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Author Notes:

Corresponding author: David G. Addiss (dga1@cdc.gov)

All authors participated fully in extensive critical discussions as the model developed and in writing the paper.

DA conceived of the study, helped develop the decision model, and was the primary author of the paper.

RR developed the decision model and helped write the paper.

NAYT-D conceived of the study, provided data, helped develop the decision model, and helped write the paper.

FOR conceived of the study, provided critical data and perspective, helped refine the model, and helped write the paper.

All authors read and approved the final manuscript.

The authors would like to thank Dr. Bjorn Thylefors, Director, Mectizan® Donation Program, for helpful discussions on study conceptualization and for his expert opinion on parameters for the model.

There are no competing interests to declare.


A Framework for Decision-Making for Mass Distribution of Mectizan® in Areas Endemic for Loa loa


Journal Title:

Filaria Journal


Volume 2


Type of Work:

Article | Final Publisher PDF


Background: The occurrence of Loa loa encephalopathy following mass treatment of onchocerciasis with Mectizan® has adversely affected onchocerciasis control efforts in central Africa. Persons with very high densities of L. loa microfilaremia are at increased risk of encephalopathy, but little is known about the geographic distribution of these persons within central Africa. RAPLOA, a new technique that correlates the proportion of community members reporting a history of eyeworm with the prevalence of high-intensity L. loa microfilaremia in that community, may be useful for rapid assessment of areas at potential risk of treatment-related L. loa encephalopathy. Validation of RAPLOA is ongoing. The operational and risk-reduction advantages of RAPLOA over the current technique of village-by-village rapid epidemiologic assessment for onchocerciasis (REA) are unknown. Methods: We developed a decision model to compare four strategies for minimizing sequelae of L. loa encephalopathy following mass treatment with Mectizan® in areas co-endemic for onchocerciasis and loiasis: REA; RAPLOA with threshold eyeworm prevalences of 40% and 20% (RAPLOA-40 and RAPLOA-20, respectively); and combined REA/RAPLOA-40. Results: In the model, all four strategies significantly reduced risk of death and neurologic complications from L. loa encephalopathy, but RAPLOA-20 and REA resulted in half as many such cases as did RAPLOA-40 or combined REA/RAPLOA-40. Conclusion: RAPLOA is likely to be useful programmatically in reducing risk of L. loa encephalopathy following mass treatment with Mectizan®. It also may be cost-saving. Before full-scale implementation, additional data are needed on geographic clustering of high-density L. loa microfilaremia and on RAPLOA's reliability and cost.
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