Johnson-Ifearulundu Y, Kaneene J B
Population Medicine Center, College of Veterinary Medicine, Michigan State University, East Lansing 48824, USA.
Am J Vet Res. 1999 May;60(5):589-96.
To determine prevalence of paratuberculosis among dairy cattle herds and to identify associated soil-related risk factors.
Serum and soil samples for 121 Michigan dairy herds.
Blood samples were collected from cows at each farm and tested for Mycobacterium paratuberculosis, using an antibody ELISA. Soil samples were collected from pastures and exercise lots; pH and available iron content were determined. A questionnaire was administered to collect data regarding farm management practices and productivity.
55% of the herds tested had > or = 2 M paratuberculosis-positive cattle. Adjusting sample prevalence for distribution of herd size strata yielded a statewide herd prevalence of 54%. Of 3,886 cattle tested, 267 had positive results. Prevalence of test-positive cattle was 6.9%. For every part per million (ppm) increase in soil iron content, there was a 1.4% increase in the risk of a herd being test-positive. An increase in soil pH of 0.1 was associated with a 5% decrease and an increase in soil iron content of 10 ppm was associated with a 4% increase in the number of test-positive cattle. Application of lime to pasture areas was associated with a herd being only 10% as likely to be paratuberculosis positive and with a 72% reduction in number of test-positive cattle.
Prevalence of paratuberculosis-positive dairy herds in Michigan (54%) was greater than expected, but prevalence of paratuberculosis-positive cattle (6.9%) was within anticipated values. These prevalences were associated positively with acidic soil and increased soil iron content. Application of lime to pasture areas was associated with reduced risk of paratuberculosis.
确定奶牛群中副结核病的患病率，并识别与之相关的土壤风险因素。
密歇根州121个奶牛群的血清和土壤样本。
从每个农场的奶牛身上采集血样，使用抗体酶联免疫吸附测定法检测副结核分枝杆菌。从牧场和运动场采集土壤样本；测定土壤pH值和有效铁含量。发放调查问卷以收集有关农场管理实践和生产力的数据。
55%的检测牛群中有≥2头副结核阳性奶牛。根据牛群规模分层分布调整样本患病率后，全州牛群患病率为54%。在3886头检测的奶牛中，267头结果呈阳性。检测阳性奶牛的患病率为6.9%。土壤铁含量每增加百万分之一（ppm），牛群检测呈阳性的风险就增加1.4%。土壤pH值每增加0.1，检测阳性奶牛数量就减少5%；土壤铁含量每增加10 ppm，检测阳性奶牛数量就增加4%。在牧场施用石灰与牛群副结核呈阳性的可能性仅为10%相关，且检测阳性奶牛数量减少72%。
密歇根州副结核阳性奶牛群的患病率（54%）高于预期，但副结核阳性奶牛的患病率（6.9%）在预期值范围内。这些患病率与酸性土壤和土壤铁含量增加呈正相关。在牧场施用石灰与副结核病风险降低相关。
