Active trachoma in children in central Ethiopia: association with altitude.
A cross-sectional study was conducted in the dry month of February 2000 in the Gurage Zone of Ethiopia (population over 1.5 million) to determine the magnitude of trachoma and blindness. A multistage cluster sampling was applied to identify the study subjects. Pre-school children (1-6 years) were examined for active trachoma by trained ophthalmic nurses. The prevalence of active trachoma in the 1-6-year-old age group was 56.5%, ranging from 5.7% (altitude > 3000 m) to 73.4% (altitude less than 2000 m) (P < 0.001). Active trachoma was more common in male children than in female children and peaked in the 3-year-old age group (63.2%), declining with age. The distance to a source of water for 45% of these households was only 15 min. Only 6% of the households had latrines. Confirmation of the association between active disease and altitude may assist with mapping of trachoma in Ethiopia and elsewhere. It is possible that fly density, higher in villages at low altitudes, contributed to the differences seen.