The Field-Testing of a Novel Integrated Mapping Protocol for Neglected Tropical Diseases

Neglected tropical diseases (NTDs) cause significant physical debilitation, lowered economic productivity, and social ostracism for afflicted individuals. Five NTDs with available preventive chemotherapy: lymphatic filariasis (LF), trachoma, schistosomiasis, onchocerciasis and the three soil-transmitted helminths (STH); have been targeted for control or elimination, but resource constraints in endemic countries have impeded progress toward these goals. We have developed an integrated mapping protocol, Integrated Threshold Mapping (ITM) for use by Ministries of Health to decide where public health interventions for NTDs are needed. We compared this protocol to the World Health Organizations disease-specific mapping protocols in Mali and Senegal. Results from both methodologies indicated the same public health interventions for trachoma, LF and STH, while the ITM methodology resulted in a more targeted intervention for schistosomiasis. Our study suggests that the integrated methodology, which is also less expensive and logistically more feasible to implement, could replace disease-specific mapping protocols in resource-poor NTD-endemic countries

Laboratory and field evaluation of a new rapid test for detecting Wuchereria bancrofti antigen in human blood

Global Program to Eliminate Lymphatic Filariasis (GPELF) guidelines call for using filarial antigen testing to identify endemic areas that require mass drug administration (MDA) and for post-MDA surveillance. We compared a new filarial antigen test (the Alere Filariasis Test Strip) with the reference BinaxNOW Filariasis card test that has been used by the GPELF for more than 10 years. Laboratory testing of 227 archived serum or plasma samples showed that the two tests had similar high rates of sensitivity and specificity and > 99% agreement. However, the test strip detected 26.5% more people with filarial antigenemia (124/503 versus 98/503) and had better test result stability than the card test in a field study conducted in a filariasis-endemic area in Liberia. Based on its increased sensitivity and other practical advantages, we believe that the test strip represents a major step forward that will be welcomed by the GPELF and the filariasis research community

Results from Mali and Senegal from the Integrated Threshold Mapping (ITM) and WHO mapping methodologies.

<p>Results from Mali and Senegal from the Integrated Threshold Mapping (ITM) and WHO mapping methodologies.</p

Indicators, tests, thresholds and interventions recommended by the World Health Organization[6], [12].

<p>Indicators, tests, thresholds and interventions recommended by the World Health Organization<a href="http://www.plosntds.org/article/info:doi/10.1371/journal.pntd.0001380#pntd.0001380-WHO1" target="_blank">[6]</a>, <a href="http://www.plosntds.org/article/info:doi/10.1371/journal.pntd.0001380#pntd.0001380-WHO2" target="_blank">[12]</a>.</p

Implementation Unit (IU) and sampling frame indicated by WHO guidelines and the Integrated Threshold Mapping methodology.

<p>Implementation Unit (IU) and sampling frame indicated by WHO guidelines and the Integrated Threshold Mapping methodology.</p

Financial resources used in the Integrated Threshold Mapping (ITM) and WHO methodologies.

<p>Financial resources used in the Integrated Threshold Mapping (ITM) and WHO methodologies.</p

Public health interventions for the Integrated Threshold Mapping methodology based on various village selections.

<p>*SAC: school-aged children.</p

Decision rules for confirmatory mapping surveys.

<p>Decision rules for confirmatory mapping surveys.</p

The rationale and cost-effectiveness of a confirmatory mapping tool for lymphatic filariasis: Examples from Ethiopia and Tanzania

<div><p>Endemicity mapping is required to determining whether a district requires mass drug administration (MDA). Current guidelines for mapping LF require that two sites be selected per district and within each site a convenience sample of 100 adults be tested for antigenemia or microfilaremia. One or more confirmed positive tests in either site is interpreted as an indicator of potential transmission, prompting MDA at the district-level. While this mapping strategy has worked well in high-prevalence settings, imperfect diagnostics and the transmission potential of a single positive adult have raised concerns about the strategy’s use in low-prevalence settings. In response to these limitations, a statistically rigorous confirmatory mapping strategy was designed as a complement to the current strategy when LF endemicity is uncertain. Under the new strategy, schools are selected by either systematic or cluster sampling, depending on population size, and within each selected school, children 9–14 years are sampled systematically. All selected children are tested and the number of positive results is compared against a critical value to determine, with known probabilities of error, whether the average prevalence of LF infection is likely below a threshold of 2%. This confirmatory mapping strategy was applied to 45 districts in Ethiopia and 10 in Tanzania, where initial mapping results were considered uncertain. In 42 Ethiopian districts, and all 10 of the Tanzanian districts, the number of antigenemic children was below the critical cutoff, suggesting that these districts do not require MDA. Only three Ethiopian districts exceeded the critical cutoff of positive results. Whereas the current World Health Organization guidelines would have recommended MDA in all 55 districts, the present results suggest that only three of these districts requires MDA. By avoiding unnecessary MDA in 52 districts, the confirmatory mapping strategy is estimated to have saved a total of $9,293,219.</p></div