Llanos-Soto Sebastian, Wiedmann Martin, Adalja Aaron, Henry Christopher, Moroni Paolo, Frye Elisha, Leal Yepes Francisco A, Ivanek Renata
Department of Population Medicine and Diagnostic Sciences, Cornell University, Ithaca, New York, United States of America.
Department of Food Science, Cornell University, Ithaca, New York, United States of America.
PLoS One. 2025 Oct 16;20(10):e0332465. doi: 10.1371/journal.pone.0332465. eCollection 2025.
Salmonella Dublin infections in heifer-raising operations (HROs) cause animal health and economic losses for these operations and represent a pathogen source for dairy farms obtaining replacement heifers from HROs. To improve control of S. Dublin, we (i) developed a mathematical model of S. Dublin transmission on a HRO, (ii) evaluated the vaccine effectiveness and cleaning improvements for controlling the infection, and (iii) evaluated the influence of infection and control strategies on the HRO's operating income. We developed a modified Susceptible-Infected-Recovered-Susceptible model of S. Dublin spread in a batch-stocking HRO post-introduction of an index case, with stochasticity introduced through Monte Carlo simulations. Epidemiological outcomes (S. Dublin-induced deaths and abortions during raising and S. Dublin carriers and asymptomatic infections among raised replacement heifers) and operating income per 100-head raised on a HRO over a 2-year simulation were compared between control scenarios. We validated our model against S. Dublin infection data in cattle. Partial rank correlation coefficient analysis and classification trees were used to determine parameter influence on model outcomes. Our model predicts a median of 37 carriers and 92 asymptomatic infections among raised replacement heifers out of 2,330 heifers that departed the operation by the end of the 2-year simulation period, suggesting a relevant role of HROs in spreading S. Dublin. Increasing barn floor cleaning frequency (to a maximum of 12x per day) meaningfully reduced the S. Dublin epidemiological outcomes and improved the HRO's operating income. Depending on the cost of cleaning, the median operating income increased between 1.2% to 10.6% in the first year when cleaning 12x per day compared to baseline (cleaning 1x per week). In most cost scenarios, predictions do not support using a vaccine that solely reduces mortality, even when paired with stringent cleaning measures. The developed model is expected to aid efforts to control S. Dublin in HROs.
在小母牛饲养场（HROs）中，都柏林沙门氏菌感染会给这些养殖场带来动物健康问题和经济损失，并且对于那些从小母牛饲养场获取后备小母牛的奶牛场而言，它还是病原体来源。为了加强对都柏林沙门氏菌的控制，我们（i）建立了一个都柏林沙门氏菌在小母牛饲养场传播的数学模型，（ii）评估了疫苗效果和清洁改进措施对控制感染的作用，以及（iii）评估了感染和控制策略对小母牛饲养场运营收入的影响。我们建立了一个改良的易感-感染-康复-易感模型，用于描述在引入首例病例后，都柏林沙门氏菌在分批饲养的小母牛饲养场中的传播情况，并通过蒙特卡罗模拟引入了随机性。在不同控制方案之间，比较了流行病学结果（在饲养过程中由都柏林沙门氏菌导致的死亡和流产，以及饲养的后备小母牛中的都柏林沙门氏菌携带者和无症状感染）和在两年模拟期内，小母牛饲养场每饲养100头牛的运营收入。我们根据牛群中都柏林沙门氏菌感染数据对模型进行了验证。使用偏秩相关系数分析和分类树来确定参数对模型结果的影响。我们的模型预测，在为期两年的模拟期结束时，从小母牛饲养场转出的2330头小母牛中，饲养的后备小母牛中都柏林沙门氏菌携带者的中位数为37头，无症状感染的中位数为92例，这表明小母牛饲养场在传播都柏林沙门氏菌方面具有重要作用。提高牛舍地面清洁频率（最高达到每天12次）能显著降低都柏林沙门氏菌的流行病学结果，并提高小母牛饲养场的运营收入。根据清洁成本不同，与基线情况（每周清洁1次）相比，在第一年每天清洁12次时，运营收入中位数增加了1.2%至10.6%。在大多数成本情况下，预测结果不支持使用仅能降低死亡率的疫苗，即使与严格的清洁措施相结合也不行。预计所建立的模型将有助于控制小母牛饲养场中的都柏林沙门氏菌。
