Antigenic relationships between the typhus and spotted fever groups of rickettsiae.

Paired sera from cases of epidemic typhus in Ethiopia and from probable cases of Rocky Mountain spotted fever (RMSF) in the United States were examined by microagglutination (MA) and microimmunofluorescence (micro-IF) tests for antibodies against Rickettsia prowazekii, Rickettsia typhi, Rickettsia canada, Rickettsia rickettsii, Rickettsia conorii and Ricksettsia akari. IgG and IgM antibodies against the various rickettsiae were titrated with specific fluorescein-conjugated anti-IgG and anti-IgM sera. Purified, particulate rickettsial antigens were employed in all tests. A majority of patients acutely ill with epidemic typhus produced both IgG and IgM antibodies against R. prowazekii, R. typhi and R. canada. Concurrently they produced IgG (but seldom IgM) antibodies against members of the spotted fever group. In contrast, patients ill with probably spotted fever, while producing IgG and IgM antibodies against R. rickettsii, R. conorii and R. akari, also produced both IgG and IgM antibodies with about equal frequency against members of the typhus group. It was concluded that a relatively broad antigenic relationship exists between rickettsiae of the typhus and spotted fever groups.     

Cross-protection between distantly related spotted fever group rickettsiae

Two excellent C3H/HeN mouse models of spotted fever rickettsioses caused by the distantly related organisms, Rickettsia conorii and Rickettsia australis, were utilized to evaluate the possibility of the stimulation of broad cross-protective immunity. Sublethal infection stimulated complete immunity, that is absence of disease, after challenge with a dose of the heterologous Rickettsia that uniformly killed na?ve mice. In contrast, heterologous immune sera did not protect mice against a lethal dose (two LD50) of rickettsiae in the mouse toxicity neutralization assay, the standard method for evaluation of rickettsial vaccine potency. These observations suggest that development of a broadly protective vaccine against spotted fever group (SFG) rickettsiae is feasible, and the results indicate that mouse toxicity neutralization is an inappropriate method for evaluation of candidate vaccines.     

Rickettsial infections and fever, Vientiane, Laos

Rickettsial diseases have not been described previously from Laos, but in a prospective study, acute rickettsial infection was identified as the cause of fever in 115 (27%) of 427 adults with negative blood cultures admitted to Mahosot Hospital in Vientiane, Laos. The organisms identified by serologic analysis were Orientia tsutsugamushi (14.8%), Rickettsia typhi (9.6%), and spotted fever group rickettsia (2.6% [8 R. helvetica, 1 R. felis, 1 R. conorii subsp. indica, and 1 Rickettsia "AT1"]). Patients with murine typhus had a lower frequency of peripheral lymphadenopathy than those with scrub typhus (3% vs. 46%, p<0.001). Rickettsioses are an underrecognized cause of undifferentiated febrile illnesses among adults in Laos. This finding has implications for the local empiric treatment of fever.     

First detection of spotted fever group rickettsiae in Ixodes ricinus from Italy

Ixodes ricinus from Italy were examined for the first time to detect whether rickettsiae were present. Using molecular methods, we detected three different spotted fever group rickettsiae, including Rickettsia helvetica. Our results raise the possibility that bacteria other than R. conorii are involved in rickettsial diseases in Italy.     

浙江省蜱标本中斑点热群立克次体rOmpA和gltA基因检测

目的了解浙江省部分山区蜱中感染斑点热群立克次体的状况,探讨以外膜蛋白A（rOmpA）和柠檬酸合成酶基因（gltA）为靶基因的PCR方法可行性。方法利用PCR方法,检测天台县左溪镇和临安县西天目地区共46组蜱类标本中rOmpA和gltA基因特异片段。对所检测到的阳性结果进行克隆与序列测定,并进行聚类分析。结果从46组蜱标本中检测发现2组长角血蜱中斑点热群立克次体的rOmpA和gltA基因片段均为阳性,核酸序列基本一致,但推测斑点热群立克次体种的进化位置存在差异。结论浙江省部分山区存在蜱中感染斑点热群立克次体的状况。利用rOmpA和gltA基因能从标本中检测到斑点热群立克次体,但从2个结果推测立克次体的分类位置存在差异。     

Serological examination of human and animal sera from six countries of three continents for the presence of rickettsial antibodies

Forty samples each of human sera collected in Guinea Bissau, Cape Verde, El Salvador and Iran, and animal sera (goat and cattle from Sri Lanka and sheep from Tanzania) were examined for the presence of antibodies to typhus group (TG) rickettsiae, spotted fever group (SFG) rickettsiae and Coxiella burnetii by enzyme-linked immunosorbent assay (ELISA) and indirect fluorescent antibody (IFA) test. Of human sera tested, a higher proportion of positive sera were found with ELISA and IFA test for TG, SFG rickettsiae and C. burnetii in El Salvador (42.5 vs 20.0%, 40.0 vs 32.5%, and 27.5 vs 27.5%, respectively) and in Iran (25.0 vs 15.0%, 45.0 vs 27.5%, and 27.5 vs 25.0%, respectively), than in Guinea Bissau and Cape Verde, where they were less than 20.0% except for antibodies to SFG rickettsiae in Guinea Bissau (25.0% with ELISA and 20.0% with IFA test). While all animal sera were negative for the presence of antibodies to TG rickettsiae, a high proportion of sera from Sri Lanka reacted in ELISA and IFA test with SFG rickettsiae and C. burnetii (37.5 vs 20.0% and 27.5 vs 25.0% for goat sera, and 40.0 vs 30.0%, and 17.5 vs 15.0% for cattle sera, respectively). The results obtained indicate that the studied rickettsial diseases can be spread in given territories and may pose a public health problem requiring greater attention than has been paid so far. The suitability of ELISA and IFA test for serological survey of rickettsial antibodies is discussed.     

Domestic cats as indicators of the presence of spotted fever and typhus group rickettsiae

Using indirect immunofluorescence assays, sera from cats in Zimbabwe (n = 119) and South Africa (n = 52) were found to contain antibodies reactive with Rickettsia conorii (34% and 19% respectively) and R. typhi (7% and 10% respectively). These results indicate that cats may become infected with members of the spotted fever and typhus groups of rickettsiae and that cats can, therefore, be used as indicators of the presence of these organisms.     

Prevalence of antibodies to spotted fever group rickettsiae in human beings and dogs from an endemic area of mediterranean spotted fever in Catalonia, Spain

We assessed the prevalence of antibodies to spotted fever group rickettsiae in human beings and dogs by indirect immunofluorescence in the region of 'Vallés Occidental', Barcelona (Spain). In the group of 150 serum samples from patients without former history of Mediterranean spotted fever, 12 had antibodies to Rickettsia conori. The overall seroprevalence was 8% (95% confidence interval, 4.6% to 13.5%). There were no statistically significant differences between the mean ages of patients with positive and negative antibodies to R. conorii. However, seropositivity was significantly more common among patients living in semi-rural areas. In the group of 138 dog serum samples, 36 (26.1%) sera had antibodies to R. conorii. When the present results were compared with those obtained in a previous seroepidemiological survey carried out in the same geographical region in 1987, no significant differences were found. Therefore, although the epidemiological markers have dropped, this does not absolutely confirm the decrease of the presence of R. conorii in this area.     

Serologic response to rickettsial antigens in patients with Astrakhan fever

Astrakhan fever is a new spotted fever group (SFG) rickettsiosis. Sera of patients with Astrakhan fever have been examined by microimmunofluorescense and western immunoblotting to determine the serologic responses to the Astrakhan strain and toR. conorii M-1 strain and the Israelian isolate of SFG rickettsiae. The serologic response to specific rickettsial agent and to Israelian isolate has been found to be similar, but was different of that toR. conorii. Immunoglobulin G (IgG) and IgM antibodies were detected in most sera and were directed against the lipopolysaccharide. Only one of tested sera contained IgG antibodies which also recognized high molecular weight proteins.     

用PCR/RFLP技术对黑龙江沿岸蜱类和鼠类中北亚蜱传斑点热的检测

为了解黑龙江沿岸部分地区斑点热自然疫源地存在情况，作者用PCR／RFLP的方法检测该地区蜱类及鼠类中的斑点热群（spottedfevergroup，SFG）立克次体。结果从该地区的森林革蜱、嗜群血蜱、黑线姬鼠、东方田鼠、麝鼠及棕背中均扩增出了斑点热群立克次体的特异片段，而对斑疹伤寒立克次体、恙虫病立克欢体、Q热立克次体则为阴性。PCR产物经PstⅠ及RsaⅠ酶切后发现它们的酶切图谱与西伯利亚立克次体完全相同，而有别于其它斑点热群立克次体标准株。作者认为黑龙江沿岸调查点可能存在北亚蜱传斑点热的自然疫源地。     

Serosurvey among Mediterranean spotted fever patients of a new spotted fever group rickettsial strain (Bar29)

Mediterranean spotted fever is an endemic disease in Catalonia, Spain. A new spotted fever group (SFG) rickettsial strain (Bar29) of unknown pathogenicity for humans was isolated by our group, in 1996, from the dog brown tick, Rhipicephalus sanguineus. Interestingly, Rickettsia conorii was not isolated in this study. The aim of the present study was to assess the possible pathogenic role of the Bar29 strain. To this purpose, serum samples from 15 patients with Mediterranean spotted fever were obtained and tested by immunofluorescence for antibodies against four related rickettsial strains (R. conorii, R. africae, R. massiliae, and Bar29). Eight of the studied sera reacted at high titers with only R. conorii and Bar29 antigens. For five of the eight sera, the titers against Bar29 were clearly higher than for R. conorii. Four of these sera were also studied by Western blot immunoassay to confirm a specific response. Two of these sera reacted with the high-molecular-mass specific proteins of Bar29 as well as with the low-molecular-mass region (LPS antigen) whereas their reactions with R. conorii were located only on bands of the LPS. This specific response would support the possible pathogenic role of the Bar29 strain for humans. According to this finding, spotted fever caused by R. conorii and rickettsial strain Bar29 may be present in our area. The epidemiological implications of spotted fever caused by R. conorii and by rickettsial strain Bar29 in the Catalonia deserve further studies with isolation and characterization of more rickettsial strains.     

内蒙通辽市斑点热群立克次体W—88株的分离与鉴定

1988年我们自通辽市一例发热、头痛、临床诊断为"上感"、用青霉素、病毒灵治疗无效的病人,分离出一株斑点热群立克次体W-88株。经动物感染试验、鸡胚卵黄嚢培养和传代,达到立克次体纯培养,用泛影葡胺密度株度离心纯化,制出立克次饵抗原,用我室建立的抗西伯利亚立克次体群和种特异性单克隆抗体进行免疫荧光检测,与斑点热群立克次体7株国际标准株同从中国分离株对比鉴定。结果确定W-88株为西伯利亚立克次体,该例病人所患的疾病属北亚蜱传斑点热,此为我国在城市发现的北亚热病例首次报道。     

Severe spotted fever group rickettsiosis, Australia

We report 3 cases of spotted fever group rickettsial infection (presumed Queensland tick typhus) in residents of northern Queensland, Australia, who had unusually severe clinical manifestations. Complications included renal failure, purpura fulminans, and severe pneumonia. Clinical illness caused by Rickettsia australis may not be as benign as previously described.     

Prevalence of antibodies to rickettsiae in the north-western part of Bosnia and Herzegovina

The prevalence of rickettsial antibodies in north-western part of Bosnia and Herzegovina was studied. Among 231 sera tested by complement fixation (CF) positive were: 61.5% forRickettsia typhi, 4.3% forR. prowazekii, 1.7% forR. conorii and 19.0% forCoxiella burnetii. Of 183 sera tested by indirect immunofluorescence assay (IFA) 37.7% reacted withR. typhi, 1.6% withR. conorii and 22.4% withC. burnetii. The results show that at leastR. typhi andC. burnetii are highly endemic in this area.Abbreviations CF complement fixation - IFA indirect immunofluorescence - SFG spotted fever group - TG typhus group     

Detection of antibodies to tick salivary antigens among patients from a region of Spain

With a view to determine which tick species bite humans most frequently in the province of Soria (Spain) and to know whether these species act as vectors of Rickettsia conorii and/or Borrelia burgdorferi, we analysed the presence of antibodies against salivary proteins of several tick species and of antibodies against R. conorii and B. burgdorferi sensu lato in 102 samples of serum. The sera were collected from 63 patients who were treated for tick bites at the health services of the Soria Health Area. Thirty-nine percent of the patients displayed antibodies against Dermacentor marginatus; 21% against Ixodes ricinus, and 6% against Rhipicephalus sanguineus. IgM antibodies against R. conorii were found in 15 patients, but none of the patients included in the study displayed IgG/IgM Abs against B. burgdorferi sensu lato. In 30% of the patients bitten by I. ricinus and in 24% bitten by D. marginatus, antibodies against R. conorii were found. None of the patients who had been bitten by R. sanguineus expressed antibodies against this pathogen. The results obtained here suggest that D. marginatus and I. ricinus are the main vectors of the spotted fever group rickettsiae in our environment and that the role of R. sanguineus in the transmission of these rickettsiae is debatable.     

Serosurvey of Rickettsia spp. in dogs and humans from an endemic area for Brazilian spotted fever in the State of São Paulo, Brazil

The present study provides a rickettsial serosurvey in 25 dogs and 35 humans in an endemic area for Brazilian spotted fever in the State of S?o Paulo, where the tick Amblyomma aureolatum is the main vector. Testing canine and human sera by indirect immunofluorescence against four Rickettsia antigens (R. rickettsii, R. parkeri, R. felis and R. bellii) showed that 16 (64%) of canine sera and 1 (2.8%) of human sera reacted to at least one of these rickettsial antigens with titers >0r= 64. Seven canine sera and the single reactive human serum showed titers to R. rickettsii at least four times those of any of the other three antigens. The antibody titers in these 7 animals and 1 human were attributed to stimulation by R. rickettsii infection. No positive canine or human serum was attributed to stimulation by R. parkeri, R. felis, or R. bellii. Our serological results showed that dogs are important sentinels for the presence of R. rickettsii in areas where the tick A. aureolatum is the main vector of Brazilian spotted fever.     

Real-time multiplex PCR assay for detection and differentiation of rickettsiae and orientiae

The high incidence of rickettsial diseases in Southeast Asia necessitates rapid and accurate diagnostic tools for a broad range of rickettsial agents, including Orientia tsutsugamushi (scrub typhus) and Rickettsia typhi (murine typhus), but also spotted fever group infections, which are increasingly reported. We present an SYBR-Green-based, real-time multiplex PCR assay for rapid identification and differentiation of scrub typhus group, typhus group and spotted fever group rickettsiae using 47kDa, gltA and ompB gene targets. Detection limits for amplification of these genes in reference strains ranged from 24 copies/microl, 5 copies/microl and 1 copy/microl in multiplex and 2 copies/microl, 1 copy/microl and 1 copy/microl in single template format, respectively. Differentiation by melt-curve analysis led to distinct melt temperatures for each group-specific amplicon. The assay was subjected to 54 samples, of which all cell-culture and 75% of characterised clinical buffy coat samples were correctly identified. Real-time PCR has the advantage of reliably detecting and differentiating rickettsial and orientia cell-culture isolates in a single-template assay, compared with the more time-consuming and laborious immunofluorescence assay. However, further optimisation and validation on samples taken directly from patients to assess its clinical diagnostic utility is required.     

Isolation of an agent of the spotted fever group rickettsia from tick eggs in Madrid, Spain.

Ticks recovered from dogs in rural villages around Madrid (Spain) were processed to isolate rickettsiae. One sample containing mixtures of ticks and four containing eggs, in which rickettsiae had been detected by indirect immunofluorescence with a human serum highly reactive to Rickettsia conorii, were decontaminated, homogenized and inoculated onto Vero cells. Two egg samples yielded a cytopathic agent that reacted positively by immunofluorescence. One sample (14H) was successfully subcultured and identified as a member of the spotted fever group rickettsia. Tick eggs provide suitable material for isolation of rickettsia.     

Epidemiology of boutonneuse fever in western Sicily. Distribution and prevalence of spotted fever group rickettsial infection in dog ticks (Rhipicephalus sanguineus)

The distribution and prevalence of spotted fever group rickettsial infection in the ixodid dog tick Rhipicephalus sanguineus were found to occur at a rate of 19.7% with variation related to geographic and sociooccupational factors. A higher rate of infection was demonstrated in ticks removed from dogs associated with documented cases of boutonneuse fever. The results fit into available clinical and seroepidemiologic data on Rickettsia conorii infection in western Sicily.