Estimating the Intracluster Correlation Coefficient for the Clinical Sign "Trachomatous Inflammation-Follicular" in Population-Based Trachoma Prevalence Surveys: Results From a Meta-Regression Analysis of 261 Standardized Preintervention Surveys Carried Out in Ethiopia, Mozambique, and Nigeria.

Sample sizes in cluster surveys must be greater than those in surveys using simple random sampling in order to obtain similarly precise prevalence estimates, because results from subjects examined in the same cluster cannot be assumed to be independent. Therefore, a crucial aspect of cluster sampling is estimation of the intracluster correlation coefficient (ρ): the degree of relatedness of outcomes in a given cluster, defined as the proportion of total variance accounted for by between-cluster variation. In infectious disease epidemiology, this coefficient is related to transmission patterns and the natural history of infection; its value also depends on particulars of survey design. Estimation of ρ is often difficult due to the lack of comparable survey data with which to calculate summary estimates. Here we use a parametric bootstrap model to estimate ρ for the ocular clinical sign "trachomatous inflammation-follicular" (TF) among children aged 1-9 years within population-based trachoma prevalence surveys. We present results from a meta-regression analysis of data from 261 such surveys completed using standardized methods in Ethiopia, Mozambique, and Nigeria in 2012-2015. Consistent with the underlying theory, we found that ρ increased with increasing overall TF prevalence and smaller numbers of children examined per cluster. Estimates of ρ for TF were independently higher in Ethiopia than in the other countries.

Impact Survey Results after SAFE Strategy Implementation in 15 Local Government Areas of Kebbi, Sokoto and Zamfara States, Nigeria.

PURPOSE: To determine prevalence of trachoma after interventions in 15 local government areas (LGAs) of Kebbi, Sokoto and Zamfara States, Nigeria. METHODS: A population-based impact survey was conducted in each LGA using Global Trachoma Mapping Project (GTMP) protocols. In each LGA, 25 villages were selected, except in Arewa LGA, where we selected 25 villages from each of four subunits to obtain finer-resolution prevalence information. Villages were selected with probability proportional to size. In each village, 25 households were enrolled and all consenting residents aged ≥1 year were examined by GTMP-certified graders for trachomatous inflammation-follicular (TF) and trachomatous trichiasis (TT). Information on sources of household water and types of sanitation facilities used was collected through questioning and direct observation. RESULTS: The number of households enrolled per LGA ranged from 623 (Kware and Tangaza) to 2488 (Arewa). There have been marked reductions in the prevalence of TF and TT since baseline surveys were conducted in all 15 LGAs. Eight of the 15 LGAs have attained TF prevalences <5% in children, while 10 LGAs have attained TT prevalences <0.2% in persons aged ≥15 years. Between 49% and 96% of households had access to water for hygiene purposes within 1 km of the household, while only 10-59% had access to improved sanitation facilities. CONCLUSION: Progress towards elimination of trachoma has been made in these 15 LGAs. Collaboration with water and sanitation agencies and community-based trichiasis surgery are still needed in order to eliminate trachoma by the year 2020.

Prevalence of Trachoma and Access to Water and Sanitation in Benue State, Nigeria: Results of 23 Population-Based Prevalence Surveys.

PURPOSE: We sought to determine the prevalence of trachoma in each local government area (LGA) of Benue State, Nigeria. METHODS: Two-stage cluster sampling was used to conduct a series of 23 population-based prevalence surveys. LGAs were the evaluation units surveyed. In each LGA, 25 households were selected in each of 25 clusters, and individuals aged 1 year and above resident in those households were invited to be examined for trachoma. Data on access to water and sanitation were also collected at household level. RESULTS: A total of 91,888 people were examined from among 93,636 registered residents across the 23 LGAs. The LGA-level prevalence of trachomatous inflammation-follicular (TF) in 1-9 year olds ranged from 0.3% to 5.3%. Two LGAs had TF prevalences of 5.0-9.9%. The LGA-level prevalence of trichiasis in ≥15-year-olds ranged from 0.0% to 0.35%. Access to improved drinking water sources ranged from 0% in Gwer West to 99% in Tarka, while access to improved sanitation ranged from 1% in Gwer West to 92% in Oturkpo. CONCLUSION: There is a need for public health-level interventions against trachoma in three LGAs of Benue State.

Prevalence of Trachoma in Kogi State, Nigeria: Results of four Local Government Area-Level Surveys from the Global Trachoma Mapping Project.

PURPOSE: To determine the prevalence of trachoma in four Local Government Areas (LGAs) of Kogi State, Nigeria. METHODS: In June 2014, we conducted population-based, cross-sectional surveys according to Global Trachoma Mapping Project (GTMP) protocols in selected LGAs of Kogi State. In each LGA, 25 clusters were selected with probability proportional to size. In each of these clusters, 25 households were enrolled for the survey. All residents of selected households aged ≥1 year were examined by GTMP-certified graders for trachomatous inflammation-follicular (TF) and trichiasis using the simplified trachoma grading scheme. Data on sources of household water and types of sanitation facilities were collected through questioning and direct observation. RESULTS: The age-adjusted TF prevalence in 1-9-year-olds ranged from 0.4% (95% CI 0.1-0.8%) in Bassa to 1.0% (95% CI 0.3-1.9%) in Omala. Across all four LGAs, only one case of trichiasis was found; this individual was in Omala, giving that LGA a trichiasis prevalence in individuals aged ≥15 years of 0.02% (95% CI 0.00-0.07%). Between 77 and 88% of households had access to water for hygiene purposes, while only 10-30% had access to improved sanitation facilities. CONCLUSION: Trachoma is not a public health problem in any of the 4 LGAs surveyed. There is, however, the need to increase access to adequate water and sanitation services to contribute to the health and social and economic well-being of these communities.

Prevalence of and risk factors for trachoma in Kwara state, Nigeria: Results of eight population-based surveys from the Global Trachoma Mapping Project.

PURPOSE: To determine the prevalence of and risk factors for trachoma in selected local government areas (LGAs) of Kwara State, Nigeria. METHODOLOGY: Population-based cross-sectional surveys were conducted in eight LGAs of Kwara State using Global Trachoma Mapping Project (GTMP) protocols. In each LGA, 25 villages were selected using probability-proportional-to-size sampling; 25 households were selected from each village using compact segment sampling. All residents of selected households aged ≥1 year were examined by GTMP-certified graders for trachomatous inflammation-follicular (TF) and trichiasis using the simplified trachoma grading scheme. Water, sanitation, and hygiene (WASH) data were also collected. RESULTS: A total of 28,506 residents were enumerated in 4769 households across the eight LGAs. TF prevalence in children aged 1-9 years ranged from 0.2% (95% CI 0.0-0.3%) to 1.3% (95% CI 0.7-2.1%), while trichiasis prevalence in persons ≥15 years was <0.2% in each LGA. Access to improved water source was the lowest in Edu (62%), while access to improved sanitation facilities was the lowest in Asa (6%) and the highest in Ilorin East (64%). Children aged 1-4 years had 0.63 (95% CI 0.40-0.99) times lower odds of having TF compared to children aged 5-9 years. Children in households with ≥5 resident 1-9-year-old children had 1.63 (95% CI 1.02-2.60) times greater odds of having TF compared to those in households with <5 resident children. CONCLUSION: Trachoma is not a public health problem in Kwara State. Provision of adequate water and sanitation services should be a priority here, as a foundation for the health of the population.

Prevalence of Trachoma in Bauchi State, Nigeria: Results of 20 Local Government Area-Level Surveys.

PURPOSE: To determine the prevalence of trachomatous inflammation - follicular (TF) and trichiasis in each of the 20 local government areas (LGAs) of Bauchi State, Nigeria. METHODS: We undertook a population-based prevalence survey in each LGA in Bauchi State, employing the Global Trachoma Mapping Project methodology. We used a 2-stage, systematic and quasi-random sampling strategy. Using probability proportional to size, we selected 25 clusters, in each of which 25 households were selected by random walk. All residents of selected households 1 year and older were examined for TF, trachomatous inflammation - intense, and trichiasis, using the World Health Organization simplified grading scheme. RESULTS: Only two LGAs in Bauchi State had TF prevalences in 1-9-year-olds over 5%, with none having TF prevalences of 10% or greater. Only one LGA had a trichiasis prevalence in adults below the elimination threshold; all the others had trichiasis at levels suggestive of public health significance. In all 20 LGAs, more than 60% of households were within 1 km of an improved source of water for hygiene. CONCLUSION: Efforts need to be made in Bauchi State to provide trichiasis surgery in order to avert trachomatous blindness. Water supplies needs to be sustained and good personal hygiene practices assured so that elimination of trachoma as a public health problem will be achieved and sustained.

Trachoma Mapping in Gombe State, Nigeria: Results of 11 Local Government Area Surveys.

PURPOSE: To determine the need or otherwise for establishment of a trachoma elimination program in Gombe State, Nigeria, by estimating the population-based prevalence of trachoma in each Local Government Area (LGA) of Gombe. METHODS: Using a multi-stage, systematic, random, and quasi-random sampling approach and Global Trachoma Mapping Project support, we selected 25 clusters in each LGA. In each cluster, we selected 25 households and all consenting residents aged 1 year and older were examined for trachomatous inflammation-follicular (TF) and trichiasis, using the World Health Organization simplified grading scheme. RESULTS: No LGA in Gombe State had a TF prevalence ≥5% in 1-9-year-olds. All LGAs had trichiasis prevalences above the elimination threshold and should be targeted for community-based delivery of trichiasis surgery. Only three LGAs had household-level improved wash water access of greater than 80%. Access to improved sanitation facilities was also poor as household access to improved sanitation facilities was above 80% in only one LGA. CONCLUSION: A trachoma program focused on delivery of trichiasis surgery is required in Gombe. Improvements in water and sanitation, through engagement with other sectors, are necessary.