Reducing the Antigen Prevalence Target Threshold for Stopping and Restarting Mass Drug Administration for Lymphatic Filariasis Elimination: A Model-Based Cost-effectiveness Simulation in Tanzania, India and Haiti.

BACKGROUND: The Global Programme to Eliminate Lymphatic Filariasis (GPELF) aims to reduce and maintain infection levels through mass drug administration (MDA), but there is evidence of ongoing transmission after MDA in areas where Culex mosquitoes are the main transmission vector, suggesting that a more stringent criterion is required for MDA decision making in these settings. METHODS: We use a transmission model to investigate how a lower prevalence threshold (<1% antigenemia [Ag] prevalence compared with <2% Ag prevalence) for MDA decision making would affect the probability of local elimination, health outcomes, the number of MDA rounds, including restarts, and program costs associated with MDA and surveys across different scenarios. To determine the cost-effectiveness of switching to a lower threshold, we simulated 65% and 80% MDA coverage of the total population for different willingness to pay per disability-adjusted life-year averted for India ($446.07), Tanzania ($389.83), and Haiti ($219.84). RESULTS: Our results suggest that with a lower Ag threshold, there is a small proportion of simulations where extra rounds are required to reach the target, but this also reduces the need to restart MDA later in the program. For 80% coverage, the lower threshold is cost-effective across all baseline prevalences for India, Tanzania, and Haiti. For 65% MDA coverage, the lower threshold is not cost-effective due to additional MDA rounds, although it increases the probability of local elimination. Valuing the benefits of elimination to align with the GPELF goals, we find that a willingness to pay per capita government expenditure of approximately $1000-$4000 for 1% increase in the probability of local elimination would be required to make a lower threshold cost-effective. CONCLUSIONS: Lower Ag thresholds for stopping MDAs generally mean a higher probability of local elimination, reducing long-term costs and health impacts. However, they may also lead to an increased number of MDA rounds required to reach the lower threshold and, therefore, increased short-term costs. Collectively, our analyses highlight that lower target Ag thresholds have the potential to assist programs in achieving lymphatic filariasis goals.

Are current preventive chemotherapy strategies for controlling and eliminating neglected tropical diseases cost-effective?

Neglected tropical diseases (NTDs) remain a significant cause of morbidity and mortality in many low-income and middle-income countries. Several NTDs, namely lymphatic filariasis, onchocerciasis, schistosomiasis, soil-transmitted helminthiases (STH) and trachoma, are predominantly controlled by preventive chemotherapy (or mass drug administration), following recommendations set by the WHO. Over one billion people are now treated for NTDs with this strategy per year. However, further investment and increased domestic healthcare spending are urgently needed to continue these programmes. Consequently, it is vital that the cost-effectiveness of preventive chemotherapy is understood. We analyse the current estimates on the cost per disability-adjusted life year (DALY) of the preventive chemotherapy strategies predominantly used for these diseases and identify key evidence gaps that require further research. Overall, the reported estimates show that preventive chemotherapy is generally cost-effective, supporting WHO recommendations. More specifically, the cost per DALY averted estimates relating to community-wide preventive chemotherapy for lymphatic filariasis and onchocerciasis were particularly favourable when compared with other public health interventions. Cost per DALY averted estimates of school-based preventive chemotherapy for schistosomiasis and STH were also generally favourable but more variable. Notably, the broader socioeconomic benefits are likely not being fully captured by the DALYs averted metric. No estimates of cost per DALY averted relating to community-wide mass antibiotic treatment for trachoma were found, highlighting the need for further research. These findings are important for informing global health policy and support the need for continuing NTD control and elimination efforts.

Ecological and Socioeconomic Predictors of Transmission Assessment Survey Failure for Lymphatic Filariasis.

The transmission assessment survey (TAS) is recommended to determine whether cessation of mass drug administration (MDA) for lymphatic filariasis (LF) is warranted. Ministries of health typically implement TASs in evaluation units (EUs) that have had more than five rounds of annual MDA. Under TAS guidelines, sample size calculations determine a decision value: if the number of individuals testing positive exceeds this threshold, then MDA continues in the EU. The objective of this study was to determine whether fine scale geospatial covariates could be used to identify predictors of TAS failure. We geo-referenced 746 TAS EUs, of which 65 failed and extracted geospatial covariates using R to estimate odds of failure. We implemented stepwise backward elimination to select covariates for inclusion in a logistic regression to estimate the odds of TAS failure. Covariates included environmental predictors (aridity, distance to fresh water, elevation, and enhanced vegetation index), cumulative rounds of MDA, measures of urbanicity and access, LF species, and baseline prevalence. Presence of Brugia was significantly associated with TAS failure (odds ratio [OR]: 4.79, 95% CI: 2.52-9.07), as was population density (OR: 2.91, 95% CI: 1.06-7.98). The presence of nighttime lights was highly protective against failure (OR: 0.22, 95% CI: 0.10-0.50), as was an increase in elevation (OR: 0.36, 95% CI: 0.18-0.732). This work identifies predictors associated with TAS failure at the EU areal level, given the data presently available, and also identifies the need for more granular data to conduct a more robust assessment of these predictors.

Prediction of Low Community Sanitation Coverage Using Environmental and Sociodemographic Factors in Amhara Region, Ethiopia.

This study developed and validated a model for predicting the probability that communities in Amhara Region, Ethiopia, have low sanitation coverage, based on environmental and sociodemographic conditions. Community sanitation coverage was measured between 2011 and 2014 through trachoma control program evaluation surveys. Information on environmental and sociodemographic conditions was obtained from available data sources and linked with community data using a geographic information system. Logistic regression was used to identify predictors of low community sanitation coverage (< 20% versus ≥ 20%). The selected model was geographically and temporally validated. Model-predicted probabilities of low community sanitation coverage were mapped. Among 1,502 communities, 344 (22.90%) had coverage below 20%. The selected model included measures for high topsoil gravel content, an indicator for low-lying land, population density, altitude, and rainfall and had reasonable predictive discrimination (area under the curve = 0.75, 95% confidence interval = 0.72, 0.78). Measures of soil stability were strongly associated with low community sanitation coverage, controlling for community wealth, and other factors. A model using available environmental and sociodemographic data predicted low community sanitation coverage for areas across Amhara Region with fair discrimination. This approach could assist sanitation programs and trachoma control programs, scaling up or in hyperendemic areas, to target vulnerable areas with additional activities or alternate technologies.

Trachoma prevalence in Niger: results of 31 district-level surveys.

BACKGROUND: The leading cause of preventable blindness worldwide is trachoma, a condition caused by an infection of the inner eyelid. In Niger, a landlocked republic in Western Africa, surveys in 1988-89 identified trachoma as endemic in all but one region and, as a result, there is a National Prevention of Blindness Program plan to eliminate trachoma by 2015. METHODS: Thirty-one districts in eastern and western Niger were surveyed for trachoma prevalence from May 2009 to March 2012 as part of routine program impact evaluations. Prevalence surveys were implemented independently in each district using a two-stage cluster random design. Probability proportional to size was used to randomly select villages and 25 households were selected in each cluster. The prevalence of trachoma of clinical grade trachomatous follicular (TF) was estimated in children aged 1-9 years, and the prevalence of blinding trachoma, trachomatous trichiasis (TT), was measured in adults aged ≥15 years. RESULTS: A total of 14 211 households was surveyed; 58 617 individuals were evaluated for clinical signs of trachoma, of whom 27 087 were children aged 1-9 years. District-wide implementation of the full SAFE strategy is warranted in 16 districts where TF prevalence exceeds 10% and targeted implementation of the SAFE strategy (surgery for trichiasis; antibiotic therapy to control transmission; facial cleanliness for hygiene promotion; environmental change for improvements in access to water and sanitation) is recommended in the remaining 15 districts. The prevalence of TT among adults exceeded 1% in nine districts, suggesting that surgical services to treat TT should be implemented district-wide. CONCLUSIONS: These results establish the need for continued SAFE strategy implementation throughout Niger.

Intestinal parasite prevalence in an area of ethiopia after implementing the SAFE strategy, enhanced outreach services, and health extension program.

BACKGROUND: The SAFE strategy aims to reduce transmission of Chlamydia trachomatis through antibiotics, improved hygiene, and sanitation. We integrated assessment of intestinal parasites into large-scale trachoma impact surveys to determine whether documented environmental improvements promoted by a trachoma program had collateral impact on intestinal parasites. METHODOLOGY: We surveyed 99 communities for both trachoma and intestinal parasites (soil-transmitted helminths, Schistosoma mansoni, and intestinal protozoa) in South Gondar, Ethiopia. One child aged 2-15 years per household was randomly selected to provide a stool sample of which about 1 g was fixed in sodium acetate-acetic acid-formalin, concentrated with ether, and examined under a microscope by experienced laboratory technicians. PRINCIPAL FINDINGS: A total of 2,338 stool specimens were provided, processed, and linked to survey data from 2,657 randomly selected children (88% response). The zonal-level prevalence of Ascaris lumbricoides, hookworm, and Trichuris trichiura was 9.9% (95% confidence interval (CI) 7.2-12.7%), 9.7% (5.9-13.4%), and 2.6% (1.6-3.7%), respectively. The prevalence of S. mansoni was 2.9% (95% CI 0.2-5.5%) but infection was highly focal (range by community from 0-52.4%). The prevalence of any of these helminth infections was 24.2% (95% CI 17.6-30.9%) compared to 48.5% as found in a previous study in 1995 using the Kato-Katz technique. The pathogenic intestinal protozoa Giardia intestinalis and Entamoeba histolytica/E. dispar were found in 23.0% (95% CI 20.3-25.6%) and 11.1% (95% CI 8.9-13.2%) of the surveyed children, respectively. We found statistically significant increases in household latrine ownership, use of an improved water source, access to water, and face washing behavior over the past 7 years. CONCLUSIONS: Improvements in hygiene and sanitation promoted both by the SAFE strategy for trachoma and health extension program combined with preventive chemotherapy during enhanced outreach services are plausible explanations for the changing patterns of intestinal parasite prevalence. The extent of intestinal protozoa infections suggests poor water quality or unsanitary water collection and storage practices and warrants targeted intervention.

Incremental cost of conducting population-based prevalence surveys for a neglected tropical disease: the example of trachoma in 8 national programs.

BACKGROUND: Trachoma prevalence surveys provide the evidence base for district and community-wide implementation of the SAFE strategy, and are used to evaluate the impact of trachoma control interventions. An economic analysis was performed to estimate the cost of trachoma prevalence surveys conducted between 2006 and 2010 from 8 national trachoma control programs in Africa. METHODOLOGY AND FINDINGS: Data were collected retrospectively from reports for 165 districts surveyed for trachoma prevalence using a cluster random sampling methodology in Ethiopia, Ghana, Mali, Niger, Nigeria, Sudan, Southern Sudan and The Gambia. The median cost per district survey was $4,784 (inter-quartile range [IQR] = $3,508-$6,650) while the median cost per cluster was $311 (IQR = $119-$393). Analysis by cost categories (personnel, transportation, supplies and other) and cost activity (training, field work, supervision and data entry) revealed that the main cost drivers were personnel and transportation during field work. CONCLUSION: Population-based cluster random surveys are used to provide the evidence base to set objectives and determine when elimination targets have been reached for several neglected tropical diseases, including trachoma. The cost of conducting epidemiologically rigorous prevalence surveys should not be a barrier to program implementation or evaluation.

Improving community participation to eliminate lymphatic filariasis in American Samoa.

In 2000, the American Samoa Department of Health initiated a campaign of annual mass drug administration (MDA) with albendazole and diethylcarbamazine (DEC) to eliminate transmission of filariasis. Drug coverage was well below prescribed targets in the first three campaigns, ranging from 24 to 52% of the total population. Evaluation findings from a variety of formative research methods identified opportunities to improve MDA coverage and ensuing program modifications resulted in increased drug coverage of 65-71% in the following four annual distributions. Partnering with churches for drug distribution and using multiple media channels for health promotion led to sustained program improvements. With the increased emphasis on the use of mass distribution for delivery of drugs for a number of neglected tropical diseases, other programs may benefit from a similar approach.

Effect of a community intervention with pit latrines in five districts of Amhara, Ethiopia.

OBJECTIVE: To evaluate the change in household latrine coverage and investigated predictors of latrine uptake after 3 years of implementation of trachoma control interventions in Dera, Ebinat, Estie, Enebsie Sarmedir and Huleteju Enese districts of Amhara, Ethiopia. METHODS: Before and after study, baseline surveys were conducted prior to programme implementation and an evaluation after 3 years of interventions. Multi-stage cluster random sampling was used in both surveys. RESULTS: A total of 1096 and 1117 households were sampled and assessed for the presence of household latrines at baseline and evaluation, respectively. The proportion of households with a pit latrine increased by 32.3% overall (95% confidence interval [CI]: 27.9-38.0), ranging from 8.0% (95% CI: 5.1-10.8) in Ebinat to 58.9% (95% CI: 51.9-66.8) in Enebsie Sarmedir. Logistic regression analysis of associations between household latrine ownership and potential factors showed that increasing household size (OR(per additional person) = 1.2[95% CI: 1.1-1.3]), higher socio-economic status (tin roof) (OR = 1.8[95% CI: 1.2-2.9]) and participation in health education (OR = 1.6[95% CI: 1.1-2.5]) were independent predictors of latrine ownership. CONCLUSION: Our study documented heterogeneous increase in household latrine coverage after 3 years of latrine promotion; two of five districts had achieved Millennium Development Goal 7.9 and halved the proportion of households without latrine access. We attribute the striking increase in household latrines to increased political commitment of the local government and intensive community mobilisation under the trachoma control programme in Amhara region.

Achieving trachoma control in Ghana after implementing the SAFE strategy.

The Ghana Health Service plans to eliminate blinding trachoma by 2010 and has implemented the SAFE strategy since 2001. The programme impact was assessed in all endemic districts. A two-stage, cluster random sample of 720 households was selected in each of 18 endemic districts in Upper West and Northern Regions. All eligible residents were examined for trachoma signs. Household environmental risk factors were assessed. In total, 74,225 persons from 12,679 households were examined. Prevalence of trachomatous inflammation-follicular in 1-9 year-old children was 0.84% (95% CI 0.63-1.05, range of point estimates by district 0.14-2.81%) and prevalence of trichiasis in adults aged > or = 15 years was 0.31% (95% CI 0.24-0.38, range by district 0.00-1.07%). An estimated 4950 persons have trichiasis, of whom 72.6% are aged > or = 60 years and 71.4% are women. Latrines were observed in 11.6% of households and 79.2% of interview respondents reported use of an improved water source. Active trachoma is no longer a public health problem in Ghana after successful implementation of the SAFE strategy. The programme should maintain health education, advocate for improved water and sanitation and focus on providing surgery. Surveillance activities are needed to ensure sustained control.

The burden of trachoma in Ayod County of Southern Sudan.

BACKGROUND: Blindness due to trachoma is avoidable through Surgery, Antibiotics, Facial hygiene and Environmental improvements (SAFE). Recent surveys have shown trachoma to be a serious cause of blindness in Southern Sudan. We conducted this survey in Ayod County of Jonglei State to estimate the need for intervention activities to eliminate blinding trachoma. METHODOLOGY AND FINDINGS: A cross-sectional two-stage cluster random survey was conducted in November 2006. All residents of selected households were clinically assessed for trachoma using the World Health Organization (WHO) simplified grading scheme. A total of 2,335 people from 392 households were examined, of whom 1,107 were over 14 years of age. Prevalence of signs of active trachoma in children 1-9 years of age was: trachomatous inflammation follicular (TF) = 80.1% (95% confidence interval [CI], 73.9-86.3); trachomatous inflammation intense (TI) = 60.7% (95% CI, 54.6-66.8); and TF and/or TI (active trachoma) = 88.3% (95% CI, 83.7-92.9). Prevalence of trachomatous trichiasis (TT) was 14.6% (95% CI, 10.9-18.3) in adults over 14 years of age; 2.9% (95% CI, 0.4-5.3) in children 1-14 years of age; and 8.4% (95% CI, 5.5-11.3) overall. The prevalence of corneal opacity in persons over 14 years of age with TT was 6.4% (95% CI, 4.5-8.3). No statistically significant difference was observed in the prevalence of trachoma signs between genders. Trachoma affected almost all households surveyed: 384/392 (98.0%) had at least one person with active trachoma and 130 (33.2%) had at least one person with trichiasis. CONCLUSIONS: Trachoma is an unnecessary public health problem in Ayod. The high prevalence of active trachoma and trichiasis confirms the severe burden of blinding trachoma found in other post-conflict areas of Southern Sudan. Based on WHO recommended thresholds, all aspects of the SAFE strategy are indicated to eliminate blinding trachoma in Ayod.