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. [52, 53, 54] Sometimes, a serosanguineous exudate oozes from the central opening, and eggs may be seen on microscopic examination.
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. [55] Detailed histopathologic findings from 86 cases, including scanning electron microscopy images, elucidated the stages of infestation. [56]
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.
Imaging Studies
Dermoscopy, which is used to examine for the characteristic surface findings 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. [57]
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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.
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A tungiasis lesion in substage 3a.
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Scanning electron micrograph of flea on day 3 after penetration. The hypertrophic zone between abdominal segments 2 and 3 is gaining a bulging shape and looks like a life-belt (x100).
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Scanning electron micrograph of flea on day 8 after penetration. The hypertrophy zone has taken the shape of a sphere. The 3 parts of abdominal segment 2 are completely bent apart. Together with the newly developed, crescent-shaped chitinous clasps, the anterior part of the flea looks like a 3-leafed clover (x32).
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Scanning electron micrograph of flea 6 hours after beginning of penetration. The penetration is almost completed; only the last abdominal segments protrude through the skin (x240).
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Scanning electron micrograph of flea in stage 2. The rear end, the genital opening, and the 4 pairs of stigmata form a miniature cone, which towers above the crater caused by pushing in abdominal segments 7 and 8 (x190).
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Life cycle of Tunga penetrans - Fortaleza stages included. Compiled and designed by Fausto Bustos and Lucas Manfield.
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Histopathologic findings in tungiasis.
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Life cycle of the chigoe flea, Tunga penetrans. Courtesy of the CDC.
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Complicated Tungiasis infection. Courtesy of Dermatology Atlas (http://www.atlasdermatologico.com.br/index.jsf) and Samuel Freire da Silva, MD.
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Tungiasis lesion under toenail. Courtesy of Dermatology Atlas (http://www.atlasdermatologico.com.br/index.jsf) and Samuel Freire da Silva, MD.
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Example of complicated infection with multiple tungiasis lesions and possible secondary infection. Courtesy of Wikimedia Commons [author R Schuster, https://commons.wikimedia.org/wiki/File:Jigger_infested_foot_(2).jpg].
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Illustration of Tunga penetrans (sand flea) in its enlarged state. Courtesy of Wikimedia Commons [https://commons.wikimedia.org/wiki/File:ChiggerBMNH.jpg].
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Removed parasite shown with needle. Courtesy of Wikimedia Commons [https://commons.wikimedia.org/wiki/File:Puce_chique_(Tonga_penetrans).jpg].
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Tunga penetrans flea. Courtesy of Wikimedia Commons [author Philipp Weigell, https://commons.wikimedia.org/wiki/File:Tunga_penetrans_%281%29.JPG].
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Image of Tungiasis infection on both feet. Courtesy of PLOS [Miller H, Ocampo J, Ayala A, Trujillo J, Feldmeier H. Very severe tungiasis in Amerindians in the Amazon lowland of Colombia: A case series. PLOS Neglected Tropical Diseases. 2019 Feb 7. Online at: https://journals.plos.org/plosntds/article?id=10.1371/journal.pntd.0007068.].
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Graphical abstract of predicted tungiasis occurrence within sub-Saharan Africa. Courtesy of MDPI [Deka MA. Mapping the Geographic Distribution of Tungiasis in Sub-Saharan Africa. Tropical Medicine and Infectious Disease. 2020 Jul 24;5(3):122. Online at: https://www.mdpi.com/2414-6366/5/3/122#.].
Tables
Medication Name |
Dosage/Application |
Contraindications |
Availability |
Notes |
|---|---|---|---|---|
Apply directly to the affected area once or twice daily.
If legion numbers are under 40 or legions are in clusters: Apply 3 drops of NYDA® (approximately 50 μL each) to the exposed posterior side of the flea. Repeat the procedure 3x over 10 minutes.
If fleas are in excessive hyper-keratotic skin and located on top of each other: NDYA® must be used to wet the skin intensely and repeatedly. |
No known contraindications. Shown to be safe for extended use. |
Available under the brand name NYDA®. But not available in all tungiasis endemic areas. |
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0.8% ivermectin, 0.2% metrifonate and 5% thiabendazole lotions, applied 2 consecutive days. |
No contraindications reported. |
All are readily available except for metrifonate, which is no longer commercially available. |
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Apply to all infected areas and areas at risk for tungiasis infection twice daily. |
No known contraindications. |
No longer commercially available, but made of ingredients that could be locally manufactured in areas where tungiasis is common. |
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One drop (approximately 0.05 ml) of a mixture of 20% cold-pressed virgin neem seed oil and 80% virgin coconut oil applied to the embedded flea’s abdominal tip on days 1 and 3. |
Actives in cold-pressed neem oil are not toxic following oral, inhalation, or dermal exposure. |
May be locally available where both neem trees and coconut palms grow. |
The mixture requires proper storage as azadirachtin has a high sensitivity to ultraviolet light, pH, and temperature. |
