云南省泸西县啮齿动物携带立克次体调查

目的 调查云南省泸西县啮齿动物携带恙虫病东方体、无形体和埃立克体的状况,了解该类病原体在当地自然界中的保存状况和基因特征。方法 用鼠笼和鼠夹在云南省泸西县捕鼠,将捕获的动物种类鉴定后解剖取脾脏,活鼠取血。采用巢式PCR扩增脾脏的恙虫病东方体groEL基因,无形体和埃立克体的16S rRNA基因特异片段;测定PCR扩增阳性产物的DNA序列,对获得序列进行序列比对和系统进化分析。IFA法检测鼠血清中恙虫病东方体IgG抗体。结果 在泸西县共捕获啮齿动物10种225只。其中黄胸鼠36.89%(83/225)、大绒鼠35.11%(79/225)和中华姬鼠13.78%(31/225)为优势鼠种。获得鼠血清85份。鼠脾脏中检测到5株东方体groEL基因阳性标本,带毒鼠种为黄胸鼠2.41%(2/83)和大绒鼠3.80%(3/79)。同源性比较显示,这5株东方体的相似性在99.02%~100%之间,他们分别与GenBank中已知立克次体序列的相似性在98.75%~100%。系统发生树显示,5株OT与来自日本、泰国和中国安徽的菌株位于同一分支。3份16S rRNA阳性标本,其中1份埃立克体阳性,来源于大绒鼠;1份沃尔巴克氏体和1份巴尔通体阳性均来源于黄胸鼠。无形体均为阴性。埃立克体株序列比对显示与来自美国、中国和巴西的埃立克体基因同源性为98.0%~100%,并与分离自美国野外工作者皮肤的伊文氏埃立克体在同一分支。鼠血清恙虫病IgG抗体阳性7份,阳性率8.24%(7/85)。结论 该地区存在以黄胸鼠和大绒鼠为主要宿主的恙虫病自然疫源地。埃立克体、巴尔通体和沃尔巴克氏体在啮齿动物中也存在感染,需注意防控。     

东北林区啮齿动物的查菲埃立克体核酸检测

目的 调查东北林区啮齿动物的查菲埃立克体感染水平。方法 采用巢式PCR检测吉林省集安和辽宁省宽甸林区野鼠脾脏样本的查菲埃立克体16S rRNA DNA;对阳性扩增产物作DNA序列测定,并对测定的序列进行同源性比较和聚类分析。结果 检测两地野鼠132只,阳性19只,阳性率14.39%。其中,集安野鼠阳性率 7.58%(5/66),宽甸野鼠阳性率 21.21%(14/66), 宽甸野鼠阳性率明显高于集安(χ²=3.9348, P=0.0473)。不同鼠种查菲埃立克体阳性率无明显差异。扩增阳性DNA片段测序后与GenBank中注册的埃立克体16S rRNA基因对应序列进行同源性比较, JA-m51(集安株)、KD-m18(宽甸株)二者基因序列相差4个核苷酸,而JA-m51与查菲埃立克体美国株及我国云南株核苷酸序列完全一致,进化树分析显示JA-m51、KD-m18与查菲埃立克体同属一个分支。结论 辽宁省、吉林省林区野鼠查菲埃立克体感染较普遍,该地区存在单核细胞埃立克体病的自然疫源地。     

云南临沧地区蜱种分子生物学鉴定及埃立克体基因序列分析

目的 了解云南临沧地区蜱虫种类及其自然感染埃立克体的情况。方法 采集耕牛体表寄生的蜱虫,经形态学鉴定和分组后,从蜱虫中提取DNA,应用PCR扩增蜱虫COI基因以及埃立克体16S rRNA和groEL基因,并测序分析。结果 共采集到蜱虫42只,其中微小牛蜱38只占90.48%、血蜱4只占9.52%。将每种蜱的2只为1组,在21组样本中,检出COI片断21份(检出率100%);在相同的4组样本中均检出埃立克体16S rRNA片断和groEL片断4份(检出率19.05%)。基因序列分析,检出的COI片断序列中有2份与澳大利亚pava血蜱(JX573136)的同源性最高(89.3%),其余19份序列与马来西亚微小牛蜱B3的同源性最高(99.5%);检出的4份16S rRNA片断序列完全一致,与美国查菲埃立克体Arkansas和埃文埃立克体Aa2FT349及中国北京查菲埃立克体BY-YQ-HME-O18株的同源性均为100%;检出的4份groEL片断序列也完全一致,与日本埃立克体Yonaguni206 株的同源性最高均为93.9%。结论 经分子检测证实云南临沧地区耕牛体表微小牛蜱中存在一种类似日本Yonaguni206株的埃立克体感染,耕牛体表还可能寄生一种新的血蜱。     

用半套式PCR检测蜱和啮齿动物中查菲埃立克体

目的　了解福建西北部林区查菲埃立克体 (Ehrlichiachaffeensis)的存在情况。方法　用 16SrRNA基因特异引物进行半套式PCR ,检测从福建武夷山和宁化采集的蜱类及野生动物中的查菲埃立克体DNA ,然后对有代表性的标本的扩增产物进行克隆和序列测定 ,并与GenBank中注册的核苷酸序列进行同源性比较。结果　从该地区的越原血蜱 ,野鼠(褐家鼠、黄毛鼠、黄胸鼠、社鼠、小家鼠 )和野兔的脾脏和 /或血块中均扩增出了查菲埃立克体的特异片段。越原血蜱成蜱 2 40组 (6 16只 ) ,31组阳性 ,最小阳性率 5 0 %。野鼠脾脏标本 39份 ,2 2份阳性。野鼠和野兔血块标本共 35份 ,14份阳性。 390bp的PCR产物经克隆、测序后分析发现其DNA序列与美国查菲埃立克体分离株对应位置一致。结论　福建西北部林区可能存在人单核细胞埃立克体病的自然疫源地。     

我国南方蜱样本中发现犬埃立克体DNA

目的 调查我国南方蜱样本埃立克体感染情况。方法 用已发表的埃立克体１６ＳｒＲＮＡ基因的属特异引物和自行设计的犬埃立克全种特异引物，对广东，广西和海南部分地区采集的蜱样本进行ＰＣＲ检测，并将阳性ＰＣＲ产物克隆测序，结果通过Ｉｎｔｅｒｎｔ提交到美国国立医学图书馆／国家健康研究所的站点，利用ＢＬＡＳＴ对核酸数据库进行同源性检索。结果 从广东采集的血红扇头蜱和广西要的微小牛蜱样本中扩增出埃立克体４２５ｂｐ     

用查菲埃立克体P28融合蛋白作免疫印迹诊断犬埃立克体感染

目的 建立以查菲埃立克体P28融合蛋白为抗原的诊断犬埃立克体感染的免疫印迹。方法 诱导PinPoint^TMXa-3/P28重组质粒在E coli细胞内高效表达查菲埃立克体P28融全蛋白,以该重组蛋白作抗原与犬血清行免疫印迹。结果 P28融合蛋白与书籍的3份犬埃立克体感染血清呈阳性反应,与正常犬血清反应为阴性,在165份来自犬埃立克体病疫区的待检犬血清中有43份（26%）与P28反应阳性。结论 查菲埃立克体P28融合蛋白可作为犬埃立克体感染的特异性诊断抗原,以其建立的免疫印迹可用于犬埃立克体病的诊断。     

从西藏微小牛蜱检出类查菲埃立克体和边缘无形体16S rDNA

目的　鉴定微小牛蜱 (Boophilusmicroplus)所携带的埃立克体病原体。方法　依据蜱传埃立克体 16SrDNA序列设计引物 ,建立埃立克体属特异性套式PCR检测微小牛蜱DNA样本 (每份DNA由 2个蜱提取 ) ;克隆DNA样本中的埃立克体 16SrDNA的 5′末端片段并测定其序列。结果　西藏某地的 4 3份蜱DNA样本中有 16份 (37% )经套式PCR扩得阳性片段 ,而四川某地的 2 7份蜱DNA样本扩增结果均为阴性。测定 16SrDNA的 5′末端片段 (～ 4 5 0bp)的序列 ,发现两种序列 ,一种与边缘无形体 16SrDNA完全一致 ,另一种与查菲埃立克体 16SrDNA最相关 ,但它们之间有 7个碱基 (～ 1 6 % )的不同。结论　西藏某地的微小牛蜱中携带有类查菲埃立克体和边缘无形体 ,该类查菲埃立克体可能是一个埃立克体新种     

查菲埃立克体P28蛋白抗原免疫印迹调查犬单核细胞埃立克体病

目的　以查菲埃立克体P2 8蛋白抗原免疫印迹法对犬单核细胞埃立克体病作流行病学调查 ,为该病的防治提供依据。方法　收集广东犬埃立克体病发生地的犬血清 ,用基因工程制备的查菲埃立克体P2 8融合蛋白抗原与犬血清作免疫印迹 ,检测犬血清中的抗P2 8抗体。结果　 2 12份犬血清行免疫印迹 ,89份 (42 % )阳性 ;这些阳性反应的血清绝大部分来自广州市和深圳市的野外工作犬 ,而南海市观赏犬的血清均为阴性。广西省南宁市的野外工作犬的 36份标本仅 3份为弱阳性。高水平的P2 8抗体出现在 4～ 10月 ,与当地蜱的活动期平行。结论　犬单核细胞埃立克体病在我国为局部流行 ,蜱可能是该病的传播媒介     

福建西北林区人单核细胞埃立克体病分子流行病学调查研究

目的 了解福建西北林区人单核细胞埃立克全病的存在情况。方法 评价以查菲埃立克体16S rRNA基因序列高变区构建引物进行的半套式PCR的敏感性和特异性，并用此种半套式PCR技术检测从福建武夷山市和宁化县采集的蜱类、野生动物内脏和血液及人群血液标本中的查菲埃立克体DNA，对有代表性的阳性标本的扩增产物进行克隆和序列测定，并与GenBank中注册的核苷酸序列进行同源性比较。应用以16S rRNA基因构建的特异和通用引物进行PCR，从越原血蜱及黄毛鼠标本中分段扩增查菲埃立克体DNA，进行克隆和序列测定，分别将其连成完整序列，与已知所有埃立克体及近缘菌的16SrRNA基因序列进行最大同源性比较，用Clustal X(1.8)软件对同源位碱基作聚类分析，应用“Tree View”程序得出遗传发育树图。结果 这种半套式PCR检测方法具有很高的特异性，仅能扩增查菲埃立克体DNA，而对其它蜱媒病病原体，如斑点热立克次体、菜姆病螺旋体的DNA及人粒细胞埃立克体病病原体的16S rRNA基因都不能扩增，同时，用有限稀释法以含EC 16S rRNA基因的质粒为模板评价其敏感度，结果显示：最低能检测到4个拷贝的查菲埃立克体DNA。用此半套式PCR法从该地区的越原血蜱、粒形硬蜱，鼠类（褐家鼠、黄毛鼠、黄胸鼠、神鼠、小家鼠）和野兔的脾脏和/或血块中均扩增出了查菲埃立克体的特异DNA片段。检测越原血蜱成蜱283组（659只），25组阳性，最小阳性率为3.8%。粒形硬蜱4只，1只阳性。野鼠脾脏、血块及野兔血块的阳性率分别为56.4%（22/39）、38.7%(12/31)和18.2%(2/11）。同时检测的其它蜱种、狐狸血块、野猪血块及人血块中均未发现查菲埃立克体DNA。越原血蜱和野鼠代表性标本的390bp的PCR产物经克隆、测序后，发现其DNA序列与美国查菲埃立克体分离株对应位置分别一致和相差一个核苷酸。从越原血蜱和黄毛鼠扩增来的全序列与美国查菲埃立克体分离株的16S rRNA基因序列分别相差6个和2个核苷酸，同源性分别为99.6%和99.9%；与犬埃立克体（E.cn-is）、 尤菌氏埃立克体（E.ewingii）、鼠埃立克体（E.muris）之间的同源性为97.6%～98.0%，属于近缘种；与其它埃立克体种的同源性在83.0%～92.4%之间。结论 上述研究结果提示福建西北部地区可能存在人单核细胞埃立克体病的自然疫源地。越原血蜱和粒形硬埤为其潜在传播媒介，鼠和野兔可能为其贮存宿主。实践证明，半套式PCR及序列分析技术可作为检测蜱和动物标本中查菲埃立克体的一种敏感、特异的方法，适用于现场流行病学调查。本研究首次测定我国南方蜱及啮齿动物中埃立克体的16S rRNA全基因序列，为进一步开展疫源地调查奠定了基础。     

内蒙古大兴安岭林区人埃立克体病自然疫源地的调查

目的人粒细胞埃立克体病和人单核细胞埃立克体病都是近10年来发现的2种经蜱传播的自然疫源性疾病。这2种病的公共卫生学意义已受到了许多国家的关注。由于病原体是专性细胞内寄生菌,直接培养和纯化较为困难。我们根据这2种埃立克体的16S rRNA基因序列,构建了一系列PCR引物对,对采自我国大兴安岭等北方地区的蜱、动物脏器和人血标本进行PCR扩增,并对扩增出的产物进行DNA序列分析,以期查清有可疑蜱媒地区是否存在埃立克体感染,并通过这次调查为今后进一步开展系统研究提供参考。方法与结果本研究采用半巢式PCR检测蜱标本2种埃立克体的带菌率。结果首次从内蒙古大兴安岭采集的全沟硬蜱和森林革蜱,新疆精河采集的全沟硬蜱和草原革蜱中扩增出390bp的特异和人单核细胞埃立克体16S rRNA基因片段;同时检测的大兴安岭的嗜群血蜱和北京灵山采集的长角血蜱均未扩增出相应的片段。大兴安岭莫尔道嘎林业局采集的全沟硬蜱携带此基因的阳性率为39.06％(25/64),森林革蜱为 10.00％(7/70),2种蜱的带菌率有显著差异(x~2=15.53,P<0.01)。新疆精河采集的蜱携带EC率也是全沟硬蜱(11组/190,最小阳性率为5.79％)高于森林革蜱(1组/60,最小阳性率为1.67％),但差别不显著(x~2=1.30,P>0.25)。还从大兴安岭林区捕捉的一只大林姬鼠的脏器中检测到这一16S rRNA基因片段。对一只从莫尔道嘎采集的全沟硬蜱蜱标本进行近1500bp的人单核细胞埃立克体 16S rRNA全基因扩增与序列分析,结果扩增出的序列与美国一株人单核细胞埃立克体(GenBank注册号U23503)的相应序列完全相同。同样应用半巢式PCR和序列分析技术,从蜱标本中扩增出441bp的特异的人粒细胞埃立克体16SrRNA基因片段。内蒙古大兴安岭莫尔道嘎采集的全沟硬蜱和森林革蜱人粒细胞埃立克体的阳性率分别是 6.25%(4/64)和 2.86%(2/70);内蒙古大兴安岭乌尔旗汗采集的全沟硬蜱和嗜群血蜱的阳性率分别为3.81％(最小阳性率,8组/210)和2%(1/50);新疆精河采集的全沟硬蜱和草原革蜱最小阳性率分别为3.16％(6组/190)和1.67%(1组/60)。这是首次在亚洲从蜱标本中检测到人粒细胞埃立克体。同时检测的北京灵山采集的长角血蜱未扩增出相应的片段。对一只从莫尔道嘎采集的全沟硬蜱标本进行近1500bp的人粒细胞埃立克体 16S rRNA全基因分析,结果扩增出的序列与美国一株人粒细胞埃立克体(GenBank注册号U02125)的相应序列完全相同,一个碱基不差。另外还从内蒙古大兴安岭采集的森林工人血标本中扩增出特异的EC和人粒细胞埃立克体16SrRNA基因片段。这是首次在亚洲从人血中扩增出人埃立克体DNA。对一份人血标本进行近1500bp的人粒细胞埃立克体 16S rRNA全基因分析,结果仅在第81位与美国这株人粒细胞埃立克体差一个碱基,相差的位置正好位于高变区。结论根据检测结果,本研究建立的系列半巢式PCR扩增方法可以快速、灵敏地检测蜱、脏器、血等标本中的EC和人粒细胞埃立克体,并能较快地分析出其16S rRNA全基因。据报道,莱姆病的流行区往往也是人埃立克体病的流行区。为此我们在大兴安岭林区进行了人埃立克体病和莱姆病的流行病学调查。血样检测发现了人粒细胞埃立克体和 EC 16S rRNA基因阳性的病例共6名,病例均有近期蜱咬史,有埃立克体病的临床表现,潜伏期也相符;血清抗体检测发现检测人群中有HGE阳性抗体。2种病例的发现均为亚洲之首次。通过莱姆病螺旋体感染流行因素的单因素和多因素Logistic回归分析,发现在调查的流行因素中,职业和蜱咬史是影响该疫区人群感染莱姆病螺旋体的主要危险因素。这一调查结果也为该地区人埃立克体病和其他蜱传病的防治提供了参考。     

Detection of Ehrlichia spp. in raccoons (Procyon lotor) from Georgia

Raccoons (Procyonis lotor) and opossums (Didelphis virginianus) acquired from six contiguous counties in the Piedmont physiographic region of Georgia were investigated for their potential role in the epidemiology of ehrlichial and anaplasmal species. Serum was tested by indirect fluorescent antibody (IFA) assay for the presence of antibodies reactive to Ehrlichia chaffeensis, E. canis, and Anaplasma phagocytophilum (HGA agent). Nested polymerase chain reaction (PCR) assay was used to test whole blood or white blood cell preparations for the presence of Ehrlichia and Anaplasma spp. 16S rRNA (rDNA) gene fragments. In addition, ticks were collected from these animals and identified. Twenty-three of 60 raccoons (38.3%) had E. chaffeensis-reactive antibodies (>1:64), 13 of 60 raccoons (21.7%) had E. canis-reactive antibodies, and one of 60 raccoons (1.7%) had A. phagocytophilum- reactive antibodies. A sequence confirmed E. canis product was obtained from one of 60 raccoons and a novel Ehrlichia-like 16S rDNA sequence was detected in 32 of 60 raccoons. This novel sequence was most closely related to an Ehrlichia-like organism identified from Ixodes ticks and rodents in Asia and Europe. Raccoons were PCR negative for E. chaffeensis and E. ewingii DNA. Five tick species, including Dermacentor variabilis, Amblyomma americanum, Ixodes texanus, I. cookei, and I. scapularis, were identified from raccoons and represent potential vectors for the ehrlichiae detected. Opossums (n = 17) were free of ticks and negative on all IFA and PCR assays. This study suggests that raccoons are potentially involved in the epidemiology of multiple ehrlichial organisms with known or potential public health and veterinary implications.     

Ehrlichia species in Rhipicephalus sanguineus ticks in Cameroon

Ehrlichia and Anaplasma species are tick-transmitted obligately intracellular bacteria that commonly cause disease in dogs worldwide. In addition to causing disease in canines, Ehrlichia chaffeensis, Ehrlichia ewingii, and Anaplasma phagocytophilum are responsible for emerging and life-threatening human zoonoses in the United States. We previously reported a high prevalence of E. canis infection in Cameroonian dogs based on serologic and molecular evidence. This study was undertaken to determine the Ehrlichia species (E. canis, E. chaffeensis, E. ewingii) present in Rhipicephalus sanguineus ticks (n = 92) collected from those dogs (n = 51). Ehrlichial DNA was detected by real-time polymerase chain reaction (PCR) in 28 (30%) unengorged R. sanguineus ticks attached to dogs. E. canis, the causative agent of canine monocytic ehrlichiosis, was detected in 19 (21%) ticks from 15 dogs, E. ewingii was detected in six (6%) ticks from 6 dogs, and E. chaffeensis, the etiologic agent of human monocytotropic ehrlichiosis, was detected in 4 (4%) ticks. Notably, 2 ticks were coinfected with E. chaffeensis and E. canis, one tick with E. canis and E. ewingii, and one tick with E. chaffeensis and E. ewingii. These findings further support our previous conclusion that multiple Ehrlichia species are present in Cameroon and identify R. sanguineus ticks primarily infected with E. canis, but suggest that they may be infected with and transmit other ehrlichial agents in Cameroon, potentially to humans.     

Persistent infection in Neotoma fuscipes (Muridae: Sigmodontinae) with Ehrlichia phagocytophila sensu lato.

Dusky-footed wood rats (Neotoma fuscipes Baird) and two species of Peromyscus mice (P. maniculatus Wagner and P. truei Shufeldt) were collected over a 16-month period from three sites in Sonoma County, California. Blood was collected from 93 wood rats and 177 mice and serum or plasma was tested for seroreactivity with Ehrlichia phagocytophila sensu lato (also known as the human granulocytic ehrlichiosis agent). Thirty-five (37.6%) wood rats and 15 (8.5%) mice were seropositive. Positive Neotoma serology by site ranged from 9.4% to 62.1%. Polymerase chain reaction (PCR) testing for the Ehrlichia groESL heat shock operon was performed on all the seropositive and selected seronegative wood rats; 24 (68.6%) seropositive animals were PCR positive. Two seroconversions and no seroreversions were detected among 18 of the seropositive wood rats that were recaptured and tested multiple times (range = 2-6). Fourteen (77.8%) of the 18 were also PCR positive with six of these positive at every testing point (range = 2-6). One wood rat remained serologically and PCR positive in six specimens collected over a 14-month period. One male of 84 questing adult Ixodes pacificus Cooley & Kohls collected was PCR-positive for E. phagocytophila. Borrelia burgdorferi, the agent of Lyme disease, was cultured from ear punch biopsies from six of seven E. phagocytophila seropositive and one of four seronegative wood rats.     

Survey for Tick-Borne Zoonoses in the State of Espirito Santo,Southeastern Brazil

Blood samples collected from 201 humans, 92 dogs, and 27 horses in the state of Espirito Santo, Brazil, were tested by polymerase chain reaction, indirect immunofluorescence assays, and indirect enzyme-linked immunosorbent assay for tick-borne diseases (rickettsiosis, ehrlichiosis, anaplasmosis, borreliosis, babesiosis). Our results indicated that the surveyed counties are endemic for spotted fever group rickettsiosis because sera from 70 (34.8%) humans, 7 (7.6%) dogs, and 7 (25.9%) horses were reactive to at least one of the six Rickettsia species tested. Although there was evidence of ehrlichiosis (Ehrlichia canis) and babesiosis (Babesia canis vogeli, Theileria equi) in domestic animals, no human was positive for babesiosis and only four individuals were serologically positive for E. canis. Borrelia burgdorferi-serologic reactive sera were rare among humans and horses, but encompassed 51% of the canine samples, suggesting that dogs and their ticks can be part of the epidemiological cycle of the causative agent of the Brazilian zoonosis, named Baggio-Yoshinari Syndrome.     

Ehrlichia chaffeensis infection in dogs in South Korea

Ehrlichia chaffeensis is one of the causative agents of canine ehrlichiosis and human monocytic ehrlichiosis (HME). Canine ehrlichiosis caused by E. chaffeensis was diagnosed in two dogs in South Korea based on clinical findings, and the diagnosis was confirmed by polymerase chain reaction (PCR) and DNA sequencing. A 5-year-old intact male American Pit bull terrier allowed outdoors was found to be concurrently infected with Babesia gibsoni and E. chaffeensis. The major clinical findings were lethargy and reddish urine, and laboratory analysis revealed severe hematuria and thrombocytopenia. In addition, a 3-year-old neutered male Shih-tzu was also found to be infected with E. chaffeensis. Although this dog was an indoor companion animal, he was frequently allowed outside for exercise. The clinical signs observed in this dog included generalized purpura with petechiae and ecchymoses due to thrombocytopenia. A 390-bp partial portion of E. chaffeensis 16S rRNA gene was amplified in both cases, and nucleotide sequence analysis revealed 99% homology of this fragment with other E. chaffeensis isolates. These findings demonstrate the presence of E. chaffeensis infection in dogs in South Korea, and this is the first report to confirm clinical cases of E. chaffeensis infection in dogs.     

Identification of Ehrlichia chaffeensis,Anaplasma phagocytophilum,and A. bovis in Haemaphysalis longicornis and Ixodes persulcatus ticks from Korea

A total of 1,467 tick (1,463 of Haemaphysalis longicornis, three of Ixodes persulcatus and one of I. turdus) collected from nine provinces of Korea were examined by TaqMan real-time PCR for the presence of Ehrlichia and Anaplasma species. One set of primers and a probe were designed for detection of all of the Ehrlichia and Anaplasma species. Template DNAs (total 803) were prepared either from pools of larvae, nymphs, adult males and females, or from the salivary gland and midgut of adult ticks. Only DNAs positive in TaqMan PCR were examined for A. phagocytophilum with nested PCR and for E. chaffeensis with PCR. Four A. phagocytophilum 16S rRNA gene PCR products were sequenced for comparison with sequences previously reported. Amplification of a 16S rRNA gene fragment of Ehrlichia and Anaplasma species was observed in 364 tick DNAs (45.3% of the total). Of these 364 positive ticks, species-specific PCRs confirmed that 35 H. longicornis and one I. persulcatus were positive for A. phagocytophilum and one I. persulcatus was positive in E. chaffeensis. Except for one (AB-GGHL, GenBank accession number [GAN] AF470698), three of the four 16S rRNA gene fragment sequences of the A. phagocytophilum-positive samples were similar or identical to the sequences of variants of A. phagocytophilum deposited in GenBank. The 16S rRNA gene fragment sequence of AB-GGHL was similar to that of Anaplasma (Ehrlichia) bovis 16S rRNA (GAN U03775). The identities of the Anaplasmataceae genus and species DNA in the 327 ticks that could not be confirmed infected with either E. chaffeensis, A. phagocytophilum, or A. bovis are not known. This study is the first to demonstrate the presence of E. chaffeensis, A. phagocytophilum and A. bovis in Korean ticks.     

Infection rates of Amblyomma americanum and Dermacentor variabilis by Ehrlichia chaffeensis and Ehrlichia ewingii in southwest Missouri

Both Ehrlichia chaffeensis and Ehrlichia ewingii are causative agents of human ehrlichiosis. Both pathogens are transmitted to humans through the bite of an infected lone star tick (Amblyomma americanum). Since Missouri has a high incidence of human monocytic ehrlichiosis, we investigated the prevalence of E. chaffeensis- and E. ewingii-infected A. americanum and Dermacentor variabilis (American dog tick) ticks to help assess the relative risk for humans exposed to these vectors. We used a nested polymerase chain reaction assay for the detection of ehrlichial DNA in the collected ticks. Infection rates for both ehrlichial species were calculated from the assay results for each of the tick species. E. chaffeensis was found to be present in 9.8% of adult A. americanum ticks (57 of 579) and 6.7% of D. variabilis ticks (eight of 120). E. ewingii DNA was present at an infection rate of 5.4% in adult A. americanum (31 of 579) and 3.3% of D. variabilis ticks (four of 120). A minimum infection rate for nymph pools of A. americanum was 1.7% for E. chaffeensis and 0.6% for E. ewingii.     

Predicting the emergence of tick-borne infections based on climatic changes in Korea

Granulocytic anaplasmosis (GA) and monocytic ehrlichiosis (ME) are maintained in wild rodent reservoirs and tick vectors in the Republic of Korea. This study investigated the prevalence of 2 tick-borne pathogens, Anaplasma phagocytophilum and Ehrlichia chaffeensis, in wild rodents and ticks in central Korea to identify any significant associations with existing or changing climatic conditions. Specifically, the goal of this study was to develop simple models for the probability of occurrence of an epidemic of GA or ME as a function of climate in an area in a given year. Climatic data from 2 regions, Munsan and Dongducheon, Gyeonggi, in central Korea (between the Demilitarized Zone and Seoul, latitude between 37 degrees N-38 degrees N and longitude between 127 degrees E-128 degrees E), were analyzed with respect to the prevalence of GA and ME in Paju, Yoncheon, Pocheon, and Dongducheon for the period from 2001 to 2005. Rates of A. phagocytophilum and E. chaffeensis decreased as the total yearly precipitation levels and daily humidity increased, and as the daily mean sunshine hours decreased. Rates of A. phagocytophilum and E. chaffeensis from rodent ticks and rodents increased in the fall season. Linear regression analyses evaluating the numbers of positive samples by sample type found that rodent ticks were 6.64 times more likely to be actively infected with A. phagocytophilum than grass ticks or rodents, though the likelihood of any samples testing positive for this pathogen decreased by 0.17 as the annual mean level of precipitation increased by 1 mm. For E. chaffeensis, rodents were 15.67 times more likely to be infected than ticks. Logistic regression analyses evaluating each sample separately found that the odds of infection with A. phagocytophilum were nearly 5 times greater for rodents than ticks. In these analyses, precipitation was one potential factor to account for the prevalence of tickborne diseases.