Tungiasis

Stefano VERALDI; Rossana SCHIANCHI

Version imprimable

Tungiasis

European Journal of Dermatology. Volume 9, Numéro 1, 57-9, January - February 1999, Votre diagnostic ?

Summary

Auteur(s) : Stefano VERALDI, Rossana SCHIANCHI, .

Illustrations

ARTICLE

A 27-year-old Caucasian woman was admitted to our Institute because of a nodular lesion localized on the sole of the left foot. The patient stated that she was in good general health, that she was not on any medication and that she had just returned a few days earlier from a trip to Madagascar, where the nodular lesion had probably developed. The lesion was round, 0.5 cm in diameter, yellowish in colour, with well-defined borders (Fig. 1), hard in consistency and painful. It was diagnosed by the patient's general doctor as a viral wart.

Tungiasis

A close examination of the lesion revealed a tiny central opening (Fig. 1), from which a small amount of sero-haematic fluid oozed: it contained numerous oval-shaped, white "bodies" that, on direct microscopic examination, were found to be eggs of Tunga penetrans L. (Fig. 2). Enlarging the opening by means of the tip of a scalpel, it was possible to remove portions of the body of the flea, numerous other eggs and necrotic material. The residual cavity was subjected to surgical debridement. Topical gentamicin (twice a day for 10 days) was prescribed. The lesion healed without any sequelae.

Discussion

Tunga penetrans L. is a flea that lives in Central and South America, sub-Saharan Africa and Central Asia. In Europe, only imported cases of tungiasis have been described so far [1-17], the majority of which by French [2, 4-6, 13, 16], German [1, 7-9] and Italian authors [10-12, 17].

The natural habitat of Tunga penetrans L. is represented by the sandy and warm soil of deserts and beaches; furthermore, the flea lives in stables and stock farms, as well as in soil and dust close to farms.

Tunga penetrans L. is a parasite of the skin. Apart from man, this flea can also infest pigs, dogs, cats, sheep, horses, mules, cattle, rats, mice and even gorillas in captivity.

Both the male and female are haematophagous. After coupling, the male dies. To complete the life cycle, which lasts just over one month and consists of four stages (egg, larva, pupa, adult), the fertilized female penetrates the skin. The mechanism by which the flea penetrates is not known: it is assumed that the flea liberates keratolytic enzymes. In the skin the flea burrows a cavity with the head turned towards the upper dermis, in order to feed on the host's blood, by means of a well-developed buccal apparatus. Only the end portion of the abdomen extrudes. Soon after penetration, the flea begins to produce eggs; the abdomen enlarges markedly: it can reach a diameter of 1 cm (the male and the non-fertilized female are about 1 mm long). Ovaries contain up to 200 eggs. Eggs and excrements are eliminated to the outside through a small foramen in the epidermis, in the proximity of the insect's anal opening; this foramen also allows respiration. The eggs are laid on the ground, where they natch in 3-4 days, liberating larvae. At this stage, the adult dies. After 10-15 days, the larvae develop into pupae, that after 7-15 days become adults.

Characteristic localizations of tungiasis are toes, particularly peri- and subungual folds, interdigital spaces, sole and heel. Walking may be markedly limited. Other possible sites of infestations are the legs, knees, thighs and hands. All the other sites are rare.

Infestation by Tunga penetrans L. is characterized clinically by the slow appearance of papular or nodular lesions, either single or multiple (very rare cases with hundreds of lesions have been described), white or greyish or yellowish in colour, with a brown-black central tip that corresponds to the posterior portion of the flea. These lesions may be more or less erythematous, occasionally covered by brownish-black crusts; sometimes they are ulcerative or pustular d'emblée.

The penetration of the tunga is asymptomatic: only when the insect increases in size do inflammatory and necrotic phenomena develop leading to pruritus and/or pain.

As shown by this case and others [14], the differential diagnosis includes mainly viral warts: a biopsy for histopathological examination is sometimes necessary.

With the exception of superinfections, mainly caused by Staphylococcus aureus and Gram negative bacteria, and the risk of tetanus, complications of tungiasis are uncommon: however, cases of gangrene, spontaneous amputation of the toes, lymphangitis, lymphadenitis and sepsis have been described.

Histopathological examination shows hyperkeratosis and acanthosis. The body of the insect is localized in the epidermis and upper dermis: it is enclosed in a pseudocystic cavity. Inside the cavity, annular-shaped digestive and respiratory organs and egg-laden ovaries are present. Eggs are round or oval, with a thickened wall and a pale centre. A perilesional inflammatory infiltrate with lymphocytes, neutrophils and, especially eosinophils is present.

Treatment consisting the surgical removal of the papular/nodular lesion or removal of the flea, possibly intact, by enlarging the orifice with a needle or the tip of a scalpel and exerting pressure at the sides. The residual cavity should then undergo surgically cleaned. Thereafter, it is necessary to apply a topical antibiotic. Also useful is anti-tetanus prophylaxis. Systemic antibiotics are necessary if numerous and/or pustular lesions are present. Fairly good results have also been reported with electrodesiccation and cryotherapy, while the application of chloroform, ether, formaldehyde and petrolatum is anecdotal. Prophylaxis consists in avoiding walking barefoot in endemic areas and the use of insecticides.

CONCLUSION

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REFERENCES