zoonoses and communicable diseases common to ... - PAHO/WHO

DERMATOPHYTOSIS 335Topical treatment should continue for two to four weeks. Naftifine is anotherpowerful antimycotic (Hay, 1990).The Disease in Animals: The most important species considered reservoirs ofdermatophytes transmissible to humans are cats, dogs, cattle, horses, and rodents.CATS AND DOGS: The most important etiologic agent in these animals is M. canis.This dermatophyte species is very well adapted to cats and approximately 90% ofinfected animals manifest no apparent lesions. When lesions do occur, they appearprimarily on the face and paws.Lesions are frequent and apparent in dogs and may appear on any part of the bodyin the form of tinea circinata (ringworm).Dogs and cats may also be infected by other dermatophytes, particularly T.mentagrophytes.CATTLE: The principal etiologic agent of tinea in cattle is T. verrucosum (T. faviforme,T. ochraceum, T. album, and T. discoides). The disease is more common incountries where animals are kept in stables during winter, and its incidence is higherin calves than in adults. Lesions may be as small as 1 cm in diameter or may coverextensive areas; they are most frequently located on the face and neck, but lesions arealso found with some frequency on other parts of the body, such as the flanks and legs.The lesion is initially characterized by grayish white, dry areas with a few brittle hairs.The lesion then thickens and resembles a light brown scab. The scab falls off, leavingan alopecic area. The condition clears up spontaneously within two to four months.HORSES: Dermatophytosis in horses is caused by T. equinum and M. equinum; thelatter is rare in the Americas. Lesions are usually found in areas where the harnesscauses friction. They are dry, bald, covered with scales, and the skin is thickened.Colts are the most susceptible. Infections caused by Trichophyton equinum are usuallymore severe, with pruritus and exudative lesions causing the hair to sticktogether in clumps. When they drop off, they leave alopecic areas. Infections due toM. equinum cause less serious lesions with small scaly areas with brittle hairs.RODENTS AND LAGOMORPHS: Tinea favus of mice, caused by T. mentagrophytesvar. quinckeanum, is widely distributed throughout the world and is transmissible todomestic animals and man. The lesion is white and scabby and localized on the headand trunk. T. mentagrophytes (var. mentagrophytes) is another dermatophyte commonto rodents. Laboratory mice and guinea pigs are mostly infected by T. mentagrophytes,and may not have apparent lesions; the agent’s presence is often detectedwhen humans contract the infection. It is also transmissible to dogs.Dermatophytosis in rabbits is also caused by T. mentagrophytes and usuallyoccurs in animals that have recently been weaned. Scabby areas of alopecia are seenclinically around the eyes and nose. Secondary lesions appear on the feet. This diseaseis self-limiting.SHEEP AND GOATS: Tinea is rare in these species. The lesions localize on the headand face. The most frequent agent is T. verrucosum. The lesions are limited to areasof the head covered by hair; they are circular, balding, and have thick scabs. Twooutbreaks of dermatophytosis caused by M. canis were described in Australia. In thefirst outbreak, transmission was attributed to cats and to the use of contaminatedshearing implements. In the second, with 20% of 90 sheep infected, it was not pos-