Section 6: Infestations

Patient Story

A 12-year-old girl presented to a homeless clinic with her mother for itching on her head. The physical examination revealed multiple nits in her long straight hair (Figure 127-1). A live adult louse was also found crawling on the hairs around her neck (Figure 127-2). The clinician also examined her mother and found a few nits on the hair behind her ears. There were no other members of the family living at the shelter so both were treated with permethrin now and in one week to kill any remaining live nits before they hatch. The clinician alerted the shelter staff of this infestation and other families were found to be infested. The girl was given permission to return to school if she completed her treatment with the permethrin cream rinse. The clinician recommended that clothes, bed clothes, combs and brushes be washed in hot water.

Introduction

Lice are ectoparasites that live on or near the body.¹ They will die of starvation within 10 days of removal from their human host. Lice have coexisted with humans for at least 10,000 years.² Lice are ubiquitous and remain a major problem throughout the world.³

Synonyms

Pediculosis, crabs (pubic lice).

Epidemiology

• Human lice (pediculosis corporis, pediculosis pubis, and pediculosis capitis) are found in all countries and climates.³

• Head lice are most common among school-age children. Each year, approximately 6 to 12 million children, ages 3 to 12 years, are infested.⁴

• Head lice infestation is seen across all socioeconomic groups and is not a sign of poor hygiene.⁵

• In the US, black children are affected less often as a result of their oval-shaped hair shafts that are difficult for lice to grasp.⁴

• Body lice infest the seams of clothing (Figure 127-3) and bed linen. Infestations are associated with poor hygiene and conditions of crowding.

• Pubic lice are most common in sexually active adolescents and adults. Young children with pubic lice typically have infestations of the eyelashes. Although infestations in this age group may be an indication of sexual abuse, children generally acquire the crab lice from their parents.⁶

Etiology and Pathophysiology

• Lice are parasites that have six legs with terminal claws that enable them to attach to hair and clothing. There are three types of lice responsible for human infestation. All three kinds of lice must feed daily on human blood and can only survive 1 to 2 days away from the host. The three types of lice are as follows:

  • Head lice (Pediculus humanus capitis)—Measure 2 to 4 mm in length (Figures 127-2 and 127-4).

  • Body lice (Pediculus humanus corporis)—Body lice similarly measure 2 to 4 mm in length (Figure 127-5).

  • Pubic or crab lice (Phthirus pubis)—Pubic lice are shorter, with a broader body and have an average length of 1 to 2 mm (Figure 127-6).

• Female lice have a lifespan of approximately 30 days and can lay approximately 10 eggs (nits) a day.⁴

• Nits are firmly attached to the hair shaft or clothing seams by a glue-like substance produced by the louse (Figure 127-7).

• Nits are incubated by the host’s body heat.

• The incubation period from laying eggs to hatching of the first nymph is 7 to 14 days.

• Mature adult lice capable of reproducing appear 2 to 3 weeks later.⁵

• Transmission of head lice occurs through direct contact with the hair of infested individuals. The role of fomites (e.g., hats, combs, brushes) in transmission is negligible.⁶ Head lice do not serve as vectors for transmission of disease among humans.

• Transmission of body lice occurs through direct human contact or contact with infested material. Unlike head lice, body lice are well-recognized vectors for transmission of the pathogens responsible for epidemic typhus, trench fever, and relapsing fever.⁵

• Pubic or crab lice are transmitted primarily through sexual contact. In addition to pubic hair (Figure 127-8), infestations of eyelashes, eyebrows, beard, upper thighs, abdominal, and axillary hairs may also occur.

Risk Factors

• Contact with an infected individual. This commonly occurs in schools or between siblings at home.

• Living in crowded quarters such as homeless shelters.

• Poor hygiene and mental illness.

Diagnosis

Clinical Features

• Nits can be seen in active disease or treated disease. Nits closer to the base of the hairs are generally newer and more likely to be live and unhatched. Unfortunately, nits that were not killed by pediculicides can hatch and start the infestation cycle over again. Note that nits are glued to the hairs and are hard to remove, whereas flakes of dandruff can be easily brushed off.

• Pruritus is the hallmark of lice infestation. It is the result of an allergic response to louse saliva.⁷ Head lice are associated with excoriated lesions that appear on the scalp, ears, neck, and back.

• Occipital and cervical adenopathy may develop, especially when lesions become superinfected.

• Body lice result in small maculopapular eruptions that are predominantly found on the trunk and in the seams of the clothing (Figure 127-3).

• Chronic infestations often result in hyperpigmented, lichenified plaques known as “vagabond’s skin.”⁸

• Pubic lice produce bluish-gray spots (macula cerulea) that can be found on the chest, abdomen, and thighs.⁸

Typical Distribution

• Head lice—Look for nits and lice in the hair especially above the ears, behind the ears, and at the nape of the neck. There are many more nits present than live adults. Finding nits without an adult louse does not mean that the infestation has resolved (Figures 127-1 and 127-6). Systematically combing wet or dry hair with a fine toothed nit comb (teeth of comb are 0.2 mm apart) better detects active louse infestation than visual inspection of the hair and scalp alone.⁹

• Body lice—Look for the lice and larvae in the seams of the clothing (Figure 127-3).

• Pubic lice—Look for nits and lice on the pubic hairs (Figure 127-8). These lice and their nits may also be seen on the hairs of the upper thighs, abdomen, axilla, beard, eyebrows, and eyelashes. Little specks of dried blood may be seen in the underwear as a clue to the infestation. The diagnosis of pubic lice in a child (under age 18) should prompt the clinician to inquire about sexual abuse.

Laboratory Testing

• Direct visualization and identification of live lice or nits are sufficient to make a diagnosis (Figures 127-1 to 127-9).

• The use of a magnification lens may aid in the detection or confirmation of lice infestation.

• Under Wood light the head lice nits fluoresce a pale blue.

• If you find an adult louse put it on a slide with a cover slip loosely above it. Look at it under the microscope on the lowest power (Figures 127-4 and 127-5). You will see the internal workings of the live organs. If the louse was not found in a typical location, you can use the morphology of the body and legs to determine the type of louse causing the infestation.

• In cases of pubic lice infestations, individuals should be screened for other sexually transmitted diseases.⁵

Differential Diagnosis

• Dandruff, hair casts, and debris should be ruled out in cases of suspected lice infestations. Unlike nits, these particles are easily removed from the hair shaft. In addition, adult lice are absent.

• Scabies is also characterized by intense pruritus and papular eruptions. Unlike lice infestations, scabies may be associated with vesicles, and the presence of burrows is pathognomonic. Diagnosis is confirmed by microscopic examination of the scrapings from lesions for the presence of mites or eggs (see Chapter 128, Scabies).

Management

Nonpharmacologic

• In young children or others who wish to avoid topical pediculicides for head lice, mechanical removal of lice by wet combing is an alternative therapy. A 1:1 vinegar: water rinse (left under a conditioning cap or towel for 15 to 20 minutes) or 8 percent formic acid crème rinse may enhance removal of tenacious nits.⁸ Combing is performed until no lice are found for 2 weeks. SOR B

  • Nits are also removed with a fine-toothed comb following the application of all treatments. This step is critical in achieving resolution.

  • Combs and hairbrushes should be discarded, soaked in hot water (at a temperature of at least 55°C [130°F]) for 5 minutes, or treated with pediculicides.¹⁰

Medications

• Pediculus humanus capitis (head lice):

  • Nonprescription 1 percent permethrin cream rinse (Nix), pyrethrins with piperonyl butoxide (which inhibits pyrethrin catabolism; RID) shampoo, or permethrin 1 percent is applied to the hair and scalp and left on for 10 minutes then rinsed out.¹¹ SOR A In Figure 127-9, a group of medical students is helping children in Ethiopia to apply permethrin to their lice infested hair.

  • Pyrethrins are only pediculicidal, whereas permethrin is both pediculicidal and ovicidal. It is important to note that treatment failure is common with these agents owing to the emergence of resistant strains of lice.

  • After 7 to 10 days repeating the application is optional when permethrin is used, but is a necessary for pyrethrin. Lice persisting after treatment with a pyrethroid may be an indication of resistance.

  • Malathion 0.5 percent (Ovide) is available by prescription only, and is a highly effective pediculicidal and ovicidal agent for resistant lice. Malathion may have greater efficacy than pyrethrins.¹² It is approved for use in children age 6 years and older. The lotion is applied to dry hair for 8 to 12 hours and then washed. Repeat application is recommended after 7 to 10 days if live lice are still present. When used appropriately, malathion is 78 percent to 95 percent effective.¹² SOR A

  • Benzyl alcohol 5 percent lotion (Ulesfia) is a newer treatment option in patients 6 months of age and older. It works by asphyxiating the parasite. It is applied for 10 minutes with saturation of the scalp and hair, and then rinsed off with water. The treatment is repeated after 7 days.¹³ SOR A

  • Spinosad (Natroba) is a new topical prescription medication approved by the FDA in 2011 for the treatment of lice. Spinosad is a fermentation product of the soil bacterium Saccharopolyspora spinosa that compromises the central nervous system of lice. It is approximately 85 percent effective in lice eradication, usually after one application. It is applied to completely cover the dry scalp and hair, and rinsed off after 10 minutes. Treatment should be repeated if live lice remain 7 days after the initial application.¹⁴ SOR A

  • In February 2012, the US FDA approved ivermectin 0.5 percent lotion for the treatment of head lice for people above 6 months of age. It is applied as a single 10-minute topical application. The safety of ivermectin in infants younger than age 6 months has not been established.¹⁵ SOR A

  • Hair conditioners should not be used prior to the application of pediculicides; these products may result in reduced efficacy.¹⁶

  • A Cochrane review found no evidence that any one pediculicide was better than another; permethrin, synergized pyrethrin, and malathion were all effective in the treatment of head lice.¹⁷ SOR A

  • Other therapeutic options include permethrin 5 percent cream and lindane 1 percent shampoo. Permethrin 5 percent is conventionally used to treat scabies; however, it is anecdotally recommended for treatment of recalcitrant head lice.⁵ SOR C

  • Lindane is considered a second-line treatment option owing to the possibility of central nervous system toxicity, which is most severe in children.

  • Oral therapy options include a 10-day course of trimethoprim-sulfamethoxazole or 2 doses of ivermectin (200 mcg/kg) 7 to 10 days apart. SOR C Trimethoprim-sulfamethoxazole is postulated to kill the symbiotic bacteria in the gut of the louse.⁴ Combination therapy with 1 percent permethrin and trimethoprim-sulfamethoxazole is recommended in cases of multiple treatment failure or suspected cases of resistance to therapy.^5,10 SOR C

• Pediculus humanus corporis (body lice):

  • Improving hygiene, and laundering clothing and bed linen at temperatures of 65°C (149°F) for 15 to 30 minutes will eliminate body lice.⁸

  • In settings where individuals cannot change clothing (e.g., indigent population), a monthly application of 10 percent lindane powder can be used to dust the lining of all clothing.⁸

  • Additionally, permethrin cream may be applied to the body for 8 to 12 hours to eradicate body lice.

• Phthirus pubis (pubic lice):

  • Pubic lice infestations are treated with a 10-minute application of the same topical pediculicides used to treat head lice.

  • Retreatment is recommended 7 to 10 days later.

  • Petroleum ointment applied 2 to 4 times a day for 8 to 10 days will eradicate eyelash infestations.

  • Clothing, towels, and bed linen should also be laundered to eliminate nit-bearing hairs.⁸

Prevention

• Washing clothing and linen used by the head or pubic lice-infested person during the 2 days prior to therapy in hot water and/or drying the items on a high-heat dryer cycle (54.5°C [130°F]). Items that cannot be washed may be dry cleaned or stored in a sealed plastic bag for 2 weeks.

Follow-Up

• Patients should be reexamined upon completion of therapy to confirm eradication of lice.

Patient Education

• Patients should be instructed to wash potentially contaminated articles of clothing, bed linen, combs, brushes, and hats.

• Nit removal is important in preventing continued infestation as a result of new progeny. Careful examination of close contacts, with appropriate treatment for infested individuals is important in avoiding recurrence.

• In cases of pubic lice, all sexual contacts should be treated.

Patient Story

A 2-year-old boy is seen with severe itching and crusting of his hands (Figures 128-1 and 128-2). He also has a pruritic rash over the rest of his body. The child has had this problem since 2 months of age and has had a number of treatments for scabies. Other adults and children in the house have itching and rash. Various attempts at treatment have only included topical preparations. A scraping was done and scabies mites and scybala (feces) were seen (Figures 128-3 and 128-4). The child and all the family members were put on ivermectin simultaneously and the Norwegian scabies cleared from the child. The family cleared as well and the child was given a repeat dose of ivermectin to avoid relapse.

Synonyms

Seven-year itch.

Epidemiology

• Three hundred million cases per year are estimated worldwide.¹ In some tropical countries, scabies is endemic.

• The prevalence of scabies among school children in Nigeria was reported to be 4.7 percent in 2005.²

• The prevalence of scabies among boarding school children in Malaysia in 2009 was found to be 8.1 percent.³

Etiology and Pathophysiology

• Human scabies is caused by the mite Sarcoptes scabei, an obligate human parasite (Figure 128-3).^1,4

• Adult mites spend their entire life cycle, around 30 days, within the epidermis. After copulation the male mite dies and the female mite burrows through the superficial layers of the skin excreting feces (Figure 128-4) and laying eggs (Figure 128-5).

• Mites move through the superficial layers of skin by secreting proteases that degrade the stratum corneum.

• Infected individuals usually have less than 100 mites. In contrast, immunocompromised hosts can have up to 1 million mites, and are susceptible to crusted scabies also called Norwegian scabies (Figures 128-1 and 128-2, and 128-6 to 128-8).¹

• Transmission usually occurs via direct skin contact (Figures 128-9). Scabies in adults is frequently sexually transmitted.⁵ Scabies mites can also be transmitted from animals to humans.¹

• Mites can also survive for 3 days outside of the human epidermis allowing for infrequent transmission through bedding and clothing.

• The incubation period is on average 3 to 4 weeks for an initial infestation. Sensitized individuals can have symptoms within hours of reexposure.

Risk Factors

• Scabies is more common in young children, health care workers, homeless and impoverished persons, and individuals who are immunocompromised or suffering from dementia.¹

• Institutionalized individuals and those living in crowded conditions also have a higher incidence of the infestation.¹

Diagnosis

Clinical Features

• Pruritus is a hallmark of the disease.¹

• Skin findings include papules (Figure 128-10), burrows (Figures 128-11 and 128-12) nodules (Figures 128-13), and vesiculopustules (Figure 128-14).

• Burrows are the classic morphologic finding in scabies and the best location to find the mite (Figures 128-11 and 128-12).

• Infants and young children can also exhibit irritability and poor feeding.

• Pruritic papules/nodules around the axillae (Figure 128-13), umbilicus, or on the penis (Figures 128-15 and 128-16) and scrotum are highly suggestive of scabies.

Typical Distribution

• Classic distribution in scabies includes the interdigital spaces (Figure 128-17), wrists (Figure 128-18), ankles (Figure 128-19), waist (Figure 128-20), groin, axillae (Figure 128-13), palms, and soles (Figures 128-1, 128-2, 128-6, and 128-7).

• Genital involvement can also occur (Figures 128-15 and 128-16).

• In children, the head can also be involved (Figure 128-21).

Laboratory Studies and Imaging

• Light microscopy of skin scrapings provides a definitive diagnosis when mites, eggs, or feces are identified (Figures 128-3 to 128-5). This can be challenging and time-consuming, even when mites, eggs, or feces are present. Packing tape stripping of skin has also been used instead of a scalpel to find mites for examination under the microscope.⁶ The inability to find these items should not be used to rule out scabies in a clinically suspicious case. In what is believed to be a recurrent case, it is helpful to find definitive evidence that your diagnosis is correct.

• Dermoscopy is a useful and rapid technique for identifying a scabies mite at the end of a burrow (see Appendix 3: Dermoscopy).⁷ The mite has been described as an arrowhead or a jet plane in its appearance (Figure 128-22). The advantage of the dermoscope is that multiple burrows can be examined quickly without causing any pain to the patient. Children are more likely to stay still for this than scraping with a scalpel or skin stripping with tape.

• If a dermoscope is available, start with this noninvasive examination. If the findings are typical, then a microscopic examination is not needed. If the findings are not convincing, or a dermoscope is not available, perform a scraping. It is best to scrape the skin at the end of a burrow. Use a #15 scalpel that has been dipped into mineral oil or microscope immersion oil. Scrape holding the blade perpendicular to the skin until the burrow (or papule) is opened (some slight bleeding is usual; Figure 128-23). Transfer the material to a slide and add a cover slip.

• Tips for microscopic examination—Start by examining the slide with the lowest power available as mites may be seen under 4 power and the slide can be scanned most quickly with the lowest power. If no mites are seen, switch to 10 power and scan the slide again looking for mites, eggs, and feces. Forty power may be used to confirm findings under 10 power.

• In one study comparing dermoscopic mite identification with microscopic examination of skin scrapings, found the former technique to be of comparable sensitivity (91% and 90%, respectively) with specificity of 86 percent (versus 100% by definition), even in inexperienced hands.⁸ Another study reported sensitivity of dermoscopy at 83 percent (95% confidence interval, 0.70 to 0.94).⁹ In this study, the negative predictive value was identical for dermoscopy and the adhesive tape test (0.85), making the latter a good screening test in resource-poor areas.

• Videodermatoscopy can also be used to diagnose scabies.¹⁰ Videodermatoscopy allows for skin magnification with incidental lighting at high magnifications for viewing mites and eggs. The technique is noninvasive and does not cause pain.

• S. scabiei recombinant antigens have diagnostic potential and are under investigation for identifying antibodies in individuals with active scabies.¹¹

Biopsy

Rarely necessary unless there are reasons to suspect another diagnosis.

Differential Diagnosis

• Atopic dermatitis—Itching is a prominent symptom in atopic dermatitis and scabies. The distribution of involved skin can help to differentiate the 2 diagnoses. Look for burrows in scabies and a history of involved family members. In children, atopic dermatitis is often confined to the flexural and extensor surfaces of the body. In adults, the hands are a primary site of involvement (see Chapter 130, Atopic Dermatitis).

• Contact dermatitis—Characterized by vesicles and papules on bright red skin, which are rare in scabies. Chronic contact dermatitis often leads to scaling and lichenification and may not be as pruritic as scabies (see Chapter 131, Contact Dermatitis).

• Seborrheic dermatitis—A papulosquamous eruption with scales and crusts that is limited to the sebum rich areas of the body; namely, the scalp, the face the postauricular areas, and the intertriginous areas. Pruritus is usually mild or absent (see Chapter 135, Seborrheic Dermatitis).

• Impetigo—Honey-crusted plaques are a hallmark of impetigo. Scabies can become secondarily infected, so consider that both diagnoses can occur concomitantly with papules and pustules present (Figure 128-24) (see Chapter 99, Impetigo).

• Arthropod bites—Bites may exhibit puncta that allow for differentiation from scabies.

• Acropustulosis of infancy (Figure 128-25)—A vesicopustular recurrent eruption limited to the hands, wrists, feet, and ankles. It is rare after 2 years of age (see Chapter 94, Pustular Diseases of Childhood).

Management

Nonpharmacologic

• Environmental decontamination is a standard component of all therapies. SOR B Clothing, bed linens, and towels should be machine washed in hot water. Clothing or other items (e.g., stuffed animals) that cannot be washed may be dry cleaned or stored in sealed bags for at least 72 hours.¹²

Medications

Treatment includes administration of an antiscabicide and an antipruritic.^1,13

• Permethrin 5 percent cream (Elimite, Acticin) is the most effective treatment based upon a systematic review in the Cochrane Database.¹³ SOR A The cream is applied from the neck down (include the head when it is involved) and rinsed off 8 to 14 hours later. Usually, this is done overnight. Repeating the treatment in 1 to 2 weeks may be more effective. SOR C In patients with crusted scabies, use of a keratolytic cream may facilitate the breakdown of skin crusts and improve penetration of the cream.¹⁴ Unfortunately, scabies resistance to permethrin is increasing.

• Ivermectin is an oral treatment for resistant or crusted scabies. Studies have demonstrated its safety and efficacy. Most studies used a single dose of ivermectin at 200 mcg/kg.¹³ SOR A Taking the drug with food may enhance drug penetration into the epidermis.¹⁴ Some experts advocate repeating a dose 1 week later. It is worth noting that the FDA has not labeled this drug for use in children weighing less than 15 kg. Ivermectin is currently available only in 3- and 6-mg tablets, so dosing often needs to be rounded up to accommodate the use of whichever tablets are available. As there is no oral suspension available, tablets may need to be cut and given with food for use in children.

• Diphenhydramine, hydroxyzine, and mid-potency steroid creams can be used for symptomatic relief of itching. SOR C. It is important to note that pruritus may persist for 1 to 2 weeks after successful treatment because the dead scabies mites and eggs still have antigenic qualities that may cause persistent inflammation.

• All household or family members living in the infested home and sexual contacts should be treated. SOR C Failure to treat all involved individuals often results in recurrences within the family. Use of insecticide sprays and fumigants is not recommended.

• Other less-effective medications include topical benzyl benzoate, crotamiton, lindane (no longer used in the US because of concerns regarding neurotoxicity), and synergized natural pyrethrins.⁹ SOR A Topical agents used more commonly in other countries include 5 to 10 percent sulfur in paraffin (widely in Africa and South America), 10 to 25 percent benzyl benzoate (often used in Europe and Australia), and malathion.¹⁴ In infants younger than 2 months of age, crotamiton or a sulfur preparation is recommended by one author instead of permethrin because of theoretical concerns of systemic absorption of permethrin.¹⁴

• Antibiotics are needed if there is evidence of a bacterial superinfection (Figure 128-23). SOR C

Complementary/Alternative Therapy

• Tea tree oil contains oxygenetic terpenoids, found to have rapid scabicidal activity.¹⁵

Prevention

• Avoid direct skin-to-skin contact with an infested person or with items such as clothing or bedding used by an infested person.

• Treat members of the same household and other potentially exposed persons at the same time as the infested person to prevent possible reexposure and reinfestation.

Prognosis

• The prognosis with proper diagnosis and treatment is excellent unless the patient is immunocompromised; reinfestation, however, often occurs if environmental risk factors continue.¹

• Postinflammatory hyper- or hypopigmentation can occur.¹

Follow-Up

• Routine follow-up is indicated when symptoms do not resolve.

• Consider an immunologic work-up for individuals with crusted scabies.

Patient Education

• Patients should avoid direct contact including sleeping with others until they have completed the first application of the medicine.

• Patients may return to school and work 24 hours after first treatment.

• Patients should be warned that itching may persist for 1 to 2 weeks after successful treatment but that if symptoms are still present by the third week, the patient should return for further evaluation.

Patient Story

A mother brought her 18-month-old son to the physician’s office for an itchy rash on his feet and buttocks (Figures 129-1 and 129-2).¹ The first physician examined the child and made the incorrect diagnosis of tinea corporis. The topical clotrimazole cream failed. The child was unable to sleep because of the intense itching and was losing weight secondary to his poor appetite. He was taken to an urgent care clinic where the physician learned that the family had returned from a trip to the Caribbean prior to the visit to the first physician. The child had played on beaches that were frequented by local dogs. The physician recognized the serpiginous pattern of cutaneous larva migrans (CLM) and successfully treated the child with oral ivermectin. The child was 15 kg so the dose was 3 mg (0.2 mg/kg), and the tablet was ground up and placed in applesauce.

Synonyms

Creeping eruption, Plumber’s itch.

Epidemiology

• Endemic in developing countries, particularly Brazil, India, South Africa, Somalia, Malaysia, Indonesia, and Thailand.^2,3

• Peak incidence in the rainy seasons.³

• During peak rainy seasons, the prevalence in children is as high as 15 percent in resource poor areas, but much less common in affluent communities in these same countries with only 1 to 2 per 10,000 individuals per year.⁴

• In the US, it is found predominantly in Florida, southeastern Atlantic states, and the Gulf Coast.²

• Children are more frequently affected than adults.⁴

Etiology and Pathophysiology

• Caused most commonly by dog and cat hookworms (i.e., Ancylostoma braziliense, Ancylostoma caninum, or Uncinaria stenocephala).⁴

• Eggs are passed in cat or dog feces.²

• Larvae are hatched in moist, warm sand or soil.²

• Infective stage larvae penetrate the skin.²

Diagnosis

The diagnosis is based on history and clinical findings.

Clinical Features

• Elevated, serpiginous, or linear reddish-brown tracks 1 to 5 cm long (Figures 129-1 to 129-3).^2,5

• Intense pruritus, which often disrupts sleep.³

• Symptoms last for weeks to months, and, rarely, years. Most cases are self-limiting.⁵

Typical Distribution

• Feet and lower extremities (73%), buttocks (13% to 18%), and abdomen (16%) (Figure 129-4).^6,7

• Areas that come in contact with contaminated sand or soil.

  • Most commonly the feet, buttocks, and thigh.³

Laboratory and Imaging

• Not indicated, but rarely blood tests shows Eosinophilia or elevated immunoglobulin E levels.⁵

Differential Diagnosis

May be confused with the following conditions:

• Cutaneous fungal infections—Lesions are typically scaling plaques and annular macules with central clearing. If the serpiginous track of CLM is circular, this can lead to the incorrect diagnosis of “ringworm.”  The irony is that ringworm is a dermatophyte fungus whereas CLM really is a worm (see Chapter 123, Tinea Corporis).

• Contact dermatitis—Differentiate by distribution of lesions, presence of vesicles, and absence of classical serpiginous tracks (see Chapter 131, Contact Dermatitis).

• Erythema migrans of Lyme disease—Lesions are usually annular macules or patches and are not raised and serpiginous (see Chapter 183, Lyme Disease).

• Phytophotodermatitis—The acute phase of phytophotodermatitis is erythematous with vesicles; this later develops into postinflammatory hyperpigmented lesions. This may be acquired while preparing drinks with lime on the beach and not from the sandy beach infested with larvae.

Management

• Oral thiabendazole was the first proven therapy with FDA approval. It was removed from the market in 2010.

• Albendazole has been successfully prescribed for more than 25 years, and is the Centers for Disease Control and Prevention (CDC) drug of choice. ^3,5 Albendazole lacks FDA approval for this indication.

  • The recommended dose is 400 mg daily for 3 days.^3,5 SOR B

  • Cure rates with albendazole exceed 92 percent, but are less with single dosage.³

• Ivermectin (Stromectol) has been well studied and is an appropriate alternative as per the CDC with dosing of 0.2 mg/kg daily for 1 to 2 days.^3,5 It also lacks FDA approval for this indication.

  • A single dose of ivermectin 0.2 mg/kg is also recommended.³ SOR B

  • Cure rates of 77 to 100 percent with a single dose.³

  • Ivermectin has been used worldwide on millions with an excellent safety profile.³

  • Ivermectin is contraindicated in pregnancy, breastfeeding mothers, and in children weighing less than 15 kg.³

  • Studies on compounded ivermectin and albendazole for topical use are limited, but promising for use in children.³

• Cryotherapy is ineffective and harmful and should be avoided.³ SOR B

Adjunct Therapy

• Antihistamines may relieve itching.

• Antibiotics may be used if secondary infection occurs.

Follow-Up

• Follow-up if lesions persist.

Patient Education

• Wear shoes on beaches where animals are allowed.

• Keep covers on sand boxes.

• Pet owners should keep pets off the beaches, deworm pets, and dispose of feces properly.