Centers for Disease Control and Prevention, Division of Vector-Borne Infectious Diseases, Bacterial Diseases Branch, 3150 Rampart Road, MS-P02, Fort Collins, CO 80521, USA.
Vector Borne Zoonotic Dis. 2012 Nov;12(11):948-52. doi: 10.1089/vbz.2012.1031. Epub 2012 Aug 27.
Plague, an often-fatal zoonotic disease caused by Yersinia pestis, is characterized by epizootic and quiescent periods. How Y. pestis is maintained during inter-epizootic periods is poorly understood, but soil has been implicated as a potential reservoir. Although previous studies have suggested that Y. pestis is able to survive in soil for weeks or months, it is unclear whether or not it is infectious to susceptible hosts. Here we investigate the potential for Y. pestis to infect mice through close contact with contaminated soil under laboratory conditions. In an attempt to approximate the natural conditions under which animals would be exposed to Y. pestis-contaminated soil, mouse cages filled with soil from a plague-endemic region were held at temperature and humidity ranges observed in ground squirrel burrows. These laboratory "burrows" were contaminated with highly bacteremic blood (>10(8) cfu/mL) to simulate the introduction of infectious material from a dying animal during an epizootic. Outbred Swiss-Webster mice with scarified skin patches were held on contaminated soil for 10 days and monitored for signs of illness. Following exposure to contaminated soil, one animal of 104 became infected with Y. pestis. None of the remaining animals seroconverted following a 21-day holding period. Under our experimental conditions, which maximized the likelihood of contact between susceptible mice and contaminated soil, transmission efficiency from soil to mice was 0.96% (95% CI 0.17, 5.25%). This suggests that although transmission of Y. pestis from contaminated soils is possible, it is not likely a major transmission route under natural conditions.
鼠疫是一种由鼠疫耶尔森菌引起的常致命的人畜共患病，其特征为动物间爆发和静止期。在动物间爆发期之间，鼠疫耶尔森菌是如何被维持的还不太清楚，但土壤已被认为是一个潜在的储存库。虽然之前的研究表明鼠疫耶尔森菌能够在土壤中存活数周或数月，但它是否对易感宿主具有传染性尚不清楚。在这里，我们研究了鼠疫耶尔森菌在实验室条件下通过与受污染的土壤密切接触感染小鼠的可能性。为了尝试模拟动物接触鼠疫耶尔森菌污染土壤的自然条件，我们将装满来自鼠疫流行地区的土壤的鼠笼保持在观察到的地松鼠洞穴的温度和湿度范围内。这些实验室“洞穴”被高菌血症血液（>10(8) cfu/mL）污染，以模拟在动物间爆发期间从垂死动物引入的传染性物质。对皮肤有划痕的近交系瑞士 Webster 小鼠在污染的土壤上饲养 10 天，并监测其患病迹象。接触污染土壤后，104 只动物中有 1 只感染了鼠疫耶尔森菌。在 21 天的潜伏期后，其余动物均未发生血清转化。在我们的实验条件下，最大限度地提高了易感小鼠与污染土壤接触的可能性，从土壤到小鼠的传播效率为 0.96%（95%CI 0.17, 5.25%）。这表明，尽管从污染土壤传播鼠疫耶尔森菌是可能的，但在自然条件下，它不太可能是主要的传播途径。
