Lam T J, DeJong M C, Schukken Y H, Brand A
Department of Herd Health and Reproduction, Utrecht University, The Netherlands.
J Dairy Sci. 1996 Jan;79(1):62-70. doi: 10.3168/jds.S0022-0302(96)76334-8.
A mathematical model was used to estimate the efficacy of postmilking teat disinfection from observations in split-udder trials with natural exposure. Data were studied from an outbreak of Staphylococcus aureus IMI during a split-udder trial in a commercial herd with low SCC. The efficacy of postmilking teat disinfection was similar when calculated based on incidence density rates or on transmission rates of IMI in dipped and control quarters. If, however, first and subsequent S. aureus IMI in a cow were not assumed to be independent and were therefore treated separately in the models, the efficacy of post-milking teat disinfection was calculated as being higher with the modeling procedure. The analysis using mathematical modeling, which includes the effect of the number of existing IMI on the number of new IMI, is presented and discussed. This analysis also allows estimation of the basic reproduction ratio. The impact of postmilking teat disinfection on transmission of pathogens is quantified, and proposals for additional preventive measures can be generated. We concluded that efficacy estimations from split-udder trials, assuming quarters to be independent observations, might underestimate the effect of postmilking teat disinfectants on udder pathogens.
使用数学模型，根据自然暴露的分侧乳房试验中的观察结果，估计挤奶后乳头消毒的效果。研究了一个低体细胞数（SCC）商业牛群在分侧乳房试验期间金黄色葡萄球菌隐性乳房炎（IMI）爆发的数据。基于发病率密度率或基于浸泡处理和对照乳腺中IMI的传播率计算时，挤奶后乳头消毒的效果相似。然而，如果不认为奶牛首次和随后发生的金黄色葡萄球菌IMI是独立的，因此在模型中分别处理，则通过建模程序计算得出的挤奶后乳头消毒效果更高。本文展示并讨论了使用数学建模的分析方法，该方法考虑了现有IMI数量对新IMI数量的影响。该分析还可以估计基本繁殖率。量化了挤奶后乳头消毒对病原体传播的影响，并可以提出额外预防措施的建议。我们得出结论，在假设各乳腺为独立观察对象的情况下，分侧乳房试验的效果估计可能低估了挤奶后乳头消毒剂对乳房病原体的影响。
