Tungiasis Workup

Updated: May 01, 2018
  • Author: Darvin Scott Smith, MD, MSc, DTM&H; Chief Editor: Mark R Wallace, MD, FACP, FIDSA  more...
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Workup

Approach Considerations

Extraction of the gravid flea using a sterile needle is diagnostic and therapeutic. A skin biopsy of a suspected papule or nodule may be performed.

In general, no laboratory studies are indicated other than a histologic examination of excised tissue to confirm the presence of the flea. No imaging studies are indicated unless there is a secondary infection with a complication such as gas gangrene.

Dermoscopy

Dermoscopy (direct skin microscopy) may be helpful in identifying typical features, including an irregular, central, brown discoloration with a plugged opening in the middle or a gray-blue discoloration. [46, 47, 48] Sometimes, a serosanguineous exudate oozes from the central opening, and eggs may be seen on microscopic examination.

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Histologic Findings

Microscopically, the flea has a thick cuticle and a band of striated muscle stretching from the head to the abdominal orifice. Also visible are hollow, ring-shaped elements from the flea's tracheal and digestive system and numerous round or oval eggs. A report from a small series of skin biopsies indicated that the exoskeleton, hypodermal layer, trachea, digestive tract, and developing eggs were present in all biopsy specimens; striated muscle and the hindquarters were present in about half of the samples; and the head was found in none of the specimens. [49] Detailed histopathologic findings from 86 cases, including scanning electron microscopy images, elucidated the stages of infestation. (See the images below.) [50]

A. Tangential cut through a fully developed, gravi A. Tangential cut through a fully developed, gravid flea embedded in the stratum corneum of the epidermis. The flea's head and thorax are enfolded in the hypertrophic anterior abdominal segments. The epidermis is hyperplastic and shows papillomatosis, parakeratosis, and hyperkeratosis.B. Tangential cut through the posterior abdominal segments of an embedded sand flea. Next to the chitinous cuticle, a microabscess has formed.C. Dead parasite; the exoskeleton of the posterior abdominal segment has remained intact; the cuticle has disintegrated at the epidermal–dermal interface. The carcass is infiltrated by neutrophils, and pus has formed.D. The head of the flea is located at the epidermal–dermal interface, has penetrated the basal membrane, and is surrounded by many erythrocytes, presumably having leaked from a blood vessel. The abdomen of the parasite is separated from host tissue by a thick, chitinous cuticle.

Histologic examination reveals an intraepidermal cavity lined by an eosinophilic cuticle, which represents the body of the flea. In the cavity are round to oval eggs, hollow ringlike components of the tracheal system, and the digestive tract (see image below). A thick band of striated muscle runs from the head to the terminal orifice. Usually, an inflammatory infiltrate is present in the subjacent dermis.

Histopathologic findings in tungiasis. Histopathologic findings in tungiasis.
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Imaging Studies

Dermoscopy, which is used to examine for the characteristic surface findings (see photos) and to identify tungiasis flea parts and eggs microscopically, is useful in definitively diagnosing tungiasis. High-resolution infrared thermography (HRIT) has also been found to be a useful tool in assessing tungiasis-associated inflammation, particularly in complicated cases of tungiasis in which diagnosis and treatment are more difficult. [51]

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