(Tokelau, Bowditch Island, Chinese, India, or Burmese ringworm; La Pita; Gune; Cascadoe; Herpes desqumans; Malabar itch)
Definition. A contagious, vegetable parasitic disease of moist tropical countries, characterized by concentrically placed, imbricated, scaly rings.
Symptoms. This disease was first discovered by Fox, and American medical officer in 1841, but has since been observed by a number of investigators, and it is from Manson’s article that the following description is chiefly drawn. After a period of inoculation of about nine days, at one or several points, slightly raised, brownish spots appear which increase in size by peripheral extension to almost a half inch in diameter. At this period the central part of the patch gives way and is shed, leaving an attached rim next to the sound skin. The lesion continues to advance at the periphery, showing through the epidermis a brown and slightly elevated rim of about one-sixteenth of an inch. This in turn shows the epidermis attached and curling at the inner side. Then a brown patch is again observed to be forming in the center and so the process continues, the ever-increasing area being made of concentrically arranged, imbricated, shingle-like rings. the process may involve whole regions, or extend to any part of the body, except the scalp. The average rate of extension of a single patch is about three-eighths of an inch apart and covered with scales which are free at their outer edge, though somewhat curled up. The gross appearance has been likened to watered silk. The scales may become large, thick and hard and, after their desquamation, pigmentary circles or lines will persist, sometimes permanently. The general health is never affected though intense local irritation and heat may cause discomfort.
Etiology and Pathology. This contagious malady is caused by a vegetable parasite similar to the trichophyton. For this reason it is often regarded as an aggravated or rare form of ringworm which does not, however, agree with the opinion of those who know best. Some authorities consider that the fungus belongs to the aspergillus family. It is not uncommon in tropical countries and is almost endemic in some localities. It apparently requires heat and moisture for its bacterial growth. While any age may be affected, children seem especially liable. The fungus, though possessing gross features like ringworm, is much more abundant and chiefly involves the corneous layer of the epidermis. It does not usually affect the stronger hairs or enter their follicles.
Diagnosis. The development by successive rings inside of the preceding and outwardly advancing circles, plus the non-involvement of the hair-follicles, should distinguish tinea imbricata from tinea circinata, which commonly clears at the center and only develops at the periphery. The microscope may assist in diagnosis, which should not be difficult in countries where the disease in endemic.
Prognosis and Treatment. This disease is readily curable be cause the fungus is superficially situated. Relapses very naturally occur owing to the great extent of surface involved and the consequent saturation of the patient’s garments with the parasite. The treatment is the same as used for the several forms of ringworm. Clothing should be destroyed or thoroughly disinfected, scales removed with alkaline baths and a parasiticide such as 30 to 60 grains of resorcin in the compound tincture of benzoin; 3 to 10 per cent. chrysarobin ointment; or a strong iodin liniment, carefully applied to one portion of the surface at a time.