Hoar Bruce R, McQuarry Alana C, Hietala Sharon K
Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California, Davis, CA 95616, USA.
J Am Vet Med Assoc. 2007 Apr 1;230(7):1038-43. doi: 10.2460/javma.230.7.1038.
To determine the prevalence and effect of Neospora caninum infection and persistent infection (PI) with bovine viral diarrhea virus (BVDV) on weight gain, morbidity, and mortality rate in dairy-breed steer calves located on a feedlot in California.
Prospective cohort observational study.
900 dairy-breed steer calves in 2 pens.
The 3- to 4-month-old calves were evaluated for serum antibodies against N caninum and infection with BVDV at entry to the feedlot. Five months later, sera were again analyzed for anti-N caninum antibodies; calves that were determined to have BVDV infection initially were retested to evaluate PI status. Average daily gain, morbidity, and deaths were recorded for all calves.
Among 900 calves, prevalence of N caninum infection was 16.7% (95% confidence interval, 14.3% to 19.3%); prevalence of BVDV-associated PI was 0.2% (95% confidence interval, 0.03% to 0.9%). Morbidity rate and time to first illness were not significantly different between calves that were seropositive or seronegative for N caninum. At the second sample collection, weight and average daily gain of calves that were seropositive for N caninum was less than that of seronegative steers in 1 pen, whereas these measures did not differ between groups in the other pen. Statistical power was insufficient to evaluate the effect of BVDV PI on any outcome measurement.
Although N caninum serostatus had no significant effect on morbidity rate, some seropositive calves had reduced growth, compared with seronegative calves, 5 months after entry to the feedlot.
确定犬新孢子虫感染及牛病毒性腹泻病毒（BVDV）持续感染（PI）对加利福尼亚州一个饲养场的奶牛品种育肥牛犊体重增加、发病率和死亡率的影响及流行情况。
前瞻性队列观察研究。
2个围栏中的900头奶牛品种育肥牛犊。
对3至4月龄的犊牛进入饲养场时进行犬新孢子虫血清抗体及BVDV感染情况评估。五个月后，再次分析血清中的抗犬新孢子虫抗体；对最初被判定为感染BVDV的犊牛重新检测以评估持续感染状态。记录所有犊牛的平均日增重、发病率和死亡情况。
在900头犊牛中，犬新孢子虫感染率为16.7%（95%置信区间，14.3%至19.3%）；BVDV相关持续感染率为0.2%（95%置信区间，0.03%至0.9%）。犬新孢子虫血清阳性或血清阴性的犊牛发病率及首次发病时间无显著差异。在第二次样本采集时，一个围栏中犬新孢子虫血清阳性的犊牛体重和平均日增重低于血清阴性的育肥牛犊，而在另一个围栏中两组之间这些指标无差异。统计效能不足以评估BVDV持续感染对任何结果指标的影响。
尽管犬新孢子虫血清状态对发病率无显著影响，但与血清阴性的犊牛相比，一些血清阳性的犊牛进入饲养场5个月后生长减缓。
