Tscheschlok L, Venner M, Steward K, Böse R, Riihimäki M, Pringle J
Equine Veterinary Clinic, Destedt, Germany.
Department of Bacteriology, Animal Health Trust, Newmarket, UK.
J Vet Intern Med. 2018 Jan;32(1):459-464. doi: 10.1111/jvim.15037.
Streptococcus equi ssp. equi causes characteristic clinical signs that are most severe in young horses, including fever, purulent nasal discharge, and lymph node abscessation in the head region.
HYPOTHESIS/OBJECTIVES: Clinical, serologic, and microbiologic factors related to unexpectedly mild disease severity in a natural outbreak of strangles in immunologically naïve weanlings were investigated.
One-hundred and twelve warmblood weanlings.
Prospective longitudinal observational study of a natural outbreak of strangles. The entire cohort was examined at the peak of the outbreak by deep nasal swabs for culture and quantitative PCR (qPCR) for the presence of S. equi and clinically and serologically in a sequential manner by an optimized ELISA from the index case throughout the outbreak until resolution. Descriptive statistics were calculated and comparisons made using a nondirectional Wilcoxon signed-rank test.
Outbreak morbidity was 53%, with 9 of 14 horses culture positive and 26 of 53 horses qPCR positive for S. equi lacking clinical signs characteristic of strangles. By resolution, 91 of 112 had seroconverted to Antigen A by ELISA but seroconversion to antigen C (part of the SeM protein) was minimal. Sequencing of the isolates detected no alterations in the SeM protein, but identified a 61 bp deletion in the gene SEQ_0402.
Absence of clinical signs alone in naïve horses may be an insufficient criterion to release horses from strangles quarantine measures. Restricted seroconversion to antigen C may have been associated with decreased clinical severity. The role of a minor gene deletion in SEQ_0402 in the virulence of S. equi warrants further investigation.
马链球菌兽疫亚种可引发特征性临床症状，在幼龄马中最为严重，包括发热、脓性鼻液以及头部区域淋巴结脓肿。
假设/目的：对免疫初免断奶幼驹自然发生的马腺疫疫情中，与疾病严重程度意外较轻相关的临床、血清学和微生物学因素进行调查。
112匹温血断奶幼驹。
对马腺疫自然疫情进行前瞻性纵向观察研究。在疫情高峰期，对整个队列进行深鼻拭子培养，并进行定量PCR（qPCR）检测马链球菌的存在情况，从首例病例开始，在整个疫情期间直至疫情结束，按顺序对其进行临床和血清学检查，采用优化的ELISA方法。计算描述性统计量，并使用非定向Wilcoxon符号秩检验进行比较。
疫情发病率为53%，14匹马中有9匹培养阳性，53匹马中有26匹qPCR检测马链球菌阳性，但缺乏马腺疫的特征性临床症状。到疫情结束时，112匹马中有91匹通过ELISA检测血清转化为抗原A，但血清转化为抗原C（SeM蛋白的一部分）的情况极少。对分离株进行测序，未检测到SeM蛋白有改变，但在SEQ_0402基因中发现了一个61bp的缺失。
仅无临床症状可能不足以作为将马匹从马腺疫隔离措施中解除的标准。抗原C的血清转化受限可能与临床严重程度降低有关。SEQ_0402基因中的一个小基因缺失在马链球菌毒力中的作用值得进一步研究。
