Infection with Chlamydia trachomatis after mass treatment of a trachoma hyperendemic community in Tanzania: a longitudinal study

Abstract

In 1998, WHO set the target of worldwide elimination of trachoma-induced blindness by the year 2020. The SAFE strategy (surgery for trichiasis, antibiotics for infection, facial cleanliness, and environmental improvements to reduce transmission of Chlamydia trachomatis) has since been implemented to control the disease. Data from studies done in communities where trachoma is mesoendemic suggest that ocular infection with Chlamydia trachomatis can be eliminated after one mass treatment with antibiotics. However, there are no comparable long-term data from trachoma hyperendemic communities. The aim of this study was (1) to ascertain the disease pattern of trachoma and ocular infection with C trachomatis in a trachoma hyperendemic community after mass treatment; and (2) to ascertain the risk factors for incident infection. The authors performed a longitudinal study of a trachoma hyperendemic community (n = 1017) in Tanzania. They did surveys, including ocular swabs at baseline, 2, 6, 12, and 18 months, to identify the presence and quantity of C trachomatis after single mass treatment of all individuals aged 6 months or older with azithromycin 20 mg per kg; pregnant women without clinical disease received topical tetracycline. They found that mass treatment (coverage 86%) significantly reduced the prevalence of infection from 57% (495 of 871) to 12% (85 of 705) at 2 months. Infection remained fairly constant to 12 months, with evidence of increasing numbers and load of infection by 18 months post-treatment. Incident infection at 6 months was 3.5-times more likely if another member of the household had more than 19 organisms per swab at 2 months. Travel outside the village, and visitors to the household, did not increase the risk of infection within households up to 12 months. The authors conclude that infection levels after high antibiotic coverage persisted at a low level to 18 months, with evidence for re-emergence after 1 year. Fairly light loads of infection were associated with household transmission. They also suggest that early mass treatment over a few years could be sufficient to eliminate infection.—Valérie Biousse