Seroprevalence and spatial distribution dynamics of Yersinia pestis antibodies in dogs and cats from plague foci in the State of Ceará, Northeastern Brazil

Abstract INTRODUCTION: In Brazil, the plague is established in several foci located mainly in the northeastern part of the country, where it alternates between active and quiescent periods. These foci in the State of Ceará have high epidemiological importance. In addition to other plague detection activities, plague areas can be monitored through serological surveys of dogs and cats (domestic carnivores), which, following feeding on plague-infected rodents, can develop mild to severe forms of the disease and produce long-lasting antibodies. This study aimed to characterize the circulation dynamics and spatial distribution of Yersinia pestis antibodies in dogs and cats in plague foci areas of Ceará. METHODS: An ecological study was conducted to analyze the temporal series and spatial distribution of secondary data obtained from domestic carnivore serum surveillance in Ceará’s plague areas from 1990 to 2014. RESULTS: Joinpoint analysis revealed that the overall trend was a reduction in antibody-positive animals. The mean proportion of antibody-positivity during the whole study period was 1.5% (3,023/203,311) for dogs, and 0.7% (426/61,135) for cats, with more than 4% antibody-positivity in dogs in 1997 and 2002. Antibody titers ranging from 1/16 to 1/64 were frequent. Despite fluctuations and a significant reduction, in recent years, there were antibody-positive animals annually throughout the study period, and the localities containing antibody-positive animals increased in number. CONCLUSION: Yersinia pestis is actively circulating in the study areas, posing a danger to the human population.引言：在巴西，鼠疫已在多个疫源地定植，这些疫源地主要分布于该国东北部，活动期与静止期交替出现。塞阿拉州的此类疫源地具有极高的流行病学意义。除其他鼠疫监测活动外，还可通过对犬、猫（家养食肉动物（domestic carnivores））开展血清学调查来监测鼠疫疫源地：此类动物因摄食感染鼠疫耶尔森菌（Yersinia pestis）的啮齿动物后，可出现轻症至重症的鼠疫感染，并产生持续时间较长的抗体。本研究旨在阐明塞阿拉州鼠疫疫源地内犬、猫体内鼠疫耶尔森菌抗体的循环动态与空间分布特征。 方法：本研究为生态学研究，分析了1990年至2014年塞阿拉州鼠疫疫源地家养食肉动物血清监测所获二手数据的时间序列与空间分布特征。 结果：连接点分析（Joinpoint analysis）显示，抗体阳性动物的整体检出率呈下降趋势。整个研究周期内，犬的抗体阳性率均值为1.5%（3023/203311），猫为0.7%（426/61135）；其中1997年与2002年犬的抗体阳性率超过4%。抗体滴度介于1/16至1/64的样本较为常见。尽管存在波动且呈显著下降趋势，但研究周期内每年均能检出抗体阳性动物，且检出阳性动物的地域数量有所增加。 结论：鼠疫耶尔森菌在本研究区域内仍处于活跃循环状态，对人群构成健康威胁。