Measuring treatment coverage for neglected tropical disease control programs: analysis of a survey design.

Monitoring of treatment coverage following mass drug administration is essential to ensure program success. Coverage results reported by drug administrators are often validated by using population surveys. This study evaluates the design of a multistage cluster sample survey conducted in 2007-2008 and implemented at the district level to assess drug coverage in the 4 African countries of Burkina Faso, Ghana, Niger, and Uganda. Estimates of precision of coverage were calculated, and factors contributing to the observed variance were analyzed. Precision of ±5 percentage points was obtained in 39% (n = 12) of cases, and precision of ±10 percentage points was obtained in 77% (n = 24) of cases. The factor having the largest impact on the actual precision obtained in these surveys was the high level of clustering, the impact of which is incorporated in the design effect. Key recommendations are made for the design and analysis of future surveys; guidelines are presented for thinking through the number of clusters that should be selected and how a cluster should be designed.

Correction: Onchocerciasis: Target product profiles of in vitro diagnostics to support onchocerciasis elimination mapping and mass drug administration stopping decisions.

[This corrects the article DOI: 10.1371/journal.pntd.0010682.].

Onchocerciasis: Target product profiles of in vitro diagnostics to support onchocerciasis elimination mapping and mass drug administration stopping decisions.

In June 2021, the World Health Organization (WHO), recognizing the need for new diagnostics to support the control and elimination of onchocerciasis, published the target product profiles (TPPs) of new tests that would support the two most immediate needs: (a) mapping onchocerciasis in areas of low prevalence and (b) deciding when to stop mass drug administration programs. In both instances, the test should ideally detect an antigen specific for live, adult O. volvulus female worms. The preferred format is a field-deployable rapid test. For mapping, the test needs to be ≥ 60% sensitive and ≥ 99.8% specific, while to support stopping decisions, the test must be ≥ 89% sensitive and ≥ 99.8% specific. The requirement for extremely high specificity is dictated by the need to detect with sufficient statistical confidence the low seroprevalence threshold set by WHO. Surveys designed to detect a 1-2% prevalence of a given biomarker, as is the case here, cannot tolerate more than 0.2% of false-positives. Otherwise, the background noise would drown out the signal. It is recognized that reaching and demonstrating such a stringent specificity criterion will be challenging, but test developers can expect to be assisted by national governments and implementing partners for adequately powered field validation.

Slaying little dragons: the impact of the Guinea Worm Eradication Program on dracunculiasis disability averted from 1990 to 2016.

Background: The objective of this study was to document the worldwide decline of dracunculiasis (Guinea worm disease, GWD) burden, expressed as disability-adjusted life years (DALYs), from 1990 to 2016, as estimated in the Global Burden of Disease study 2016 (GBD 2016). While the annual number of cases of GWD have been consistently reported by WHO since the 1990s, the burden of disability due to GWD has not previously been quantified in GBD. Methods: The incidence of GWD was modeled for each endemic country using annual national case reports. A literature search was conducted to characterize the presentation of GWD, translate the clinical symptoms into health sequelae, and then assign an average duration to the infection. Prevalence measures by sequelae were multiplied by disability weights to estimate DALYs. Results: The total DALYs attributed to GWD across all endemic countries (n=21) in 1990 was 50,725 (95% UI: 35,265-69,197) and decreased to 0.9 (95% UI: 0.5-1.4) in 2016. A cumulative total of 12,900 DALYs were attributable to GWD from 1990 to 2016. Conclusions: Using 1990 estimates of burden propagated forward, this analysis suggests that between 990,000 to 1.9 million DALYs have been averted as a result of the eradication program over the past 27 years.

The cost-effectiveness of an eradication programme in the end game: Evidence from guinea worm disease.

BACKGROUND: Of the three diseases targeted for eradication by WHO, two are so-called Neglected Tropical Diseases (NTDs)-guinea worm disease (GWD) and yaws. The Guinea Worm Eradication Programme (GWEP) is in its final stages, with only 25 reported in 2016. However, global eradication still requires certification by WHO of the absence of transmission in all countries. We analyze the cost-effectiveness of the GWEP in the end game, when the number of cases is lower and the cost per case is higher than at any other time. Ours is the first economic evaluation of the GWEP since a World Bank study in 1997. METHODS: Using data from the GWEP, we estimate the cost of the implementation, pre-certification and certification stages. We model cost-effectiveness in the period 1986-2030. We compare the GWEP to two alternative scenarios: doing nothing (no intervention since 1986) and control (only surveillance and outbreak response during 2016-2030). We report the cost per case averted, cost per disability adjusted life year (DALY) averted and cost per at-risk life year averted. We assess cost-effectiveness against a threshold of about one half GDP per capita (less than US$ 500 in low income countries). All costs are expressed in US$ of 2015. RESULTS: The GWEP cost an estimated US$ 11 (95% uncertainty interval, 4.70-12.49) per case averted in the period 1986-2030. The pre-certification and certification phases can cost as much as US$ 0.0041 and US$ 0.0015 per capita per year. The cost per DALY averted by the GWEP relative to doing nothing is estimated at US$ 222 (118-372) in 1986-2030. The GWEP is probably more cost-effective than control by the year 2030. The GWEP is certainly more cost-effective than control if willingness to pay for one year of life lived without the risk of GWD exceeds US$ 0.10. DISCUSSION: Even if economic costs are two times as high as the financial costs estimated for the period to 2020, the GWEP will still be cost-effective relative to doing nothing. Whether the GWEP turns out to be the most cost-effective alternative in the period beyond 2015 depends on the time horizon. When framed in terms of the number of years of life lived without the risk of GWD, a case can be made more easily for finishing the end game, including certification of the absence of transmission.

Dracunculiasis (guinea worm disease): eradication without a drug or a vaccine.

Dracunculiasis, commonly known as guinea worm disease, is a nematode infection transmitted to humans exclusively via contaminated drinking water. The disease prevails in the most deprived areas of the world. No vaccine or medicine is available against the disease: eradication is being achieved by implementing preventive measures. These include behavioural change in patients and communities--such as self-reporting suspected cases to health workers or volunteers, filtering drinking water and accessing water from improved sources and preventing infected individuals from wading or swimming in drinking-water sources--supplemented by active surveillance and case containment, vector control and provision of improved water sources. Efforts to eradicate dracunculiasis began in the early 1980s. By the end of 2012, the disease had reached its lowest levels ever. This paper reviews the progress made in eradicating dracunculiasis since the eradication campaign began, the factors influencing progress and the difficulties in controlling the pathogen that requires behavioural change, especially when the threat becomes rare. The challenges of intensifying surveillance are discussed, particularly in insecure areas containing the last foci of the disease. It also summarizes the broader benefits uniquely linked to interventions against dracunculiasis.

The epidemiology of trachoma in the five northern districts of Sierra Leone.

PURPOSE: In 2008, a trachoma prevalence survey was conducted in the five northern districts of Sierra Leone to determine if and where specific components of the SAFE strategy (Surgery, Antibiotics, Face washing, Environmental change) should be initiated. METHODS: A cross-sectional survey at district level was implemented using two-stage random cluster sampling: probability proportionate sampling was used to select villages in the first stage and compact segment sampling of households in the second stage. Both eyes of 16,780 individuals were examined using the World Health Organization simplified trachoma grading system. Data were also collected on village- and household-level behavior and environmental factors related to trachoma. RESULTS: Prevalence of trachomatous inflammation-follicular (TF) in children aged 1-9 years was highest in Kambia at 3.52% (95% Confidence Interval (CI): 2.28-4.75%), while the prevalence of trachomatous trichiasis (TT) in persons over 15 years of age was highest in Port Loko at 0.27% (95% CI: 0.03-0.50%). Across all districts, the percentage of households reporting washing children's faces less than once per day was very low, while latrine coverage and accessible and safe water sources were not highly prevalent. CONCLUSIONS: In all districts but Koinadugu, TT prevalence was greater than the WHO elimination threshold, indicating the need for 1,016 TT surgeries to prevent blindness. District TF prevalence rates did not warrant mass antibiotic distribution. Although not required given the low prevalence of TF, we recommend the construction of 35,941 household latrines and provision of water sources within a 30-minute walk roundtrip for 17,551 households to bring Sierra Leone closer to reaching Millennium Development Goal 7.