A sero-epidemiological survey of asymptomatic cases of Boutonneuse fever in western Sicily

Mediterranean Spotted Fever: Current Knowledge and Recent Advances

Mediterranean spotted fever (MSF) is an emerging tick-borne rickettsiosis of the spotted fever group (SFG), endemic in the Mediterranean basin. By virtue of technological innovations in molecular genetics, it has been determined that the causative agent of MSF is Rickettsia conorii subspecies conorii. The arthropod vector of this bacterium is the brown dog tick Rhipicephalus sanguineus. The true nature of the reservoir of R. conorii conorii has not been completely deciphered yet, although many authors theorize that the canine population, other mammals, and the ticks themselves could potentially contribute as reservoirs. Typical symptoms of MSF include fever, maculopapular rash, and a characteristic eschar (“tache noire”). Atypical clinical features and severe multi-organ complications may also be present. All of these manifestations arise from the disseminated infection of the endothelium by R. conorii conorii. Several methods exist for the diagnosis of MSF. Serological tests are widely used and molecular techniques have become increasingly available. Doxycycline remains the treatment of choice, while preventive measures are focused on modification of human behavior and vector control strategies. The purpose of this review is to summarize the current knowledge on the epidemiology, pathogenesis, clinical features, diagnosis, and treatment of MSF.

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).

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.

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.

Investigation of Rickettsia conorii antibodies in the Antalya area

Mediterranean spotted fever, caused by Rickettsia conorii, is a tick-borne infection. Serum samples for screening R. conorii antibodies of professionally exposed persons in the Antalya region, on the Mediterranean coast of Turkey, were analyzed. R. conorii IgG antibodies were detected in 13 of 98 (13.3%) serum samples. Mediterranean spotted fever antibodies were found to be positive in 9.4% of the men and 15.2% of the women (a total of 13 cases). Only three cases had a history of fever and rash.

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%).

Canine seroprevalence of Rickettsia conorii infection (Mediterranean spotted fever) in Castilla y León (northwest Spain)

A seroepidemiological study was conducted in 308 dogs to determine the presence of antibodies to Rickettsia conorii, using an indirect immunofluorescence assay (IFA). Seven of the provinces of the Castilla y León region (Burgos, León, Palencia, Salamanca, Soria, Valladolid, and Zamora) were covered by the study. Of the 308 dogs analysed, 72 (23.4%) showed significant titers by IFA (1/40 or higher). Seroprevalences were significantly different between provinces of origin of the animals. These were below 30% in almost all the provinces studied, except for Salamanca province, where the percentage of seropositive dogs was much greater (93.3%). Potential risk factors (presence of ticks on the animals, age, sex, use, habitat, and season) relating to the presence of Mediterranean spotted fever, or Boutonneuse fever, were evaluated. Animals used for guard or pastor activities and those living in rural areas (these factors are closely linked), together with those suffering from tick infestation, had significantly higher seroprevalence than the remainder. The frequency of seropositive dogs increased during the summer months, and these coincide with the period of greatest activity by the vector. Sex and age variables were not identified as risk factors.

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.

Western blot as a seroepidemiologic tool for detecting foci of Mediterranean spotted fever (MSF)

We conducted a serosurvey on Mediterranean spotted fever (MSF), in a nonendemic area using western blot and microimmunofluorescence. Among 262 tested sera, 53 were positive by micro-immunofluorescence at a titer of 50. When 48 positive sera were western blot tested, 15 did not exhibited any reaction, 17 reacted against the non-specific lipopolysaccharide, and only 16 reacted against the specific protein antigens. Fourteen of the sera with a specific reaction were sampled in a village with a unique submediterranean climate. Western blot may be a more specific tool to determine the real seroprevalence of MSF.

Antigens of Rickettsia conorii recognized by seropositive healthy people from Salamanca (central-west Spain)

The antigenic reactivity in Western immunoblotting assay of individual Rickettsia conorii components with sera of healthy people living in Salamanca Province, an endemic zone of Mediterranean spotted fever, is evaluated. Polypeptides of molecular weights 100 kDa (92.7%), 135 kDa (75.6%), 160 kDa (70.7%) and 115 kDa (48.8%) were recognized by a higher proportion of sera with indirect immunofluorescent antibody test titers > or = 1:80. Reaction with apparent rickettsial lipopolysaccharide was found in 15 (36.6%) of these samples. The involvement of different rickettsial strains, atypical routes of inoculation, varying content of the inoculum, and host factors may be determinants of the clinical expression of the spotted fever group rickettsial infection in people who produce antibodies reactive with Rickettsia conorii antigens.

Evidence of the presence of spotted fever group rickettsiae in dogs and dog ticks of the central provinces in Spain

To assess canine exposure to spotted fever group rickettsiae in the central provinces of Spain, ticks removed from dogs were studied by immunofluorescence (IF) staining. Twenty-eight out of 65 (43.0%) samples from ticks were positive. Sera from 58 dogs were also collected and the presence of antibodies to Rickettsia conorii studied. Thirty-four (58.6%) dogs presented significant titers by IF. Surveillance data from these provinces show the presence of Boutonneuse fever cases during recent years, evidence that dogs could serve as an indicator of rickettsial activity in these areas.

Intrafamilial outbreak of Mediterranean spotted fever

The existence of intrafamilial outbreaks of spotted-fever group rickettsioses has seldom been reported, and their true incidence is not known. We here report the occurrence of Mediterranean spotted fever (MSF) in three members of a family: a boy, his grandmother and his grandfather. The infection resolved uneventfully in the boy, and followed a more protracted course in the two older patients, who suffered complications including drowsiness, clotting defects and acute renal failure. This finding highlights the importance of conditioning factors such as age and associated illnesses in the prognosis of infection due to Rickettsia conorii, and suggests that strict surveillance of individuals at risk of infection is necessary for prompt recognition of the onset of the illness and initiation of antibiotic treatment without delay.

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.

Flinders Island spotted fever: a newly recognised endemic focus of tick typhus in Bass Strait. Part 2. Serological investigations

Twenty-six cases of a spotted-fever-like illness have been identified on Flinders Island, Tasmania, over a 17 year period. These patients and 335 healthy persons from the island were investigated serologically using the Weil-Felix agglutination test (Proteus sp. antigens OX2, OX19, OXK) and rickettsia-specific microimmunofluorescence. The antigens used in these latter tests comprised one member of the typhus group (Rickettsia typhi) and three members of the spotted fever group (Rickettsia rickettsii, Rickettsia australis and Rickettsia conorii). Patients with Flinders Island spotted fever showed a higher prevalence of positive reactions to the Weil-Felix tests (with OX2 and OX19 antigens) and a higher prevalence of positive results to rickettsia-specific serological tests (with the exception of antibodies to Rickettsia typhi) than did healthy persons; OX2 (36% v. less than 1%); OX19 (36% v. less than 1%); Rickettsia rickettsii (42% v. 1%); Rickettsia australis (46% v. 1%); Rickettsia conorii (42% v. 1%); Rickettsia typhi (4% v. 4%). In seven of the 26 patients (27%) seroconversion was demonstrated by means of Weil-Felix tests, confirming recent infection. In six of these patients seroconversion was also demonstrated in rickettsia-specific tests. Although these results support the clinical evidence that the illness on Flinders Island is caused by a rickettsia of the spotted fever group, the aetiological agent remains to be isolated.

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.

[Lymphatic cutaneous rickettsiosis caused by Rickettsia conorii in Uruguay]

Three autochthonous cases of cutaneous-ganglionar rickettsiosis transmitted by dogs ticks (Amblyomma maculatum in one of them) are reported. Two of the three cases were undoubtely produced by Rickettsia conorii according to the results of the specific indirect immunofluorescence technique IEF-IgM anti R. conorii. A third case is included due to the clinical epidemiological similarity, the positive serum reactivity with Proteus O x 19 and the rapid response to tetracycline. Autochthonous rickettsiosis by R. conorii has not been previously registered in the American area what confers special interest to this communication. The search of the disease in the other countries of the region is suggested.

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.

Mediterranean spotted fever in Lombardy: an epidemiological, clinical and laboratory study of 76 cases in the years 1977-1986

This paper describes the epidemiological, clinical and laboratory features of 76 cases of Mediterranean spotted fever occurring during the years 1977-1986. The patients observed all lived in the Lombardy region of Italy, which is not located on the Mediterranean Basin. Our data show the highest prevalence of the disease, as reported by other authors, in southern regions of Italy, in the same years: 1979-1983. No differences were noted between age groups or sexes, and the late spring-summer seasonality was confirmed. The clinical signs and symptoms in our cases were those common to the disease. The microimmunofluorescence method was found to be more sensitive and specific than the Weil-Felix test for serological diagnosis. Finally, we showed that doxycycline and oxytetracycline both induce rapid remission of fever.

Laboratory diagnosis of boutonneuse fever by enzyme-linked immunosorbent assay

Little is known about the use of the enzyme-linked immunosorbent assay (ELISA) in the diagnosis of boutonneuse fever, and the reports which do exist have concerned the use of a strain of African origin and a peroxidase-labelled conjugate. We have used, as antigen, a Sicilian strain of Rickettsia conorii recently isolated from a patient with boutonneuse fever and anti-human immunoglobulins G and M labelled with alkaline phosphatase as conjugate. 432 (84.6%) of 500 sera from patients with boutonneuse fever, 4.4% of 384 sera from patients with various other pathologies, and 2.9% of 204 sera from blood donors gave positive reactions. The ELISA was highly sensitive and specific in the diagnosis of boutonneuse fever, and seems to be the test of choice for sero-epidemiological investigations, and when a large number of specimens must be examined. The test is more sensitive than the indirect immunofluorescence test, at least in the early stage of the disease (44.9% vs 21.3% positive respectively), and a long time after an acute attack.

Mediterranean spotted fever in Salamanca, Spain. Epidemiological study in patients and serosurvey in animals and healthy human population

Mediterranean spotted fever is a spotted fever group rickettsiosis caused by Rickettsia conorii. The fever has a recognized incidence in large geographic areas, and its presence in Salamanca Province (Spain) has been well documented since 1981. This work presents the results of the centralized prospective survey carried out in this area and was designed to study the epidemiological behavior of the disease and the prevalence of antibodies against R. conorii among animals and healthy human population. In 110 patients with confirmed diagnosis by an immunofluorescent antibody test we have observed a bimodal temporal curve of incidence of Mediterranean spotted fever in our zone and their predominant origin in villages under 2000 inhabitants. The serosurvey in a statistically representative sample of the human population of Salamanca shows a rate of 73.5% of reactive sera and percentages as high as 82% in samples from small villages. The seroepidemiological study of 300 animals reveals a widespread response to rickettsial antigens throughout the province. Immunofluorescent antibody titers of greater than or equal to 1:40 are present in 93% of dogs and high rates and titers are detected in other domestic mammals, suggesting their feasible epidemiological role in Mediterranean spotted fever.

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.

Imported rickettsial disease: clinical and epidemiologic features

PURPOSE AND METHODS

The rickettsioses continue to constitute major health problems in many parts of the world. With increasing international travel, recognition of rickettsial diseases by physicians is becoming more important. The clinical features of four cases of rickettsial disease imported into Canada over a five-year period are presented; two patients with tick typhus (Rickettsia conorii), one patient with scrub typhus (R. tsutsugamushi), and one patient with murine typhus (R. typhi). We also present the North American data over the past 10 years from the Centers for Disease Control (CDC) (Atlanta).

RESULTS

Since 1983 in the United States, three cases of imported scrub typhus, all after travel to India, were confirmed, as well as six cases of murine typhus after travel to southeast Asia. At the CDC, 67 imported cases of tick typhus have been confirmed by indirect fluorescent antibody test since 1976; most illnesses occurred after travel to Africa.

CONCLUSION

Rickettsial diseases are underrecognized by physicians, who should consider these diagnoses in travelers returning from endemic areas. Since effective treatment is available, prompt diagnosis and treatment are important. In all cases, specific serologic confirmation should be obtained.

Familial cases of boutonneuse fever

Pairs of cases of Boutonneuse Fever (BF) occurred in three families. The illness appeared almost simultaneously in both members of each family, but was generally more serious in one as judged by clinical and laboratory parameters. The possibility of a "bed rickettsiosis", that is reactivation of rickettsiae by the blood meal obtained from the first individual by the same tick which fed upon the second individual, could be excluded in two of the three pairs of cases. In only one of the case pairs were the individuals sharing the same bed. The differences in severity of symptoms may be related to the different immunological pattern observed in these patients. Previous rickettsial infection may have provided partial immune protection, as is repeatedly reported in the literature. In one couple, the more seriously ill patient had antibodies of the IgM class, suggesting that this was his first exposure to Rickettsia conorii. The less severely ill patient had antibodies of the IgG class only, presumably as the result of re-exposure after previous asymptomatic infection with spotted-fever-group rickettsia.

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

Three hundred and twenty-five sera from blood donors in the south of France were examined by means of the indirect fluorescent antibody test. 18% of the sera had antibodies to Rickettsia conorii, with a significantly higher prevalence (26%) in urban and suburban areas than in semi-rural areas (13 to 16%). This supports the view that in the south of France the highest prevalence of Mediterranean Spotted Fever is suburban. 5% of the sera had antibodies to Coxiella burnetti in this area, in which Q fever is endemic.

Analysis of T-cell-dependent and -independent antigens of Rickettsia conorii with monoclonal antibodies

Four monoclonal antibodies from euthymic mice and two monoclonal antibodies from athymic mice were directed against antigens of Rickettsia conorii, as shown by both indirect immunofluorescence and an enzyme immunoassay. There was extensive cross-reactivity with other spotted fever group rickettsiae. Euthymic monoclonal antibodies 3-2 and 9-2 (immunoglobulin G2a [IgG2a]) and 27-10 (IgG1) distinctly outlined the acetone-fixed rickettsial surface, as determined by indirect immunofluorescence; only monoclonal antibody 3-2 reacted with the intact rickettsial surface, as determined by colloidal gold-protein A negative-stain electron microscopy. Athymic monoclonal antibodies 32-2 and 35-3 (IgM) and euthymic monoclonal antibody 31-15 (IgG3) all demonstrated an irregular, extrarickettsial morphology, as determined by immunofluorescence, and ultrastructural cell wall blebs that were readily shed from the rickettsial surface. Monoclonal antibody 3-2, the only antibody to confer protection in lethally challenged mice, reacted with a high-molecular-weight protein in Western immunoblots. Monoclonal antibodies 31-15, 32-2, and 35-3 reacted with a "ladder" of proteinase K-resistant, lipopolysaccharidelike antigens. None of the monoclonal antibodies stabilized the ultrastructural rickettsial slime layer, but both athymic and euthymic polyclonal antibodies to R. conorii did. This is, to the best of our knowledge, the first report of the production of monoclonal antibodies to R. conorii and their use for antigenic analysis.