Bowie W R, King A S, Werker D H, Isaac-Renton J L, Bell A, Eng S B, Marion S A
Division of Infectious Diseases, University of British Columbia, Vancouver, Canada.
Lancet. 1997 Jul 19;350(9072):173-7. doi: 10.1016/s0140-6736(96)11105-3.
Outbreaks of toxoplasmosis are recognised infrequently. In March, 1995, a sudden increase of serologically diagnosed cases of acute toxoplasmosis was noted in the Greater Victoria area of British Columbia, Canada. Concurrently, but independently, seven cases of acute toxoplasma retinitis were diagnosed against a background of no cases in the previous 5 years.
Cases were defined by serological testing, clinical presentation, and residence in Greater Victoria. A screening programme for women who were or had been pregnant was started. Geographical mapping of cases, and case-control studies of symptomatic cases and of women enrolled in the screening programme were done.
100 individuals aged 6 to 83 years met the definition for an acute, outbreak-related case. 94 resided in Greater Victoria and six had visited it; 19 had retinitis, 51 had lymphadenopathy, four others had symptoms consistent with toxoplasmosis, seven had other symptoms, 18 were symptom-free, and one would not provide information. 36 (0.9%) of 3812 screened pregnant and postnatal women were cases. Excess cases were not detected outside Greater Victoria and no conventional source of toxoplasmosis was implicated. Mapping studies of cases and of the screened women, and both case-control studies showed significant associations between acute infection and residence in the distribution system of one reservoir supplying water to Greater Victoria (ORs or RRs: 3.53, 3.05, 8.27, and 5.42, respectively). The epidemic curve appeared bimodal, with peaks in December, 1994, and March, 1995, that were preceded by increased rainfall and turbidity in the implicated reservoir.
A municipal water system that uses unfiltered, chloraminated surface water was the likely source of this large community-wide outbreak of toxoplasmosis.
弓形虫病暴发很少被识别。1995年3月，加拿大不列颠哥伦比亚省大维多利亚地区血清学诊断的急性弓形虫病病例突然增加。同时，在过去5年无病例的背景下，独立诊断出7例急性弓形虫性视网膜炎。
根据血清学检测、临床表现和在大维多利亚地区的居住情况来定义病例。启动了针对曾怀孕或正在怀孕女性的筛查项目。对病例进行地理定位，并对有症状的病例以及参与筛查项目的女性进行病例对照研究。
100名年龄在6至83岁的个体符合急性、与暴发相关病例的定义。94人居住在大维多利亚地区，6人曾到访过该地区；19人患有视网膜炎，51人有淋巴结病，另外4人有与弓形虫病相符的症状，7人有其他症状，18人无症状，1人未提供信息。在3812名接受筛查的孕妇和产后女性中，有36例（0.9%）为病例。在大维多利亚地区以外未检测到额外病例，也未发现弓形虫病的传统来源。对病例和接受筛查女性的地理定位研究以及两项病例对照研究均显示，急性感染与居住在为大维多利亚地区供水的一个水库的供水系统分布区域之间存在显著关联（比值比或相对危险度分别为：3.53、3.05、8.27和5.42）。流行曲线呈双峰型，在1994年12月和1995年3月出现高峰，之前涉事水库的降雨量和浊度增加。
一个使用未经过滤、含氯胺地表水的市政供水系统可能是此次大规模社区范围弓形虫病暴发的源头。
