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Evaluation of age-dependent susceptibility in calves infected with two doses of Mycobacterium avium subspecies paratuberculosis using pathology and tissue culture

机译:使用病理学和组织培养评估两剂鸟分枝杆菌副结核病感染小牛的年龄敏感性

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The longstanding assumption that calves of more than 6 months of age are more resistant to Mycobacterium avium subspecies paratuberculosis (MAP) infection has recently been challenged. In order to elucidate this, a challenge experiment was performed to evaluate age- and dose-dependent susceptibility to MAP infection in dairy calves. Fifty-six calves from MAP-negative dams were randomly allocated to 10 MAP challenge groups (5 animals per group) and a negative control group (6 calves). Calves were inoculated orally on 2 consecutive days at 5 ages: 2 weeks and 3, 6, 9 or 12 months. Within each age group 5 calves received either a high – or low – dose of 5 × 109 CFU or 5 × 107 CFU, respectively. All calves were euthanized at 17 months of age. Macroscopic and histological lesions were assessed and bacterial culture was done on numerous tissue samples. Within all 5 age groups, calves were successfully infected with either dose of MAP. Calves inoculated at
机译:长期以来的假设是,大于6个月大的犊牛对鸟分枝杆菌亚种副结核病(MAP)感染具有更强的抵抗力。为了阐明这一点,进行了挑战实验以评估乳牛犊中MAP感染的年龄和剂量依赖性。将来自MAP阴性大坝的56头犊牛随机分配到10个MAP攻击组(每组5只动物)和一个阴性对照组(6头犊牛)。在2个星期和3、6、9或12个月的5个年龄连续2天口服小牛。在每个年龄组中,有5只小牛分别接受高剂量或低剂量5×10 9 CFU或5×10 7 CFU。所有小牛均在17个月大时被安乐死。评估宏观和组织学损伤,并在许多组织样本上进行细菌培养。在所有5个年龄组中,小牛均成功感染了两种剂量的MAP。小牛接种于

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