Rickettsial antibody in southern France: antibodies to Rickettsia conorii and Coxiella burnetii among urban, suburban and semi-rural blood donors

Waning population immunity prior to a large Q fever epidemic in the south of The Netherlands

Historical survey data suggest that the seroprevalence of antibodies against Coxiella burnetii in the general population of The Netherlands decreased from more than 40% in 1983 to 2·4% in 2007, just before the start of the large 2007-2010 Q fever epidemic. To assess whether the sharp decline in seroprevalence was real, we performed a cross-sectional study using historical samples. We tested samples using a contemporary commercial indirect immunofluorescence assay. In plasma samples from the south of The Netherlands from 1987, we found an age- and sex-standardized seroprevalence of 14·4% (95% confidence interval 11·2-18·3). This was significantly lower than a 1983 estimate from the same area (62·5%), but significantly higher than 2008 (1·0%) and 2010 (2·3%) estimates from the same area. The study suggests that there was a steady and sharp decline in Q fever seroprevalence in the south of The Netherlands from 1987 to 2008. We assume that seroprevalence has decreased in other parts of The Netherlands as well and seroprevalence surveys in other European countries have shown a similar declining trend. Waning population immunity in The Netherlands may have contributed to the scale of the 2007-2010 Q fever epidemic. For a better understanding of the infection dynamics of Q fever, we advocate an international comparative study of the seroprevalence of C. burnetii.

Q fever and pregnancy: experience from the Limoges Regional University Hospital

INTRODUCTION

Q fever is an ubiquitous zoonosis caused by Coxiella burnetii. Its tropism for the uterus is a potential source of obstetric complications.

MATERIALS AND METHODS

We describe the obstetric consequences of Q fever diagnosed during pregnancy from a series of cases. When an antenatal diagnosis was made, antibiotic therapy with roxithromycin (Rulid(®)) was started until delivery.

RESULTS

Between 2007 and 2012, 30 patients were treated for Q fever diagnosed during pregnancy, i.e. 1.9 cases per 1000 people. The most common reasons for performing serology was intrauterine growth retardation, preterm labor and oligoamnios. Q fever was diagnosed as acute and chronic in 26 and 4 cases, respectively. Progression to chronic disease occurred in 8 % of acute forms of the diseases. The prevalence of obstetric complications was 66 %, including 10 % foetal deaths, 31 % preterm delivery and 27 % low birthweight <10th percentile. The obstetric complication rate amongst the 22 patients treated with ante partum macrolides was 60, 30 % of which involved prematurity and 33 % involved low growth. No cases of foetal death were found on treatment and no congenital malformation and placental or neonatal injury was found. No case of disease reactivation was diagnosed in the eight patients who became pregnant again.

CONCLUSION

Q fever during pregnancy is responsible for severe obstetric complications. It must be diagnosed early and its clinical forms known in order to start appropriate antibiotic therapy.

High seroprevalence for spotted fever group rickettsiae, is associated with higher temperatures and rural environment in Mbeya region, Southwestern Tanzania

Background

Rickettsioses are endemic in sub-Sahara Africa. Burden of disease, risk factors and transmission are hitherto sparsely described.

Methods

From the EMINI (Evaluating and Monitoring the Impact of New Interventions) population cohort, we randomly selected 1,228 persons above the age of 5 years from the nine participating communities in Mbeya region, Southwestern Tanzania, stratified by age, altitude of residence and ownership of domestic mammals, to conduct a cross-sectional seroprevalence study in. The aim was to estimate the seroprevalence of IgG antibodies against Spotted Fever Group (SFG) rickettsiae and to assess socioeconomic and environmental risk factors. Serology (indirect immunofluorescence) was performed at a dilution of 1:64.

Results

SFG-seropositivity in the cohort was found to be 67.9% (range among nine sites: 42.8–91.4%). Multivariable analysis revealed an association with age (prevalence ratio, PR per 10 years: 1.08; 95% CI 1.06–1.10), warmer temperatures (PR per °C: 1.38; 1.11–1.71), male gender (PR 1.08; 1.00–1.16), and low population density (PR per 1.000 persons/km²increase 0.96; 0.94–0.99). At higher elevations, higher cattle density was associated with higher seroprevalence.

Conclusion

SFG rickettsial infection seems to be common in the more rural population of Mbeya Region. Spread seems to be further limited by temperature and higher elevation. Examination of the contribution of SFG to febrile illnesses seems warranted in a prospective study to estimate the disease burden in the population. This will also allow determination of the causative pathogens.

We report a high seroprevalence for antibodies against Spotted Fever Group (SFG) rickettsiae in Southwestern Tanzania, a group of bacteria that is mostly transmitted by ectoparasites such as fleas, lice, mites, and ticks. Serum samples from 1.228 persons were selected, and 67.9% were positive indicating past infection. Seropositivity was clearly associated with warmer temperature, low population density and elevations below 1,500 m. These infections may have been caused by Rickettsia africae, which is transmitted to humans by a cattle tick, and was found in similar settings in Africa. To investigate further on the significance of SFG rickettsioses on disease burden in the area, investigations in acutely febrile patients should be conducted.

Molecular and serological study of rickettsial infection in humans, and in wild and farm animals, in the province of Burgos, Spain

Limited information is available on the presence of rickettsial infection in humans and animal reservoirs in Spain. Exposure to spotted fever group rickettsia in healthy humans and in farm and wild animals in the Province of Burgos, Spain, was examined by serological methods. Rickettsial DNA was also sought by PCR in animal samples. Of 102 human serum samples examined by indirect immunofluorescence assays (IFA), 5.88% were positive for antibodies against Rickettsia conorii (titers 1/128-1/512). Significant differences were detected in human seroprevalence with respect to age. In further IFAs, 102 out of 375 (27.2%) serum samples from the wild animals reacted with R. conorii antigens (titers 1/64-1/1024); 32 out of 281 (11.38%) samples from farm animals were also positive for R. conorii (titers 1/64-1/2048). The prevalence detected among total wild animals was significantly higher than among total farm animals. No rickettsial DNA was found by PCR in any farm or wild animal sample.

Absence of antibodies to Rickettsia spp., Bartonella spp., Ehrlichia spp. and Coxiella burnetii in Tahiti, French Polynesia

BACKGROUND

In the Pacific islands countries and territories, very little is known about the incidence of infectious diseases due to zoonotic pathogens. To our knowledge, human infections due to Rickettsia spp., Coxiella burnetii, Ehrlichia spp. and Bartonella spp. have never been reported in French Polynesia; and infections due to C. burnetti have been reported worldwide except in New Zealand. To evaluate the prevalence of this disease, we conducted a serosurvey among French Polynesian blood donors.

METHODS

The presence of immunoglobulin G antibodies against R. felis, R. typhi, R. conorii, C. burnetii, B. henselae, B. quintana, and E. chaffeensis was evaluated by indirect immunofluorescence assay in sera from 472 French Polynesian blood donors collected from 2011 to 2013. In addition, 178 ticks and 36 cat fleas collected in French Polynesia were also collected and tested by polymerase chain reaction to detect Rickettsia spp., B. henselae and Ehrlichia spp.

RESULTS

None of the blood donors had antibodies at a significant level against Rickettsia spp., Coxiella burnetii, Ehrlichia spp. and Bartonella spp. All tested ticks and cat fleas were PCR-negative for Rickettsia spp., B. henselae, and Ehrlichia spp.

CONCLUSION

We cannot conclude that these pathogens are absent in French Polynesia but, if present, their prevalence is probably very low. C. burnetii has been reported worldwide except in New Zealand. It may also be absent from French Polynesia.

The seroprevalence of human infection withRickettsia slovaca, in an area of northern Spain

An epidemiological survey was undertaken to explore human exposure to Rickettsia slovaca in two provinces of northern Spain. When IFAT were used to test 200 members of the general population for antibodies to rickettsiae of the spotted-fever group, six (3.3%) were found positive, presumably, since Dermacentor is one of the most common genera of human-biting tick in the study area, for antibodies to R. slovaca. Thirty-one (16.9%) of an additional 183 subjects who presented shortly after being bitten by ticks were also found seropositive. The difference in seroprevalence between the general and the tick-bitten populations was significant. Subject gender had no influence on seroprevalence in either population, although, in the tick-bitten group, age and occupation did have a significant influence on the prevalence recorded. Immunoblotting was used to confirm the presence of antibodies in the five subjects, all from the tick-bitten group, found to have acute infections. Three D. marginatus ticks obtained from three of these acute cases were found PCR-positive for R. slovaca DNA.

Synanthropic birds associated with high prevalence of tick-borne rickettsiae and with the first detection of Rickettsia aeschlimannii in Hungary

The aim of this study was to analyze synanthropic birds as risk factors for introducing ticks and tick-borne pathogens into human settlements, with an emphasis on rickettsiae. Altogether 184 subadult ticks were found on 5846 birds. Tick infestation was most prevalent during the spring. In this sample group the majority of ticks were molecularly identified as Ixodes ricinus, and three individuals collected from the European robin as Hyalomma marginatum marginatum. The latter is the first molecularly confirmed occurrence of this species in Hungary. Rickettsia aeschlimannii was detected in H. marginatum, also for the first time in Hungary, and in ticks from an urbanized bird species north of the Mediterranean countries. The overall prevalence range of rickettsiae (including R. helvetica and R. monacensis) in ticks of synanthropic birds was 29-40%, exceeding that in questing ticks of relevant species reported earlier. Additionally, in specimens of I. ricinus, the presence of Borrelia burgdorferi sensu lato (s.l.), Anaplasma phagocytophilum, and a new Francisella-like genotype was also verified. Thus, it can be concluded that birds with urban or periurban habitats pose a high risk as tick carriers and reservoirs of zoonotic agents, especially of rickettsiae.

Prevalence of antibodies to spotted fever group rickettsiae in the region of Split (southern Croatia)

The prevalence of IgG antibodies to spotted fever group rickettsiae (SFG) was investigated by the indirect immunofluorescence assay in a sample of 1207 healthy residents of the central part of southern Croatia (eastern coast of Adriatic Sea). Sera obtained from subjects living in three different places of residency (urban, suburban and rural environs of the region) were tested. Overall 528 (43.7%) persons had significant antibody titers (1:40 or higher), with a significantly higher prevalence in suburban and rural areas. The results show that inhabitants in the area are clearly being exposed to SFG rickettsiae. Risk factors significantly associated with seropositivity to SFG rickettsiae were: living in suburban and rural settlements (odds ratio [OR] = 1.81; 95% confidence interval [CI] = 1.35-2.4), contact with animals (OR: 1.52; 95% CI: 1.15-1.99), and increase of age (OR: 1.18; 95% CI: 1.09-1.26).

Prevalence of antibodies to spotted fever group rickettsiae in human beings and dogs from and 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.

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.

Coxiella burnetii blood cultures from acute and chronic Q-fever patients

Q fever, a worldwide zoonosis caused by Coxiella burnetii, may present as either an acute or a chronic disease. We correlated the results of 844 C. burnetii blood cultures with serological, clinical, and therapeutic data. C. burnetii was isolated from 17% of untreated patients with acute Q fever and from 53% of untreated patients with chronic Q fever. C. burnetii was not isolated from patients who were receiving antibiotics active against C. burnetii. For seven culture-positive patients with acute Q fever, serology was negative when C. burnetii was isolated. One patient with acute Q fever had a positive blood culture 25 days after the discontinuation of specific antibiotic therapy, and another had a positive blood culture after the resolution of symptoms. In one case of chronic Q fever, a positive blood culture resulted from noncompliance with treatment. The culture method described in this report is suitable for all laboratories with cell culture facilities. Our findings suggest that blood samples must be collected prior to the initiation of an antibiotic regimen if C. burnetii is to be successfully isolated.

Seroepidemiology of rickettsial infections in Morocco

The prevalence of antibodies reactive with Rickettsia conorii, Rickettsia typhi, Coxiella burnetii and Ehrlichia chaffeensis was investigated using indirect immunofluorescence (IFA) test on human sera obtained from 300 blood donors in Casablanca and 126 sera obtained from clinical laboratories in Fez. In sera from Casablanca, antibodies reactive at titers > or = 1:32 were found against R. conorii (7%), and R. typhi (1.7%), but not against E. chaffeensis. In the sera from Fez, antibodies were also detected against R. conorii (5.6%), R. typhi (4%), but not against E. chaffeensis. By Western immunoblotting, seroprevalence for R. conorii was in Casablanca and 4.8% in Fez. Antibodies reactive at titers > or = 1:50 against C. burnetii (phase II) were present in sera from Casablanca (1%) and Fez (18.3%).

Current concepts on the transmission of bacteria and parasites by blood components

Several bacterial and parasite transfusion-transmitted diseases have been described in the medical literature. This review deals with the main bacterial (Syphilis, Lyme disease, Gram positive and Gram negative agents), parasite (Chagas disease, malaria, leishmaniasis, toxoplasmosis and babesiosis) and rickettsial diseases that are carried by blood products. Preventional aspects (e.g. storage, screening tests, use of leukocyte-depleted components), diagnosis, geographical distribution and the incidence of these transfusional hazards are also discussed.

The seroprevalence of ten zoonoses in two villages of Crete, Greece

The seroprevalence and incidence of 10 zoonoses due to Rickettsia typhi, R. conorii, Coxiella burnetii, Burcella sp., Borrelia sp., Toxoplasma sp., Leishmania sp., Entamoeba histolytica, Echinococcus granulosus and Fasciola hepatica were studied in an animal husbandry and a farming village in Crete, Greece. The serum conversion incidence of each infectious agent was determined by testing 2 blood samples, collected in 1985 and in 1987. The surveillance was conducted using detailed transparent maps of the 2 villages studied, on which epidemiological data were interrelated to the results obtained from the serological tests. Thus the importance and spread of each infection were visualized. C. burnetii, Toxoplasma sp., R. conorii, and E. granulosus, were the most common infectious agents encountered during this study.

Seroepidemiological survey of rickettsial infections among blood donors in central Tunisia

In this report we attempt to evaluate the prevalence of antibodies against Rickettsia conorii, R. typhi, Coxiella burnettii, and Ehrlichia chaffeensis in central Tunisia. Five hundred sera from blood donors, collected between March and June 1993, were tested for these 4 antibodies using an indirect immunofluorescence antibody assay (IFA). Nine percent of the sera had antibodies against R. conorii (IgG > 1:32) by IFA, and 8% by Western blotting; with IFA, 3.6% had antibodies to R. typhi, 26% to C. burnetii (> 1:50), and none to E. chaffeensis. Infection rates with R. conorii and R. typhi did not differ significantly between the sexes, but fewer young people had antibodies to R. typhi. A significantly higher prevalence of antibodies to C. burnetii was noted for males with no difference between age classes. No significant difference was detected between urban and rural areas. This study confirmed the endemicity of rickettsioses, and revealed a high seroprevalence of Q fever, in central Tunisia.

Prevalence of antibodies to spotted fever group rickettsiae along the eastern coast of the Adriatic sea

A seroepidemiological survey in coastal Croatia detected antibodies reactive with Rickettsia conorii in 4.2% of sera by immunofluorescence assay and in 5.0% of sera by enzyme immunoassay. Western immunoblotting demonstrated antibodies to the 120-kDa surface protein in all 20 positive serum samples examined and to rickettsial lipopolysaccharide in 3 of these serum samples. Humans in this area are clearly being exposed to spotted fever rickettsiae.

Epidemiologic features and clinical presentation of acute Q fever in hospitalized patients: 323 French cases

PURPOSE

To contribute to the knowledge of epidemiologic and clinical features of patients hospitalized with Q fever in France.

METHODS

We conducted a retrospective analysis of 22,496 sera submitted between 1982 and 1990 to the French National Reference Center for Rickettsial Diseases (NRC). The diagnosis of acute Q fever was based on an IgG titer greater than or equal to 1:200 and an IgM titer greater than or equal to 1:25 against phase II Coxiella burnetii antigen on an indirect immunofluorescence test (IFA). Fifteen cases prior to 1985 were diagnosed on the basis of a complement fixation titer greater than or equal to 1:8. A serosurvey of blood donors from Marseille was also conducted in 1988 on 924 sera, using IFA with a cutoff titer of 1:25.

RESULTS

The serosurvey conducted in 1988 showed a seroprevalence of 4.03%, without age or sex prediction. The incidence rate of acute Q fever detection at the NRC was 0.58 per 100,000 inhabitants over the 9-year period. Three hundred twenty-three clinical cases were diagnosed, rising from 1 in 1982 to 107 in 1990. In patients hospitalized for acute Q fever, there was a significantly higher sex ratio of males to females (2.3), which, coupled with the age distribution, indicated that elder males, who are overrepresented due to our recruitment bias, are more susceptible to C. burnetii infections. The mean age of the patients was 45.5 years, while the risk was increased in the 30 to 39 age group as well as in the 60 to 69 age group. Usual epidemiologic risk factors were found in 20.1% of the cases. Hepatitis (61.9%) was a more common clinical presentation in our patients with Q fever than pneumonia (45.8%). This might reflect differences in strains of C. burnetii or the biology of the host. However, French farmers and stock breeders commonly drink unpasteurized raw milk from their cattle, which might indicate a relationship between hepatitis and infection via the digestive tract.

CONCLUSION

Our results indicate that many cases of acute Q fever are undiagnosed. A greater awareness of the disease and more extensive serologic testing of patients with symptoms compatible with Q fever may improve the situation.

Comparison of serologic typing, sodium dodecyl sulfate-polyacrylamide gel electrophoresis protein analysis, and genetic restriction fragment length polymorphism analysis for identification of rickettsiae: characterization of two new rickettsial strains

In 1990, 17 adult Rhipicephalus turanicus ticks were collected in the south of France. Two spotted fever group rickettsiae, Mtu1 and Mtu5, were isolated from the hemolymphs of two of these ticks by the centrifugation shell-vial technique by using HEL cells. These isolates were compared with reference spotted fever group rickettsial serotypes by using three identification methods: microimmunofluorescence serologic typing, sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), and polymerase chain reaction followed by restriction endonuclease fragment length polymorphism analysis. The results obtained by all these techniques showed that Mtu1 and Mtu5 are each previously undescribed rickettsial serotypes. A comparison of the three methods used to identify the isolates led us to the conclusion that, in large-scale epidemiological studies, the simplest way to identify isolates in ticks is to first use the polymerase chain reaction-restriction fragment length polymorphism analysis directly on triturated ticks as a screening method to detect interesting rickettsiae, and then attempt to isolate rickettsiae from ticks for identification by microimmunofluorescence and SDS-PAGE, both of which are time-consuming and expensive to carry out.

Epidemiology of rickettsial diseases

Rickettsial diseases have a diversity of epidemiologic characteristics reflective of the variety of ecologic situations in which the obligate intracellular bacteria are transmitted to humans. For the spotted fever group (SFG) rickettsiae, Rickettsia typhi, R. tsutsugamushi, Coxiella burnetii, and the human ehrlichial agent, humans are a dead-end host who plays no role in the maintenance of the organism in nature. All rickettsioses exist as zoonoses. Moreover, all rickettsiae are found in infected arthopods, which generally serve as the natural hosts and can transmit the infection to the next generation of ticks, mites, chiggers, or fleas. From our anthropocentric viewpoint, Q fever aerosol infection from parturient animals and Brill-Zinsser disease ignited epidemics of louse-borne epidemic typhus are exceptions. However, silent cycles of C. burnetii in ticks and R. prowazekii in the flying squirrel flea may have maintained these agents in transovarial or enzootic cycles for eons before humans and their domestic animals arrived on the scene. Thus, the epidemiology of rickettsial diseases must be recognized as an unfortunate aberration of the rickettsial economy. Several excellent reviews of rickettsial ecology contain a wealth of useful information.

Transmission of parasitic and bacterial infections through blood transfusion within the U.S

The American public has become aware that viral infections can be transmitted by blood transfusions; however, less attention has been paid to nonviral agents that are similarly transmitted. Although donors are tested routinely for serologic evidence of Treponema pallidum infection (syphilis), there are no other bacterial infections for which donors are routinely tested, and no testing is done routinely to detect parasitic infections. Although current preventive strategies appear effective in preventing the transmission of nonviral agents by transfusion, changing population demographics, increased travel and immigration, and increased occurrence of certain asymptomatic bacterial infections in blood donors may require new policies to maintain the safety of the U.S. blood supply. This review focuses on the parasitic and bacterial infections that might pose a risk to transfusion recipients in the U.S.

Prevalence of antibodies to Rickettsia conorii Coxiella burnetii and Rickettsia typhi in Salamanca Province (Spain). Serosurvey in the human population

The Salamanca Province of Spain is an endemic zone for Mediterranean spotted fever. In this area, only one case of Q fever has been reported and typhus group rickettsial diseases have never been diagnosed. To obtain a panoramic view of the presence of antibodies to the most ubiquitous rickettsial agents, 400 sera specimens from a statistically representative sample of the human population of Salamanca City and its surrounding province were subjected to indirect microimmunofluorescent test for antibodies against Rickettsia conorii, Coxiella burnetti, phase II, and Rickettsia typhi antigens. Titers greater than or equal to 1:40 to R. conorii were found in 73.5% of the sera. Positivity was more common in subjects who reported closer contact with the natural environment and/or with domestic animals. Seropositivity to C. burnetti, phase II, was detected in 50.2% of sera. These positive cases were related to rural environmental factors and to previous contact with animals. The frequency of antibodies increased with age showing a progressive exposure to the rickettsial antigen. The prevalence of antibodies to R. conorii and C. burnetii in the human population of Salamanca Province is higher than that reported from any other geographic zone. The study of antibodies to R. typhi showed that 12.5% of the sera had titers greater than or equal to 1:40. According to our results, seropositivity to this rickettsial antigen cannot be related to any particular group of population nor interpreted totally as cross reactivity with R. conorii. Our data show a wide distribution of R. conorii and C. burnetii antigens in Salamanca Province, and also indicate the presence of R. typhi antigens in this area.

Isolation by a sensitive centrifugation cell culture system of 52 strains of spotted fever group rickettsiae from ticks collected in France

Boutonneuse fever caused by Rickettsia conorii is transmitted mainly by the brown dog tick, Rhipicephalus sanguineus. We collected 540 ticks in Marseille, France, and tried to isolate as many strains of rickettsia as possible. Ticks were evaluated for the presence of rickettsia by the hemolymph test and by a new culture system, the centrifugation-shell vial technique. We avoided contamination in the culture system. Prior to ticks being submitted to the hemolymph test, they were disinfected. Only 5.6% (27 of 478) of the cultures were contaminated. A drop of hemolymph from each of 478 R. sanguineus ticks was cultured in two shell vials, and another drop was stained by the Gimenez method or indirect immunofluorescence. Since Gimenez staining in our hands was not satisfactory, comparison of the hemolymph test and culture is based on the results of indirect immunofluorescence. Thus, 50 of 369 (13.5%) examined ticks were hemolymph test positive, and 44 (11.9%) cultures were positive. After disinfection, another pool of 62 ticks were examined by the hemolymph test. The ticks were kept individually in a sterile environment. A few days later, the hemolymph of these ticks was collected again and cultured. The contamination rate was not significantly higher (6.4%) than in the above-described conditions. It allowed us to isolate eight more strains. Thus, we recommend screening ticks with the hemolymph test and culturing only the hemolymph test-positive ticks.

The prevalence of IgG antibodies to spotted-fever group rickettsiae among urban and rural dwelling children in southern Israel

The prevalence of IgG antibodies to spotted-fever group rickettsiae was studied in a sample of 1,055 healthy children aged 2-17 years, residents of the desert Negev region of southern Israel. Groups of children from 5 different places of residency were tested: (1) urban children from the city of Beer-Sheva; (2) children from Omer, a suburb of the city; (3) children from rural communes ("kibbutz"); (4) children from small agricultural settlements ("moshav"); and (5) seminomadic bedouin children. Overall 40 sera (3.8%) were positive by the indirect immunofluorescent antibody assay at a titer of 40. The prevalence rate was 3.6% in males and 4.0% in females. Age-specific prevalence rates for the 2-5, 6-9, 10-13 and 14-17 year old groups were 2.0, 5.4, 4.1 and 3.6% respectively. The prevalence rates by place of residency were: urban 3.3%, suburban 3.3%, "kibbutz" 3.8%, "moshav" 5.1% and seminomadic children 3.3%, and did not differ by socio-economic status as measured by degree of crowding. The results indicate that spotted fever is endemic in all human habitats in the Negev region. Our data do not support association to sex or socio-economic status of the children tested. Lack of cumulative prevalence rates with increasing age suggests that antibodies may wane to undetectable levels in the years following the infection.

Line blot and western blot immunoassays for diagnosis of Mediterranean spotted fever

The line blot, a new immunoassay in which antigens are placed on nitrocellulose as narrow lines, was evaluated for its sensitivity and specificity relative to the microimmunofluorescence assay for the diagnosis of Mediterranean spotted fever (MSF). The line blot assay was only slightly less sensitive and less specific than the microimmunofluorescence assay for detection of immunoglobulin M (IgM) or IgG in 100 serum specimens from 42 patients with MSF. No line blot reactions were observed among 50 control serum specimens from febrile patients with other illnesses. The line blot assay was largely group reactive for spotted fever rickettsiae, but 26% of the positive serum specimens also cross-reacted by IgM with Rickettsia typhi. Western immunoblotting was used to characterize the antigenic components recognized by 19 MSF serum specimens. For both IgM and IgG, lipopolysaccharide was the cross-reactive group antigen, whereas the high-molecular-weight species-specific protein antigens (SPAs) were the only reactive proteins. Relative to the other nine rickettsiae, Rickettsia bellii was unique both in exhibiting no SPA reactions and in having a lipopolysaccharide with a predominantly high-molecular-weight distribution. Although most of the 19 MSF serum specimens examined by Western blotting exhibited preferential reactivity to SPAs of two strains of R. conorii and weaker reactions to the other rickettsiae, 2 serum specimens exhibited SPA reactions consistent with typhus infections. In comparison with other assays, the line blot and Western blot immunoassays have advantages which may permit an improvement in the general availability and commercialization of assays for the serodiagnosis of rickettsial infections.

Lack of co-transmission of Rickettsia conorii and Ehrlichia canis in human beings in the south of France

Ehrlichia canis is the agent of canine Ehrlichiosis, commonly known as canine tropical pancytopenia. This canine disease is frequent in our area, as is Mediterranean Spotted Fever in humans. Recently a few cases of human Ehrlichiosis have been described in the USA. The supposed vector of both diseases is Rhipicephalus sanguineus. In order to evaluate the co-transmission of these two diseases, we selected 498 human sera positive for R. conorii and tested them for Ehrlichia canis. None of them were positive, suggesting the lack of co-transmission of the diseases.