ROLE OF ZOOPHILIC DERMATOPHYTES IN THE ETIOLOGY OF HUMAN RINGWORM
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Date
2001
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AAU, Anand
Abstract
A clinico-epidemiological study of 124 clinically diagnosed cases of dermatophytosis was conducted at the Department of Veterinary Public Health, College of Veterinary Science and Animal Husbandry, Gujarat Agricultural University, Anand Campus, Anand, to ascertain the prevalence of zoophilic dermatophytes in the suspected patients with tinea infections, attending the Skin O. P. D. at the Shree Krishna Hospital, Pramukhswami Medical College, Karamsad, Anand and also other Skin Clinics in and around Anand. The. various types of tinea infections diagnosed clinically based on the typical lesions presented by 124 patients included tinea corporis (36), tinea unguium (25), tinea pedis (19), tinea cruris (15), tinea manuum (10), tinea capitis (8), tinea barbae (5), tinea faciei (4) along with mixed tinea infection (2). Detailed mycological investigation was performed on 124 clinical specimens (99 skin scrapings including hairs and 25 nail clippings) to elucidate the presence of zoophilic dermatophytes in the suspected patients. The overall prevalence rate of dermatophytosis was determined to be 19.35 per cent. Tinea corporis (37.5 per cent) was the most predominant clinical type among the patients followed by tinea manuum (16.67per cent), tinea capitis (12.5 per cent), tinea cruris,tinea faciei and tinea pedis (8.33 per cent); tinea barbae and tinea unguium (4.17 per cent each). The zoophilic dermatophytes identified as the causative agents, in order of their frequencies were T. mentagrophytes (41.67 per cent), T. verrucosum (29.16 per cent), M. canis (25.0 per cent) and T. simii (4.17 per cent). Maximum number of dermatophytic patients were between 31 to 40 years of age (41.67). The males (75.0 per cent) were affected by the zoophilic dermatophytes more than the females (25.0 per cent). Epidemiological investigations indicated that the infected patients were mainly from the low socio-economic background (33.33 per cent). Moreover, T. mentagrophytes (33.33 per cent) and T. verrucosum (25.0 per cent) played the major role in causing dermatophytosis in persons, residing in the villages whereas M. canis (16.67 per cent) was identified as the chief etiologic agent in the city dwellers. Further studies signified that patients from rural communities (66.67 per cent) with history of contact with animals were the frequent victims of zoophilic dermatophytes. Altogether the overall prevalence of zoophilic dermatophjrtes was higher in rural areas (66.67 per cent) than the urban areas (33.33 per cent). Among various occupational groups, with greater opportunity of exposure to animals, the most vulnerable group to be infected with the zoophilic species comprised of the dairy farmers working in the villages (37.5 per cent). Likewise in the urban localities, the animal handlers (16.67) were identified as the most susceptible group. However, even animal owners belonging to the urban areas were considered as a risk group. Through retrospective epidemiology the source of infection was established in 14 out of 24 positive patients, with a history of contact with animals. Isolation of similar zoophilic dermatophytes (14) from the human patients as well as their respective in-contact animals confirmed the zoonotic significance of the animal dermatophyties. It can be concluded that ringworm was prevalent (19.35 per cent) among the suspected patients, to a considerable extent. This potential mycotic dermatological hazard, affected the males more frequently than the females. Most of the dermatophytic cases were observed in adults of 31 to 40 years of age. The frequency of T. mentagrophytes in causing tinea infections in man was higher than the other zoophilic species namely T. verrucosum, M. canis and T. simii. Among all the clinical types of tinea, tinea corporis was recorded as the most common form in the positive patients. Maximum number of dermatophytic patients with history of close association with animals, were exclusively from the rural localities owing to their low socioeconomic status and poor personal hygiene. Moreover, T. mentagrophytes and T. verrucosum were detected primarily in persons residing in the villages while M. canis was recovered from the city dwellers. This was attributed to the close contact of the rural people to farm animals, which were principal sources of these dermatophytes. Increased contacts with pets led to the spread of ringworm to the urban people. Dermatophytosis due to zoophilic species was recognized as an occupational hazard, predominantly of the dairy farmers followed by animal handlers, owing to their increased exposure to animals due to occupational obligations. However, animal owners were also at greater risk. Animals of different species namely buffalo, cattle, camel, dog, goat, hen and horse were established as the source of infection in 14 positive patients, thereby establishing the role of zoophilic dermatophytes in the etiology of human ringworm. This heralded the need of thorough medical investigation of patients with cutaneous lesions having history of exposure to animals. As far as it could be ascertained, the isolation of T. mentagrophytes as the etiologic agent of ringworm in camel, dog and horse and T. simii in a hen constitutes the first report of its kind from Gujarat. Moreover, zoonotic. potential of these dermatophytes have also been established for the first time in Gujarat.
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VETERINARY PUBLIC HEALTH, A STUDY