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The 32nd Meeting of the Mectizan Expert Committee/Albendazole Coordination

Onchocerciasis

New data presented from the recent RAPLOA validation exercises in DRC and Congo-Brazzaville indicate that RAPLOA methodology is valid for use outside of the original area in which it was developed (i.e. Nigeria and Cameroon) and can now be used to estimate the prevalence of L. loa in areas suspected to be endemic.

In addition, progress has been made in mapping L. loa leading to a simplified version of the probability contour map (PCM) that illustrates "danger", "uncertain", and "safe" zones regarding the risk of developing L. loa encephalopathy following Mectizan treatment. TDR plans to use data from the RAPLOA validation studies in Congo-Brazzaville and DRC as well as data from recent RAPLOA surveys in Angola, to update the Environmental Risk Model for loiasis and to increase the accuracy of the map. The PCM will be particularly useful for operational planning of L. loa mapping and Mectizan treatment in Loa-endemic areas and will eventually be used as an annex to the MEC/TCC guidelines on Mectizan treatment in L. Loa endemic areas when they have been refined.

Revisions to the MEC/TCC guidelines for mass treatment with Mectizan for onchocerciasis in areas co-endemic for onchocerciasis and loiasis were finalized during this meeting following suggestions made during MEC 31, subsequent feedback from TCC 18, and reports on the validation of RAPLOA. The MEC amended and approved the guidelines for implementation (see page 7).

The Committee expressed concern over the higher than expected incidence of SAEs recently reported from the Bas Congo Province of the Democratic Republic of Congo (DRC), a region suspected to be highly endemic for L. loa. Consequently, the Committee recommended that mass treatment with Mectizan for onchocerciasis in Bas Congo be halted for the time being and that a mission be conducted to investigate the potential causes of these SAEs as soon as possible. Following the investigation, discussions will be held between the stakeholders on how to proceed with mass treatment, if possible, in Bas Congo. In addition, the Committee recommended that extensive RAPLOA surveys be conducted there in the next few months to better define the risk of SAEs potentially associated with L. loa in the region.

The Committee welcomed the conclusions arising from the spatial analysis of encephalopathic SAE cases from Cameroon. The Committee recommended continuation of a case-control study on individuals to determine co-factors, other than L. loa, that may explain the clustering effect of encephalopathic SAEs in Central Province and other areas where clustering is observed. Consideration should be given to developing similar community and individual level studies of encephalopathic SAEs being reported from DRC.

Findings from studies on possible measures to prevent L. loa associated SAEs following treatment with Mectizan in L. loa endemic areas were presented during the meeting. Following the presentation of results from a study on the use of low dose Mectizan as a possible pre-treatment agent to reduce the intensity of L. loa infection, the MEC recommended further exploration of even lower doses of Mectizan for this purpose. The Committee endorsed a proposed study on the use of multiple doses of albendazole as a pre-treatment agent and recommended implementation of the study as soon as possible. Finally, the Committee welcomed the comprehensive review of the literature for compounds, other than Mectizan, albendazole, and DEC, that may have efficacy against L. loa. Recognizing the potential leads that oxantel, praziquantel, and chloroquine may represent, the Committee endorsed the pursuit of small-scale studies to investigate these possibilities. Ongoing schistosomiasis control activities offer an opportunity to study the efficacy of praziquantel in reducing L. loa microfilaremia.

The proposed safety studies on albendazole and Mectizan use in individuals infected with L. loa were also endorsed and recommended for immediate implementation to determine the feasibility of expanding LF treatment programs into L. loa endemic areas.

Lymphatic Filariasis

The Committee commended WHO on the progress made so far in mapping LF in Africa and Yemen and endorsed the WHO schedule to complete all the mapping exercises in the region in 2005.

It was noted that several African countries are preparing to initiate mass drug administration (MDA) in the absence of sufficient funding for effective drug delivery. In agreement with the recommendations of the 4th Meeting of the African Regional Programme Review Group, the Committee recommended that MDA should not be initiated in a country unless there are reasonable assurances that funds for the first 2 years are forthcoming. There is also concern over countries planning to upscale existing MDA with limited or insufficient financial support. It was recommended that MDP, in collaboration with other interested parties, facilitate the identification of funding sources to ensure maintenance of the previous years' achievements with MDA, and, if possible, enable the planned expansion. Once there is reasonable assurance that sufficient funds are available, MDP, on behalf of the MEC/AC, may approve the requested number of tablets of Mectizan and albendazole.

The Committee requested detailed prevalence information on the potential L. loa endemic areas that the program may be expanding into this year so as to ensure that these areas are excluded from the MDA since mass treatment of LF with Mectizan and albendazole in L. loa endemic areas remains prohibited until the safety studies of the co-administration of these two drugs in such areas have been conducted. If prevalence data are not available, the program is recommended to conduct RAPLOA surveys according to the TDR protocol.

The Committee welcomed the preliminary findings from the cost analysis of the MDA program in Burkina Faso and urged that these findings, and those from the studies in Ghana and Tanzania, be finalized and published in peer-reviewed journals as soon as possible.

The Committee was informed of plans to develop regional LF support centers in support of the Global Alliance to Eliminate Lymphatic Filariasis. The Committee recommends the pursuit of this matter, which could allow for more effective program implementation and support to national capacity building. In particular, the Committee endorsed the ongoing development of the first of such centers in West Africa at the Noguchi Memorial Institute for Medical Research in Accra, Ghana.

The next meeting of the MEC/AC will be held in Paris, France 13-14 October, 2004.