Garms R, Lakwo T L, Ndyomugyenyi R, Kipp W, Rubaale T, Tukesiga E, Katamanywa J, Post R J, Amazigo U V
Bernhard Nocht Institute for Tropical Medicine, Bernhard-Nocht-Strasse 74, D-20359 Hamburg, Germany.
Acta Trop. 2009 Sep;111(3):203-10. doi: 10.1016/j.actatropica.2009.04.001. Epub 2009 Apr 11.
The Itwara focus of onchocerciasis covers an area of approximately 600 km(2) in western Uganda about 20 km north of Fort Portal. The vector is Simulium neavei, whose larvae and pupae live in a phoretic association on freshwater crabs. The phoretic host in the Itwara focus is the crab Potamonautes aloysiisabaudiae. Before any onchocerciasis control, ATPs were estimated to reach between 4500 and 6500 infective larvae per person per year. S. neavei was found to be a very efficient vector with 40% of parous flies harbouring developing larvae of Onchocerca volvulus. After 4 years of community-based distribution of ivermectin transmission was still considerable and in 1995 monthly treatment of streams with the larvicide temephos commenced in the first of three sub-foci, and was gradually extended to the whole focus. Biting S. neavei disappeared from the first sub-focus (Itwara main) in June 1996, and the last infested crab was caught in November 1996. In the second sub-focus (Siisa) treatment commenced towards the end of 1995, and the last biting fly was caught in March 1997, but a deterioration in the security situation interrupted the programme (after only three treatments in the third sub-focus). Monthly treatments restarted in the second and third sub-foci (Aswa) in September 1998, and when the situation was reassessed in 2003 no biting flies were found anywhere, and the flies had not reinvaded the first sub-focus, but infected crabs were found in the second and third sub-foci. The last treatments were carried out in April-June 2003, and since then no infested crabs have been found. In summary, no S. neavei-infested crabs have been found anywhere in the focus since June 2003 and the vector is considered eliminated from that date. However, transmission had already been halted since February 2001, when the last biting flies had been collected. The parasite reservoir should die out in the human population by 2016.
伊特瓦拉盘尾丝虫病疫源地位于乌干达西部，在波特尔堡以北约20公里处，面积约600平方公里。传播媒介是纳维蚋，其幼虫和蛹与淡水蟹形成携带关系。伊特瓦拉疫源地的携带宿主是阿洛伊斯萨巴乌迪河蟹。在开展任何盘尾丝虫病防治工作之前，估计每年每人感染性幼虫的接触率在4500至6500条之间。已发现纳维蚋是一种非常高效的传播媒介，40%的经产蚋携带有盘尾丝虫发育中的幼虫。在以社区为基础分发伊维菌素4年后，传播情况仍然很严重，1995年，在三个子疫源地中的第一个子疫源地开始每月用杀幼虫剂双硫磷处理溪流，并逐渐扩大到整个疫源地。1996年6月，纳维蚋在第一个子疫源地（伊特瓦拉主区）不再叮咬人，1996年11月捕获了最后一只受感染的螃蟹。在第二个子疫源地（锡萨），1995年底开始进行处理，1997年3月捕获了最后一只叮咬人的蚋，但安全局势的恶化中断了该项目（第三个子疫源地只进行了三次处理）。1998年9月，第二个和第三个子疫源地（阿斯瓦）重新开始每月处理，2003年重新评估情况时，在任何地方都没有发现叮咬人的蚋，蚋也没有重新侵入第一个子疫源地，但在第二个和第三个子疫源地发现了受感染的螃蟹。最后一次处理是在2003年4月至6月进行的，从那时起，没有发现受感染的螃蟹。总之，自2003年6月以来，在该疫源地的任何地方都没有发现受纳维蚋感染的螃蟹，自该日起，传播媒介被认为已被消灭。然而，自2001年2月收集到最后一批叮咬人的蚋以来，传播就已经停止。到2016年，人群中的寄生虫宿主应该会灭绝。
