A method to determine the coverage of ivermectin distribution in onchocerciasis-control programmes

Estimation of population coverage for antibiotic distribution for trachoma control: a comparison of methods

Trachoma control includes mass drug administration (MDA) with antibiotics targeting coverage of at least 80%. Coverage is traditionally calculated by dividing doses distributed by population estimate, which is unreliable. We compared a verifiable coverage assessment method against self-reported participation and the traditional calculation, and examined factors associated with MDA participation in Akobo County, Southern Sudan. During MDA, recipients were marked with indelible ink and followed-up using a two-stage household survey: 25 clusters from three districts, and 10 households per cluster. All household members were enumerated; asked about self-reported participation and observed for indelible marks. Household heads were interviewed to assess factors associated with MDA. Overall 11 419 treatments were given and 1358 residents from 247 households surveyed. By traditional methods MDA coverage was 20.9% (95% CI: 20.6-21.3); 61.5% (95 % CI: 49.4-73.6) by self-reporting; and 37.5% (95% CI: 25.1%-49.9%) from observed ink marks. Controlling for other factors, presence of a health worker (OR 2.3, 95% CI: 1.5-3.6); head of household knowledge of azithromycin (OR 1.6, 95% CI: 1.5-3.1); and head of household advance notice of MDA (OR 34.9, 18.1-66.3) were independent predictors of participation. Cluster randomised surveys can estimate MDA coverage better than the traditional method and implementation of indelible marking merits investigation.

The rapid monitoring of ivermectin treatment: will school-based surveys provide the answer?

The data on ivermectin-treatment coverage recorded in household surveys sometimes conflict with those recorded in school-based surveys or in the relevant treatment registers maintained by community-directed distributors (CDD). An attempt has now been made, in two sites in Nigeria (Enugu and Kaduna states) and one in Sudan (Abu Hamad province), to determine how well these three sets of data are correlated (and to explore the effectiveness of several alternative channels for the delivery of treatment-monitoring forms to schools). Using a cross-sectional approach, data were collected from primary schools, households and treatment registers. Calculation of Pearson's correlation coefficients (r) indicated that, overall, the data from the household surveys were very similar to those collected using the school-based strategy (r=0.66; P<0.0001) or from the treatment registers of the CDD (r=0.86; P<0.0001). The information recorded in the CDD registers also closely matched that recorded in the school-based surveys (r=0.67; P<0.0001). These encouraging results for the pooled data masked some inter-site differences. The correlation between the household-survey and treatment-register data was, for example, only good in Enugu (r=0.89; P<0.001), and was too weak to be statistically significant in Abu Hamad or Kaduna. Although the results of the school-based survey in Kaduna also did not closely correlate with those of the corresponding household survey (r=0.10; P=0.71), the household survey at this site was probably not conducted as well as those at the two other sites. In general, it appears that school-based surveys are an effective means of monitoring community coverage with ivermectin, rapidly, accurately and at relatively low cost. It is therefore recommended that school-based methods of monitoring of coverage are adopted by programme managers.

Methods for estimating population coverage of mass distribution programmes: a review of practices in relation to trachoma control

In the context of trachoma control, population coverage with mass drug administration (MDA) using antibiotics is measured using routine data. Due to the limitations of administrative records as well as the potential for bias from incomplete or incorrect records, a literature review of coverage survey methods applied in neglected tropical disease control programmes and immunisation outreach was conducted to inform the design of coverage surveys for trachoma control. Several methods were identified, including the '30 × 7' survey method for the Expanded Programme on Immunization (EPI 30×7), other cluster random sampling (CRS) methods, lot quality assurance sampling (LQAS), purposive sampling and routine data. When compared against one another, the EPI and other CRS methods produced similar population coverage estimates, whilst LQAS, purposive sampling and use of administrative data did not generate estimates consistent with CRS. In conclusion, CRS methods present a consistent approach for MDA coverage surveys despite different methods of household selection. They merit use until standard guidelines are available. CRS methods should be used to verify population coverage derived from LQAS, purposive sampling methods and administrative reports.

The delivery of ivermectin (Mectizan)

Over a comparatively short period of time, the development and distribution of ivermectin (Mectizan) has radically altered the consequences of infection with Onchocerca volvulus. To achieve this required the fostering of many partnerships and the development of new tools and methods. The long-term commitment of Merck, the World Bank and other sponsors, as well as governments and non-governmental organizations, has been crucial. Yet the enthusiasm with which communities have taken up the delivery of ivermectin among themselves is perhaps the greatest reason for the success of this programme. The present challenge is sustaining the methods that have brought success so far, and making them part of health services and disease control programmes in some of the world's most impoverished and unstable areas. A major part of this challenge is continuing the commitment to controlling onchocerciasis as memory of the disease is fading, and while the hope of elimination or eradication for most endemic countries remains distant.

Human onchocerciasis: the essential partnership between research and disease control efforts

Twenty years ago onchocerciasis was a disease generally ignored by the medical world, except by those who actually worked with the affected people in Africa and Latin America. Now, largely as a result of the success of mass vector control and drug treatment programs, this is a disease management model for developing countries. The recent literature on onchocerciasis has, not surprisingly, mainly focused on various aspects of control. Investigation into the more basic questions is needed to ensure continued effective disease control. The present mass drug control program is based on a single pharmaceutical, ivermectin (Mectizan), which acts almost exclusively on the microfilarial stage of the infection. Efforts are being made to identify other useful drugs; however, no major candidates have yet appeared. The identification of potential biochemical targets for anti-filarial compounds through a better understanding of the biochemistry of these worms is being pursued. The Onchocerca volvulus endosymbiont Wolbachia may provide a target for therapeutic intervention. An improved understanding of the genomics of O. volvulus has made possible the identification of strain differences in the parasites, and an appreciation of the relevance of these strain differences to the clinical disease, onchocerciasis. There is a need for a better understanding of the clinical disease, and the various pathogenic mechanisms that underly the different syndromes. It is particularly important to understand the pathological basis and mechanisms underlying the adverse responses that can occur with chemotherapy. Present control programs now need to be carefully monitored for effectiveness using new assessment tools, such as antigen assays and the identification of organisms in pools of vectors. Current efforts to control onchocerciasis must be coordinated with new chemotherapy-based control programs for other worm diseases that are emerging. The results of laboratory studies are increasingly being applied to improve the effectiveness of field-based control programs and their assessment. Such research is essential for progress towards the goals of controlling and eliminating onchocerciasis.

The control of the human filariases

There is a growing momentum for the global control and elimination of the major human filariases as public health problems worldwide. The renewed optimism for undertaking this objective reflects the development of simple and potentially cost-effective strategies for mass drug delivery in onchocerciasis and the availability of new extremely effective drug combinations to treat infection, and new methods of morbidity control in lymphatic filariasis. It also reflects the development and current availability of very effective diagnostic, surveillance and control modeling tools for both parasites. Control programming will also be aided by our greater understanding of the biology of transmission, host immunity and disease pathogenesis.