, including bacterial dermatitis
(i.e., skin inflammation) and folliculitis
(i.e., hair follicle inflammation). General symptoms are insomnia
(i.e., persistent difficulties to sleep) and restlessness
. A considerable proportion of children suffer from anorexia
(i.e., loss of appetite), weight loss
, irritability
, emotional instability, and enuresis
(i.e., inability to control urination
).
Pinworms cannot damage the skin, and they do not normally migrate through tissues
. However, in women they may move onto the vulva
and into the vagina
, from there moving to external orifice of the uterus
, and onwards to the uterine cavity, fallopian tubes, ovaries, and peritoneal cavity
. This can cause vulvovaginitis, i.e. an inflammation of the vulva and vagina. This causes vaginal discharge
and pruritus vulvae
, i.e., itch
iness of the vulva. The pinworms can also enter the urethra
, and presumably, they carry intestinal bacteria with them. According to Gutierrez (2000), a statistically significant correlation between pinworm infection and urinary tract infection
s has been shown, however Burkhart & Burkhart (2005) maintain that the incidence of pinworms as a cause of urinary tract infections remains unknown. Incidentally, one report indicated that 36% of young girls with urinary tract infection
also had pinworms. Dysuria
(i.e., painful urination
) has been associated with pinworm infection.
The relationship between pinworm infestation and appendicitis
has been researched, but there is a lack of clear consensus in the matter: while Gutierres (2005) maintains that there exists a consensus that pinworms do not produce the inflammatory reaction, Cook (1994) states that it is controversial whether pinworms are causatively related to acute appendicitis, and Burkhart & Burkhart (2004) state that pinworm infection causes symptoms of appendicitis to surface.
The cause of a pinworm infection is the worm Enterobius vermicularis. The entire lifecycle — from egg to adult — takes place in the human gastrointestinal tract of a single human host. Cook et al. (2009) and Burkhart & Burkhart (2005) disagree over the length of this process, with Cook et al. stating two to four weeks, while Burkhart & Burkhart states that it takes from four to eight weeks.
The lifecycle begins with eggs being ingested
. The eggs hatch in the duodenum
(i.e., first part of the small intestine
). The emerging pinworm larva
e grow rapidly to a size of 140 to 150 micrometers in size, and migrate through the small intestine towards the colon
. During this migration they moult
twice and become adults. Females survive for 5 to 13 weeks, and males about 7 weeks. The male and female pinworms mate in the ileum
(i.e., last part of the small intestine), whereafter the male pinworms usually die, and are passed out with stool. The gravid female pinworms settle in the ileum
, caecum (i.e., beginning of the large intestine
), appendix
and ascending colon
, where they attach themselves to the mucosa and ingest colonic contents. Almost the entire body of a gravid female becomes filled with eggs. The estimations of the number of eggs in a gravid female pinworm ranges from about 11,000 to 16,000. The egg-laying process begins approximately five weeks after initial ingestion of pinworm eggs by the human host. The gravid female pinworms migrate through the colon
towards the rectum
at a rate of 12 to 14 centimeters per hour. They emerge from the anus
, and while moving on the skin near the anus, the female pinworms deposit eggs either through (1) contracting and expelling the eggs, (2) dying and then disintegrating, or (3) bodily rupture due to the host scratching the worm. After depositing the eggs, the female becomes opaque
and dies. The reason the female emerges from the anus is to obtain the oxygen necessary for the maturation of the eggs.
Pinworm infection spreads through human-to-human transmission
, by ingesting (i.e., swallowing) infectious pinworm eggs. The eggs are hardy and can remain viable (i.e., infectious) in a moist environment for up to three weeks. They do not tolerate heat well, but can survive in low temperatures: two-thirds of the eggs are still viable after 18 hours at −8 degrees Celsius (18 °F).
After the eggs have been initially deposited near the anus, they are readily transmitted to other surfaces through contamination
. The surface of the eggs is sticky when laid, and the eggs are readily transmitted from their initial deposit near the anus to fingernails, hands, night-clothing and bed linen. From here, eggs are further transmitted to food, water, furniture, toys, bathroom fixtures
and other objects. Household pets often carry the eggs in their fur, while not actually being infected. Dust containing eggs can become airborne and widely dispersed when dislodged from surfaces, for instance when shaking out bed clothes and linen. Consequently the eggs can enter the mouth and nose through inhalation, and be swallowed later. Although pinworms do not strictly multiply inside the body of their human host, some of the pinworm larvae may hatch on the anal mucosa, and migrate up the bowel and back into the gastrointestinal tract
of the original host. This process is called retroinfection. According to Burkhart (2005), when this retroinfection occurs, it leads to a heavy parasitic load and ensures that the pinworm infestation continues. This statement is contradictory to a statement by Caldwelli (1982), who contends that retroinfection is rare and not clinically significant. Despite the limited, 13 week lifespan of individual pinworms, autoinfection
(i.e., infection from the original host to itself), either through the anus-to-mouth route or through retroinfection, causes the pinworms to inhabit the same host indefinitely.
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Diagnosis depends on finding the eggs or the adult pinworms. Individual eggs are invisible to the naked eye, but they can be seen using a low-power microscope
. On the other hand, the light-yellowish thread-like adult pinworms are clearly visually detectable, usually during the night when they move near the anus, or on toilet paper. Transparent adhesive tape
(e.g. Scotch Tape
) applied on the anal area will pick up deposited eggs, and diagnosis can be made by examining the tape with a microscope. This test is most successful if done every morning for several days, because the females do not lay eggs every day, and the number of eggs vary.
Pinworms do not lay eggs in the feces
, but sometimes eggs are deposited in the intestine. As such, routine examination of fecal material gives a positive diagnosis in only 5 to 15% of infected subjects, and is therefore of little practical diagnostic use. In a heavy infection, female pinworms may adhere to stools
that pass out through the anus, and they may thus be detected on the surface on the stool. Adult pinworms are occasionally seen during colonoscopy
. On a microscopic level, pinworms have an identifying feature of alae
(i.e., protruding ridges) running the length of the worm.
al status are typically high. The stigma associated with pinworm infection is hence considered a possible over-emphasis. Counselling is sometimes needed for upset parents that have discovered their children are infected, as they may not realize how prevalent the infection is.
Preventative action revolves around personal hygiene and the cleanliness of the living quarters. The rate of reinfection can be reduced through hygienic measures, and this is recommended especially in recurring cases.
The main measures are keeping fingernails short, and washing and scrubbing hands and fingers carefully, especially after defecation
and before meals. Under ideal conditions, bed covers, sleeping garments, and hand towels should be changed daily. Simple laundering of clothes and linen disinfects them. Children should wear gloves while asleep, and the bedroom floor should be kept clean. Food should be covered to limit contamination with dust-borne parasite eggs. Household detergents have little effect on the viability of pinworm eggs, and cleaning the bathroom with a damp cloth moistened with an antibacterial agent or bleach
will merely spread the viable eggs. Similarly, shaking clothes and bed linen will detach and spread the eggs.
is the primary treatment for pinworm infection. The existing pharmaceutical drugs against pinworms are so effective that many medical scientists regard hygienic measures as impractical. However, reinfection is frequent regardless of the medication used. Total elimination of the parasite in a household may require repeated doses of medication for up to a year or more. Because the drugs kill the adult pinworms, but not the eggs, the first retreatment is recommended in two weeks. Also, if one household member spreads the eggs to another, it will be a matter of two or three weeks before those eggs become adult worms and thus amenable to treatment. Asymptomatic
infections, often in small children, can serve as reservoirs of infection, and therefore the entire household should be treated regardless of whether or not symptoms are present.
The benzimidazole
compounds albendazole
(brand names e.g., Albenza, Eskazole, Zentel and Andazol) and mebendazole
(brand names e.g., Ovex, Vermox, Antiox and Pripsen) are the most effective. They work by inhibiting the microtubule
function in the pinworm adults, causing glycogen
depletion, thereby effectively starving the parasite. A single 100 milligram dose of mebendazole
with one repetition after a week, is considered the safest, and is usually effective with cure rate of 96%. Mebendazole has no serious side effects
, although abdominal pain
and diarrhea
have been reported. Pyrantel pamoate
(also called pyrantel embonate, brand names e.g., Reese's Pinworm Medicine, Pin-X, Combantrin, Anthel, Helmintox, and Helmex) kills adult pinworms through neuromuscular blockade, and is considered as effective as the benzimidazole
compounds. Other medications are piperazine
, which causes flaccid paralysis
in the adult pinworms, and pyrvinium pamoate (also called pyrvinium embonate), which works by inhibiting oxygen
uptake of the adult pinworms. Pinworms located in the genitourinary system
(in this case, female genital area) may require other drug treatments.
has been similarly associated. Because it spreads from host to host through contamination
, pinworms are common among people living in close contact, and tends to occur in all people within a household. The prevalence of pinworms is not associated with gender, nor with any particular social class
, race, or culture. Pinworms are an exception to the tenet that intestinal parasites are uncommon in affluent communities. The earliest known instance of pinworms is evidenced by pinworm eggs found in coprolite
, carbon dated to 7837 BC at western Utah
.
Parasitic worm
Parasitic worms or helminths are a division of eukaryoticparasites that, unlike external parasites such as lice and fleas, live inside their host. They are worm-like organisms that live and feed off living hosts, receiving nourishment and protection while disrupting their hosts' nutrient...
infections in the developed world. It is caused by infestation with the parasitic roundworm Enterobius vermicularis, commonly called the human pinworm. Infection usually occurs through the ingestion of pinworm eggs, either through contaminated
Contamination
Contamination is the presence of a minor and unwanted constituent in material, physical body, natural environment, at a workplace, etc.-Specifics:"Contamination" also has more specific meanings in science:...
hands, food, or less commonly, water. The chief symptom is itch
Itch
Itch is a sensation that causes the desire or reflex to scratch. Itch has resisted many attempts to classify it as any one type of sensory experience. Modern science has shown that itch has many similarities to pain, and while both are unpleasant sensory experiences, their behavioral response...
ing in the anal
Anus
The anus is an opening at the opposite end of an animal's digestive tract from the mouth. Its function is to control the expulsion of feces, unwanted semi-solid matter produced during digestion, which, depending on the type of animal, may be one or more of: matter which the animal cannot digest,...
area. The incubation time from ingestion of eggs to the first appearance of new eggs around the anus is 4 to 6 weeks. Pinworms are usually considered a nuisance rather than a serious disease. Treatment is straightforward in uncomplicated cases, however, elimination of the parasite from a family group or institution often poses significant problems—either due to an incomplete cure or reinfection. Pinworm infection has no association with any socioeconomic level, race or culture.
Signs and symptoms
One third of individuals with pinworm infection are totally asymptomaticAsymptomatic
In medicine, a disease is considered asymptomatic if a patient is a carrier for a disease or infection but experiences no symptoms. A condition might be asymptomatic if it fails to show the noticeable symptoms with which it is usually associated. Asymptomatic infections are also called subclinical...
. The main symptoms are pruritus ani
Pruritus ani
Pruritus ani is the irritation of the skin at the exit of the rectum, known as the anus, causing the desire to scratch. The intensity of anal itching increases from moisture, pressure, and rubbing caused by clothing and sitting...
and perineal
Perineum
In human anatomy, the perineum is a region of the body including the perineal body and surrounding structures...
pruritus, i.e., itch
Itch
Itch is a sensation that causes the desire or reflex to scratch. Itch has resisted many attempts to classify it as any one type of sensory experience. Modern science has shown that itch has many similarities to pain, and while both are unpleasant sensory experiences, their behavioral response...
ing in and around the anus and around the perineum
Perineum
In human anatomy, the perineum is a region of the body including the perineal body and surrounding structures...
. The itching occurs mainly during the night, and is caused by the female pinworms migrating to lay eggs around the anus. Both the migrating females and the clumps of eggs are irritating, but the mechanisms causing the intense pruritus have not been explained. The intensity of the itching varies, and it can be described as tickling
Tickling
Tickling is the act of touching a part of the body so as to cause involuntary twitching movements and/or laughter. The word evolved from the Middle English tikelen, perhaps frequentative of ticken, to touch lightly. The idiom tickled pink means to be pleased or delighted.In 1897, psychologists G...
, crawling sensations, or even acute pain. The itching leads to continuously scratching the area around the anus, which can further results in tearing of the skin and complications such as secondary bacterial infections, including bacterial dermatitis
Dermatitis
-Etymology:Dermatitis derives from Greek derma "skin" + -itis "inflammation" and genetic disorder.-Terminology:There are several different types of dermatitis. The different kinds usually have in common an allergic reaction to specific allergens. The term may describe eczema, which is also called...
(i.e., skin inflammation) and folliculitis
Folliculitis
Folliculitis is the inflammation of one or more hair follicles. The condition may occur anywhere on the skin with the exception of the palms of the hands and soles of the feet.- Causes :...
(i.e., hair follicle inflammation). General symptoms are insomnia
Insomnia
Insomnia is most often defined by an individual's report of sleeping difficulties. While the term is sometimes used in sleep literature to describe a disorder demonstrated by polysomnographic evidence of disturbed sleep, insomnia is often defined as a positive response to either of two questions:...
(i.e., persistent difficulties to sleep) and restlessness
Psychomotor agitation
Psychomotor agitation is a series of unintentional and purposeless motions that stem from mental tension and anxiety of an individual. This includes pacing around a room, wringing one's hands, pulling off clothing and putting it back on and other similar actions...
. A considerable proportion of children suffer from anorexia
Anorexia (symptom)
Anorexia is the decreased sensation of appetite...
(i.e., loss of appetite), weight loss
Weight loss
Weight loss, in the context of medicine, health or physical fitness, is a reduction of the total body mass, due to a mean loss of fluid, body fat or adipose tissue and/or lean mass, namely bone mineral deposits, muscle, tendon and other connective tissue...
, irritability
Irritability
Irritability is an excessive response to stimuli. The term is used for both the physiological reaction to stimuli and for the pathological, abnormal or excessive sensitivity to stimuli; It is usually used to refer to anger or frustration....
, emotional instability, and enuresis
Enuresis
Enuresis refers to an inability to control urination. Use of the term is usually limited to describing individuals old enough to be expected to exercise such control.Types of enuresis include:* Nocturnal enuresis* Diurnal enuresis...
(i.e., inability to control urination
Urination
Urination, also known as micturition, voiding, peeing, weeing, pissing, and more rarely, emiction, is the ejection of urine from the urinary bladder through the urethra to the outside of the body. In healthy humans the process of urination is under voluntary control...
).
Pinworms cannot damage the skin, and they do not normally migrate through tissues
Tissue (biology)
Tissue is a cellular organizational level intermediate between cells and a complete organism. A tissue is an ensemble of cells, not necessarily identical, but from the same origin, that together carry out a specific function. These are called tissues because of their identical functioning...
. However, in women they may move onto the vulva
Vulva
The vulva consists of the external genital organs of the female mammal. This article deals with the vulva of the human being, although the structures are similar for other mammals....
and into the vagina
Vagina
The vagina is a fibromuscular tubular tract leading from the uterus to the exterior of the body in female placental mammals and marsupials, or to the cloaca in female birds, monotremes, and some reptiles. Female insects and other invertebrates also have a vagina, which is the terminal part of the...
, from there moving to external orifice of the uterus
External orifice of the uterus
The external orifice of the uterus is a small, depressed, somewhat circular aperture on the rounded extremity of the vaginal portion of the cervix. Through this aperture, the cervical cavity communicates with that of the vagina.The external orifice is bounded by two lips, an anterior and a posterior...
, and onwards to the uterine cavity, fallopian tubes, ovaries, and peritoneal cavity
Peritoneal cavity
The peritoneal cavity is a potential space between the parietal peritoneum and visceral peritoneum, that is, the two membranes that separate the organs in the abdominal cavity from the abdominal wall...
. This can cause vulvovaginitis, i.e. an inflammation of the vulva and vagina. This causes vaginal discharge
Vaginal discharge
Vaginal discharge is term given to biological fluids contained within or expelled from the vagina.While most discharge is normal and can reflect the various stages of a woman's cycle, some discharge can be a result of an infection, such as a sexually transmitted disease.The term blennorrhea is...
and pruritus vulvae
Pruritus vulvae
Pruritus vulvae is pruritus of the vulva, which is the counterpart of pruritus scroti, and may be caused by many different causes.- Causes :This condition is a symptom of an underlying condition more often than it is a primary condition....
, i.e., itch
Itch
Itch is a sensation that causes the desire or reflex to scratch. Itch has resisted many attempts to classify it as any one type of sensory experience. Modern science has shown that itch has many similarities to pain, and while both are unpleasant sensory experiences, their behavioral response...
iness of the vulva. The pinworms can also enter the urethra
Urethra
In anatomy, the urethra is a tube that connects the urinary bladder to the genitals for the removal of fluids out of the body. In males, the urethra travels through the penis, and carries semen as well as urine...
, and presumably, they carry intestinal bacteria with them. According to Gutierrez (2000), a statistically significant correlation between pinworm infection and urinary tract infection
Urinary tract infection
A urinary tract infection is a bacterial infection that affects any part of the urinary tract. Symptoms include frequent feeling and/or need to urinate, pain during urination, and cloudy urine. The main causal agent is Escherichia coli...
s has been shown, however Burkhart & Burkhart (2005) maintain that the incidence of pinworms as a cause of urinary tract infections remains unknown. Incidentally, one report indicated that 36% of young girls with urinary tract infection
Urinary tract infection
A urinary tract infection is a bacterial infection that affects any part of the urinary tract. Symptoms include frequent feeling and/or need to urinate, pain during urination, and cloudy urine. The main causal agent is Escherichia coli...
also had pinworms. Dysuria
Dysuria
In medicine, specifically urology, dysuria refers to painful urination.Difficult urination is also sometimes described as dysuria.It is one of a constellation of irritative bladder symptoms, which includes urinary frequency and haematuria....
(i.e., painful urination
Urination
Urination, also known as micturition, voiding, peeing, weeing, pissing, and more rarely, emiction, is the ejection of urine from the urinary bladder through the urethra to the outside of the body. In healthy humans the process of urination is under voluntary control...
) has been associated with pinworm infection.
The relationship between pinworm infestation and appendicitis
Appendicitis
Appendicitis is a condition characterized by inflammation of the appendix. It is classified as a medical emergency and many cases require removal of the inflamed appendix, either by laparotomy or laparoscopy. Untreated, mortality is high, mainly because of the risk of rupture leading to...
has been researched, but there is a lack of clear consensus in the matter: while Gutierres (2005) maintains that there exists a consensus that pinworms do not produce the inflammatory reaction, Cook (1994) states that it is controversial whether pinworms are causatively related to acute appendicitis, and Burkhart & Burkhart (2004) state that pinworm infection causes symptoms of appendicitis to surface.
Cause
The lifecycle begins with eggs being ingested
Ingestion
Ingestion is the consumption of a substance by an organism. In animals, it normally is accomplished by taking in the substance through the mouth into the gastrointestinal tract, such as through eating or drinking...
. The eggs hatch in the duodenum
Duodenum
The duodenum is the first section of the small intestine in most higher vertebrates, including mammals, reptiles, and birds. In fish, the divisions of the small intestine are not as clear and the terms anterior intestine or proximal intestine may be used instead of duodenum...
(i.e., first part of the small intestine
Small intestine
The small intestine is the part of the gastrointestinal tract following the stomach and followed by the large intestine, and is where much of the digestion and absorption of food takes place. In invertebrates such as worms, the terms "gastrointestinal tract" and "large intestine" are often used to...
). The emerging pinworm larva
Larva
A larva is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle...
e grow rapidly to a size of 140 to 150 micrometers in size, and migrate through the small intestine towards the colon
Colon (anatomy)
The colon is the last part of the digestive system in most vertebrates; it extracts water and salt from solid wastes before they are eliminated from the body, and is the site in which flora-aided fermentation of unabsorbed material occurs. Unlike the small intestine, the colon does not play a...
. During this migration they moult
Moult
In biology, moulting or molting , also known as sloughing, shedding, or for some species, ecdysis, is the manner in which an animal routinely casts off a part of its body , either at specific times of year, or at specific points in its life cycle.Moulting can involve the epidermis , pelage...
twice and become adults. Females survive for 5 to 13 weeks, and males about 7 weeks. The male and female pinworms mate in the ileum
Ileum
The ileum is the final section of the small intestine in most higher vertebrates, including mammals, reptiles, and birds. In fish, the divisions of the small intestine are not as clear and the terms posterior intestine or distal intestine may be used instead of ileum.The ileum follows the duodenum...
(i.e., last part of the small intestine), whereafter the male pinworms usually die, and are passed out with stool. The gravid female pinworms settle in the ileum
Ileum
The ileum is the final section of the small intestine in most higher vertebrates, including mammals, reptiles, and birds. In fish, the divisions of the small intestine are not as clear and the terms posterior intestine or distal intestine may be used instead of ileum.The ileum follows the duodenum...
, caecum (i.e., beginning of the large intestine
Large intestine
The large intestine is the third-to-last part of the digestive system — — in vertebrate animals. Its function is to absorb water from the remaining indigestible food matter, and then to pass useless waste material from the body...
), appendix
Vermiform appendix
The appendix is a blind-ended tube connected to the cecum , from which it develops embryologically. The cecum is a pouchlike structure of the colon...
and ascending colon
Ascending colon
The ascending colon is smaller in caliber than the cecum.It passes upward, from its commencement at the cecum, opposite the colic valve, to the under surface of the right lobe of the liver, on the right of the gall-bladder, where it is lodged in a shallow depression, the colic impression; here it...
, where they attach themselves to the mucosa and ingest colonic contents. Almost the entire body of a gravid female becomes filled with eggs. The estimations of the number of eggs in a gravid female pinworm ranges from about 11,000 to 16,000. The egg-laying process begins approximately five weeks after initial ingestion of pinworm eggs by the human host. The gravid female pinworms migrate through the colon
Colon (anatomy)
The colon is the last part of the digestive system in most vertebrates; it extracts water and salt from solid wastes before they are eliminated from the body, and is the site in which flora-aided fermentation of unabsorbed material occurs. Unlike the small intestine, the colon does not play a...
towards the rectum
Rectum
The rectum is the final straight portion of the large intestine in some mammals, and the gut in others, terminating in the anus. The human rectum is about 12 cm long...
at a rate of 12 to 14 centimeters per hour. They emerge from the anus
Anus
The anus is an opening at the opposite end of an animal's digestive tract from the mouth. Its function is to control the expulsion of feces, unwanted semi-solid matter produced during digestion, which, depending on the type of animal, may be one or more of: matter which the animal cannot digest,...
, and while moving on the skin near the anus, the female pinworms deposit eggs either through (1) contracting and expelling the eggs, (2) dying and then disintegrating, or (3) bodily rupture due to the host scratching the worm. After depositing the eggs, the female becomes opaque
Opacity (optics)
Opacity is the measure of impenetrability to electromagnetic or other kinds of radiation, especially visible light. In radiative transfer, it describes the absorption and scattering of radiation in a medium, such as a plasma, dielectric, shielding material, glass, etc...
and dies. The reason the female emerges from the anus is to obtain the oxygen necessary for the maturation of the eggs.
Pinworm infection spreads through human-to-human transmission
Transmission (medicine)
In medicine and biology, transmission is the passing of a communicable disease from an infected host individual or group to a conspecific individual or group, regardless of whether the other individual was previously infected...
, by ingesting (i.e., swallowing) infectious pinworm eggs. The eggs are hardy and can remain viable (i.e., infectious) in a moist environment for up to three weeks. They do not tolerate heat well, but can survive in low temperatures: two-thirds of the eggs are still viable after 18 hours at −8 degrees Celsius (18 °F).
After the eggs have been initially deposited near the anus, they are readily transmitted to other surfaces through contamination
Contamination
Contamination is the presence of a minor and unwanted constituent in material, physical body, natural environment, at a workplace, etc.-Specifics:"Contamination" also has more specific meanings in science:...
. The surface of the eggs is sticky when laid, and the eggs are readily transmitted from their initial deposit near the anus to fingernails, hands, night-clothing and bed linen. From here, eggs are further transmitted to food, water, furniture, toys, bathroom fixtures
Plumbing fixture
A plumbing fixture is an exchangeable device which can be connected to an existing plumbing system to deliver and drain away water but which is also configured to enable a particular use.-Common fixtures:The most common plumbing fixtures are:*Bathtubs...
and other objects. Household pets often carry the eggs in their fur, while not actually being infected. Dust containing eggs can become airborne and widely dispersed when dislodged from surfaces, for instance when shaking out bed clothes and linen. Consequently the eggs can enter the mouth and nose through inhalation, and be swallowed later. Although pinworms do not strictly multiply inside the body of their human host, some of the pinworm larvae may hatch on the anal mucosa, and migrate up the bowel and back into the gastrointestinal tract
Gastrointestinal tract
The human gastrointestinal tract refers to the stomach and intestine, and sometimes to all the structures from the mouth to the anus. ....
of the original host. This process is called retroinfection. According to Burkhart (2005), when this retroinfection occurs, it leads to a heavy parasitic load and ensures that the pinworm infestation continues. This statement is contradictory to a statement by Caldwelli (1982), who contends that retroinfection is rare and not clinically significant. Despite the limited, 13 week lifespan of individual pinworms, autoinfection
Autoinfection
Autoinfection is 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. Therefore, the primary host is at the same time the secondary host of the...
(i.e., infection from the original host to itself), either through the anus-to-mouth route or through retroinfection, causes the pinworms to inhabit the same host indefinitely.
Diagnosis
Microscope
A microscope is an instrument used to see objects that are too small for the naked eye. The science of investigating small objects using such an instrument is called microscopy...
. On the other hand, the light-yellowish thread-like adult pinworms are clearly visually detectable, usually during the night when they move near the anus, or on toilet paper. Transparent adhesive tape
Adhesive tape
Adhesive tape is one of many varieties of backing materials coated with an adhesive. Several types of adhesives can be used.-Types:Pressure sensitive tape...
(e.g. Scotch Tape
Scotch Tape
Scotch Tape is a brand name used for certain pressure sensitive tapes manufactured by 3M as part of the company's Scotch brand.- History :The precursor to the current tapes was developed in the 1930s in Minneapolis, Minnesota by Richard Drew to seal a then-new transparent material known as...
) applied on the anal area will pick up deposited eggs, and diagnosis can be made by examining the tape with a microscope. This test is most successful if done every morning for several days, because the females do not lay eggs every day, and the number of eggs vary.
Pinworms do not lay eggs in the feces
Human feces
Human feces , also known as a stool, is the waste product of the human digestive system including bacteria. It varies significantly in appearance, according to the state of the digestive system, diet and general health....
, but sometimes eggs are deposited in the intestine. As such, routine examination of fecal material gives a positive diagnosis in only 5 to 15% of infected subjects, and is therefore of little practical diagnostic use. In a heavy infection, female pinworms may adhere to stools
Human feces
Human feces , also known as a stool, is the waste product of the human digestive system including bacteria. It varies significantly in appearance, according to the state of the digestive system, diet and general health....
that pass out through the anus, and they may thus be detected on the surface on the stool. Adult pinworms are occasionally seen during colonoscopy
Colonoscopy
Colonoscopy is the endoscopic examination of the large bowel and the distal part of the small bowel with a CCD camera or a fiber optic camera on a flexible tube passed through the anus. It may provide a visual diagnosis and grants the opportunity for biopsy or removal of suspected...
. On a microscopic level, pinworms have an identifying feature of alae
Alae (anatomy)
The alae is a protruding ridge that forms longitudinally on many nematodes.In the Caenorhabditis elegans nematode they are present in the L1, dauer and adult stages. The alae is most pronounced during the dauer larval stage and not present in the L2, and L3 C...
(i.e., protruding ridges) running the length of the worm.
Prevention
Pinworm infection cannot be totally prevented under most circumstances. This is due to the prevalence of the parasite and the ease of transmission through soiled night clothes, airborne eggs, contaminated furniture, toys and other objects. Infection may occur in the highest strata of society, where hygiene and nutritionNutrition
Nutrition is the provision, to cells and organisms, of the materials necessary to support life. Many common health problems can be prevented or alleviated with a healthy diet....
al status are typically high. The stigma associated with pinworm infection is hence considered a possible over-emphasis. Counselling is sometimes needed for upset parents that have discovered their children are infected, as they may not realize how prevalent the infection is.
Preventative action revolves around personal hygiene and the cleanliness of the living quarters. The rate of reinfection can be reduced through hygienic measures, and this is recommended especially in recurring cases.
The main measures are keeping fingernails short, and washing and scrubbing hands and fingers carefully, especially after defecation
Defecation
Defecation is the final act of digestion by which organisms eliminate solid, semisolid or liquid waste material from the digestive tract via the anus. Waves of muscular contraction known as peristalsis in the walls of the colon move fecal matter through the digestive tract towards the rectum...
and before meals. Under ideal conditions, bed covers, sleeping garments, and hand towels should be changed daily. Simple laundering of clothes and linen disinfects them. Children should wear gloves while asleep, and the bedroom floor should be kept clean. Food should be covered to limit contamination with dust-borne parasite eggs. Household detergents have little effect on the viability of pinworm eggs, and cleaning the bathroom with a damp cloth moistened with an antibacterial agent or bleach
Bleach
Bleach refers to a number of chemicals that remove color, whiten, or disinfect, often via oxidation. Common chemical bleaches include household chlorine bleach , lye, oxygen bleach , and bleaching powder...
will merely spread the viable eggs. Similarly, shaking clothes and bed linen will detach and spread the eggs.
Treatment
MedicationMedication
A pharmaceutical drug, also referred to as medicine, medication or medicament, can be loosely defined as any chemical substance intended for use in the medical diagnosis, cure, treatment, or prevention of disease.- Classification :...
is the primary treatment for pinworm infection. The existing pharmaceutical drugs against pinworms are so effective that many medical scientists regard hygienic measures as impractical. However, reinfection is frequent regardless of the medication used. Total elimination of the parasite in a household may require repeated doses of medication for up to a year or more. Because the drugs kill the adult pinworms, but not the eggs, the first retreatment is recommended in two weeks. Also, if one household member spreads the eggs to another, it will be a matter of two or three weeks before those eggs become adult worms and thus amenable to treatment. Asymptomatic
Asymptomatic
In medicine, a disease is considered asymptomatic if a patient is a carrier for a disease or infection but experiences no symptoms. A condition might be asymptomatic if it fails to show the noticeable symptoms with which it is usually associated. Asymptomatic infections are also called subclinical...
infections, often in small children, can serve as reservoirs of infection, and therefore the entire household should be treated regardless of whether or not symptoms are present.
The benzimidazole
Benzimidazole
Benzimidazole is a heterocyclic aromatic organic compound. This bicyclic compound consists of the fusion of benzene and imidazole. The most prominent benzimidazole compound in nature is N-ribosyl-dimethylbenzimidazole, which serves as an axial ligand for cobalt in vitamin B12. Benzimidazole, in...
compounds albendazole
Albendazole
Albendazole, marketed as Albenza, Eskazole, Zentel and Andazol, is a member of the benzimidazole compounds used as a drug indicated for the treatment of a variety of worm infestations. Although this use is widespread in the United States, the U.S. Food and Drug Administration has not approved...
(brand names e.g., Albenza, Eskazole, Zentel and Andazol) and mebendazole
Mebendazole
Mebendazole or MBZ is a benzimidazole drug developed by Janssen Pharmaceutica and marketed as Vermox, Ovex, Antiox, and Pripsen...
(brand names e.g., Ovex, Vermox, Antiox and Pripsen) are the most effective. They work by inhibiting the microtubule
Microtubule
Microtubules are a component of the cytoskeleton. These rope-like polymers of tubulin can grow as long as 25 micrometers and are highly dynamic. The outer diameter of microtubule is about 25 nm. Microtubules are important for maintaining cell structure, providing platforms for intracellular...
function in the pinworm adults, causing glycogen
Glycogen
Glycogen is a molecule that serves as the secondary long-term energy storage in animal and fungal cells, with the primary energy stores being held in adipose tissue...
depletion, thereby effectively starving the parasite. A single 100 milligram dose of mebendazole
Mebendazole
Mebendazole or MBZ is a benzimidazole drug developed by Janssen Pharmaceutica and marketed as Vermox, Ovex, Antiox, and Pripsen...
with one repetition after a week, is considered the safest, and is usually effective with cure rate of 96%. Mebendazole has no serious side effects
Side Effects
Side Effects is an anthology of 17 comical short stories written by Woody Allen between 1975 and 1980, all but one of which were previously published in, variously, The New Republic, The New York Times, The New Yorker, and The Kenyon Review. It includes Allen's 1978 O...
, although abdominal pain
Abdominal pain
Abdominal pain can be one of the symptoms associated with transient disorders or serious disease. Making a definitive diagnosis of the cause of abdominal pain can be difficult, because many diseases can result in this symptom. Abdominal pain is a common problem...
and diarrhea
Diarrhea
Diarrhea , also spelled diarrhoea, is the condition of having three or more loose or liquid bowel movements per day. It is a common cause of death in developing countries and the second most common cause of infant deaths worldwide. The loss of fluids through diarrhea can cause dehydration and...
have been reported. Pyrantel pamoate
Pyrantel pamoate
Pyrantel pamoate or Pyrantel Embonate , is used as a deworming agent in the treatment of hookworms and roundworms in domesticated animals such as horses, cattle, sheep, pigs, cats, dogs, and many other species. It is a combination of pyrantel and pamoic acid...
(also called pyrantel embonate, brand names e.g., Reese's Pinworm Medicine, Pin-X, Combantrin, Anthel, Helmintox, and Helmex) kills adult pinworms through neuromuscular blockade, and is considered as effective as the benzimidazole
Benzimidazole
Benzimidazole is a heterocyclic aromatic organic compound. This bicyclic compound consists of the fusion of benzene and imidazole. The most prominent benzimidazole compound in nature is N-ribosyl-dimethylbenzimidazole, which serves as an axial ligand for cobalt in vitamin B12. Benzimidazole, in...
compounds. Other medications are piperazine
Piperazine
Piperazine is an organic compound that consists of a six-membered ring containing two opposing nitrogen atoms. Piperazine exists as small alkaline deliquescent crystals with a saline taste....
, which causes flaccid paralysis
Flaccid paralysis
Flaccid paralysis is a clinical manifestation characterized by weakness or paralysis and reduced muscle tone without other obvious cause .-Polio:...
in the adult pinworms, and pyrvinium pamoate (also called pyrvinium embonate), which works by inhibiting oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
uptake of the adult pinworms. Pinworms located in the genitourinary system
Genitourinary system
In anatomy, the genitourinary system or urogenital system is the organ system of the reproductive organs and the urinary system. These are grouped together because of their proximity to each other, their common embryological origin and the use of common pathways, like the male urethra...
(in this case, female genital area) may require other drug treatments.
Epidemology
Pinworm infection occurs worldwide, and is the most common helminth (i.e., parasitic worm) infection in the United States and Western Europe. In the United States, a study by the Center of Disease Control reported an overall incidence rate of 11.4% among people of all ages. Pinworms are particularly common in children, with prevalence rates in this age group having been reported as high as 61% in India, 50% in England, 39% in Thailand, 37% in Sweden, and 29% in Denmark. Finger sucking has been shown to increase both incidence and relapse rates, and nail bitingNail biting
Onychophagia, or nail biting, is a common oral compulsive habit in children and adults.-Classification:Nail biting is considered an impulse control disorder in the DSM-IV-R; the ICD-10 classifies it as "other specified behavioral and emotional disorders with onset usually occurring in childhood and...
has been similarly associated. Because it spreads from host to host through contamination
Contamination
Contamination is the presence of a minor and unwanted constituent in material, physical body, natural environment, at a workplace, etc.-Specifics:"Contamination" also has more specific meanings in science:...
, pinworms are common among people living in close contact, and tends to occur in all people within a household. The prevalence of pinworms is not associated with gender, nor with any particular social class
Social class
Social classes are economic or cultural arrangements of groups in society. Class is an essential object of analysis for sociologists, political scientists, economists, anthropologists and social historians. In the social sciences, social class is often discussed in terms of 'social stratification'...
, race, or culture. Pinworms are an exception to the tenet that intestinal parasites are uncommon in affluent communities. The earliest known instance of pinworms is evidenced by pinworm eggs found in coprolite
Coprolite
A coprolite is fossilized animal dung. Coprolites are classified as trace fossils as opposed to body fossils, as they give evidence for the animal's behaviour rather than morphology. The name is derived from the Greek words κοπρος / kopros meaning 'dung' and λιθος / lithos meaning 'stone'. They...
, carbon dated to 7837 BC at western Utah
Utah
Utah is a state in the Western United States. It was the 45th state to join the Union, on January 4, 1896. Approximately 80% of Utah's 2,763,885 people live along the Wasatch Front, centering on Salt Lake City. This leaves vast expanses of the state nearly uninhabited, making the population the...
.