Data_Sheet_1_Identification of equine mares as reservoir hosts for pathogenic species of Leptospira.PDF

Equine leptospirosis can result in abortion, stillbirth, neonatal death, placentitis, and uveitis. Horses can also act as subclinical reservoir hosts of infection, which are characterized as asymptomatic carriers that persistently excrete leptospires and transmit disease. In this study, PCR and culture were used to assess urinary shedding of pathogenic Leptospira from 37 asymptomatic mares. Three asymptomatic mares, designated as H2, H8, and H9, were PCR-positive for lipL32, a gene specific for pathogenic species of Leptospira. One asymptomatic mare, H9, was culture-positive, and the recovered isolate was classified as L. kirschneri serogroup Australis serovar Rushan. DNA capture and enrichment of Leptospira genomic DNA from PCR-positive, culture-negative samples determined that asymptomatic mare H8 was also shedding L. kirschneri serogroup Australis, whereas asymptomatic mare H2 was shedding L. interrogans serogroup Icterohaemorrhagiae. Sera from all asymptomatic mares were tested by the microscopic agglutination test (MAT) and 35 of 37 (94.6%) were seropositive with titers ranging from 1:100 to 1:3200. In contrast to asymptomatic mares, mare H44 presented with acute spontaneous abortion and a serum MAT titer of 1:102,400 to L. interrogans serogroup Pomona serovar Pomona. Comparison of L. kirschneri serogroup Australis strain H9 with that of L. interrogans serogroup Pomona strain H44 in the hamster model of leptospirosis corroborated differences in virulence of strains. Since lipopolysaccharide (LPS) is a protective antigen in bacterin vaccines, the LPS of strain H9 (associated with subclinical carriage) was compared with strain H44 (associated with spontaneous abortion). This revealed different LPS profiles and immunoreactivity with reference antisera. It is essential to know what species and serovars of Leptospira are circulating in equine populations to design efficacious vaccines and diagnostic tests. Our results demonstrate that horses in the US can act as reservoir hosts of leptospirosis and shed diverse pathogenic Leptospira species via urine. This report also details the detection of L. kirschneri serogroup Australis serovar Rushan, a species and serotype of Leptospira, not previously reported in the US.

马源性钩端螺旋体病可导致流产、死产、新生幼畜死亡、胎盘炎和虹膜炎。马匹亦可能充当亚临床感染储存宿主，其特征为无症状携带者，持续排出钩端螺旋体并传播疾病。在本研究中，采用聚合酶链反应和培养方法对37匹无症状母马尿液中的致病性钩端螺旋体进行检测。三匹无症状母马，分别标记为H2、H8和H9，其lipL32基因PCR检测结果呈阳性，该基因特异性针对致病性钩端螺旋体。其中一匹无症状母马H9培养结果呈阳性，分离株被归类为李斯特菌属的澳大利亚血清群Rushan血清型。对PCR阳性、培养阴性的样本进行DNA捕获和富集，证实无症状母马H8亦排出李斯特菌属的澳大利亚血清群，而无症状母马H2排出李斯特菌属的问号血清群。所有无症状母马的血清均经显微凝集试验（MAT）检测，37匹中有35匹（94.6%）呈血清阳性，滴度范围为1:100至1:3200。与无症状母马相比，母马H44出现急性自发性流产，血清MAT滴度为1:102,400，针对李斯特菌属的庞马血清群庞马血清型。将李斯特菌属的澳大利亚血清群菌株H9与问号血清群菌株H44在钩端螺旋体病仓鼠模型中的比较证实了菌株间毒力的差异。鉴于脂多糖（LPS）是菌苗疫苗中的保护性抗原，因此将菌株H9（与亚临床携带相关）的LPS与菌株H44（与自发性流产相关）的LPS进行了比较，结果显示不同的LPS谱和与参考抗血清的免疫反应性。了解在马匹群体中循环的钩端螺旋体物种和血清型对于设计有效的疫苗和诊断测试至关重要。我们的研究结果表明，美国的马匹可以作为钩端螺旋体的储存宿主，并通过尿液排出多种致病性钩端螺旋体。本报告还详细描述了李斯特菌属澳大利亚血清群Rushan血清型的检测，这是一种以前未在美国报道的钩端螺旋体物种和血清型。