Aly Sharif S, Anderson Randall J, Whitlock Robert H, Fyock Terry L, McAdams Susan C, Byrem Todd M, Jiang Jiming, Adaska John M, Gardner Ian A
Veterinary Medicine Teaching and Research Center, University of California, Davis, 18830 Road 112, Tulare, CA 93724, USA.
J Vet Diagn Invest. 2012 Sep;24(5):821-32. doi: 10.1177/1040638712452107. Epub 2012 Jul 17.
Diagnostic strategies to detect Mycobacterium avium subsp. paratuberculosis (MAP) super-shedder cows in dairy herds have been minimally studied. The objective of the current study was to compare the cost-effectiveness of strategies for identification of MAP super-shedders on a California dairy herd of 3,577 cows housed in free-stall pens. Eleven strategies that included serum or milk enzyme-linked immunosorbent assay (ELISA), quantitative real-time polymerase chain reaction (qPCR) or culture of environmental samples, pooled or individual cow fecal samples, or combinations thereof were compared. Nineteen super-shedders (0.5%) were identified by qPCR and confirmed by culture as cows shedding ≥ 10,000 colony forming units (CFU)/g feces (median of 30,000 CFU/g feces). A stratified random sample of the study herd based on qPCR results of fecal pools was the most sensitive (74%) strategy and had the highest cost ($5,398/super-shedder). The reference strategy with the lowest cost ($1,230/super-shedder) and sensitivity (47%) included qPCR testing of fecal samples from ELISA-positive lactating (milk) and nonlactating (serum) cows housed in pens with the highest MAP bioburden. The most cost-effective alternative to the reference was to perform qPCR testing of fecal samples from ELISA-positive cows (milk and serum for milking and dry cows, respectively) for a sensitivity of 68% and cost of $2,226/super-shedder. In conclusion, diagnostic strategies varied in their cost-effectiveness depending on the tests, specimen type, and labor costs. Initial qPCR testing of environmental samples from free-stall pens to target cows in pens with the highest MAP bioburden for further testing can improve the cost-effectiveness of strategies for super-shedder identification.
检测奶牛群中副结核分枝杆菌（MAP）超级排菌母牛的诊断策略研究较少。本研究的目的是比较在加利福尼亚州一个有3577头奶牛的自由牛舍奶牛群中识别MAP超级排菌牛的策略的成本效益。比较了11种策略，包括血清或牛奶酶联免疫吸附测定（ELISA）、定量实时聚合酶链反应（qPCR）或环境样本、合并或个体奶牛粪便样本的培养，或它们的组合。通过qPCR鉴定出19头超级排菌牛（0.5%），并通过培养确认其粪便中排菌量≥10000菌落形成单位（CFU）/克（粪便中值为30000 CFU/克）。基于粪便池qPCR结果的研究牛群分层随机样本是最敏感（74%）的策略，成本最高（每头超级排菌牛5398美元）。成本最低（每头超级排菌牛1230美元）且灵敏度最低（47%）的参考策略包括对MAP生物负荷最高的牛舍中ELISA阳性泌乳（牛奶）和非泌乳（血清）奶牛的粪便样本进行qPCR检测。参考策略最具成本效益的替代方案是对ELISA阳性奶牛（分别对泌乳奶牛和干奶牛检测牛奶和血清）的粪便样本进行qPCR检测，灵敏度为68%，成本为每头超级排菌牛2226美元。总之，诊断策略的成本效益因检测、样本类型和劳动力成本而异。对自由牛舍环境样本进行初始qPCR检测，以确定MAP生物负荷最高的牛舍中的牛进行进一步检测，可以提高识别超级排菌牛策略的成本效益。
