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Pinworm infection (threadworm)
Page content: Victorian statutory requirement | Infectious agent | Identification | Incubation period | Public health significance & occurrence | Reservoir | Mode of transmission | Period of communicability | Susceptibility & resistance | Control measures | Outbreak measures | Additional sources of information
Victorian statutory requirement
Notification and school exclusion are not required.
Infectious agent
Enterobius vermicularis is an intestinal nematode.
Identification
Clinical features
In the majority of children and adults infection is asymptomatic. Migration of the female worm from the rectum then anus to lay eggs on the perianal skin during the night can lead to perianal pruritus or disturbed sleep or irritability. Sometimes secondary infection of the scratched skin occurs. In children the pinworm can cause vulvovaginitis during its migration from the anus.
Pinworms or their eggs have occasionally been detected at other sites such as the liver and lung. Rarer clinical manifestations include salpingitis, pelvic pain and the formation of granulomas in the peritoneal cavity.
Method of diagnosis
The diagnosis should be suspected in children with a perianal itch and this is confirmed by detection of their characteristic eggs. Applying clear sticky tape ({with sticky side outward) to the perianal skin and examining it for eggs is the best way to make the diagnosis. This is best done in the morning prior to bathing, as the worms migrate during resting periods. Microscopy on faeces can be conducted although finding eggs is exceptional.
Incubation period
The lifecycle requires two to six weeks to complete. The eggs are fully embryonated and are infective within a few hours of being deposited. Male and female pinworms vary in size ranging between 2–13mm in length, up to 0.5mm wide and are yellowish white in colour. A long, thin and sharply pointed tail distinguishes the female worm.
Public health significance & occurrence
The pinworm is the most common helminth parasite of temperate regions. These infections are found worldwide and affect all socio-economic groups.
Less attention is paid to the pinworm in tropical regions of the world presumably because of the prevalence of more important parasites. Pinworm infections predominantly affect paediatric populations where the prevalence is reported to between 10–50% in some groups.
Reservoir
Humans are the only reservoir. Pinworms of other animals are not transmissible to humans.
Mode of transmission
Pinworms are transmitted by direct transfer of infected eggs by hand from anus to mouth of the same or another person. It can also be transmitted indirectly through bedding, clothing, food or other articles. Spread is facilitated by conditions of overcrowding.
Period of communicability
Communicability continues as long as the eggs are being discharged on the perianal area. The eggs can survive for several days in the right conditions. Reinfection from contaminated hands is common.
Susceptibility & resistance
Infection does not confer immunity.
Control measures
Preventive measures
- Effective hand washing, particularly before eating or preparing food.
- Keep nails short, discourage scratching bare anal area and nail biting.
- Daily bathing or showering.
- Change to clean underwear, nightclothes and bed sheets frequently preferably after bathing.
Control of case
There are a number of drugs available for treatment including pyrantel pamoate, mebendazole or albendazole. Consult the current version of Therapeutic guidelines: antibiotic (Therapeutic Guidelines Limited).
Care should be taken to change linen and underwear of infected person daily for several days after treatment with care to avoid dispersing the eggs into the air.
Control of contacts
Not applicable.
Special settings
Public health education on the importance of hand washing may assist.
Outbreak measures
Not applicable.
Additional sources of information
Markell, E, John, D, Krotoski, W 1999, Markell and Voge’s medical parasitology, 8th edn, ed Saunders.
