Verdugo Cristobal, Marquez Diego, Paredes Enrique, Moroni Manuel, Navarrete-Talloni María José, Tomckowiack Camilo, Salgado Miguel
Instituto de Medicina Preventiva Veterinaria, Facultad de Ciencias Veterinarias, Universidad Austral de Chile, Valdivia, Chile.
Center for the Surveillance and Evolution of Infectious Diseases (CSEID), Universidad Austral de Chile, Valdivia, Chile.
Front Vet Sci. 2023 Jan 12;9:962241. doi: 10.3389/fvets.2022.962241. eCollection 2022.
The objective was to evaluate the association between the severity of histopathological lesions caused by subspecies (MAP) infection and the molecular diversity of this pathogen. Blood, ileum, and mesenteric lymph node samples were collected at slaughter, from 1,352 adult cattle [source population 1 (SP1)]. In addition, 42 dairy herds ( = 4,963 cows) were followed for 2 years, and samples from compatible clinical cases [source population 2 (SP2)] were collected. MAP infection was confirmed using an ELISA test, liquid media culture, and PCR. Isolates were genotyped using five MIRU-VNTR markers. Tissues from confirmed samples were subjected to a histopathological examination. A histopathological severity score (HSS) system was developed and used to grade (0 to 5) the magnitude of lesions caused by MAP. In general, the HSS system assesses the number of foci and degree of macrophage infiltration, together with the presence of multinucleated giant cells (MGCs) and acid-fast bacilli (AFB), in addition to the fusion of the intestinal villi and hyperplasia of the crypts. Despite the large sampling effort, only 79 MAP isolates were successfully genotyped, where 19 different haplotypes were described. A mixed-effect Poisson regression model was used to assess the relationship between haplotypes and HSS values. The model was controlled by animal age, and the farm was used as a random effect. Haplotypes were grouped based on their relative frequency: the most frequent haplotype (group , 49.4%), the second most frequent haplotype (group , 12.7%), and all other haplotypes (group , 37.9%). Model outputs indicated that group had significantly higher HSS values than group . In addition, group was also associated with higher optical density (OD) values of the ELISA test. These results support the existence of differences in pathogenicity between MAP haplotypes. However, results were based on a relatively small sample size; thus, these should be taken with caution. Despite this, study findings suggest that haplotypes would be associated with differences in disease progression, where the dominant haplotype tends to generate more severe lesions, which could be linked to a greater shed of MAP cells than non-dominant haplotypes, increasing their chances of transmission.
目的是评估亚种（MAP）感染所致组织病理学损伤的严重程度与该病原体分子多样性之间的关联。在屠宰时从1352头成年牛[源种群1（SP1）]采集血液、回肠和肠系膜淋巴结样本。此外，对42个奶牛群（共4963头奶牛）进行了为期2年的跟踪，并采集了符合条件的临床病例[源种群2（SP2）]的样本。使用ELISA检测、液体培养基培养和PCR确认MAP感染。使用五个MIRU-VNTR标记对分离株进行基因分型。对确诊样本的组织进行组织病理学检查。开发了一种组织病理学严重程度评分（HSS）系统并用于对MAP所致病变的程度进行分级（0至5级）。一般来说，HSS系统评估病灶数量、巨噬细胞浸润程度，以及多核巨细胞（MGCs）和抗酸杆菌（AFB）的存在情况，此外还评估肠绒毛融合和隐窝增生情况。尽管采样量很大，但仅成功对79株MAP分离株进行了基因分型，共描述了19种不同的单倍型。使用混合效应泊松回归模型评估单倍型与HSS值之间的关系。该模型以动物年龄作为对照，并将养殖场作为随机效应。单倍型根据其相对频率进行分组：最常见的单倍型（组1，49.4%）、第二常见的单倍型（组2，12.7%）以及所有其他单倍型（组3，37.9%）。模型输出结果表明，组1的HSS值显著高于组3。此外，组1还与ELISA检测的更高光密度（OD）值相关。这些结果支持MAP单倍型之间存在致病性差异。然而，结果基于相对较小的样本量；因此，应谨慎对待这些结果。尽管如此，研究结果表明单倍型与疾病进展差异相关，其中优势单倍型往往会产生更严重的病变，这可能与MAP细胞比非优势单倍型有更大的脱落量有关，从而增加其传播机会。
