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TUNGIASIS IN A YOUNG CHILD ADOPTED FROM SOUTH AMERICA

2000; Lippincott Williams & Wilkins; Volume: 19; Issue: 5 Linguagem: Inglês

10.1097/00006454-200005000-00024

1532-0987

Gary L. Darmstadt, Julie S. Francis,

Insects and Parasite Interactions

Tungiasis is an inflammatory infestation caused by burrowing of the female flea, Tunga penetrans, into the skin. Although tungiasis is rarely diagnosed in the United States, it is likely to be seen more frequently than in the past among those entering the United States from endemic areas because of increases in the volume and speed of international travel and migration. We present the first report of tungiasis diagnosed in a child in the United States. Case report. A 15-month-old girl was seen in hospital with a 1-month history of a red, swollen, asymptomatic distal right fifth toe. One month before her presentation the patient was adopted from a foster home in Paraguay. When the child arrived in the United States, her adoptive parents noted redness and swelling of the right fifth toe. The swelling increased during the next 2 weeks, and the lesion appeared to blister, prompting a visit to a community physician who prescribed cephalexin. When no improvement was noted 1 week later and purulent-appearing material was expressed from the edge of the lesion, she was referred to us for evaluation. She had no fever or other constitutional symptoms, has no other skin problems and had a normal gait. The right fifth toe was swollen and erythematous distal to the metatarsophalangeal joint. On the distal dorsal surface, extending under the distal nail plate, was a 7-mm pale, firm, hyperkeratotic papule with a black central core. A roentgenogram of the toe showed no foreign body, no gas in the tissue and no periosteal elevation. The distal nail was clipped back and the papule was unroofed under sterile conditions with a scalpel. Whitish material with a pasty consistency and the appearance of fine tapioca was expressed. The wound was debrided of all devitalized tissue, irrigated with normal saline and dressed with bacitracin ointment. The wound healed uneventfully. Microscopic examination of the exudate in the microbiology laboratory revealed numerous eggs (Fig. 1) and insect parts which were consistent with T. penetrans.Fig. 1: Eggs of the flea T. penetrans recovered from a pale papule with a black central core on the right fifth toe of a 15-month-old girl adopted from Paraguay.Discussion.History. Tungiasis was first described in 1526 by Oveido among members of Columbus' crew from the Santa Maria who were left in Haiti after being shipwrecked.1 It appears to have originated in the region of the West Indies and became widespread in Africa after 1872 when the flea was transported there in the sand ballast of an English ship. The first case reported in the United States was in 1930 in a man who had lived his entire life in New Orleans but had probably contracted the infestation from a hemp pile which had come from Mexico.2 The first imported case in the United States occurred in 1966 in a traveler returning from Gabon, Africa.3 Only 22 reported cases of tungiasis, including our patient, have been diagnosed in the United States; all except the first case2 occurred in individuals who had been in Africa or South America a few days to weeks before presentation.3-13 Ours is the first report of tungiasis diagnosed in a pediatric patient in the United States and the first in an international adoptee, expanding the list of potential illnesses in these children. Prevalence. Tungiasis is now prevalent in Central and South America, the Caribbean Islands, tropical Africa, the Seychelles, Pakistan and the west coast of India. Reappearance of the infestation was reported recently in Mexico, where no cases had been seen since 1948.14 Prevalence of tungiasis was 15 to 40% among children in Nigeria15-18 and Trinidad.19-20 All ages are affected although boys 5 to 9 years old have the highest prevalence of infestation because they frequently walk barefoot.19 Risk factors for contracting tungiasis include walking barefoot in an endemic area and contact with animal reservoirs. The flea. T. penetrans is a wingless, reddish-brown flea of the order Siphonaptera. It is among the smallest of fleas, measuring ∼1 mm long when unfed. It has a more angular head and triangular-shaped thorax than the common flea, Pulex irritans. Other names for the flea include sand flea, chigoe flea, chigo, chica, jigger, chique, nigua, pico and bicho de pe (bug of the foot). It should not be confused with the mite Trombicula alfreddugesi, which causes "chiggers" in North America. The flea lives in warm, dry, shady, sandy soil on beaches and around houses and farms, particularly in cattle stables or pigsties, or in dust or ashes in poorly kept human dwellings. The flea's proliferation depends on a warm temperature, sandy soil and the presence of a suitable host. Both sexes of flea feed on the blood of mammals, particularly cows, pigs, dogs, cats, mice, rats, occasionally on some birds and humans, but only the pregnant female burrows into human skin. After being impregnated the female flea jumps repeatedly up to 35 cm off the ground until she dies or is able to attach to the skin by her mouth parts and insinuate into the stratum corneum by clawing. Because the flea is a poor jumper, she is able to attach most readily to the toes and feet. Individuals who frequently squat may develop lesions on the perineum or buttocks. The pregnant female flea burrows until her head reaches the dermis, where she feeds on blood, and her terminal thoracic segment is flush with the outer skin surface, allowing her to obtain air through the last pair of abdominal stomata. In the epidermis she ovulates and grows to reach a diameter of up to 1 cm. In 1 to 2 weeks, ∼150 to 200 fertilized eggs are released through a posteroabdominal orifice. The flea then dies within 3 weeks of the initial bite and is sloughed by the host. The eggs fall to the soil and hatch in 3 to 4 days. Occasionally larvae develop within the skin. Larvae thrive best in dry sandy soil or in the dust of human dwellings. Larvae go through two to three instars during 1 week in a warm climate but may take as long as 3 months in cool weather, before spinning a cocoon. The pupa transforms into an adult flea within 1 week under favorable conditions; the pupal period, however, may be as long as 1 year. The entire life cycle lasts an average of ∼1 month. Clinical presentation. Burrowing of the flea into the epidermis results in a papule, vesicle, or pustule with a black dot in the center. The most common sites of infestation are the pulp and sides of the toes, toe webs, subungual or periungual areas, soles of the feet and ankles. As the female flea's abdomen swells with white ova, it becomes evident clinically as a whitish to erythematous papule or nodule with a central dark punctum. The lesion becomes hyperkeratotic, and the central punctum may ulcerate and become crusted. Lesions are usually asymptomatic initially but may become pruritic or painful as the head of the flea burrows into the dermis. Lesions are usually solitary, but multiple lesions occur. Those with impaired sensation because of leprosy or diabetes mellitus are particularly prone to multiple, widespread infestation that can produce a honeycombed appearance to the affected areas such as the hands and feet. Complications of tungiasis include severe pruritus, pain, impetigo, lymphangitis, erysipelas, cellulitis, gangrene, sepsis, inflammation leading to autoamputation of the infested digit (ainhum), tetanus and death. Diagnosis. Definitive diagnosis rests on demonstration of the flea within a lesion on a patient with an appropriate travel history. Under magnification the ovipositor of the flea on the posterior abdominal segment is visible within the central punctum of the lesion; this is diagnostic of tungiasis. Histopathologically the epidermis is hyperkeratotic and is often buttressed next to the flea. In the subadjacent dermis is an inflammatory infiltrate of lymphocytes, plasma cells and eosinophils. Histopathologic sections through the flea reveal an intraepidermal cystic cavity lined by a thick, eosinophilic cuticle and ring-shaped structures representing the trachea, digestive tract and ovaries containing numerous eggs.11 When the nodule is excised a whitish substance exudes from the lesion. Direct smear of the contents and examination under low power magnification reveals the presence of numerous whitish eggs.21 Differential diagnosis includes foreign body, acute paronychia, ingrown nail, arthropod bite, folliculitis, wart, creeping eruption (Ancyclostoma spp.), cercarial dermatitis, dracunculiasis, cutaneous leishmaniasis and cutaneous myiasis. In myiasis a blood-sucking fly drops ova from the abdomen into the bite lesion. Only the larvae of the fly penetrate the skin, producing a furunculoid lesion. Treatment. Treatment of an early lesion consists of peeling back the keratin around the punctum with a sterile needle and extracting the flea with the needle. This was such a common practice in the Caribbean that some women would pierce their lip with a needle to provide a place to carry it.3 Nodular lesions are best treated by unroofing the nodule and removing the contents completely by sterile curettage. Alternatively the nodule can be excised. Chemical means of treatment that have been advocated, but are not now recommended, include immersion of the affected limb in 4% formalin solution or spraying it with chlorophenothane. Systemic niridazole (Ambilhar) 30 mg/kg as a single dose was effective in a double blind placebo-controlled trial in Nigeria; this may be the best treatment if multiple sites of infestation are present.22 Treated lesions generally heal within 2 to 3 weeks. Given the potential for Clostridium tetani secondary infection, up-to-date tetanus vaccination is required. Secondary infection, reported in 6% of cases in a large series of patients in Trinidad,20 also should be treated with appropriate antibiotics. Prophylaxis consists of wearing shoes, sweeping floors in dwellings or spraying the floors with malathion. Control measures in endemic areas consist of encouraging residents to wear shoes; treatment of infested areas with insecticides; treatment of infected human hosts, including education on extraction of fleas using sterile instruments, use of wound dressings and tetanus immunization; and improved animal husbandry practices to reduce transmission to humans. Application of malathion to infested sandy areas in Trinidad reduced the incidence of tungiasis by 80%.20 Methoprene is an insect growth regulator that is being used successfully in some endemic areas such as Brazil to prevent immature fleas from developing into adults.9 Gary L. Darmstadt, M.D. Julie S. Francis, M.D. Divisions of Dermatology (GLD, JSF) and Infectious Diseases (GLD); Department of Pediatrics; Children's Hospital and Regional Medical Center Division of Dermatology; Department of Medicine (GLD) University of Washington School of Medicine; Seattle, WA