Schrader J S, Singer R S, Atwill E R
Department of Population, Health, and Reproduction and Veterinary Extension, University of California, Davis, Veterinary Medicine Teaching and Research Center, Tulare, CA 93274, USA.
Avian Dis. 2004 Sep;48(3):522-30. doi: 10.1637/7125.
Cellulitis has emerged as an economically important disease of broiler chickens. The impact of environmental risk factors on the incidence of cellulitis has not been evaluated in the United States. Escherichia coli (E. coli), the causative agent, is introduced through skin scratches during the grow out. Our previous work suggested that the litter was an important reservoir for cellulitis-associated E. coli. We hypothesized that factors contributing to a positive environment for E. coli growth would increase the opportunity for exposure of a broiler to an infectious dose of E. coli, capable of initiating a cellulitis lesion. This prospective study of 304 flocks on five farms from two integrated broiler companies was conducted to determine the effect of environmental factors on the prevalence of cellulitis in California broiler flocks. Environmental variables included temperature, wind velocity, and relative humidity (RH) at the litter surface. Litter variables measured included E. coli and total gram-negative bacteria load (colony forming units/g dry matter), water activity, and pH. Management variables such as clean out, the number of flocks reared on the same litter (litter run, LR), and downtime (DT) between flocks were also evaluated. Cellulitis ranged from 0.197% to 6.04%. Significant associations were identified using linear regression between farm, LR, DT, ambient temperature during the brooding period, gram-negative bacteria load in the litter during the brooding period, RH mid-grow out, and E. coli load late in the grow out. The significant variation in the rate of cellulitis between farms combined with the strong association of LR and DT with cellulitis demonstrated that management choices were highly influential in this disease syndrome. Based on these data and our previous findings, managers would be advised to increase DT between flocks and perform a total clean out of the house when a flock processes with a high incidence of cellulitis.
蜂窝织炎已成为肉鸡的一种具有重要经济影响的疾病。在美国，尚未评估环境风险因素对蜂窝织炎发病率的影响。致病菌大肠杆菌是在肉鸡生长过程中通过皮肤擦伤进入体内的。我们之前的研究表明，垫料是与蜂窝织炎相关的大肠杆菌的重要储存库。我们假设，有利于大肠杆菌生长的环境因素会增加肉鸡接触具有感染剂量的、能够引发蜂窝织炎病变的大肠杆菌的机会。本前瞻性研究对来自两家一体化肉鸡公司的五个农场的304个鸡群进行了调查，以确定环境因素对加利福尼亚州肉鸡群中蜂窝织炎患病率的影响。环境变量包括垫料表面的温度、风速和相对湿度（RH）。所测量的垫料变量包括大肠杆菌和革兰氏阴性菌总载量（菌落形成单位/克干物质）、水分活度和pH值。还评估了诸如清栏、在同一垫料上饲养的鸡群数量（垫料使用次数，LR）以及鸡群之间的停机时间（DT）等管理变量。蜂窝织炎的发病率在0.197%至6.04%之间。通过线性回归分析确定，农场、LR、DT、育雏期的环境温度、育雏期垫料中的革兰氏阴性菌载量、生长中期的RH以及生长后期的大肠杆菌载量之间存在显著关联。不同农场之间蜂窝织炎发病率的显著差异，以及LR和DT与蜂窝织炎的强烈关联表明，管理选择对这种疾病综合征具有高度影响。基于这些数据和我们之前的研究结果，建议管理人员增加鸡群之间的DT，并在蜂窝织炎发病率高的鸡群出栏后对鸡舍进行全面清理。
