Phoosangwalthong Pornkamol, Hii Sze Fui, Kamyingkird Ketsarin, Kengradomkij Chanya, Pinyopanuwat Nongnuch, Chimnoi Wissanuwat, Traub Rebecca J, Inpankaew Tawin
Department of Parasitology, Faculty of Veterinary Medicine, Kasetsart University, Bangkok, Thailand.
Australian Rickettsial Reference Laboratory, Geelong, Victoria 3220, Australia.
Vet Parasitol Reg Stud Reports. 2018 Aug;13:188-192. doi: 10.1016/j.vprsr.2018.07.001. Epub 2018 Jul 3.
Rickettsia felis is an obligate intracellular alpha-proteobacteria and the cause of flea-borne spotted fever (FBSF), an emerging zoonosis of global public health importance, for which dogs and cats have been implicated as potential mammalian reservoirs hosts. The purpose of this study was to determine the prevalence and associated risk factors for R. felis-like species in semi-domesticated cats and their fleas in aim of understanding public health risks posed by cats and their fleas in Bangkok, Thailand. Single whole blood samples (n = 432) and where observed, fleas (n = 234), were collected from cats from 53 temple communities in Bangkok. Fleas were morphologically and genetically identified to a species level. Cat blood and fleas were subjected to a spotted fever group (SFG)-specific PCR targeting the partial outer membrane protein B (ompB). Those that were positive, were further characterised using an R. felis-specific nested PCR targeting the partial citrate synthase A (gltA) gene. All fleas were identified as Ctenocephalides felis felis. In total SFG Rickettsiae were detected in the blood of 82/482 (17.01%) cats and 3/234 fleas (1.28%). DNA sequencing of the partial ompB characterised all positive amplicons from cat blood and their fleas as 100% identical to Rickettsia endosymbiont of Ctenocephalides felis orientis isolate (Rickettsia sp. genotype RF2125) and Rickettsia asemboensis (GenBank accession no. KP256362 and KY650699, respectively). The gltA gene targeting R. felis was successfully amplified from 12/82 PCR-positive cat blood samples and these clustered with 99% bootstrap support with isolates within the Rickettsia sp. genotype RF2125 clade. Cats that were permitted to roam freely inside monasteries were more likely to be infected with R. felis compared with cats confined indoors. The results suggest that cats in Thailand are potential mammalian reservoir hosts for Rickettsia sp. genotype RF2125.
猫立克次氏体是一种专性细胞内α-变形菌，是蚤传斑点热（FBSF）的病原体，FBSF是一种新出现的具有全球公共卫生重要性的人畜共患病，狗和猫被认为是潜在的哺乳动物储存宿主。本研究的目的是确定半驯化猫及其跳蚤中猫立克次氏体样物种的流行率和相关危险因素，以了解泰国曼谷猫及其跳蚤所带来的公共卫生风险。从曼谷53个寺庙社区的猫身上采集了单份全血样本（n = 432），并在有跳蚤的情况下采集了跳蚤样本（n = 234）。通过形态学和遗传学方法将跳蚤鉴定到物种水平。对猫血和跳蚤进行针对部分外膜蛋白B（ompB）的斑点热群（SFG）特异性PCR。对阳性样本，使用针对部分柠檬酸合酶A（gltA）基因的猫立克次氏体特异性巢式PCR进一步进行鉴定。所有跳蚤均被鉴定为猫栉首蚤指名亚种。总共在82/482（17.01%）只猫的血液和3/234（1.28%）只跳蚤中检测到SFG立克次氏体。对部分ompB进行DNA测序，结果表明来自猫血及其跳蚤的所有阳性扩增子与东方猫栉首蚤内共生立克次氏体分离株（立克次氏体属基因型RF2125）和阿森博立克次氏体（GenBank登录号分别为KP256362和KY650699）100%相同。从12/82份PCR阳性猫血样本中成功扩增出靶向猫立克次氏体的gltA基因，这些样本与立克次氏体属基因型RF2125分支内的分离株在99%的自展支持率下聚类。与圈养在室内的猫相比，允许在寺庙内自由活动的猫感染猫立克次氏体的可能性更大。结果表明，泰国的猫是立克次氏体属基因型RF2125的潜在哺乳动物储存宿主。
