This is a fungus disease of the hairs in which small nodules form along the shaft. They are about the size of the nits of head lice but more or less surround the hair instead of projecting off at an angle as do the ovoid lice nits. These little masses are black in color and very hard, hence the name piedra—stone. The disease is chiefly found in Colombia and is thought to be due to the application, by the women, of a mucilaginous preparation to their hair. If an infected hair be examined in liquor potassae the nodule will be found to be made up of faceted bodies matted to the side of or, at times, encircling the hair. These bodies are the spores of Trichosporum giganteum.
Besides piedra there are also other nodular affections of the hairs due to species of Nocardia. Chalmers has recently reported several cases of trichonocardiasis where the axillary hairs were matted together and the skin of the region inflamed. Castellani called attention to this condition in 1911 and reported a narrow, bacillus-like fungus as the cause, Nocardia tenuis. The nodules are rather soft and may be yellow, black or red in color. Microscopical examination shows the fungus.
Chalmers had excellent results by treating the affected hairs with a 2% formalin solution in alcohol. At night a 2% ointment of sulphur was applied. A 5% alcoholic solution of salicylic acid has also been recommended.
Fig. 133.—Insects in which the larval stage is important. (1) Chrysomyia macellaria; (2) larva; (3) Dermatobia cyaniventris larva, early stage (ver macaque); (4) D. cyaniventris larva, later stage (torcel or berne); (5) D. cyaniventris; (6) Auchmeromyia luteola; (7) A. luteola, larva; (8) Sarcophaga magnifica; (9) S. magnifica larva; (10) Anthomyia pluvialis; (11) A. pluvialis larva.
Cutaneous Myiases
Ver Macaque.—The best known of these myiases is that due to the larva of a botfly (Oestridae), Dermatobia cyaniventris.
The larva is at first club shaped and in this stage is called ver macaque. Later on it becomes worm shaped and is then called torcel in Venezuela or berne in Brazil. The natives of most of the countries where the infection is found have called the larvae “mosquito worms” or “gusano de zancudo” and they have even incriminated large mosquitoes belonging to the genus Psorophora as being responsible for the infections.