Khol Johannes L, Pinedo Pablo J, Buergelt Claus D, Neumann Laura M, Rae D Owen
Clinic for Ruminants, Department for Farm Animals and Veterinary Public Health, University of Veterinary Medicine, Vienna, Austria.
Texas A&M AgriLife Research, College of Veterinary Medicine & Biomedical Sciences, Texas A&M University System, Amarillo, TX, USA.
Vet Microbiol. 2014 Aug 6;172(1-2):301-8. doi: 10.1016/j.vetmic.2014.05.022. Epub 2014 May 29.
Johne's disease (JD), caused by Mycobacterium avium subsp. paratuberculosis (MAP), can cause considerable economic losses in affected herds. Early diagnosis of JD is hampered by the chronic nature of the disease with a slow subclincal progression. The aim of the present study was to challenge the hypothesis that lymphatic fluid is of diagnostic value in the early stages of the disease. Lymphatic fluid from 122 animals was collected and tested for MAP by nested PCR for IS900 and compared to the results of testing for MAP in feces (culture), blood and milk (ELISA) in 110 of these samples. MAP was detected by PCR in 27.1% of the lymph samples. Agreement between the tests was poor: 6.9% of the lymph positive cows were also positive in all other tests applied, and 69.0% had negative results in fecal culture, blood and milk ELISA. Resampling of 25 cows after 8 to 12 and 16 to 20 months revealed 20.0% lymph positive animals at the first, 5.5% at the second and 27.8% at the third sampling, respectively. Only one cow showed positive lymph-PCR results at more than one sampling date. Lymph-positive cows had a 7.2 times greater likelihood of being culled within 8 to 12 months after sampling, compared to negative cows, mainly due to other health issues than JD. It can be concluded, that lymphatic fluid might be promising for the detection of early MAP-infection in cows, but further studies to elucidate the potential of this diagnostic approach are needed.
副结核分枝杆菌（MAP）引起的副结核病（JD）会给受影响的畜群造成巨大经济损失。JD的早期诊断因该病具有慢性特征且亚临床进展缓慢而受到阻碍。本研究的目的是验证淋巴液在疾病早期具有诊断价值这一假说。收集了122只动物的淋巴液，通过针对IS900的巢式PCR检测其中的MAP，并将结果与110份样本中粪便（培养）、血液和牛奶（ELISA）的MAP检测结果进行比较。通过PCR在27.1%的淋巴样本中检测到MAP。各项检测之间的一致性较差：6.9%的淋巴液检测呈阳性的奶牛在所有其他检测中也呈阳性，69.0%的奶牛在粪便培养、血液和牛奶ELISA检测中呈阴性。在8至12个月以及16至20个月后对25头奶牛重新采样，结果显示首次采样时20.0%的动物淋巴液呈阳性，第二次采样时为5.5%，第三次采样时为27.8%。只有一头奶牛在多个采样日期的淋巴液PCR检测结果呈阳性。与检测呈阴性的奶牛相比，淋巴液检测呈阳性的奶牛在采样后8至12个月内被淘汰的可能性高7.2倍，主要原因是除JD之外的其他健康问题。可以得出结论，淋巴液可能有望用于检测奶牛早期的MAP感染，但需要进一步研究以阐明这种诊断方法的潜力。
