Semiquantitative study of tinea capitis and the asymptomatic carrier state in inner-city school children.

OBJECTIVE: To quantify and characterize the asymptomatic carrier state of tinea capitis in school children from the inner city.

METHODS: All students attending a parochial school (kindergarten through seventh grade) in the city of Philadelphia were cultured for tinea capitis periodically over 16 months (1404 hemi-scalp cultures from 224 children).

RESULTS: Our initial prevalence study of this all-black population (ages 5 to 13 years) found a 3% rate of index cases (symptomatic) and a 14% rate of asymptomatic carriers (without black-dot lesions, obvious hair loss, scaling, crusts, pustules, or erythema). Trichophyton tonsurans was the predominant dermatophyte (96% of 125 positive cultures; Microsporum canis was the only other isolate). Fifty percent of all positive cultures came from children in kindergarten and first grade; first grade had the highest rate of index cases. The overall prevalence of asymptomatic carriers was not higher in the classes containing index cases. Fifty-nine percent of asymptomatic carriers had a 1+ spore load (1 to 10 colonies isolated per scalp), while 74% of index cases had a 4+ spore load (> 150 total colonies). Forty-five untreated asymptomatic carriers were followed for 2 to 5 months: 19 (42%) became culture-negative; of these, 17 (90%) had a 1+ spore load.

CONCLUSIONS: We found that inner-city black school children who are asymptomatic carriers of T tonsurans had lower spore loads than index cases. Index cases did not appear to be the primary mode of transmission within a classroom. More than half of untreated asymptomatic carriers remained culture-positive after 2 months and probably play a role in the transmission of tinea capitis within this population.