Food Animal Health Research Program, The Ohio State University, Wooster, OH 44691, USA.
J Environ Qual. 2009 Oct 29;38(6):2394-401. doi: 10.2134/jeq2008.0432. Print 2009 Nov-Dec.
Most waterborne outbreaks of cryptosporidiosis have been attributed to agricultural sources due to the high prevalence of Cryptosporidium oocysts in animal wastes and manure spreading on farmlands. No-till, an effective conservation practice, often results in soil having higher water infiltration and percolation rates than conventional tillage. We treated six undisturbed no-till and six tilled soil blocks (30 by 30 by 30 cm) with 1 L liquid dairy manure containing 10(5) C. parvum oocysts per milliliter to test the effect of tillage and rainfall on oocyst transport. The blocks were subjected to rainfall treatments consisting of 5 mm or 30 mm in 30 min. Leachate was collected from the base of the blocks in 35-mL increments using a 64-cell grid lysimeter. Even before any rain was applied, approximately 300 mL of water from the liquid manure (30% of that applied) was transported through the no-till soil, but none through the tilled blocks. After rain was applied, a greater number and percentage of first leachate samples from the no-till soil blocks compared to the tilled blocks tested positive for Cryptosporidium oocysts. In contrast to leachate, greater numbers of oocysts were recovered from the tilled soil, itself, than from the no-till soil. Although tillage was the most important factor affecting oocyst transport, rainfall timing and intensity were also important. To minimize transport of Cryptosporidium in no-till fields, manure should be applied at least 48 h before heavy rainfall is anticipated or methods of disrupting the direct linkage of surface soil to drains, via macropores, need to be used.
大多数隐孢子虫病的水源性爆发都归因于农业源，因为动物粪便和农田施肥中的隐孢子虫卵囊的高流行率。免耕是一种有效的保护措施，通常会导致土壤的水分渗透和渗流率高于传统耕作。我们用 1 升含有 10(5)个 C. parvum 卵囊/毫升的液体奶牛粪便处理了 6 个未扰动的免耕和 6 个耕作土壤块（30 厘米×30 厘米×30 厘米），以测试耕作和降雨对卵囊运输的影响。这些块体接受了 5 毫米或 30 毫米的降雨处理，持续 30 分钟。用 64 细胞网格淋滤计从块体底部以 35 毫升增量收集淋出液。甚至在施加任何雨水之前，大约有 300 毫升来自液体粪便的水（施加量的 30%）通过免耕土壤运输，但没有通过耕作块体运输。在施加雨水后，与耕作块体相比，更多的免耕土壤块体的第一批淋出液样本对隐孢子虫卵囊检测呈阳性。与淋出液相比，从耕作土壤中回收的卵囊数量更多，而不是从免耕土壤中回收的卵囊数量更多。虽然耕作是影响卵囊运输的最重要因素，但降雨时间和强度也很重要。为了最大限度地减少隐孢子虫在免耕土壤中的传播，应至少在预计有大雨之前 48 小时施用粪便，或者需要使用破坏表面土壤与排水系统之间直接联系的方法，例如通过大孔。
