Passalurus ambiguus (pinworms)

Passalurus ambiguus is the common pinworm of domestic rabbits, representing the most frequently encountered intestinal nematode parasite in pet rabbits worldwide. This small white worm, typically measuring 4-11 millimeters in length, resides primarily in the cecum and large intestine of infected rabbits where it attaches to the intestinal mucosa and feeds on intestinal contents. Pinworm infection, also called oxyuriasis, is extremely common in rabbit populations, with prevalence studies finding the parasite in a substantial percentage of domestic rabbits regardless of housing conditions or husbandry practices. Importantly, Passalurus ambiguus is host-specific, meaning it can only infect rabbits and related lagomorphs and poses no risk of transmission to humans, dogs, cats, or other species.

The life cycle of Passalurus ambiguus is direct and remarkably efficient, contributing to the high prevalence of this parasite. Adult worms in the cecum and large intestine produce eggs that are immediately infective when passed in the feces. Unlike many parasites that require environmental development, pinworm eggs are ready to cause infection as soon as they are shed. Rabbits become infected by ingesting these eggs, which can occur through consuming contaminated feces (including through normal cecotrophy), or through contact with contaminated environmental surfaces. The eggs hatch in the small intestine, and larvae migrate to the cecum where they mature into adults. The entire life cycle from egg ingestion to new egg production takes approximately 15-26 days.

Despite being common, Passalurus ambiguus typically causes minimal health problems in infected rabbits. Many rabbits harbor pinworms without showing any clinical signs, and heavy infections are required to produce symptoms. When symptoms do occur, they most commonly include perianal irritation manifesting as scratching or biting at the hindquarters, and mild skin inflammation around the anal area. The parasite does not cause significant intestinal damage and is not associated with serious illness in otherwise healthy rabbits. Some owners discover pinworm infection only when they observe small white worms in the feces or around the rabbit's anus. While the parasite itself is relatively harmless, treatment may be desired for aesthetic reasons or to reduce heavy worm burdens.

Treatment of pinworms in rabbits involves antiparasitic medications such as fenbendazole or piperazine, but complete elimination can be challenging due to the parasite's direct life cycle and the rabbit's normal behavior of coprophagy (consumption of cecotropes). Rabbits frequently reinfect themselves during and after treatment by ingesting eggs from their own feces. Successful management typically requires combining medication with intensive environmental cleaning to reduce egg contamination. Because the infection is generally benign and treatment outcomes are often temporary, some veterinarians and owners choose to manage rather than aggressively treat pinworm infections, focusing on maintaining rabbit health while accepting that complete elimination may not be achieved or necessary.

The primary cause of pinworm infection in rabbits is ingestion of infective eggs of Passalurus ambiguus shed by other infected rabbits or through reinfection with the rabbit's own previously passed eggs. The eggs are remarkably efficient at establishing infection because they are immediately infective when shed, requiring no environmental development period. This direct life cycle means that any rabbit ingesting viable eggs, whether from contaminated surfaces, food, water, or during normal cecotrophy, can become infected. The eggs are also relatively hardy and can survive for considerable periods in the environment, particularly in cool, humid conditions, further facilitating transmission.

Genetic factors do not play a role in susceptibility to Passalurus ambiguus, as all rabbits are equally capable of becoming infected when exposed to infective eggs. The host-specific nature of this pinworm means it exclusively infects rabbits and cannot establish in other species. Both wild and domestic rabbits can harbor Passalurus ambiguus, and the parasite has been found in rabbit populations worldwide. No breed, age, or sex predilection has been definitively established, though some studies suggest higher prevalence in adult rabbits compared to juveniles, possibly reflecting cumulative exposure over time and the difficulty of achieving complete elimination.

Environmental and lifestyle factors significantly influence the likelihood of pinworm infection and the ease of transmission. Multi-rabbit households face elevated risk because infected rabbits continuously shed eggs that can infect companions. Even single rabbits commonly acquire infection at some point in their lives, often obtaining initial infection from their parents, littermates, or the environment at breeding facilities, pet stores, or shelters. The normal rabbit behavior of cecotrophy, in which rabbits consume specialized feces called cecotropes directly from the anus for nutritional purposes, can facilitate reinfection when the rabbit consumes its own eggs. Housing conditions influence egg survival and transmission, with environments that are difficult to clean thoroughly potentially maintaining higher egg contamination.

Several factors contribute to the high prevalence and persistence of pinworm infections. The direct life cycle with immediately infective eggs is the primary factor enabling efficient transmission. The rabbit's coprophagic behavior creates opportunity for continuous reinfection. Environmental persistence of eggs means that contaminated spaces remain infectious for extended periods. Some pinworm populations have shown apparent resistance to certain antiparasitic medications, though this is not definitively established for all populations. Even after apparently successful treatment, residual eggs in the environment or incomplete clearance of worms can lead to rapid reestablishment of infection.

The mechanism by which Passalurus ambiguus causes effects in rabbits is primarily mechanical rather than pathological. Adult worms attach to the cecal and colonic mucosa using their mouthparts but cause minimal tissue damage. The worms feed on intestinal contents rather than blood or tissue. Female worms migrate to the distal colon and perianal region to deposit eggs, which can cause local irritation resulting in the scratching behavior sometimes observed in infected rabbits. Heavy worm burdens may theoretically compete with the host for nutrients or cause mild intestinal irritation, but clinically significant effects from this are rarely documented. The parasite has evolved a highly successful commensal relationship with rabbits, causing minimal harm while efficiently maintaining its population.

Early warning signs of Passalurus ambiguus infection may be nonexistent in many rabbits, as the majority of infections remain subclinical throughout their course. When early signs do occur, they may include subtle behavioral changes such as occasional attention to the hindquarters that might not be immediately recognized as abnormal. Some rabbits may show slightly increased grooming of the perianal area. Because many rabbits carry pinworms without any obvious symptoms, early detection often occurs incidentally when owners observe worms in feces or during routine veterinary examination rather than through recognition of specific symptoms. The benign nature of most infections means that subtle early signs are easily overlooked without causing problems.

The most commonly recognized symptoms of pinworm infection, when they occur, relate to perianal irritation caused by egg deposition by female worms. Affected rabbits may scratch, bite, or rub their hindquarters against surfaces in response to itching or irritation. Some rabbits show increased attention to grooming the area around the anus. Skin inflammation, redness, or irritation may be visible around the anal region and on the perineum in cases with significant symptoms. Small white worms, visible to the naked eye, may be observed around the anus or in freshly passed feces; these adult worms are typically 4-11 millimeters long and thread-like in appearance. The presence of visible worms is often what prompts owners to seek veterinary attention.

Behavioral changes specifically attributable to pinworm infection are limited, as the infection rarely affects overall health or behavior. Most infected rabbits continue to eat, drink, and behave normally without obvious changes in activity or temperament. Some rabbits with significant perianal irritation may show restlessness or discomfort, particularly after defecation when egg deposition occurs. Occasional cases may show decreased appetite or mild behavioral changes, though these are uncommon and may indicate either unusually heavy infection or concurrent problems. True behavioral changes more commonly suggest other health issues rather than uncomplicated pinworm infection.

Physical signs of pinworm infection beyond the perianal symptoms are minimal in typical cases. Coat quality, body condition, and overall appearance usually remain normal. Severe chronic infections theoretically could contribute to poor condition, but this is rarely documented in clinical practice. Fecal output typically remains normal in character, though owners may notice small white worms in fresh feces. The rabbit's general health is usually unaffected, and physical examination findings are often unremarkable except for possible perianal irritation. Weight loss, lethargy, or significant changes in condition suggest other problems rather than pinworms alone.

Symptom progression in pinworm infection typically does not follow a deteriorating course. Most infections establish and persist at a relatively stable level without worsening over time. The number of worms present may fluctuate but does not progressively increase to dangerous levels in healthy rabbits. Some infected rabbits never develop symptoms regardless of infection duration. Those with perianal symptoms may experience intermittent irritation correlating with egg deposition cycles. Rare cases of very heavy infection, particularly in young, debilitated, or immunocompromised rabbits, might show more significant symptoms, but this is exceptional rather than typical.

Emergency symptoms are rarely if ever caused by pinworm infection alone. However, owners should be aware of general warning signs in rabbits that require immediate veterinary attention regardless of parasitic status. Any rabbit that stops eating for twelve hours or more needs urgent care due to risk of GI stasis. Severe scratching or self-trauma to the hindquarters causing significant skin damage or bleeding warrants veterinary attention. If perianal irritation is accompanied by signs of more serious illness such as lethargy, hunched posture, or changes in fecal output, comprehensive evaluation is needed. Rectal prolapse, while rare, has been reported in association with severe pinworm infection and requires immediate veterinary care. Generally, any symptoms that go beyond mild perianal irritation suggest either unusually severe pinworm burden or concurrent health problems requiring investigation.

Initial examination for suspected pinworm infection in rabbits begins with history-taking and physical examination by a veterinarian. The veterinarian will ask about observed symptoms, whether worms have been seen, the rabbit's housing and husbandry, and any concerns the owner has. Physical examination includes general health assessment and specific examination of the perianal area for signs of irritation, inflammation, or visible worms. In many cases, owners report observing worms as the primary concern, which helps direct the diagnostic approach. While pinworm infection does not require rabbit-specialist expertise to diagnose, a veterinarian familiar with rabbit parasitology can provide appropriate guidance on whether treatment is necessary and how to manage ongoing infection.

Diagnostic testing for Passalurus ambiguus utilizes specific techniques because the eggs are not consistently detected by standard fecal flotation methods. The most sensitive test is the cellophane tape test (also called the scotch tape test), which involves pressing clear adhesive tape against the perianal area to collect eggs deposited there by female worms, then examining the tape microscopically for characteristic eggs. This test is most effective when performed during afternoon or evening hours due to the circadian rhythm of egg excretion. Standard fecal flotation can detect pinworm eggs but has relatively low sensitivity and may yield false negative results even in infected rabbits. Direct observation of adult worms in feces or around the anus provides immediate confirmation without need for further testing.

Differential diagnosis for perianal symptoms in rabbits includes conditions other than pinworms that can cause similar signs. Urine scald or fecal soiling can cause perianal irritation and may mimic or co-occur with pinworm symptoms. Skin conditions including bacterial dermatitis, fungal infection, or allergic reactions can affect the perianal area. Anal gland problems, though less common in rabbits than in some species, may cause similar symptoms. Musculoskeletal or neurological problems preventing normal grooming can lead to perianal soiling and secondary irritation. Dietary issues causing soft feces or cecotrope accumulation may cause perianal problems. Thorough examination helps differentiate these conditions from simple pinworm infection.

Confirmation of pinworm infection is achieved through demonstration of characteristic eggs on tape test or fecal examination, or through observation of adult worms. The eggs of Passalurus ambiguus are distinctive when examined microscopically, being asymmetrical with one flattened side. Adult worms are readily identifiable as small, white, thread-like organisms. Because the infection is common and often incidental, finding pinworms does not necessarily explain all clinical signs if present; concurrent conditions should be considered if symptoms seem disproportionate to expected effects from pinworms alone. False negative test results can occur, particularly with fecal flotation, so negative results do not definitively rule out infection if clinical suspicion is high.

Emergency treatment is not typically applicable to pinworm infection, as this condition does not cause acute illness requiring emergency intervention. Pinworms do not cause life-threatening disease in rabbits, and treatment can be scheduled at the owner's and veterinarian's convenience rather than on an urgent basis. If a rabbit with known or suspected pinworms develops emergency symptoms such as complete appetite loss, signs of GI stasis, severe self-trauma, or rectal prolapse, these complications require appropriate urgent treatment, but such scenarios are rare and likely involve concurrent problems beyond simple pinworm infection.

Medical management of pinworm infection typically employs benzimidazole antiparasitic medications, with fenbendazole being the most commonly used option. Effective protocols include fenbendazole at 10-20 mg/kg orally once daily for five days, repeated after 10-14 days to address immature stages. Alternative medications include thiabendazole (50 mg/kg orally, repeated in 10-14 days) and piperazine, which can be administered to individual rabbits at 200 mg/kg orally repeated in 14 days, or added to drinking water (100 mg/100 mL for one day, repeated in 10 days) for treating groups. Mebendazole is another option. Notably, ivermectin has shown poor efficacy against Passalurus ambiguus in studies and is not recommended as a primary treatment for pinworms despite its effectiveness against other parasites.

Surgical intervention is not applicable to pinworm treatment. The infection is managed entirely through medical therapy and environmental management. Surgical care would only be relevant if a rare complication such as rectal prolapse developed, which would be treated for the complication itself rather than as part of pinworm management.

Supportive care for pinworm infection is minimal because the condition rarely affects the rabbit's overall health. For rabbits with significant perianal irritation, gentle cleaning of the area may provide comfort and prevent secondary skin problems. Ensuring the rabbit is eating well and maintaining normal fecal output remains important as general rabbit care practice. Rabbits do not typically require nutritional support, fluid therapy, or other intensive supportive measures for uncomplicated pinworm infection. Maintaining good overall husbandry, appropriate diet, and a clean living environment supports recovery and helps reduce reinfection pressure.

Environmental management is crucial for successful pinworm treatment and may be more important than medication alone. Because eggs are immediately infective and environmental contamination facilitates reinfection, thorough cleaning must accompany antiparasitic treatment. The rabbit's entire living area should be cleaned daily during treatment, with removal of all feces. Litter should be changed completely rather than spot-cleaned. Hard surfaces can be cleaned with hot water or steam. Pinworm eggs are resistant to many disinfectants but susceptible to heat and desiccation. All accessories, toys, and enrichment items should be cleaned. If multiple rabbits are housed together, all must be treated simultaneously to prevent cross-infection.

Treatment decisions should acknowledge the benign nature of pinworm infection and the challenges of achieving complete elimination. Some veterinarians and owners choose not to treat asymptomatic infections, accepting the parasite's presence while focusing on overall rabbit health. When treatment is undertaken, realistic expectations about outcomes are important; reinfection is common even after apparently successful treatment due to environmental egg persistence and the rabbit's coprophagic behavior. Repeated treatment courses may be needed, and ongoing environmental management is essential. For rabbits in multi-rabbit households, coordinated treatment of all animals is necessary to reduce transmission.

Recovery timeline for rabbits treated for pinworm infection depends on the goals of treatment and the thoroughness of environmental management. Visible worms in feces typically disappear within days of starting effective antiparasitic treatment as adult worms are killed. Perianal irritation symptoms, if present, usually improve within one to two weeks as the worm burden decreases. Complete elimination of infection, confirmed by negative tape tests, may be achieved within two to four weeks of comprehensive treatment with repeat dosing and intensive environmental cleaning. However, reinfection is common, and some rabbits show evidence of renewed infection within weeks of completing treatment if environmental management lapses or if exposure to infected rabbits continues.

Post-treatment care focuses on preventing reinfection through ongoing environmental hygiene. Daily litter box cleaning should continue after treatment completion. Regular cleaning of the rabbit's living area helps reduce any residual environmental egg contamination. Monitoring for visible worms in feces provides indication of reinfection if treatment was initially successful. Follow-up tape testing can confirm elimination if desired, though given the benign nature of infection, many owners simply monitor for symptom recurrence. For rabbits in multi-rabbit households, ongoing attention to hygiene helps reduce transmission between animals.

Prognosis for pinworm infection is excellent in terms of rabbit health, as the condition does not cause serious illness. Rabbits tolerate pinworm infection well and are not harmed by the presence of the parasites even when complete elimination is not achieved. Prognosis for achieving complete elimination is more guarded, as reinfection commonly occurs despite treatment. Factors improving prospects for elimination include single-rabbit households, ability to perform thorough environmental cleaning, and sustained commitment to hygiene practices. Multi-rabbit environments, housing that is difficult to clean thoroughly, and inconsistent husbandry practices make elimination more challenging.

Long-term outlook for rabbits with pinworm infection is unaffected by the parasite's presence in terms of health and lifespan. Many rabbits carry pinworms throughout their lives without developing health problems. Ongoing management may involve acceptance of chronic low-level infection in some cases, with treatment reserved for symptomatic episodes or heavy burdens causing visible worms. Periodic recurrence of visible infection is common and does not indicate treatment failure or owner negligence so much as the inherent difficulty of eliminating a parasite perfectly adapted to its host. Owners should be reassured that pinworm presence does not indicate poor care and does not threaten their rabbit's wellbeing.

Primary prevention of pinworm infection is challenging because the parasite is highly prevalent in rabbit populations and transmitted efficiently through the direct life cycle. Complete prevention would require isolation from all other rabbits and maintenance in a pathogen-free environment, which is impractical for most pet rabbit situations. More realistic prevention goals include minimizing the level of environmental contamination and reducing exposure opportunities. Obtaining rabbits from sources with good husbandry practices and health screening may reduce but not eliminate initial infection risk. Quarantining and testing new rabbits before introduction to existing pets allows identification of infection before it spreads.

Environmental management represents the most practical approach to limiting pinworm transmission and burden. Regular thorough cleaning of the rabbit's living space removes eggs before they can be ingested. Daily litter box cleaning reduces the primary reservoir of eggs. Hard surfaces can be cleaned with hot water or steam; pinworm eggs are susceptible to heat and drying. Good ventilation and dry conditions make the environment less hospitable for egg survival. Separate housing for quarantined or newly treated rabbits prevents immediate recontamination of cleaned areas. For multi-rabbit households, coordinated cleaning and treatment of all animals together is more effective than isolated efforts.

Dietary factors do not directly affect pinworm infection risk, but good nutrition supports overall rabbit health and immune function. A proper hay-based diet maintains gut health and general wellbeing. Clean food and water sources, while not specifically preventing pinworm transmission (which occurs through fecal contamination), represent good husbandry practice. The normal coprophagic behavior of rabbits, which involves consuming cecotropes for nutritional purposes, is a natural and beneficial behavior that should not be discouraged despite its role in potential self-reinfection with pinworms; the nutritional benefits outweigh the minimal health impact of pinworm carriage.

Health maintenance practices support rabbits' ability to tolerate pinworm infection without developing clinical problems. Regular veterinary care allows monitoring of overall health and can identify pinworm infection through routine fecal examination. Good general husbandry including appropriate diet, clean housing, environmental enrichment, and stress reduction supports immune function and overall health. For rabbits known to have recurring pinworm issues, periodic preventive treatment may be considered, though this approach must be balanced against the limited harm caused by infection and the challenge of achieving lasting elimination.

Early intervention when heavy infection develops helps manage symptoms before significant irritation or discomfort occurs. Owners familiar with their rabbit's normal behavior can recognize early signs of perianal discomfort. Observation of visible worms prompts investigation and treatment decisions. Regular attention to the rabbit's hindquarters during grooming or handling allows early detection of perianal irritation. Working with a veterinarian to develop a management plan appropriate to the individual situation, whether that involves aggressive treatment attempts or accepting chronic low-level infection, provides guidance for ongoing care.

Daily management of rabbits with pinworm infection focuses on environmental hygiene and monitoring for symptoms. Whether actively treating infection or managing ongoing presence of the parasite, daily litter box cleaning removes the primary source of reinfection. Observation of feces for visible worms provides ongoing information about infection status. Monitoring the rabbit's behavior for signs of perianal discomfort, such as excessive grooming of the hindquarters or rubbing against surfaces, alerts owners to potential symptomatic episodes. During active treatment, medication administration follows prescribed protocols, typically once-daily oral dosing. Food and water intake should be monitored to ensure the rabbit maintains normal eating habits throughout any treatment period.

Home environment management for rabbits with pinworms emphasizes cleanliness and practicality. Housing should be designed for easy cleaning, with solid flooring or appropriate bedding that can be completely replaced rather than spot-cleaned. All cage components, dishes, and accessories should be cleanable with hot water. Litter boxes should be emptied and cleaned daily during treatment and at least every one to two days for ongoing management. Hard surfaces can be sanitized with hot water or steam. Soft materials that cannot be thoroughly cleaned may harbor eggs and should be washed in hot water or discarded if heavily contaminated. Practical environmental management balances thorough hygiene with realistic expectations about the difficulty of complete egg elimination.

Maintaining quality of life for rabbits with pinworm infection requires no special accommodations in most cases. The infection is generally benign and does not impair the rabbit's ability to enjoy normal activities, social interaction, or environmental enrichment. Rabbits with pinworms can participate in normal exercise, play, and bonding with owners and companion rabbits. Dietary management follows standard rabbit nutrition guidelines without modification for pinworm status. Social housing with other rabbits is appropriate, though owners should be aware that transmission between companions is essentially inevitable and all rabbits should be managed together. The presence of pinworms should not diminish the rabbit's quality of life or the owner's enjoyment of their pet.

Ongoing monitoring involves periodic attention to signs of infection without excessive concern over this generally harmless parasite. Owners may choose to perform occasional visual checks for worms in feces. Any development of perianal irritation or behavioral changes warrants evaluation and possible treatment. Routine veterinary visits provide opportunity for professional assessment and discussion of management approaches. Long-term management decisions balance the benefits and limitations of repeated treatment against acceptance of chronic infection. For most pet rabbits, ongoing presence of pinworms at low levels poses no health concern and requires only routine attention.

Caregiver support for managing pinworm infection involves education about the benign nature of the condition and realistic expectations about treatment outcomes. Many owners feel distressed upon discovering their rabbit has worms, and reassurance about the minimal health impact helps alleviate concerns. Understanding that pinworms are common in rabbits, not indicative of poor care, and not transmissible to humans provides important context. The House Rabbit Society and other rabbit welfare organizations provide educational resources about common rabbit health conditions including parasites. Financial impact of pinworm management is modest, typically involving only medication costs and possibly veterinary consultation, making this one of the less burdensome conditions to address from a practical standpoint.

Passalurus ambiguus infection does not show breed predilection, as all domestic rabbit breeds are equally susceptible to infection. The parasite has been documented across the full range of rabbit breeds, from dwarf varieties to giant breeds and all types between. Susceptibility is determined by exposure rather than genetic factors, and no breed demonstrates increased resistance or vulnerability to pinworm infection. Studies of pinworm prevalence in rabbit populations have not identified breed as a significant risk factor. Both purebred and mixed-breed rabbits acquire infection at similar rates under comparable exposure conditions.

Age and housing factors influence pinworm prevalence more than breed characteristics. Some studies suggest higher prevalence in adult rabbits compared to juveniles, possibly reflecting cumulative exposure over time and the difficulty of eliminating established infection. Rabbits from breeding facilities, pet stores, and shelters often have higher prevalence due to population density and varied exposure histories. Indoor versus outdoor housing does not significantly affect pinworm risk in the same way it affects other parasites, because Passalurus ambiguus transmission occurs primarily through direct fecal contamination and coprophagy rather than through environmental stages that require outdoor exposure. Multi-rabbit households maintain higher transmission pressure than single-rabbit homes.

Screening recommendations apply universally rather than targeting specific breeds. Fecal examination or tape testing for pinworms may be included in routine health assessments for any rabbit, particularly new acquisitions from unknown backgrounds. Screening before introduction to existing rabbits can identify infection, though given the high prevalence and low pathogenicity, positive results do not necessarily preclude introduction. Symptomatic rabbits showing perianal irritation warrant examination regardless of breed. Routine screening of healthy asymptomatic rabbits specifically for pinworms is optional given the benign nature of infection, though comprehensive parasite screening during annual veterinary visits can identify this and other parasitic conditions.

Pinworm infection may co-occur with other parasitic conditions and can exist alongside various health problems in rabbits. Coccidia (Eimeria species) are common intestinal parasites that frequently coexist with pinworms; both parasites may be found during fecal examination of the same rabbit. E. cuniculi, while affecting different organ systems, can be present in rabbits also harboring pinworms. Other intestinal nematodes, though less common than pinworms in pet rabbits, may occasionally be found concurrently. In studies of mixed infections, combinations of pinworms, coccidia, and other organisms have been associated with more significant clinical signs than single-pathogen infections, though pinworms alone typically cause minimal problems.

Conditions producing similar symptoms to pinworm infection include various causes of perianal irritation in rabbits. Urine scald from urinary problems or mobility issues causes perianal wetness and irritation that may mimic pinworm-related symptoms. Fecal soiling from soft feces or inability to consume cecotropes properly can cause perianal matting and secondary skin irritation. Bacterial dermatitis or fungal infection of perianal skin can cause itching and inflammation. Anal gland issues, while uncommon in rabbits, may cause similar symptoms. Arthritis or spinal problems preventing normal grooming lead to perianal hygiene problems. Careful examination helps differentiate these conditions from pinworm infection, though multiple problems may coexist.

Potential complications directly attributable to pinworm infection are rare given the benign nature of typical infection. Perianal dermatitis may develop secondary to irritation and scratching, particularly if the skin is broken. Severe chronic irritation could theoretically lead to self-trauma, though significant self-inflicted injury is uncommon. Rectal prolapse has been rarely reported in association with heavy pinworm infection, though other contributing factors are usually present. Secondary bacterial infection of irritated perianal skin is possible. Generally, complications from pinworms are uncommon, and development of significant problems should prompt investigation for concurrent conditions or underlying factors beyond simple pinworm infection.