Exploring the spatial heterogeneity of trachomatous trichiasis

Prolonged conjunctival infection with Chlamydia trachomatis leads to an inflammatory response, trachomatous inflammation follicular (TF). Over time, repeat infection can progress to scarring of the conjunctiva causing the eyelid to turn inward, resulting in lashes rubbing against the cornea. This painful stage of the disease is called trachomatous trichiasis (TT). TT can damage the cornea, leading to vision impairment or blindness. Trachoma is targeted for elimination as a public health problem by the year 2020, which for TT is defined as less than 1 TT-positive person, who is not already known to the health system, per 1,000 population. For trachoma to meet the elimination targets, massive resources are required for both mapping and intervention. A particularly large knowledge gap exists around identifying areas where TT is likely to be found. To better align resources and plan for elimination, the trachoma community needs to understand how much TT currently exists and requires management, how to accurately measure TT prevalence, and where TT cases are mostly likely to be located. Understanding these elements will help position trachoma control programs to meet the TT elimination targets. In my thesis I first calculate an updated global estimate of TT cases and describe the methods involved. Second, I provide a survey design for measuring TT with adequate precision for control activities, along with validation exercise results and a brief time-cost analysis. I then examine the spatial structure of TF and TT and identify areas of spatial autocorrelation. Finally, I identify environmental factors associated with higher than expected TT prevalence to identify TT hot spots. The outcomes of these activities provide an updated global estimate of existing TT cases, a validated tool for measuring TT prevalence at the implementation unit (district) level, and insight on where to begin case finding activities in the context of the “end game”. These outputs are critical to the continued effort of trachoma elimination as a public health problem, specifically providing targeted direction for TT resources

Prevalence of Trachomatous Trichiasis in Ten Evaluation Units of Embu and Kitui Counties, Kenya.

BACKGROUND: Late-stage blinding sequalae of trachoma such as trachomatous trichiasis (TT) typically take decades to develop and often do so in the absence of ongoing ocular Chlamydia trachomatis infection. This suggests that most TT risk accumulates in early life; as a result, population-level TT incidence and prevalence can remain high years after C. trachomatis transmission among children has decreased. In Embu and Kitui counties, Kenya, the prevalence of trachomatous inflammation - follicular is low in children. In this survey, we set out to determine the prevalence of TT in ten evaluation units (EUs) in these counties. METHODS: We undertook ten cross-sectional prevalence surveys for TT. In each EU, people aged ≥15 years were selected by a two-stage cluster sampling method and examined for TT. Those with TT were asked questions on whether they had been offered management for it. Prevalence was adjusted to the underlying age and gender structure of the population. RESULTS: A total of 18,987 people aged ≥15 years were examined. Per EU, the median number of examined participants was 1,656 (range: 1,451 - 3,016) and median response rate was 86% (range: 81 - 95%). The prevalence of TT unknown to the health system in people aged ≥15 years was above the threshold for elimination (≥0.2%) in all ten EUs studied (range: 0.2-0.7%). TT was significantly more common in older than younger individuals and in women than in men. DISCUSSION: Provision of surgical services should be strengthened in Embu and Kitui counties of Kenya to achieve the World Health Organization threshold for eliminating TT as a public health problem

Progress Towards Elimination of Trachoma as a Public Health Problem in Eritrea: Results of a Systematic Review and Nine Population-based Prevalence Surveys Conducted in 2014

PURPOSE: To assess Eritrea's progress towards elimination of trachoma as a public health problem, we reviewed and compiled current knowledge on the distribution and burden of trachoma in Eritrea, then undertook further population-based surveys where indicated, with support from the Global Trachoma Mapping Project (GTMP). METHODS: For the systematic review, undertaken in March 2014, we searched (1) PubMed, using the terms ((blind* or trachoma or trichiasis) AND Eritrea); (2) the online database of rapid assessments of avoidable blindness; (3) our own grey literature collections; and (4) the Global Atlas of Trachoma database. In June and July 2014, we conducted nine population-based prevalence surveys, for each of which 30 villages were systematically selected with probability proportional to population size; in each village, 30 households were systematically selected. All consenting residents of selected households aged ≥1 year were examined by GTMP-certified graders for signs of trachoma. Data on household-level access to water and sanitation were also collected. RESULTS: One previous rapid assessment of avoidable blindness, three peer-reviewed publications, and two grey literature reports detailing sets of trachoma prevalence surveys conducted in 2006 and 2011, respectively, were located. Post-intervention impact surveys were needed in seven evaluation units (EUs, framed at sub-Zoba-level: population range 40,000-120,000) of Debub and Northern Red Sea, while baseline surveys were needed in two EUs of Anseba. Four of the seven impact survey EUs and both baseline survey EUs returned trachomatous inflammation-follicular prevalences in 1-9-year-olds of ≥5%; six of the seven impact survey EUs and one of the two baseline survey EUs returned trichiasis prevalences in ≥15-year-olds of ≥0.2%. The prevalence of access to water and sanitation varied widely between EUs. CONCLUSION: Interventions are still required in Eritrea to eliminate trachoma as a public health problem. Data from these surveys will guide the Ministry of Health to undertake programme planning using a sound evidence base

Prevalence of trachoma in four marakez of Elmenia and Bani Suef Governorates, Egypt

PURPOSE: In 2015, to determine where interventions are needed to eliminate trachoma as a public health problem from Egypt, we initiated population-based prevalence surveys using the Global Trachoma Mapping Project platform in four suspected-endemic marakez (districts; singular: markaz) of the governorates of Elmenia and Bani Suef. METHODS: In each markaz, 30 households were selected in each of 25 villages. Certified graders examined a total of 3682 children aged 1-9 years in 2993 households, noting the presence or absence of trachomatous inflammation-follicular (TF) and trachomatous inflammation-intense (TI) in each eye. A total of 5582 adults aged ≥15 years living in the same households were examined for trachomatous trichiasis (TT). Household-level access to water and sanitation was recorded. RESULTS: Three of four marakez had age-adjusted TF prevalence estimates in 1-9-year olds of >10%; the other markaz had a TF prevalence estimate of 5-9.9%. Estimates of the age- and gender-adjusted prevalence of unmanaged TT in adults ranged from 0.7% to 2.3%. Household-level access to water and sanitation was high. (We did not, however, measure use of water or sanitation facilities.) Conclusions: Each of the four marakez surveyed has trachoma as a public health problem, with a need for implementation of the SAFE (surgery, antibiotics, facial cleanliness, environmental improvement) strategy. Further mapping is also required to determine the need for interventions in other areas of Egypt