Animal Parasitic Diseases Laboratory, Agricultural Research Service, United States Department of Agriculture, Beltsville, MD 20705.
Mountaire Farms Inc., Millsboro, DE 19966.
Avian Dis. 2020 Sep 1;64(3):401-406. doi: 10.1637/aviandiseases-D-19-00118.
The purpose of the present study was to determine whether a correlation existed between chick mortality and the presence of Clostridium perfringens alpha-toxin and NetB-toxin genes (cpa and netB) in C. perfringens recovered from litter in commercial broiler houses. Because coccidiosis predisposes chickens to necrotic enteritis, the concentration of Eimeria oocysts in these samples was measured, and the numbers were used in similar correlation analyses. Litter samples were collected at 0, 2, and 4 wk growout from six broiler farms (18 houses total) during an anticoccidial drug (ACD) control program and from nine broiler farms (23 houses total) during an Eimeria vaccine (VAC) control program. Of these, litter samples were collected from five farms during both ACD and VAC programs. The litter samples were processed for Eimeria oocyst and C. perfringens spore enumerations by standard parasitologic and microbiologic techniques. DNA was also extracted for C. perfringens DNA for PCR detection of genes coding for alpha- and NetB-toxin. A general trend during the ACD programs was a transient decrease in both Eimeria maxima and non-E. maxima (Eamipt) numbers at 2 wk growout. The pattern was slightly different during VAC with E. maxima and Eamipt levels increasing over time. Average concentrations of C. perfringens in litter were highest at 2 wk (∼105-106 spores/g) during ACD and at placement during VAC (∼105-106 spores/g). During the ACD program, a strong correlation was observed between 0 and 3-wk chick mortality and the presence at placement (0 wk) of netB (r = 0.42-0.48) or cpa (r = 0.55-0.67). A very strong correlation was observed in 0-5-wk chick mortality and the presence of netB at 4 wk growout (0.73-0.95). During a VAC program, a strong correlation was only observed between the presence of netB at placement and 0-1-wk chick mortality (r = 0.67).
本研究的目的是确定从商业肉鸡舍垫料中回收的产气荚膜梭菌中存在的α-毒素和 NetB-毒素基因（cpa 和 netB）与雏鸡死亡率之间是否存在相关性。因为球虫病使鸡易患坏死性肠炎，所以测量了这些样本中的艾美耳球虫卵囊浓度，并将数量用于类似的相关性分析。在抗球虫药（ACD）控制计划中，从 6 个肉鸡场（共 18 个鸡舍）和在艾美耳球虫疫苗（VAC）控制计划中从 9 个肉鸡场（共 23 个鸡舍）的第 0、2 和 4 周龄鸡舍中采集垫料样本。其中，5 个农场同时在 ACD 和 VAC 计划中采集了垫料样本。通过标准寄生虫学和微生物学技术处理垫料样本，以进行艾美耳球虫卵囊和产气荚膜梭菌孢子计数。还提取了产气荚膜梭菌 DNA 用于 PCR 检测编码α-和 NetB-毒素的基因。在 ACD 计划中，在第 2 周龄育雏时，E. maxima 和非 E. maxima（Eamipt）数量都呈现出短暂下降的趋势。在 VAC 期间，模式略有不同，E. maxima 和 Eamipt 水平随时间增加。在 ACD 期间，垫料中产气荚膜梭菌的平均浓度在第 2 周龄（约 105-106 孢子/g）最高，在 VAC 时放置时（约 105-106 孢子/g）最高。在 ACD 计划中，在放置（0 周）时 netB（r = 0.42-0.48）或 cpa（r = 0.55-0.67）的存在与 0-3 周龄雏鸡死亡率之间存在很强的相关性。在 0-5 周龄雏鸡死亡率和 4 周龄垫料中 netB 的存在之间观察到非常强的相关性（0.73-0.95）。在 VAC 计划中，仅在放置时 netB 的存在与 0-1 周龄雏鸡死亡率之间观察到强相关性（r = 0.67）。
