Report of a Scientific Working Group on Serious Adverse Events following Mectizan® treatment of onchocerciasis in Loa loa endemic areas

Abstract

The occurrence of Serious Adverse Experiences (SAEs) following Mectizan® treatment of onchocerciasis in Loa loa endemic areas has been increasingly reported over the past decade. These SAEs include a severely disabling, and potentially fatal, encephalopathy, which appears to correlate with a high load of L. loa microfilariae (> 30,000 mf/ml). Previous consultations organized by the Mectizan® Donation Program (MDP) in 1995 and 1999 have developed useful "case" definitions of encephalopathic SAEs following Mectizan® treatment and have summarized available evidence on its pathogenesis and optimal clinical management. At both meetings, the need for better understanding of the pathogenesis of the encephalopathy was emphasized, including the need for biological and autopsy specimens from the affected cases. Following a recommendation at the Joint Action Forum of the African Programme for Onchocerciasis Control in December 2001, the MDP, on behalf of the Mectizan® Expert Committee, organized a Scientific Working Group on L. loa associated SAEs following Mectizan® treatment in May 2002. The present report includes the background, new evidence, conclusions and recommendations from that Scientific Working Group. The following points represent a summary of the present status: 1. Although there are more and better quality clinical and epidemiological data on L. loa, the pathogenesis of the Mectizan®-related L. loa encephalopathy remains obscure. 2. Very limited progress has been made in research on the pathogenesis of encephalopathy, because of the lack of specimens from cases, and the lack of animal models. 3. There has been no particular breakthrough in terms of the medical management of patients with L. loa encephalopathy; however, a favorable outcome usually results from prompt general nursing and nutritional care which remain the major interventions. The main recommendations for future actions are as follows: 1. Validate and update the mapping of L. loa with a combination of remote sensing and RAPLOA techniques. 2. Conduct an expert analysis of the apparent clustering of encephalopathic SAEs reported so far. 3. Investigate a possible "pre-treatment" scheme with high-dose albendazole in L. loa endemic communities at high risk of encephalopathic SAEs if treated with Mectizan®; this study will be conducted in collaboration with WHO/TDR. 4. Establish a post of Loiasis Technical Advisor for research and operational support in Cameroon, to conduct population surveys and to facilitate better data collection from SAE cases, including postmortem studies as appropriate. 5. Investigate the possibility of developing an animal model of L. loa encephalopathy; this activity would be linked to the above-mentioned research agenda in Cameroon. 6. Investigate the best care model for encephalopathic SAEs, including identification of early warning signs and therapeutic interventions. 7. Develop further models for health education messages needed for community compliance with Mectizan® treatment, and family support for SAE cases. 8. Conduct research studies on the safety of combination therapy of Mectizan® and albendazole in areas co-endemic for L. loa and lymphatic filariasis (LF) with coordination from the relevant technical bodies that oversee these issues. The above recommendations will be implemented through a continuing collaboration between the interested parties represented at the Scientific Working Group, involved in onchocerciasis control and/or the Global Programme to Eliminate Lymphatic Filariasis.