Wanji Samuel, Tendongfor Nicholas, Esum Mathias, Yundze Siker Sj, Taylor Mark J, Enyong Peter
University of Buea, Faculty of Science, Department of Life Sciences, P,O, Box 63, Buea, Cameroon.
Filaria J. 2005 Apr 7;4(1):2. doi: 10.1186/1475-2883-4-2.
Individuals with high microfilarial loads of Loa loa are at increased risk of neurologic serious adverse (SAE) events following ivermectin treatment against onchocerciasis. RAPLOA (Rapid Assessment Procedure for loiasis), a newly developed rapid assessment procedure for loiasis that relates the prevalence of key clinical manifestation of loiasis (history of eye worm) to the level of endemicity of the infection (prevalence of high intensity), is a very useful tool to identify areas at potential risk of L. loa post ivermectin treatment encephalopathy. In a perspective of treatment decision making in areas of co-endemicity of loiasis/onchocerciasis, it would be advantageous (both in time and cost savings) for national onchocerciasis control programmes to use RAPLOA and the Rapid epidemiologic assessment for onchocerciasis (REA), in combination in given surveys. Since each of the two rapid assessment tools have their own specificities, the workability of combining the two methods needed to be tested. METHODS: We worked in 10 communities of a forest area presumed co-endemic for loiasis and onchocerciasis in the North-West Province of Cameroon where the mass-treatment with ivermectin had not been carried out. A four-step approach was used and comprised: (i) generating data on the prevalence and intensity of loiasis and onchocerciasis in an area where such information is scarce; (ii) testing the relationship between the L. loa microfilaraemia prevalence and the RAPLOA prevalence, (iii) testing the relationship between the O. volvulus microfiladermia prevalence and the REA prevalence, (iv) testing the workability of combining RAPLOA/REA by study teams in which a single individual can perform the interview for RAPLOA and the nodule palpation for REA. RESULTS: The microfilaraemia prevalence of loiasis in communities ranged from 3.6% to 14.3%. 6 (0.61%) individuals had L. loa microfilarial loads above 8000 mf/ml but none of them attained 30,000 mf/ml, the threshold value above which the risk of developing neurologic SAE after ivermectin treatment is very high. None of the communities surveyed had RAPLOA prevalence above 40%. All the communities had microfiladermia prevalence above 60%. The microfiladermia results could be confirmed by the rapid epidemiologic method (nodule palpation), with all the 10 communities having REA prevalence above 20%. For the first time, this study has demonstrated that the two rapid assessment procedures for loiasis and onchocerciasis can be carried out simultaneously by a survey team, in which a single individual can administer the questionnaire for RAPLOA and perform the nodule palpation for REA. CONCLUSION: This study has: (i) Revealed that the Momo valley of the North West province of Cameroon is hyperendemic for onchocerciasis, but is of lower level of endemicity for L. loa. (ii) Confirmed the previous relationships established between RAPLOA and the L. loa microfilaraemia prevalence in one hand and between the REA and the O. volvulus microfiladermia prevalence in another hand (iii) Shown that RAPLOA and REA could be used simultaneously for the evaluation of loiasis and onchocerciasis endemicity in areas targeted by the African Programme for onchocerciasis Control for community-directed treatment with ivermectin (CDTI).
感染罗阿丝虫且微丝蚴负荷高的个体，在接受伊维菌素治疗盘尾丝虫病后发生神经系统严重不良事件（SAE）的风险增加。RAPLOA（罗阿丝虫病快速评估程序）是一种新开发的罗阿丝虫病快速评估程序，它将罗阿丝虫病关键临床表现（眼虫病史）的患病率与感染的流行程度（高强度患病率）相关联，是识别伊维菌素治疗后发生罗阿丝虫病脑病潜在风险地区的非常有用的工具。从盘尾丝虫病/罗阿丝虫病共流行地区的治疗决策角度来看，国家盘尾丝虫病控制项目在特定调查中联合使用RAPLOA和盘尾丝虫病快速流行病学评估（REA）将是有利的（在时间和成本节约方面）。由于这两种快速评估工具各有其特点，因此需要测试两种方法联合使用的可行性。
我们在喀麦隆西北部一个森林地区的10个社区开展工作，这些社区被认为是罗阿丝虫病和盘尾丝虫病的共流行地区，且尚未开展伊维菌素大规模治疗。采用了四步方法，包括：（i）在缺乏此类信息的地区收集罗阿丝虫病和盘尾丝虫病的患病率和感染强度数据；（ii）测试罗阿丝虫微丝蚴血症患病率与RAPLOA患病率之间的关系；（iii）测试盘尾丝虫微丝蚴皮症患病率与REA患病率之间的关系；（iv）测试由单个个体可以同时进行RAPLOA访谈和REA结节触诊的研究团队联合使用RAPLOA/REA的可行性。
各社区罗阿丝虫病微丝蚴血症患病率在3.6%至14.3%之间。6名（0.61%）个体的罗阿丝虫微丝蚴负荷高于8000 mf/ml，但均未达到30000 mf/ml，超过该阈值后伊维菌素治疗后发生神经系统SAE的风险非常高。所有调查社区的RAPLOA患病率均未超过40%。所有社区的微丝蚴皮症患病率均超过60%。微丝蚴皮症结果可通过快速流行病学方法（结节触诊）得到证实，所有10个社区的REA患病率均超过20%。本研究首次证明，罗阿丝虫病和盘尾丝虫病的两种快速评估程序可由一个调查团队同时进行，其中单个个体可以进行RAPLOA问卷调查并进行REA结节触诊。
本研究：（i）表明喀麦隆西北部的莫莫山谷盘尾丝虫病高度流行，但罗阿丝虫病的流行程度较低。（ii）一方面证实了之前建立的RAPLOA与罗阿丝虫微丝蚴血症患病率之间以及另一方面REA与盘尾丝虫微丝蚴皮症患病率之间的关系。（iii）表明RAPLOA和REA可同时用于非洲盘尾丝虫病控制规划针对伊维菌素社区定向治疗（CDTI）目标地区的罗阿丝虫病和盘尾丝虫病流行程度评估。
