Departamento de Clínica Médica, Faculdade de Medicina Veterinária e Zootecnia, Universidade de São Paulo, São Paulo, São Paulo, Brasil.
Departamento de Medicina Veterinária Preventiva e Saúde Animal, Faculdade de Medicina Veterinária e Zootecnia, Universidade de São Paulo, São Paulo, São Paulo, Brasil.
PLoS One. 2018 Jul 11;13(7):e0200384. doi: 10.1371/journal.pone.0200384. eCollection 2018.
Dogs are highly susceptible to the leptospiral infection, notably stray and sheltered dogs. Unsanitary conditions often observed in dog shelters may predispose the introduction and spread of leptospires among sheltered populations, potentially increasing the chances for the inadvertent adoption of asymptomatically infected animals. The present work describes a longitudinal study using a multidisciplinary approach for the identification of chronically infected dogs and the characterization of potentially pathogenic strains circulating among stray and sheltered dog populations in São Paulo, Brazil. A total of 123 dogs from three populations were included. The initial evaluation consisted of blood and urine quantitative PCR testing (qPCR), the detection of specific antibodies by microscopic agglutination test (MAT), physical examination and hematological and serum biochemistry analyses. The qPCR-positive dogs were prospectively examined, and reevaluations also included culture from urine samples. Positive qPCR samples were subjected to 16S rRNA and secY gene phylogenetic analysis. The recovered strains were characterized by Multilocus Sequence Typing, polyclonal serogroup identification and virulence determination. Leptospiruria was detected in all populations studied (13/123), and phylogenetic analysis revealed that 10 dogs had L. interrogans infection. Three dogs (3/13) had L. santarosai infection. The secY phylogenetic analysis revealed that the L. santarosai sequences clustered separately from those obtained from other hosts. Ten leptospiruric dogs were reevaluated, and three dogs presented persistent leptospiruria, allowing culturing from two dogs. The strains were characterized as L. interrogans serogroup Canicola (virulent) and L. santarosai serogroup Sejroe (not virulent). Serum samples were retested by MAT using the DU92 and DU114 strains as antigens, and no increased seroreactivity was detected. Asymptomatic L. santarosai infection was observed in all populations studied, suggesting a possible role of dogs in the chain of transmission of this leptospiral species. The results suggest a genetic distinction between lineages of Brazilian L. santarosai maintained by dogs and other animal hosts. Our findings revealed that dogs could act as maintenance hosts for distinct pathogenic Leptospira, highlighting also that asymptomatically infected dogs can be inadvertently admitted and adopted in dog shelters, potentially increasing the risks of zoonotic transmission.
狗极易感染钩端螺旋体病，尤其是流浪狗和收容所的狗。收容所中经常观察到的不卫生条件可能导致钩端螺旋体在收容人群中引入和传播，从而增加了无意中收养无症状感染动物的可能性。本研究采用多学科方法对巴西圣保罗的流浪狗和收容所狗进行了一项纵向研究，以确定慢性感染的狗，并对流行于这些狗中的潜在致病株进行了特征描述。共纳入三个群体的 123 只狗。初步评估包括血液和尿液定量 PCR 检测（qPCR）、显微镜凝集试验（MAT）检测特异性抗体、体格检查以及血液学和血清生化分析。对 qPCR 阳性的狗进行前瞻性检查，重新评估还包括尿液样本培养。对 qPCR 阳性样本进行 16S rRNA 和 secY 基因系统发育分析。从回收菌株进行多位点序列分型、多克隆血清群鉴定和毒力测定。在所有研究的群体中都检测到了钩端螺旋体尿症（13/123），系统发育分析显示 10 只狗感染了问号钩端螺旋体。3 只狗（3/13）感染了 santarosai 钩端螺旋体。secY 系统发育分析显示，santarosai 序列与其他宿主获得的序列分开聚类。10 只钩端螺旋体尿症的狗进行了重新评估，其中 3 只狗持续存在钩端螺旋体尿症，允许从 2 只狗中培养。这些菌株被鉴定为 Canicola 血清群的问号钩端螺旋体（毒力）和 Sejroe 血清群的 santarosai 钩端螺旋体（非毒力）。使用 DU92 和 DU114 株作为抗原，用 MAT 对血清样本进行了重新检测，未检测到血清反应性增加。在所有研究的群体中都观察到无症状的 santarosai 感染，这表明狗可能在这种钩端螺旋体的传播链中发挥作用。研究结果表明，巴西 santarosai 的遗传谱系在狗和其他动物宿主中有所不同。我们的研究结果表明，狗可能作为不同致病性钩端螺旋体的维持宿主，这也突出表明，无症状感染的狗可能会被无意中收容和收养在收容所中，从而增加了人畜共患病传播的风险。
