Ochoa J O, Castro J C, Barrios V M, Juarez E L, Tada I
Departmento de Oncocercosis, Division de Malaria, Guatemala City, Guatemala.
Ann Trop Med Parasitol. 1997 Jul;91(5):471-9. doi: 10.1080/00034989760833.
Between 1984 and 1989, the onchocerciasis-vector control zone on the pilot area of San Vicente Pacaya, Guatemala, which had been subject to experimental control since 1979, was extended from 91.3 to 148.6 km2. Temephos was used as a larvicide against Simulium ochraceum s.l. the target species. As a new strategy, only breeding sites with water discharges of 0.1-10 litres/s were treated, every 2 weeks. This approach provided a substantial reduction in effort, number of treated sites, time and cost. To assess the effect of the temephos, nine sites were selected in which standardized collections of adult Simulium were made twice a month, by human bait. There was an obvious difference between the pre- and post-control mean densities of flies at each site. In the northern area, which includes the Lavaderos, Barretal, Colina and Rodeo sites, the biting density in 1979, before treatment, varied between 10 and 64 flies/man-hour (FMH). Four years later, this had been reduced to 0.1-3.2 FMH, and by the end of the present study, in 1989, the mean density was zero FMH. In the southern area, which lies south-east of Lavaderos (and includes Guachipilin, Ingerto, Pena Blanca and Sierra Morena), the density during the pre-control phase was 24 FMH at one of the two sites investigated at the time and 39.3 FMH at the other. It fell to 0.1-0.5 FMH after 5 years of control and to zero (three sites) or close to zero (< or = 0.5 FMH; one site) for the last 4 years of the present study. To assess the effect of vector control on onchocerciasis prevalence and incidence, 1280 residents from six endemic communities, out of 12,000 permanent inhabitants, were examined. In Santa Cruz, Patrocinio and Los Rios, the prevalence of skin microfilariae in the subjects from each community fell from 8.1%-37.8% during the pretreatment, base-line period to 0.0%-31.5% when the study foci were totally integrated into the vector-control operation following treatment. Incidence among children (aged < or = 9 years) varied from 0%-25% for the period 1982-1984 but, thereafter, not a single case appeared in four of the six study communities (Santa Cruz, Patrocinio, Los Rios and Berlin). Incidence in Guachipilin did not decline appreciably, probably because of human migration into the area from other onchocerciasis foci. The prevalence of nodules followed a similar trend to those of the prevalence and incidence of skin microfilariae, falling from 9.1%-45.0% pre-control to 1.8%-14.3% 10 years later.
1984年至1989年间，危地马拉圣维森特帕卡亚试验区自1979年起实施盘尾丝虫病病媒控制，控制区面积从91.3平方公里扩大至148.6平方公里。使用双硫磷作为杀幼虫剂，防治目标物种——奥氏蚋复合种。作为一项新策略，每两周仅对水流流量为0.1至10升/秒的孳生地进行处理。这种方法大幅减少了工作量、处理地点数量、时间和成本。为评估双硫磷的效果，选取了9个地点，每月两次通过人饵法对成年蚋进行标准化采集。每个地点防治前后的蝇平均密度存在明显差异。在包括拉瓦德罗斯、巴雷塔尔、科利纳和罗德奥等地点的北部地区，1979年处理前的叮咬密度为每小时每人数10至64只蝇。四年后，该密度降至每小时每人数0.1至3.2只蝇，到本研究结束的1989年，平均密度为每小时每人数零只蝇。在位于拉瓦德罗斯东南部的南部地区（包括瓜奇皮林、因格托、佩尼亚布兰卡和莫雷纳山脉），在防治前阶段，当时调查的两个地点之一的密度为每小时每人数24只蝇，另一个为每小时每人数39.3只蝇。经过5年防治后降至每小时每人数0.1至0.5只蝇，在本研究的最后4年，有三个地点降至零（每小时每人数），一个地点接近零（每小时每人数≤0.5只蝇）。为评估病媒控制对盘尾丝虫病患病率和发病率的影响，在12,000名常住居民中，对来自6个流行社区的1280名居民进行了检查。在圣克鲁斯、帕特罗西尼奥和洛斯里奥斯，每个社区受试者皮肤微丝蚴的患病率在治疗前的基线期为8.1% - 37.8%，在研究地点在治疗后完全纳入病媒控制行动时降至0.0% - 31.5%。1982 - 1984年期间，儿童（年龄≤9岁）的发病率为0% - 25%，但此后，6个研究社区中的4个（圣克鲁斯、帕特罗西尼奥、洛斯里奥斯和柏林）未出现一例病例。瓜奇皮林的发病率没有明显下降，可能是因为有其他盘尾丝虫病疫源地的人迁入该地区。结节的患病率与皮肤微丝蚴的患病率和发病率趋势相似，从防治前的9.1% - 45.0%降至10年后的1.8% - 14.3%。
