Department of Infectious Disease Epidemiology and London Centre for Neglected Tropical Disease Research, Imperial College London, Norfolk Place, W2 1 PG, London, UK; Department of Pathobiology and Population Sciences and London Centre for Neglected Tropical Disease Research, Royal Veterinary College, Hawkshead Lane, Hatfield, AL9 7TA, UK.
Department of Public Health, Erasmus MC, University Medical Center Rotterdam, Rotterdam, The Netherlands.
Epidemics. 2017 Mar;18:4-15. doi: 10.1016/j.epidem.2017.02.005.
The onchocerciasis transmission models EPIONCHO and ONCHOSIM have been independently developed and used to explore the feasibility of eliminating onchocerciasis from Africa with mass (annual or biannual) distribution of ivermectin within the timeframes proposed by the World Health Organization (WHO) and endorsed by the 2012 London Declaration on Neglected Tropical Diseases (i.e. by 2020/2025). Based on the findings of our previous model comparison, we implemented technical refinements and tested the projections of EPIONCHO and ONCHOSIM against long-term epidemiological data from two West African transmission foci in Mali and Senegal where the observed prevalence of infection was brought to zero circa 2007-2009 after 15-17 years of mass ivermectin treatment. We simulated these interventions using programmatic information on the frequency and coverage of mass treatments and trained the model projections using longitudinal parasitological data from 27 communities, evaluating the projected outcome of elimination (local parasite extinction) or resurgence. We found that EPIONCHO and ONCHOSIM captured adequately the epidemiological trends during mass treatment but that resurgence, while never predicted by ONCHOSIM, was predicted by EPIONCHO in some communities with the highest (inferred) vector biting rates and associated pre-intervention endemicities. Resurgence can be extremely protracted such that low (microfilarial) prevalence between 1% and 5% can be maintained for 3-5 years before manifesting more prominently. We highlight that post-treatment and post-elimination surveillance protocols must be implemented for long enough and with high enough sensitivity to detect possible residual latent infections potentially indicative of resurgence. We also discuss uncertainty and differences between EPIONCHO and ONCHOSIM projections, the potential importance of vector control in high-transmission settings as a complementary intervention strategy, and the short remaining timeline for African countries to be ready to stop treatment safely and begin surveillance in order to meet the impending 2020/2025 elimination targets.
盘尾丝虫病传播模型 EPIONCHO 和 ONCHOSIM 是分别独立开发的，并被用于探索在世界卫生组织（WHO）提出的时间框架内（即 2020 年/2025 年之前），通过大规模（每年或每两年一次）伊维菌素分发来消除非洲盘尾丝虫病的可行性。这些模型得到了 2012 年伦敦被忽视热带病宣言的认可。基于我们之前模型比较的结果，我们对技术进行了改进，并根据马里和塞内加尔两个西非传播中心的长期流行病学数据对 EPIONCHO 和 ONCHOSIM 的预测进行了测试，在经过 15-17 年大规模伊维菌素治疗后，这些中心的感染流行率于 2007-2009 年左右降至零。我们使用关于大规模治疗的频率和覆盖范围的规划信息模拟了这些干预措施，并使用来自 27 个社区的纵向寄生虫学数据对模型预测进行了训练，评估了消除（局部寄生虫灭绝）或再现的预测结果。我们发现，EPIONCHO 和 ONCHOSIM 能够充分捕捉大规模治疗期间的流行病学趋势，但 ONCHOSIM 从未预测到的再现，在一些具有最高（推断的）媒介叮咬率和相关的干预前流行率的社区中，EPIONCHO 预测到了这种情况。再现可能极其持久，以至于在更明显地出现之前，1%-5%的低（微丝蚴）流行率可能会持续 3-5 年。我们强调，必须实施足够长时间和足够高敏感性的治疗后和消除后监测方案，以检测可能表明再现的潜在潜伏感染。我们还讨论了 EPIONCHO 和 ONCHOSIM 预测之间的不确定性和差异，在高传播环境中作为补充干预策略的媒介控制的潜在重要性，以及非洲国家在安全停止治疗并开始监测方面的剩余时间很短，以便能够及时达到即将到来的 2020 年/2025 年消除目标。
