Department of Veterinary Sciences, University of Turin, Largo Paolo Braccini 2, 10095, Grugliasco, TO, Italy.
Veterinary Service (A.S.L. AT), 14100, Asti, AT, Italy.
Parasit Vectors. 2021 Apr 23;14(1):223. doi: 10.1186/s13071-021-04722-5.
Cattle are intermediate hosts of six Sarcocystis species, among which Sarcocystis hominis and Sarcocystis heydorni can infect humans through the consumption of raw or undercooked meat. In addition to the zoonotic potential, there is increasing interest in these protozoa because of the evidence supporting the role of Sarcocystis spp. in the occurrence of bovine eosinophilic myositis (BEM), a specific inflammatory myopathy which leads to carcass condemnation and considerable economic losses. Actually, all the prevalence studies carried out on cattle in Italy have been based on either morphological or 18S rDNA-based molecular techniques, most likely leading to misidentification of closely related species. Therefore, there is a strong need for new data on the prevalence of the different Sarcocystis spp. in cattle in Italy and their association with bovine eosinophilic myositis.
To reach our aim, individual striated muscle samples from BEM condemned carcasses (N = 54) and diaphragm muscle samples from randomly sampled carcasses (N = 59) were obtained from Northwest Italy slaughterhouses. Genomic DNA was extracted and analyzed by multiplex-PCR targeting 18S rDNA and cox1 genes. PCR products amplified using the genus-specific primer set in absence of the specific fragment for S. hirsuta, S. cruzi, S. hominis or S. bovifelis were sequenced to achieve species identification.
Sarcocystis DNA was detected in 67.8% of the samples from slaughter cattle and in 90.7% of the samples from BEM condemned carcasses. S. cruzi was identified as the most prevalent species in slaughter cattle (61%), followed by S. bovifelis (10.2%), S. hominis (8.5%) and S. hirsuta (1.7%). Notably, among the different Sarcocystis spp. detected, the presence of S. bovifelis and S. hominis was significantly higher in samples isolated from BEM condemned carcasses (46.3% and 40.7% respectively), while there was no statistically significant difference between the presence of S. cruzi or S. hirsuta in BEM condemned carcasses (42.6% and 1.8%, respectively) and randomly sampled carcasses. Furthermore, DNA sequence analysis revealed the presence of a putative new species in two carcasses.
Our study contributes to updating the data on the prevalence of the different Sarcocystis spp. in cattle in Italy, highlighting the presence of three Sarcocystis spp., S. cruzi, S. hominis and S. bovifelis, in BEM lesions and allowing us to speculate on the possible role of S. hominis and S. bovifelis as the major sarcosporidian species involved in bovine eosinophilic myositis.
牛是六种肉孢子虫的中间宿主，其中人肉孢子虫和海多氏肉孢子虫可通过食用生肉或未煮熟的肉感染人类。除了人畜共患病的潜力外，这些原生动物也越来越受到关注，因为有证据支持肉孢子虫属在牛嗜酸性肌炎（BEM）发生中的作用，BEM 是一种特定的炎症性肌病，导致胴体废弃和相当大的经济损失。实际上，在意大利对牛进行的所有流行率研究都是基于形态学或 18S rDNA 为基础的分子技术，这很可能导致对密切相关物种的错误鉴定。因此，需要有关意大利牛中不同肉孢子虫属的流行率及其与牛嗜酸性肌炎的关系的新数据。
为了达到我们的目的，从意大利西北部的屠宰场获得了来自 BEM 废弃胴体的横纹肌样本（N=54）和来自随机抽样胴体的膈肌样本（N=59）。提取基因组 DNA 并通过靶向 18S rDNA 和 cox1 基因的多重 PCR 进行分析。使用属特异性引物组在不存在 S. hirsuta、S. cruzi、S. hominis 或 S. bovifelis 特异性片段的情况下扩增 PCR 产物，并对其进行测序以实现物种鉴定。
在屠宰牛的 67.8%的样本和 BEM 废弃胴体的 90.7%的样本中检测到肉孢子虫 DNA。在屠宰牛中，鉴定出克氏肉孢子虫为最常见的物种（61%），其次是牛肉孢子虫（10.2%）、人肉孢子虫（8.5%）和细粒肉孢子虫（1.7%）。值得注意的是，在所检测到的不同肉孢子虫属中，在来自 BEM 废弃胴体的样本中，牛肉孢子虫和人肉孢子虫的存在显著更高（分别为 46.3%和 40.7%），而在 BEM 废弃胴体和随机抽样胴体中，克氏肉孢子虫或细粒肉孢子虫的存在无统计学差异（分别为 42.6%和 1.8%）。此外，DNA 序列分析显示在两个胴体中存在一种推定的新种。
本研究有助于更新意大利牛中不同肉孢子虫属流行率的数据，突出了三种肉孢子虫，即克氏肉孢子虫、人肉孢子虫和牛肉孢子虫，在 BEM 病变中的存在，并使我们能够推测人肉孢子虫和牛肉孢子虫可能作为主要的肉孢子虫物种参与牛嗜酸性肌炎。
