1College of Veterinary Medicine, Department of Veterinary Preventive Medicine, The Ohio State University, Columbus, OH.
2College of Food, Agricultural, and Environmental Sciences, Department of Animal Sciences, The Ohio State University, Columbus, OH.
J Am Vet Med Assoc. 2022 Sep 1;260(14):1839-1843. doi: 10.2460/javma.22.05.0204.
To estimate the prevalence of Anaplasma marginale, the causative agent of bovine anaplasmosis, in beef herds from Ohio; evaluate farm identity and animal age as risk factors; and examine serologic cross-reactivity with Anaplasma phagocytophilum, an emerging disease agent.
4 beef cattle herds (n = 327) sampled between December 2020 and December 2021.
To address the broader investigation of characterizing Anaplasma spp and genotypes in Ohio, herds with a history of clinical anaplasmosis were targeted. Blood was screened for antibodies to Anaplasma spp using a competitive enzyme-linked immunosorbent assay with seropositive samples tested for A marginale using real-time PCR. If negative, samples were also tested for A phagocytophilum.
We estimated a statewide molecular prevalence of 38.53% (95% CI, 33.26% to 43.81%), with some farms exhibiting higher prevalence than others (19.40% to 56.86%). Accounting for farm identity, the odds of an animal becoming infected increased by 1.41 (95% CI, 1.28 to 1.58) for every year in age. Forty-four animals tested seropositive but PCR negative for A marginale. Out of these, 2 tested positive for A phagocytophilum.
Our study was the first to report prevalence estimates for bovine anaplasmosis in Ohio. Although prevalence was higher than other states, this is most likely due to our sampling approach. Our results suggested that older animals are more likely to be infected with A marginale, and when animals are instead infected with A phagocytophilum, serology alone can be misleading wherever the 2 species co-occur. Our study can guide wider epidemiological studies for informing management in Ohio.
估计俄亥俄州肉牛群中导致牛环形泰勒虫病的边缘无形体的流行率；评估农场身份和动物年龄作为风险因素；并研究与新兴疾病因子嗜吞噬细胞无形体的血清交叉反应性。
2020 年 12 月至 2021 年 12 月间采样的 4 个肉牛群（n=327）。
为了更广泛地研究俄亥俄州特征性无形体和基因型，我们针对有临床环形泰勒虫病病史的牛群进行了靶向采样。使用竞争酶联免疫吸附试验检测血液中抗无形体的抗体，对血清阳性样本进行实时 PCR 检测以确定是否为边缘无形体感染。如果为阴性，则进一步检测是否为嗜吞噬细胞无形体感染。
我们估计全州范围内的分子流行率为 38.53%（95%置信区间，33.26%至 43.81%），一些农场的流行率高于其他农场（19.40%至 56.86%）。考虑到农场身份，动物每增加 1 岁，感染的几率就会增加 1.41 倍（95%置信区间，1.28 至 1.58）。44 只动物血清学检测呈阳性，但边缘无形体 PCR 检测为阴性。其中 2 只对嗜吞噬细胞无形体检测呈阳性。
我们的研究首次报告了俄亥俄州牛环形泰勒虫病的流行率估计值。尽管流行率高于其他州，但这很可能是由于我们的采样方法所致。我们的结果表明，年龄较大的动物更有可能感染边缘无形体，而当动物感染嗜吞噬细胞无形体时，在这两种病原体共同存在的地方，仅通过血清学检测可能会产生误导。我们的研究可以为俄亥俄州的更广泛的流行病学研究提供指导，为管理提供信息。
