Occurrence of Ehrlichia canis and Hepatozoon canis and probable exposure to Rickettsia amblyommatis in dogs and cats in Natal, RN

Abstract Occurrence of infection or exposure to Ehrlichia canis, Hepatozoon canis and Rickettsia spp. was detected in feral cats living in two fragments from Atlantic rainforest, in Natal, RN, Brazil, and in dogs living around the parks. While serum samples were collected from 155 animals (53 cats living in the parks; 29 dogs living in human homes around the parks; and 73 dogs living at an animal control center - ACC), spleen samples were collected from 20 dogs that were euthanized at ACC. Serum samples were analyzed to Rickettsia spp. and E. canis antibodies using the indirect immunofluorescence assay. Seventeen of the 102 dogs (17%) had E. canis antibodies and 13% (20/155) of all dogs and cats (i.e. 3% (3/102) of the dogs and 32% (17/53) of the cats) were seropositive for Rickettsia spp. antigens. The animals were therefore been exposed to R. amblyommatis or by a very closely related genotype. Among the 20 dog spleen samples analyzed, eight were PCR positive for E. canis and two for H. canis (GenBank accession number MG772657 and MG772658, respectively). In none of the spleen samples were obtained amplicons for Babesia spp. through PCR. This study provided the first evidence that Rickettsia of the spotted fever group is circulating among dogs and cats in Natal.

摘要：本研究在巴西里约格兰德州纳塔尔市两处大西洋热带雨林片段的野生猫只，以及公园周边犬只中，检测到犬埃立克体（Ehrlichia canis）、犬肝簇虫（Hepatozoon canis）与立克次体属（Rickettsia spp.）的感染或暴露情况。本次研究共采集155份血清样本：其中53份来自公园栖息的野生猫只，29份来自公园周边居民家庭饲养的犬只，73份来自动物管控中心（ACC）的犬只；另采集了20只在该管控中心实施安乐死的犬只的脾脏样本。研究采用间接免疫荧光试验（indirect immunofluorescence assay）检测血清样本中的立克次体属与犬埃立克体抗体。结果显示，102份犬只血清样本中，17份（17%）呈犬埃立克体抗体阳性；所有受试动物（犬只与猫只）的血清样本中，共13%（20/155）对立克次体属抗原呈血清学阳性，其中犬只阳性率为3%（3/102），猫只阳性率为32%（17/53），提示受试动物曾暴露于钝眼蜱立克次体（R. amblyommatis）或与其亲缘关系极近的基因型。对20份犬只脾脏样本的PCR检测结果显示，8份样本呈犬埃立克体阳性，2份呈犬肝簇虫阳性，二者对应的GenBank登录号分别为MG772657与MG772658；未在任何脾脏样本中通过PCR扩增出巴贝斯虫属（Babesia spp.）的目的扩增片段。本研究首次证实，斑点热群立克次体在巴西纳塔尔市的犬只与猫只种群间存在传播循环。